JP7194628B2 - Wastewater treatment equipment and wastewater treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wastewater treatment apparatus and a wastewater treatment method using an intermittent aeration method that can be applied relatively inexpensively, for example, to an existing large-scale municipal sewage treatment plant.

Conventionally, in sewage treatment plants that treat urban sewage discharged into lakes and closed sea areas, it is necessary to remove nitrogen and phosphorus from the wastewater in order to prevent eutrophication of the discharge destination.

The principle of the nitrogen removal process consists of a nitrification tank (an aerobic tank in which oxygen is supplied by air aeration) in which ammonia nitrogen in the water to be treated is oxidized to nitrate nitrogen by nitrifying bacteria, and a denitrification tank to denitrify the nitrified nitrate nitrogen. Ammonia nitrogen is finally converted to nitrogen gas by a combination of denitrification tanks (anoxic tanks that are stirred and mixed by a stirrer without air aeration) that are reduced by bacteria and released into the atmosphere as nitrogen gas. Several nitrogen removal processes have been developed by arranging and combining the nitrification and denitrification tanks.

A large-scale municipal sewage treatment plant uses the standard activated sludge method in which the entire reaction tank consists of a single aerobic tank. There is a history of maintenance, and in order to change this single aerobic tank into a nitrification tank and a denitrification tank for the purpose of nitrogen removal, the cost of changing the structure of the tank itself and an air diffuser to send air into the tank , the cost of introducing a stirrer, and the cost of increasing power, etc., and the cost of changing is enormous. It hinders the progress of diffusion.

On the other hand, the intermittent aeration method performs biological nitrogen removal by repeating the aeration state and the aeration stop state in one reaction tank. (See, for example, Patent Document 1, FIG. 8B, column “0094”).

The present inventors have noticed that if this intermittent aeration method is applied to a large-scale municipal sewage treatment plant using the standard activated sludge method, it will not be necessary to rearrange the aeration device and introduce an agitator. Since then, we have made efforts to develop a low-cost nitrogen-removing wastewater treatment system and a wastewater treatment method that enable the intermittent aeration method to be applied to large-scale treatment plants.

JP 2015-54271 A

However, since the sewage inflow conditions and treatment facility conditions differ between small-scale facilities and large-scale facilities, intermittent aeration systems for small-scale facilities cannot be used as they are for large-scale sewage treatment facilities.

That is, in small-scale urban sewage treatment plants, an inflow control tank is generally provided, so there are many cases where the intermittent aeration method is applied under conditions in which fluctuations in both water quality and water volume are suppressed to some extent. In addition, the hydraulic retention time (treatment time) of a small-scale municipal sewage treatment plant applying the intermittent aeration method, or the reaction tank capacity per amount of treated water, does not correspond to that of a large-scale sewage treatment applying the standard activated sludge method. It is two to three times as large as the facility, and in small-scale facilities, the reaction tank itself also plays the role of a flow control tank. Therefore, the knowledge of the intermittent aeration method in small-scale sewage treatment plants cannot be applied to large-scale treatment plants where there are large fluctuations in water quality and water volume, and where flow control tanks are generally not installed.

In addition to the above treatment time, there is a reaction tank type as a difference in treatment facility conditions. In small-scale municipal sewage treatment plants, the intermittent aeration method using the oxidation ditch method, which is an endless waterway with a reaction tank treatment time of about 24 hours, is widely used due to loose land restrictions. On the other hand, large-scale urban sewage treatment plants use push-flow reaction tanks that process in one pass with a treatment time of about 8 hours, or 10 hours at the longest. Examples of the intermittent aeration method are not helpful for large-scale sewage treatment plants. Against this background, there are no examples of application of the intermittent aeration method to large-scale sewage treatment plants with a treated water volume of 50,000 m ³ /day or more.

Another difference in treatment facility conditions is the difference in the type and capacity of blowers between small and large scales. The blowers used in small-scale treatment plants are mainly of the type called positive displacement blowers, which are small and easy to start and stop, and which rotate at low speed, and are suitable for intermittent aeration. Furthermore, in small-scale treatment plants, the number of reaction tanks is often 2 to 3 for 2 to 3 water channels, and the positive displacement blowers are often 2 to 3 units. It is also suitable for intermittent aeration because it can be separated without affecting it.

On the other hand, in large-scale treatment plants, a type called a turbo blower is used, in which a large impeller rotates at high speed with inertia. When intermittent aeration is introduced into a large-scale treatment plant with many reaction tanks, the difference in the amount of air blown during aeration and when aeration is stopped fluctuates greatly. For this reason, it is necessary to start and stop the blower frequently, but with a turbo blower, frequent start and stop takes time due to the principle of the turbo blower, and damages the bearings of the impeller. There is no application example of the intermittent aeration method to a large-scale treatment plant because it is impossible because it gives a large amount of air and shortens the service life of the blower.

In addition, many reaction tanks will not be changed to the intermittent aeration method all at once, and if they are changed, it will take several years. It is necessary to minimize fluctuations in airflow due to intermittent aeration even during mixed periods.

Also, it is not uncommon for large-scale treatment plants to have reaction tanks in excess of 10 channels. On the other hand, since a large-sized blower is used, the number of blowers is less than about 5 units including the spare blower. Under these conditions, if some of the reaction tanks are changed to the intermittent aeration method, and the operation of starting and stopping some of the fans is changed to correspond to the intermittent aeration method, the air flow rate of the entire treatment plant becomes unstable. unavoidable.

The treatment apparatus of Patent Document 1 discloses an intermittent aeration method in which a plurality of aeration means are provided in one reaction tank as shown in FIG. 8B, and the aeration means are alternately aerated and stopped. There is no specific disclosure as to whether such aeration control is to be performed or how to control the air flow, and it is unclear whether or not this device can be applied to large-scale treatment plants.

Therefore, in order to introduce the intermittent aeration method to large-scale sewage treatment plants, it is necessary to devise a new intermittent aeration blowing method that is different from the knowledge of the intermittent aeration method used in small-scale treatment plants. be.

The present invention has been made in view of the conventional problems as described above, and as an intermittent aeration method for solving the above problems, the present invention is an intermittent aeration method in which a small amount of constant air is diffused instead of stopping aeration. In a pair of aerobic tanks, the diffusion operation of the other aerobic reaction tank is reversed in phase with respect to the diffusion operation of the other aerobic reaction tank. To provide a wastewater treatment apparatus and a wastewater treatment method using an intermittent aeration method capable of avoiding large fluctuations in the amount of air blown and stoppage of the blower and applicable to large-scale municipal sewage treatment plants.

In order to achieve the above object, the present invention
First, each of the at least two waterways is provided with a push-flow type aerobic reaction tank, and sludge is transferred from each final sedimentation tank downstream of each aerobic reaction tank to the upstream side of each aerobic reaction tank. In a wastewater treatment apparatus provided with means for returning sludge to be returned, the aerobic reaction tank of each water channel includes air diffusion means provided in each tank, and air is sent to each air diffusion means. an air supply pipe for air supply, an air volume adjustment valve provided in the air supply pipe for adjusting the air diffusion amount blown to the air diffusion means, and an air flow meter capable of measuring the air flow rate of each of the air supply pipes An aeration adjustment unit consisting of A valve opening/closing driving means capable of adjusting the amount of air diffusion to the air diffusion means while detecting the flow rate of each air flow meter is provided for each of the air volume adjustment valves of each aeration adjustment unit, and from the blower In a state in which air is being blown to the air pipes of the water channels, in one of the aerobic reaction tanks of the pair of aerobic reaction tanks, the air volume corresponding to one of the valve opening/closing driving means corresponding thereto By controlling the opening and closing of the regulating valve, a positive phase intermittent aeration operation is performed in which aeration with a large amount of air diffusion and fine aeration with a small amount of air diffusion are repeated in the same cycle, and the other aerobic reaction tank is operated. Then, by controlling the opening and closing of the corresponding air volume control valve by the other valve opening/closing driving means corresponding to it, the positive phase consisting of slight aeration during aeration of the one aerobic reaction tank and aeration during slight aeration The intermittent aeration operation is composed of a wastewater treatment device that performs reversed-phase intermittent aeration operation at the same period and at the same timing.

The sludge return means can be composed of, for example, a return sludge pipe (6). The air diffuser can be composed of, for example, air diffusers (5A, 5B, 5C). According to such a configuration, by intermittent aeration operation in each aerobic reaction tank, the ammonium nitrogen in the water to be treated is oxidized to nitrate nitrogen by the nitrifying bacteria during aeration, and the nitrified nitrate nitrogen is processed during slight aeration. Nitrogen in the wastewater can be removed by performing a treatment in which nitrogen is reduced by denitrifying bacteria and released into the atmosphere as nitrogen gas. In addition, in one of the aerobic reaction tanks, the positive phase intermittent aeration operation by opening and closing the air volume adjustment valve (for example, at the cycle T, the air diffusion amount is "5" (aeration) and the air diffusion amount is "1" (slight aeration). intermittent aeration operation), and in the other aerobic reaction tank, in the same cycle and at the same timing by opening and closing the air volume adjustment valve, reverse phase intermittent aeration operation , an intermittent aeration operation that repeats an air diffusion amount of "5" (aeration), so that a predetermined air volume, for example, an air diffusion amount during aeration, can be achieved without stopping the operation of the blower during the intermittent aeration operation. If it is constant, the operation can be continued with a constant air volume (for example, air volume "18"), and even if the air diffusion amount during aeration fluctuates, the amount of increase or decrease in air volume is small (for example, the air volume fluctuation is " 18" to "21", or "15" to "12", etc.), and the operation of the fan can be continued. Therefore, nitrogen can be removed by intermittent aeration treatment in a large-scale municipal sewage treatment plant using a large turbo-type blower, for example, without significantly changing the configuration of the aerobic reaction tank and air diffusion means. It can be realized at relatively low cost.

Second, an even number of at least two waterways are added in addition to the two waterways, and each additional waterway is equipped with the sludge return means including the final sedimentation tank and the aeration adjustment unit. The aerobic reaction tanks of the type are provided respectively, the blower is provided in common to each of the water channels for sending air to the air pipes, and the control unit includes the air volume adjustment valve of the added water channel. Each aerobic reaction tank is provided with a valve opening/closing drive means capable of adjusting the amount of air diffusion to the air diffusion means while detecting the flow rate of each air flow meter, and is installed separately from the pair of aerobic reaction tanks. In a pair of aerobic reaction tanks in a plurality of aerobic reaction tanks, in one of the aerobic reaction tanks, one valve opening/closing driving means corresponding to the aerobic reaction tank corresponds to the air volume control valve The positive phase intermittent aeration operation is performed by controlling the opening and closing of the other aerobic reaction tank. It is composed of the waste water treatment apparatus according to the first aspect, which performs an intermittent aeration operation.

With this configuration, the blower during the intermittent aeration operation of the aerobic reaction tank can continue to operate at a predetermined air volume. In a sewage treatment plant, it becomes possible to change to a wastewater treatment system using an intermittent aeration operation capable of removing nitrogen at a relatively low cost.

Thirdly, any one of the plurality of aerobic reaction tanks is provided with a load concentration confirmation sensor and a dissolved oxygen concentration sensor, and the control unit can detect data from each of the sensors. The control unit includes load concentration comparing means for comparing the measured value of the load concentration confirmation sensor with the measured value at the time of the previous measurement, and blower driving means for instructing an increase or decrease in the air volume of the blower. , dissolved oxygen concentration comparison means for detecting whether the measured value of the dissolved oxygen concentration sensor has reached the upper limit value or the lower limit value, and period comparison means for detecting whether the period has reached the upper limit value or the lower limit value. and in the one aerobic reaction tank performing the positive phase intermittent aeration operation, the load concentration comparison means determines that the measured value of the load concentration confirmation sensor is lower than the previous load concentration. In this case, the blower driving means instructs to decrease the air volume of the blower, and the measured value of the dissolved oxygen concentration sensor and the period are set to the lower limit based on the comparison of the dissolved oxygen concentration comparing means and the period comparing means. until the one valve opening/closing drive means reduces the period and the air diffusion amount during aeration for each of the air volume control valves of the one aerobic reaction tank, and the air diffusion during slight aeration When the load concentration comparing means judges that the measured value of the load concentration confirmation sensor is higher than the previous load concentration, the blower driving means gives an instruction to increase the air volume of the blower, and the one of the The valve opening/closing driving means increases the period and the air diffusion amount during aeration for each of the air volume control valves of the one aerobic reaction tank, and maintains the air diffusion amount during slight aeration at the above constant value. When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration, the blower driving means causes the air volume of the blower to increase. and the one valve opening/closing driving means instructs each of the air volume control valves of the one aerobic reaction tank to maintain the period and the air diffusion volume, and the reverse phase intermittent In the other aerobic reaction tank that performs the aeration operation, the other valve opening/closing driving means is set to the increased or decreased period and air diffusion amount after the change in the positive phase intermittent aeration operation during aeration, The wastewater treatment apparatus according to the above first or second aspect performs anti-phase control for maintaining the above constant value for the amount of air diffused during slight aeration.

The value measured by the load concentration confirmation sensor at the time of the previous measurement means, for example, the value of the load concentration measured at the end of the slight aeration. The fact that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration means that the load concentration does not change, or if it does change, it remains within a small and constant range. With this configuration, only by providing a load concentration confirmation sensor and a dissolved oxygen concentration sensor in any one of the aerobic reaction tanks, air diffusion during aeration according to the load concentration can be performed in all the aerobic reaction tanks. It is possible to increase or decrease the amount and period, and it is possible to realize appropriate air diffusion amount and period change in response to the increase or decrease of the load concentration in the aerobic reaction tank corresponding to all waterways. Become. In addition, one aerobic reaction tank and the other aerobic reaction tank are controlled in reverse phase, there is no need to stop the blower even during slight aeration, and even if the amount of air diffuser is increased or decreased, the blower Therefore, it is possible to realize a wastewater treatment apparatus that can be applied to large-scale urban sewage treatment plants that use large turbo-type blowers, for example.

Fourth, any one of the plurality of aerobic reaction tanks is provided with a load concentration confirmation sensor and a dissolved oxygen concentration sensor, and the control unit can detect data from each of the sensors and The control unit includes load concentration comparing means for comparing the measured value of the load concentration confirmation sensor with the measured value at the time of the previous measurement, and blower driving means for instructing an increase or decrease in the air volume of the blower. , the one aerobic reaction tank which is equipped with dissolved oxygen concentration comparison means for detecting whether the measured value of the dissolved oxygen concentration sensor has reached the upper limit or the lower limit, and which performs the positive phase intermittent aeration operation wherein, when the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is lower than the previous load concentration, the blower driving means instructs the blower to decrease the air volume, and Until the measured value of the dissolved oxygen concentration sensor reaches the lower limit based on the comparison by the dissolved oxygen concentration comparison means, the one valve opening/closing driving means is operated to the air volume control valve of the one aerobic reaction tank. , while the period remains the same, only the air diffusion amount during aeration is decreased, and the air diffusion amount during slight aeration is instructed to be maintained at a constant value. When it is determined that the measured value of the concentration confirmation sensor is higher than the previous load concentration, the blower driving means instructs to increase the air volume of the blower, and the dissolved oxygen concentration comparison means makes a comparison based on the comparison. Until the measured value of the dissolved oxygen concentration sensor reaches the upper limit, the one valve opening/closing driving means is operated to the air volume control valves of the one aerobic reaction tank to disperse air during aeration while maintaining the same cycle. Only the air volume is increased, and the air diffusion volume during slight aeration is instructed to be maintained at the above constant value. , the blower driving means maintains the air volume of the blower, and the one valve opening/closing driving means for each air volume adjustment valve of the one aerobic reaction tank, In the other aerobic reaction tank that performs the reverse phase intermittent aeration operation, the other valve opening/closing drive means is operated to maintain the above cycle and the air diffusion amount during aeration. The waste water treatment apparatus according to the first or second aspect, wherein the air diffusion amount is increased or decreased after the change in the aeration operation, and the air diffusion amount during slight aeration is controlled in the opposite phase to maintain the above constant value. configured be

With this configuration, it is possible to increase or decrease only the air diffusion amount according to the increase or decrease of the load concentration while maintaining the cycle at a constant value, which is simpler than the control that also increases or decreases the cycle. However, it is possible to realize a wastewater treatment apparatus that can be applied to large-scale wastewater treatment facilities that can remove nitrogen by intermittent aeration.

Fifth, a load concentration confirmation sensor is provided in any one of the plurality of aerobic reaction tanks, and the control unit compares the measured value of the load concentration confirmation sensor with the measured value of the previous measurement. blower drive means for instructing the air volume of the blower to increase or decrease, air diffusion amount comparison means for detecting whether the air diffusion amount has reached the upper limit or lower limit, and the cycle is the upper limit or the lower limit In the one aerobic reaction tank which is equipped with a cycle comparison means for detecting whether or not the value has been reached and which performs the positive phase intermittent aeration operation, the load concentration comparison means measures the load concentration confirmation sensor. When it is determined that the value is lower than the previous load concentration, the blower driving means instructs to decrease the air volume of the blower, and based on the comparison of the air diffusion amount comparison means and the period comparison means until the air diffusion amount and period reach the lower limit values, the one valve opening/closing drive means controls the air volume control valves of the one aerobic reaction tank to maintain the period and the air diffusion amount during aeration. is decreased and the amount of air diffusion during slight aeration is maintained at a constant value. When it is determined that there is an upper limit of the air diffusion amount and period based on the comparison of the air diffusion amount comparison means and the period comparison means, the blower drive means instructs to increase the air volume of the blower. until the value is reached, the one valve opening/closing driving means increases the period and the air diffusion amount during aeration for each air volume adjustment valve of the one aerobic reaction tank, and the air diffusion amount during slight aeration is increased. When the load concentration comparison means determines that the measured value of the load concentration confirmation sensor is the same as the previous load concentration, the blower The driving means maintains the air volume of the blower, and the one valve opening/closing driving means instructs each air volume control valve of the one aerobic reaction tank to maintain the period and the air diffusion volume, In the other aerobic reaction tank that performs the reverse phase intermittent aeration operation, the other valve opening/closing drive means is the cycle and the air diffusion amount that have been changed after the change in the positive phase intermittent aeration operation during aeration, The wastewater treatment apparatus according to the above first or second aspect performs anti-phase control for maintaining the above constant value for the amount of air diffused during slight aeration.

With this configuration, it is possible to realize a wastewater treatment facility that enables nitrogen removal by intermittent aeration without using a dissolved oxygen concentration sensor. It is possible to realize a waste water treatment device applicable to

Sixthly, an anoxic tank for denitrification is provided upstream of each of the aerobic reaction tanks in each of the water channels, and part of the wastewater present on the downstream side of each of the aerobic reaction tanks of each of the water channels. to the anoxic tank, and the sludge returning means of each waterway returns the sludge to the anoxic tank instead of the aerobic reaction tank. It is constituted by the waste water treatment apparatus according to any one of 1 to 5.

The drainage circulation means can be composed of, for example, a drainage circulation pipe (12). With this configuration, in addition to the function of removing nitrogen by intermittent aeration operation in the aerobic reaction tank, the denitrification reaction is also actively performed in the anoxic tank on the upstream side, so nitrogen removal is performed more effectively. becomes possible.

Seventh, an anaerobic tank for discharging phosphorus is provided upstream of each anaerobic tank in each water channel, and the sludge returning means returns the sludge to the anaerobic tank instead of the anaerobic tank. It is composed of the waste water treatment apparatus according to the sixth aspect.

With this configuration, in addition to the function of nitrogen removal by the anoxic tank and the aerobic reaction tank, the phosphorus-accumulating bacteria in the returned sludge release phosphoric acid when the sludge is returned to the anaerobic tank, which is preferable. Phosphorus can also be removed by flowing into the aerobic reaction tank and absorbing phosphorus into the activated sludge in the tank.

Eighth, an anaerobic tank for discharging phosphorus is provided upstream of the aerobic reaction tank in each water channel, and the sludge returning means returns the sludge to the anaerobic tank instead of the aerobic reaction tank. It is composed of the waste water treatment apparatus according to any one of the above 1 to 5.

With this configuration, nitrogen removal is performed by intermittent aeration of the aerobic reaction tank, and phosphorous can also be removed by providing an anaerobic tank upstream of the aerobic reaction tank.

Ninth, it is composed of the waste water treatment apparatus according to any one of the first to eighth above, wherein the period is 20 to 90 minutes.

Tenth, an inflow water meter for measuring the amount of water flowing into each waterway is provided for each waterway, and the controller is provided with a waterway corresponding to one aerobic reaction tank that performs the positive phase intermittent aeration operation. Air ratio calculation storage means is provided for obtaining an air ratio from the water amount of the inflow water meter and the air flow rate of the air flow meter corresponding to the one aerobic reaction tank, and storing the air ratio as a reference air ratio. And, in order to match the air magnification of the aerobic reaction tank of the other waterway with the reference air magnification, the air flow rate of the aerobic reaction tank of the other waterway is calculated based on the inflow water amount of the inflow water meter of the other waterway. is provided, and the control unit adjusts the air volume adjustment valve of the other water passage based on the air flow rate after fine adjustment calculated by the fine adjustment amount calculation means. , the wastewater treatment apparatus according to any one of the first to ninth above, which is finely adjusted to match the air amount after the fine adjustment.

The air magnification calculation storage means can be composed of an air magnification calculation means (13u) and a reference air magnification storage means (13v). With this configuration, by calculating the standard air ratio for one channel, it is possible to adjust the air flow rate of the aerobic reaction tank of the other channel so as to match the air ratio for the other channels with the standard air ratio. For example, when there are a plurality of water channels, the air ratio of the aerobic reaction tank of each water channel can be adjusted to the standard air ratio with a simple configuration.

Eleventh, each of at least two waterways is provided with a push-flow type aerobic reaction tank, and sludge is returned from each final sedimentation tank on the downstream side of each aerobic reaction tank to the upstream side of each aerobic reaction tank. A wastewater treatment method in a wastewater treatment apparatus provided with sludge returning means for each,
The aerobic reaction tank of each water channel includes an air diffuser provided in each tank, an air pipe for sending air to each air diffuser, and the air diffuser provided in the air pipe. An aeration adjustment unit comprising an air volume adjustment valve for adjusting the amount of air diffused to be blown to the air means and an air flow meter capable of measuring the air flow rate of each air pipe is provided, and air is supplied to each of the air pipes. A common blower is provided for each water channel for sending air, and the air diffusion amount to the air diffusion means can be adjusted by controlling the opening and closing of each air volume adjustment valve while detecting the flow rate of each air flow meter. A part is provided, and the control part controls opening and closing of each of the air volume adjustment valves when air is being blown from the blower to the air pipe of each water channel, thereby causing the pair of aerobic reaction tanks to: In one of the aerobic reaction tanks, positive-phase intermittent aeration is performed in which aeration with a large amount of air diffusion and fine aeration with a small amount of air diffusion are repeated in the same cycle, while the other aerobic reaction tank performs a positive-phase intermittent aeration operation. In wastewater treatment in a wastewater treatment apparatus that performs a negative phase intermittent aeration operation with the same cycle and timing as the above positive phase intermittent aeration operation consisting of slight aeration during aeration of the one aerobic reaction tank and aeration during slight aeration. Constructed by a method.

Twelfth, in addition to the two waterways, an even number of at least two waterways are added, and each additional waterway is equipped with the sludge return means including the final sedimentation tank and the aeration adjustment unit. The aerobic reaction tank is provided respectively, the blower is provided in common to each water channel for sending air to each air pipe, and the control unit detects the flow rate of each air flow meter in the added water channel. By controlling the opening and closing of each of the air volume control valves while adjusting the amount of air diffused to each of the air diffuser means, a plurality of the preferred aerobic reaction tanks are added separately from the pair of aerobic reaction tanks. In a pair of aerobic reaction tanks, in which two aerobic reaction tanks constitute a set, the control unit controls the opening and closing of the air volume control valve, thereby causing the positive phase intermittent operation in one of the aerobic reaction tanks. The wastewater treatment method in the wastewater treatment apparatus according to the above eleventh aspect, wherein the aeration operation is performed and the reversed-phase intermittent aeration operation is performed in the other aerobic reaction tank.

Thirteenth, any one of the plurality of aerobic reaction tanks is provided with a load concentration confirmation sensor and a dissolved oxygen concentration sensor, and the control section can detect data from each of the sensors and the blower. In the one aerobic reaction tank that performs the positive phase intermittent aeration operation, the control unit determines that the measured value of the load concentration confirmation sensor is lower than the previous load concentration. When it is determined, an instruction is given to reduce the air volume of the blower, and the air volume control valve of the one aerobic reaction tank is controlled until the measured value and cycle of the dissolved oxygen concentration sensor reach the lower limit. , to decrease the period and the air diffusion rate during aeration, and to maintain the air diffusion rate during slight aeration at a constant value. If it is determined that it is, an instruction is given to increase the air volume of the blower, and the air volume of the one aerobic reaction tank is adjusted until the measured value of the dissolved oxygen concentration sensor and the period reach the upper limit. The valve is instructed to increase the period and the air diffusion amount during aeration, and to maintain the above constant value for the air diffusion amount during slight aeration, and the measured value of the load concentration confirmation sensor is the previous value. If it is determined that the load concentration is equivalent, the air volume of the blower is maintained, and the period and air diffusion volume are maintained for each of the air volume control valves of the one aerobic reaction tank. In the other aerobic reaction tank that instructs and performs the reverse phase intermittent aeration operation, the control unit sets the increased or decreased period and air diffusion amount after the change in the positive phase intermittent aeration operation during aeration, The wastewater treatment method in the wastewater treatment apparatus according to the above eleventh or twelfth aspect, wherein the amount of air diffused during aeration is controlled in reverse phase to maintain the constant value.

Fourteenth, any one of the plurality of aerobic reaction tanks is provided with a load concentration confirmation sensor and a dissolved oxygen concentration sensor, and the control section can detect data from each of the sensors and the blower. In the one aerobic reaction tank that performs the positive phase intermittent aeration operation, the control unit determines that the measured value of the load concentration confirmation sensor is lower than the previous load concentration. When it is determined, an instruction is given to reduce the air volume of the blower, and the air volume control valve of the one aerobic reaction tank is operated until the measured value of the dissolved oxygen concentration sensor reaches the lower limit value. At the same cycle, only the air diffusion amount during aeration is decreased, and the air diffusion amount during slight aeration is instructed to be maintained at a constant value, and the measured value of the load concentration confirmation sensor is higher than the previous load concentration. If it is determined that the air volume is increasing, an instruction is given to increase the air volume of the blower, and the air volume control valve of the one aerobic reaction tank is adjusted until the measured value of the dissolved oxygen concentration sensor reaches the upper limit. For the above cycle, only the air diffusion amount during aeration is increased with the same period, and the air diffusion amount during slight aeration is instructed to maintain the above constant value, and the measured value of the load concentration confirmation sensor is If it is determined that the load concentration is the same as the previous load concentration, the air volume of the blower is maintained, and the cycle and air diffusion volume are maintained for each air volume adjustment valve of the one aerobic reaction tank. In the other aerobic reaction tank in which the reverse phase intermittent aeration operation is performed, the control unit makes the air diffusion amount increased or decreased after the change in the positive phase intermittent aeration operation at the time of aeration, The wastewater treatment method in the wastewater treatment apparatus according to the above eleventh or twelfth aspect, wherein the amount of air diffused during aeration is controlled in reverse phase to maintain the constant value.

Fifteenth, any one of the plurality of aerobic reaction tanks is provided with a load concentration confirmation sensor, the control unit detects data from the sensor, controls the air volume of the blower, and controls the current In the one aerobic reaction tank that performs the positive phase intermittent aeration operation, the control unit is configured to store the air diffusion amount storage means for storing the air diffusion amount of the previous When it is determined that the concentration is lower than the load concentration, an instruction is given to decrease the air volume of the blower, and the previous air diffusion volume stored in the period and the air diffusion volume storage means reaches the lower limit. Until then, for each of the air volume control valves of the one aerobic reaction tank, the period and the air diffusion amount during aeration are reduced, and the air diffusion amount during slight aeration is maintained at a constant value. If it is determined that the measured value of the load concentration confirmation sensor is higher than the previous load concentration, an instruction to increase the air volume of the blower is given, and the period and the air diffusion amount storage means are stored. Until the previous air diffusion amount memorized reaches the upper limit, the period and the air diffusion amount at the time of aeration are increased for each of the air volume control valves of the one aerobic reaction tank, The amount of air diffusion during aeration is instructed to maintain the above constant value, and if it is determined that the measured value of the load concentration confirmation sensor is the same as the previous load concentration, the air volume of the blower is maintained. At the same time, instructing each air volume control valve of the one aerobic reaction tank to maintain the cycle and the air diffusion amount, and performing the reverse phase intermittent aeration operation In the other aerobic reaction tank, During aeration, the control unit controls the cycle and the air diffusion amount that have been increased or decreased after the change in the positive phase intermittent aeration operation, and controls the air diffusion amount during slight aeration to maintain the above constant value. It is constituted by the wastewater treatment method in the wastewater treatment apparatus according to the eleventh or twelfth above.

Sixteenth, an inflow water meter for measuring the amount of water flowing into each waterway is provided for each waterway, and the control unit is provided with the waterway corresponding to the one aerobic reaction tank that performs the positive phase intermittent aeration operation. an air ratio calculation storage means for obtaining an air ratio from the water amount of the inflow water meter and the air flow rate of the air flow meter corresponding to the one aerobic reaction tank, and storing the air ratio as a reference air ratio; , calculating the air volume of the aerobic reaction tank of the other channel based on the inflow volume of the inflow water meter of the other channel in order to match the air magnification of the aerobic reaction tank of the other channel with the reference air magnification. A fine adjustment amount calculation means is provided for adjusting the fine adjustment amount calculation means, and the control unit adjusts the air amount adjustment valve of the other water passage to the fine adjustment amount based on the air amount after the fine adjustment calculated by the fine adjustment amount calculation means. The wastewater treatment method in the wastewater treatment apparatus according to any one of the eleventh to fifteenth above-mentioned items performs fine adjustment so as to match the adjusted air amount.

As described above, the present invention performs fine aeration instead of mechanical agitation during the aeration stop time period in the conventional intermittent aeration operation, so that the air volume does not become zero, and positive phase intermittent in one aerobic reaction tank By performing the aeration operation and performing the reverse phase intermittent aeration operation in the other aerobic reaction tank, the operation can be continued at a predetermined air volume without stopping the air volume of the fan during the intermittent aeration operation. High performance that can remove nitrogen by intermittent aeration treatment without significantly changing the configuration of aerobic reaction tanks and air diffusion means in urban large-scale sewage treatment plants that use large turbo blowers. A change to the wastewater treatment facility can be realized at a relatively low cost.

In addition, for example, even in large-scale urban sewage treatment plants with multiple waterways (for example, an even number of waterways of 4 or more), high-performance wastewater treatment facilities that can remove nitrogen by intermittent aeration operation at relatively low cost. Changes can be made.

In addition, by simply installing a load concentration confirmation sensor and a dissolved oxygen concentration sensor in any one of the aerobic reaction tanks, all the aerobic reaction tanks can be controlled to increase or decrease the amount of air diffusion and the period during aeration according to the load concentration. can be performed, and it becomes possible to realize appropriate changes in the amount of air diffusion and the cycle corresponding to the increase or decrease of the load concentration in the aerobic reaction tanks corresponding to all water channels.

In addition, one aerobic reaction tank and the other aerobic reaction tank are controlled in reverse phase, and a small constant air volume is maintained during slight aeration, so even if the air diffusion volume is changed, There is no need to stop the blower, and fluctuations in the air volume of the blower can be kept to a minimum. For example, high-performance wastewater treatment that can be applied to urban large-scale sewage treatment plants that use large turbo-type blowers. An apparatus and wastewater treatment method can be realized.

In addition, while the period is always maintained at a constant value, only the air diffusion amount can be increased or decreased according to the increase or decrease of the load concentration. It is possible to realize a highly functional wastewater treatment apparatus and a wastewater treatment method that are applicable to large-scale wastewater treatment plants that enable nitrogen removal by aeration operation.

In addition, it is possible to realize a wastewater treatment facility that can remove nitrogen by intermittent aeration without using a dissolved oxygen concentration sensor. A treatment apparatus and a wastewater treatment method can be realized.

In addition, by providing an anoxic tank, in addition to the function of removing nitrogen by intermittent aeration in the aerobic reaction tank, active denitrification reaction also occurs in the upstream anoxic tank, so nitrogen is more effectively Removal can be done.

Further, by providing an anaerobic tank upstream of the anoxic tank, phosphorus can be removed in addition to the function of removing nitrogen by the anoxic tank and the aerobic reaction tank.

Further, by providing an anaerobic tank upstream of the aerobic reaction tank, nitrogen can be removed by the intermittent aeration operation of the aerobic reaction tank, and phosphorus can also be removed.

Moreover, when there are a plurality of water channels, the air ratio of the aerobic reaction tank of each water channel can be matched with the standard air ratio by a simple configuration.

1 is a block diagram of a first embodiment of a waste water treatment apparatus and a waste water treatment method according to the present invention; FIG. It is a block diagram of the whole structure of the control part of a processing apparatus same as the above, and a processing method. It is a block diagram which shows the functional structure of the control part of a processing apparatus same as the above, and a processing method. It is a block diagram which shows the functional structure of the control part of a processing apparatus same as the above, and a processing method. It is a flowchart which shows the operation|movement procedure of the control part of a processing apparatus same as the above, and a processing method. It is a flowchart which shows the operation|movement procedure of the control part of a processing apparatus same as the above, and a processing method. It is a flowchart which shows the operation|movement procedure of the control part of a processing apparatus same as the above, and a processing method. FIG. 2 is a diagram showing intermittent aeration operation of the same treatment apparatus and treatment method in positive phase and reverse phase, (a) is intermittent aeration operation, (b) is intermittent aeration operation when the air volume and period during aeration are reduced, ( c) shows the intermittent aeration operation when the air volume and period during aeration are increased. It is a timing chart of the positive phase and reverse phase intermittent aeration operation of the same treatment apparatus and treatment method, (a) is the positive phase intermittent aeration operation of one aerobic tank, (b) is one of the other water channels. Anti-phase intermittent aeration operation of the air tank, (c) shows the total air volume of (a) and (b). FIG. ₂ is a block diagram showing the functional configuration of a control unit after water channel W3 in the same treatment apparatus and treatment method; In the same device and method, it is a diagram showing intermittent aeration operation with a constant period of positive phase and reverse phase, (a) is intermittent aeration operation, (b) is intermittent when the air volume during aeration is reduced Indicates the aeration action. It is a partial block which shows the functional structure of the control part when not using a dissolved oxygen concentration sensor of an apparatus and method same as the above. FIG. 4 is a block diagram of the case where an oxygen-free tank is added in the same processing apparatus and processing method. FIG. 4 is a block diagram of the case where an anoxic tank and an anaerobic tank are added in the same treatment apparatus and treatment method. FIG. 10 is a block diagram of the case where an anaerobic tank is added in the same treatment apparatus and treatment method. FIG. 4 is a conceptual diagram showing another embodiment of intermittent aeration operation in the same treatment apparatus and treatment method. FIG. 4 is a diagram showing changes in concentrations of ammonia nitrogen and nitrate nitrogen during intermittent aeration operation. It is a block diagram which shows the functional structure of the control part of a processing apparatus same as the above, and a processing method.

Hereinafter, the wastewater treatment apparatus and wastewater treatment method according to the present invention will be described in detail.

FIG. 1 shows a block diagram of a waste water treatment apparatus of a first embodiment according to the present invention. This wastewater treatment equipment is assumed to be a large-scale wastewater treatment plant with a wastewater treatment capacity of, for example, 50,000 m ³ /day or more, and is basically composed of a primary sedimentation tank 1, an aerobic reaction tank 2, and a final sedimentation tank 3. Water channels W (W ₁ , W ₂ , .

In the following description, the symbols W ₁ , W ₂ and the like are used when each channel is specified, and the symbol W is used when no channel is specified. In addition, when the waterway is not specified for the members constituting each waterway W (for example, the aerobic reaction tank 2, the air diffuser 5A, etc.), symbols such as "2" and "5A" are used, and when each waterway is specified Subscripts of "2 ₁ , 2 ₂ , etc., 5A ₁ , etc." are used (same for other components).

In addition, the air blower 10 for blowing air to _each air diffuser 5A, 5B, 5C, etc. of _{each water channel W 1 ,} W ₂ . , from the common air blower 10 to the aerobic reaction tanks _{2 1 , 2 of the water channels W 1 , W 2 , etc.} via the air pipes 8 ₁ , 8 ₂ , Air is blown to _each air diffuser 5A ₁ , 5B ₁ , 5C ₁ , 5A ₂ , 5B ₂ , 5C ₂ . The blower 10 is, for example, a single turbo blower for blowing, or a facility composed of two or more turbo blowers connected in parallel for blowing. say. Therefore, in the following description, a single turbo blower or two or more turbo blowers connected in parallel are used to set a predetermined air volume (for example, an air volume of "18" or an air volume of "21", which will be described later). , etc.) is referred to as a blower 10 .

Also, the aerobic reaction tank ₂₁ of the waterway W1 is the "reference control tank", and _all the _other waterway W2 _, W3 _, ... and subsequent aerobic reaction tanks ₂₂ , ₂₃ , 24, It is called a "dependent control tank".

A load concentration confirmation sensor (for example, an ammonia sensor) A and a dissolved oxygen concentration sensor D are provided _only in the aerobic reaction tank 21 as the reference control tank. _The configuration of _each water channel W is the same except that the water channel W1 is provided with the sensors _A and D, and the rest is the same. , W ₃ .

In this description, nitric acid means nitric acid (NO ₃ ), nitrous acid (NO ₂ ), nitrate nitrogen (NO ₃ —N), nitrite nitrogen (NO ₂ —N), nitrate nitrogen and nitrite It is a term that also means NOx, which is a combination of nitrogen and nitric acid, and also shows nitric acid and nitrous acid. Further, ammonia is a name that means ammonia nitrogen together with ammonia. Further, the ammonia concentration is a term that means the concentration of both ammonia (NH ₃ ) and ammonia nitrogen (NH ₄ —N). In addition, nitric acid concentration is a term that means any concentration of nitric acid, nitrous acid, nitrate nitrogen, nitrite nitrogen, a set of nitrate nitrogen and nitrite nitrogen, and NOx indicating both nitric acid and nitrous acid. is.

A primary sedimentation tank 1 is provided on the upstream side of each aerobic reaction tank 2. Raw water flows into the primary sedimentation tank 1, and treated water after sedimentation flows into the aerobic reaction tank 2. It is _On the upstream _side of the _primary sedimentation tanks 11, ₁₂ , . . . , inflow water meters 41, 42, .

The aerobic reaction tank 2 is a push-flow type reaction tank, and the treated water forms a flow from the upstream side to the downstream side (in the direction of arrow M). A plurality of air diffusers 5 (5A, 5B, 5C) are provided at the bottom of these aerobic reaction tanks 2, and air is sent into the tank 2 from the air diffusers 5, and a large amount of air is diffused. and microaeration with a small amount of air diffusion are repeated, and in the aerobic reaction tank 2, microorganisms decompose organic matter in the treated water, and the organic matter contained in the treated water Nitrogen removal is performed.

Here, the aeration time and the slight aeration time are the same, and the total time of the aeration and the slight aeration time is defined as one cycle T. Further, during aeration, the same "aeration" is continued for T/2 hours in each of the aerobic tanks 2A ₁ , 2B ₁ and 2C ₁ of the aerobic reaction tank 2 ₁ (aerobic tank 2A ₁ = aeration , 2B ₁ = aeration, 2C ₁ = aeration), and thereafter, in the aerobic tanks 2A ₁ , 2B ₁ , 2C ₁ , the same “slight aeration” is continued for T/2 hours in any of the tanks (2A ₁ = slight Aeration, 2B ₁ =slight aeration, 2C ₁ =slight aeration) is repeated with a period T (see FIG. 8(a)).

Further, the intermittent aeration operation is such that, for example, the reference control tank (one aerobic reaction tank 2 ₁ ) of the waterway W ₁ is aerated (T/2 cycle, for example, air diffusion amount “5”), fine aeration (T/2 At the timing of the cycle, for example, the air diffusion amount "1"), the subordinate control tank (the other aerobic reaction tank 2 ₂ ) of the water channel W ₂ performs slight aeration (T/2 cycle), aeration (T/2 cycle _{) . _ _ 8} waterway W1, see waterway _W2 ).

This relationship is the same even if the number of waterways W is increased _, and a pair of aerobic reaction tanks ₍ for example _, one aerobic reaction tank 23 in waterways W3 and W4 and the other aerobic reaction tank Also in the tank 2 ₄ , one aerobic reaction tank 2 ₅ and the other aerobic reaction tank 2 ₆ in the water channels W ₅ and W ₆ ), aeration and micro-aeration are performed at mutually opposite timings. Here, the intermittent aeration operation of the reference control tank of the waterway W1 is called "positive _phase intermittent aeration operation", and the intermittent aeration operation in which the timing of aeration and microaeration is opposite to this is called "negative phase intermittent aeration operation". Therefore, the _aerobic reaction tanks of the odd _- numbered waterways ₍ W ₁ , W ₃ , W ₅ . In the gas reaction tank, the reverse phase intermittent aeration operation is performed at the same cycle and timing as the normal phase intermittent aeration operation.

In addition, the reference control tank that performs the positive phase intermittent aeration operation and the dependent control tank that performs the positive phase intermittent aeration operation are called "one aerobic reaction tank", and the dependent control tank that performs the reverse phase intermittent aeration operation is called "the other preferred tank". It's called an aerobic reaction tank. In addition, the valve opening/closing drive means for each one of the aerobic reaction tanks performing the positive phase intermittent aeration operation is replaced with the valve opening/closing drive means for each one of the aerobic reaction tanks performing the reverse phase intermittent aeration operation. These are called valve opening/closing drive means of each other.

Wastewater from which organic matter and nitrogen have been removed in the aerobic reaction tank 2 is sent to a final sedimentation tank 3, where microbial flocs contained in the wastewater are precipitated and separated from the wastewater, and part of the precipitated and separated microbial flocs is returned to the _{most upstream tank (aerobic tank 2A 1 , 2A 2} . be done. The treated water, which is the supernatant after the sedimentation, is sent from the final sedimentation tank 3 to a contact tank (not shown), disinfected in the contact tank, and finally discharged into a river or the like.

The aerobic reaction tank 2 of the waterway W is divided into a plurality of aerobic tanks 2A, 2B and 2C. In this embodiment, a case is shown in which the tank is divided into three aerobic tanks. Moreover, the partition walls 7 between the aerobic tanks 2A, 2B, and 2C may or may not be provided, but when the partition walls 7 are provided, the treated water passes through, for example, the upper side or the lower side of each partition wall 7. Installed so that the water flows downstream.

At the bottom of each of the aerobic tanks 2A, 2B and 2C of the aerobic reaction tank 2, the aeration device 5 (5A to 5C) is provided. This air diffuser 5 may be provided with one air diffuser 5 covering the entire bottom of each of the aerobic tanks 2A, 2B, and 2C, or an independent air diffuser for each of the aerobic tanks 2A, 2B, and 2C. Devices 5A, 5B, 5C may be provided. In this embodiment, as shown in FIG. 1, each aerobic tank 2A, 2B, 2C shall be provided with each independent air diffuser 5A, 5B, 5C. Regarding the aerobic tank 2 and the air diffuser 5, the symbols "2" and "5" are used when the positions are not individually specified, and the symbols "A", "B" etc. are used when the positions are specified. An alphabetic character is added (the same applies to the diffuser control valve 9).

Diffusion adjustment valves 9A, 9B, and 9C are connected to the air diffusion devices 5A, 5B, and 5C, respectively. An air blower 10 for sending air to the air diffusers 5A, 5B and 5C of the aerobic reaction tanks 21 is provided at _one end of each air pipe 8 in common. Except for the embodiment shown in FIG. 16 and the case where a tapered aeration system, which will be described later, is employed, in the embodiment of the present invention, the aeration control valves 9A, 9B, and 9C operate during the intermittent aeration operation. It is assumed that a constant opening is maintained. Therefore, from the blower ₁₀ , the air pipes ₈₁ , ₈₂ , . . . of the _respective water _{channels W1} , _W2 , _. , _{9B 2} , _{9C 2} . . . of the water _{channels W 1} , W _{2 .} In addition, it is configured such that air for diffusion is blown to the air diffusers 5A ₂ , 5B ₂ , 5C ₂ and the like.

Further, between the blowers 10 of the air pipes 8 ₁ , 8 ₂ . . . of the water channels W ₁ , W ₂ . ₁ , _{11 2} . . . and air flow meters G ₁ , G _{2 . Therefore} , the air diffusion amount to the air pipes 8 ₁ , _{8 2} . . . of the water channels W ₁ , W ₂ . . . . can be adjusted independently of each other. Here, an aeration adjustment unit is configured by the air diffusers 5A, 5B, 5C, the air pipe 8 ₁ , the air volume adjustment valve 11 ₁ , and the air flow meter G ₁ .

The load concentration confirmation sensor A and the dissolved oxygen concentration sensor D are provided in one of the aerobic tanks 2A ₁ , 2B ₁ and 2C ₁ of the one aerobic reaction tank 2 ₁ only. Although the two sensors A and D are installed in the middle aerobic tank 2B- ₁ in FIG. 1, they may be installed in the area of the aerobic tank 2A- ₁ or the aerobic tank 2C- ₁ .

The output portion of the load concentration confirmation sensor A is connected to the control portion 13 (FIGS. 2 and ₃ , load concentration detection means 13a), and constantly measures the load concentration of the aerobic reaction tank 2B1, The measured value is configured to be detected by the control section 13 (the load concentration detecting means 13a). The dissolved oxygen concentration sensor D has its output portion connected to the control portion 13 (FIGS. 2 and ₃ , dissolved oxygen concentration detection means 13b), and constantly measures the dissolved oxygen concentration in the aerobic tank 2B1. The measured value can be detected by the control section 13 (dissolved oxygen concentration detecting means 13b).

Further, _{each output part of the air flow meters G 1 , G 2 . .} . provided in the air pipes 8 ₁ , 8 ₂ . (FIGS. 2 and 4, flow rate detecting means 13c ₁ , 13c ₂ . . . ), and the air flow rate of each of the air pipes 8 ₁ , 8 ₂ . 13c ₁ , 13c ₂ . . . ).

The blower 10 is connected to the control unit 13 (FIGS. ₂ and 3, blower driving means 13d), and the air volume control valves 11 ₁ , _{11 2 ,} . _{. _} In addition, the diffusion control valves 9A ₁ to 9C ₁ , 9A ₂ to 9C ₂ and the like are independently connected to the control unit 13 (FIGS. 2 and 3, diffusion control valve driving means 13f). .

Then, the control unit 13 detects the load concentration in the positive phase intermittent aeration operation of _one of the aerobic reaction tanks 21, and when the load concentration in the tank 21 tends to increase, the air volume of the blower ₁₀ is increased. is increased, the air volume control valve ₁₁₁ is controlled to increase the air diffusion amount during aeration of the air diffuser 5, and the period T is also increased, and during slight aeration, the air diffusion amount during aeration is increased. Regardless of the increase, the amount of diffused air is always kept at _a small constant value, and when the load concentration in the tank 21 tends to decrease, the air volume of the blower 10 is reduced and the air volume adjustment valve ₁₁₁ is controlled. During aeration, the air diffusion amount of the air diffusion device 5 is reduced and the period T is also decreased, and during slight aeration, the air diffusion amount is always kept constant regardless of the decrease in the air diffusion amount during aeration. If there is no change in the load concentration, control is performed such that both the air diffusion amount and the period T are maintained at the previous values. _In addition, in the other aerobic reaction tank 22, the reverse phase intermittent aeration operation is similarly performed.

In this way, at the timing when "aeration" or "slight aeration" is performed in _one of the aerobic reaction tanks ₂₁ , the other aerobic reaction tank 22 performs a reverse diffusion operation, that is, "slight aeration". or "aeration" is defined as "anti-phase". Here, in the "reverse phase" intermittent aeration operation, even if the amount of air diffused during aeration in _one or the other aerobic reaction tank 21 or 22 increases or decreases, the other or _one aerobic reaction tank The air diffusion amount during slight aeration in 2 ₂ or 2 ₁ does not change and is always a constant value (for example, air diffusion amount "1"), including such a relationship is defined as "antiphase" .

Even when the water channel W is expanded, the odd-numbered aerobic reaction tanks _{2 1} , _{2 3} . Intermittent aeration operation is performed, and all of these controls are based on the load concentration confirmation sensor A and / or dissolved oxygen concentration sensor D used only in one aerobic reaction tank 2 ₁ (reference control tank). A single controller 13 provided for _one aerobic reaction tank 21 is used.

Here, the circumstances that led the inventors to make the present invention will be described. In the conventional intermittent aeration method, the method of repeatedly aerating and stopping the operation of the blower cannot be applied to a large-scale urban sewage treatment plant using a large blower such as a turbo blower. , Instead of stopping the aeration, micro-aeration is used to diffuse a small amount of air, the aeration time and the micro-aeration time are set to the same time, and two push-flow type aerobic reaction tanks are used as a set for both aeration. By intermittent aeration in which aeration and micro-aeration are repeated in the opposite phase, I came to think that the total air volume of the aeration and micro-aeration fans can be kept constant during the same period of time.

By this intermittent aeration method, it is possible to avoid large fluctuations in the blowing amount of the blower and the stoppage of the blower due to the intermittent aeration. It can also be applied in urban sewage treatment plants.

In addition, the present inventor assumed an urban large-scale sewage treatment plant without a flow control tank, and used a single push flow type aerobic reaction tank with an air diffuser to intermittently perform aeration and microaeration. Aeration was performed, and changes in ammonia nitrogen concentration as a reference of load concentration and changes in nitrate nitrogen concentration as a reference of nitrification reaction were measured and recorded. The results are shown in FIG. As the flow rate fluctuation, 120% artificial flow fluctuation was given based on the average inflow water flow rate.

In FIG. 17, the horizontal axis represents time, and aeration and micro-aeration were performed every 25 minutes at a cycle of 50 minutes. The vertical axis indicates the relationship between changes in concentrations of ammonia nitrogen and nitrate nitrogen as relative concentrations. As a result, during the aeration period, ammonia nitrogen decreased due to nitrification reaction, and nitrate nitrogen increased corresponding to the decreased concentration. is found to rise. A decrease in nitrate nitrogen means that nitrogen gas is being released due to the denitrification reaction, and an increase in ammonia nitrogen means that new water containing a high concentration of ammonia nitrogen is entering the tank from the previous tank. It shows that it is flowing.

The increasing concentration or rate of increase of ammoniacal nitrogen differs depending on the time of day. For example, the time zone (arrow a in the figure) in which the increase is large from 75 minutes to 200 minutes means that the influent ammonia nitrogen concentration is high. Using this as a criterion, the amount of air diffusion is increased in the time period when the ammonia nitrogen concentration is high in order to increase the nitrification rate, and conversely, when the ammonia nitrogen is low (400 minutes to 550 minutes, arrow b in the figure). It has been found that reducing the amount of air diffusion is effective for nitrification reaction control and energy saving.

In addition, the rate of decrease in nitrate nitrogen concentration (denitrification rate) in the slight aeration time zone at 200 to 350 minutes when ammonia nitrogen is high (c in the figure) is It can be seen that the rate of decrease in the nitrate nitrogen concentration is faster than the rate of decrease (d in the figure). From this, the concentration of organic matter required for denitrification increases in proportion to the concentration of ammonia nitrogen, and in the time period when the load concentration is high, even if the amount of air aeration is increased, the denitrification rate during slight aeration is reduced. It was found to not reduce In a single aerobic reaction tank, when intermittent aeration consisting of aeration and micro-aeration is performed, even if the load concentration becomes high and the amount of air diffused during aeration is increased, the It was found that the denitrification reaction was rather active, and that nitrogen gas could be released even during the high load concentration period.

In addition, the nitrate nitrogen at 50 minutes in the time zone when the ammonia nitrogen is low is almost 0, and if the period is longer than 50 minutes, there is a possibility that the time will pass while the nitrate nitrogen is 0, resulting in denitrification. It means that it becomes a useless minute aeration time zone that does not occur. From this, it was found that it is effective to shorten the period as the concentration of ammoniacal nitrogen becomes lower, and conversely, to lengthen the period as the concentration of ammoniacal nitrogen becomes higher.

Based on the findings described above, in the intermittent aeration method consisting of aeration and micro-aeration applied to the wastewater treatment apparatus and wastewater treatment method according to the present invention, intermittent aeration operations of opposite phases are performed in a pair of aerobic reaction tanks. It is possible to suppress large fluctuations in the air volume of the blower, and when the load concentration increases, the period increases with the air diffusion amount of aeration, and when the load concentration decreases, the period increases accordingly. Decreasing period with air sparge was found to be beneficial for nitrification and denitrification. Specific contents of the present invention will be described below.

The control unit 13 (see FIGS. 2 to 4) is a computer having a CPU, and the operation procedures shown in the flow charts of FIGS. 5 to 7 are stored as a program in an internal memory. It performs the intermittent aeration operation described below. 3 and 4 show the functions of the control section 13 in blocks, and the control section 13 will be described below.

The control unit 13 (see FIG. 3) has load concentration storage means 13g for storing the load concentration at the time of the previous slight aeration in the intermittent aeration operation in which aeration and slight aeration are repeated, and stores the current load concentration and the previous load concentration. A load concentration comparing means 13h is provided for comparing, detecting whether the current load concentration is larger or smaller than the previous load concentration, and sending the comparison result to the dissolved oxygen concentration comparing means 13i in the next stage. The load concentration comparing means 13h maintains the current air volume in the blower driving means 13d and the air volume changing means 13t (see FIG. 4) when there is no change in the load concentration (when the load concentration is equal to the previous load concentration). (3) in FIG. 3), and to the cycle determining means 13r (see FIG. 4) to maintain the current cycle (see (1) in FIG. 3).

The control unit 13 has DO upper limit storage means 13j storing the upper limit of the dissolved oxygen concentration and DO lower limit storage means 13k storing the lower limit of the dissolved oxygen concentration. When the comparison result is notified from the load concentration comparison means 13h, the comparison means 13i detects the current dissolved oxygen concentration detected by the dissolved oxygen concentration detection means 13b and the DO upper limit stored in the storage means 13j and 13k. (upper limit of dissolved oxygen concentration) or lower limit of DO (lower limit of dissolved oxygen concentration). "DO" is an abbreviation for "Dissolved Oxygen".

Then, the dissolved oxygen concentration comparison means 13i determines whether the current dissolved oxygen concentration detected by the dissolved oxygen concentration detection means 13b is greater than the DO lower limit value, based on the comparison result of the load concentration comparison means 13h. Alternatively, if the load concentration is decreased (see P11 in FIG. 5) by comparing whether it is smaller than the DO upper limit, and if the current dissolved oxygen concentration is greater than the DO lower limit, the air volume of the blower 10 is reduced. A command is issued to the blower driving means 13d (see P14 in FIG. 5). On the other hand, when the load concentration is increasing (see P12 in FIG. 5), if the dissolved oxygen concentration is lower than the DO upper limit, the blower driving means 13d is instructed to increase the air volume of the blower 10. Further, when the dissolved oxygen concentration comparing means 13i decreases or increases the amount of air diffusion, it simultaneously commands the air amount changing means 13t (see FIG. 4) to decrease or increase the amount of air diffusion (see FIG. 3 (3 )reference). Furthermore, the dissolved oxygen concentration comparison means 13i notifies the comparison result to the period comparison means 13m in the next stage at the same time.

The control unit 13 has cycle storage means 13s for storing the basic cycle T, and cycle upper limit value storage means 13n for storing the upper limits of the cycles of the aeration time and the slight aeration time. It has a cycle lower limit value storage means 13o that stores the cycle lower limit value. When the period comparison means 13m receives the notification of the comparison result from the dissolved oxygen concentration comparison means 13i, the period comparison means 13m stores the current period recognized by the current period recognition means 13p and the storage means 13n and 13o. Compare with the upper or lower period limit.

Here, the cycle is defined as one cycle (T) of the aeration time and the micro-aeration time, and since the aeration time (T/2) and the micro-aeration time (T/2) are the same time (both T/2), As the period increases or decreases, the aeration time and microaeration time increase or decrease by the same amount.

Here, for simplicity of explanation (see FIG. 8(a)), in both aerobic reaction tanks 2 ₁ and 2 ₂ at the same timing, on the water channel W ₁ side, each air diffuser 5A of the aerobic reaction tank 2 _{1 1} , 5B ₁ , 5C ₁ at the time of aeration is, for example, "5", "5", "5", the air volume of the air pipe 8 ₁ after the air volume adjustment valve 11 ₁ is "15" (5 × 3) , the opening of the air volume adjustment valve 11 ₁ is also set to "15" according to the air volume, and on the water channel W ₂ side, the air volume at the time of slight aeration of each air diffuser 5A ₂ , 5B ₂ , 5C ₂ of the aerobic reaction tank 2 ₂ is "1", "1", "1", the air _volume of the air pipe 82 after the air volume adjustment valve 11-2 is " ₃ " (1 x 3), and the opening of the air _volume adjustment valve 11-2 also depends on the air volume. The total air volume of the blower 10 at this time is assumed to be "18", which is the total air volume (15+3) of the air pipes 8 ₁ and 8 ₂ . The same applies to the air volume and opening of each part when the air volume increases or decreases during aeration.

In the aerobic reaction tank _2-1 of the waterway W1 in FIG. ₁ , intermittent aeration operation, that is, aeration and micro-aeration are repeated at a cycle of T/2 (see FIG. 8(a)). For example, the air volume of the blower 10 is "18" (the aerobic reaction tanks 2A ₁ , 2B ₁ and 2C ₁ have air diffusion amounts of "5", "5" and "5", and the aerobic reaction tanks 2A ₂ and 2B ₂ , _2C2 blow air with an air diffusion amount of " ₁ ", " ₁ ", "1", total 18). 11 ₁ is maintained at a predetermined opening degree of "15 (5×3)" for _a period of T/ ₂ during aeration. , "5", and "5" are performed (see FIG. 8(a)), and after T/2 has passed, the valve opening/closing drive means _13e1 throttles the opening of the valve, and then T/ 2, by maintaining the predetermined degree of opening "3 (1×3)", the aerobic reaction tanks 2A ₁ to 2C ₁ each have a small amount of air diffusion "1", "1", "1 After that, the opening and closing operation of the air volume control valve ₁₁₁ is repeated every cycle T/2 (see FIG. 8(a)). Here, the air diffusion amount during slight aeration is always maintained at a constant air diffusion amount (air diffusion amount "1" in this embodiment) even if the air diffusion amount during aeration increases or decreases.

That is, each one of the valve opening/closing driving means _13e1 , _{13e3 , 13e5} , ... connected to the water passage W1 and the odd _- numbered water passages W3 _, W5, _W7 , . At T/2, the valve opening degrees of the air volume control valves 11 ₁ , 11 ₃ , 11 ₅ . When there is an instruction to increase or decrease the amount of air diffusion and an instruction to increase or decrease the period from the period determining means 13r (the air volume of the blower 10 is also increasing or decreasing), the valve is opened during aeration according to the above instruction By adjusting the degree and valve opening time, the air diffusion amount and period during aeration are changed (see P14 or P16, P18 or P20 in FIG. 5). In addition, the valve opening/closing drive means 13e ₁ , 13e ₃ , 13e ₅ . The air volume control valves _{11 1} , 11 ₃ , 11 ₁ , 11 ₃ , . 11 ₅ ... Adjust the opening degree of the valve (see P6 in FIG. 5).

At the same _time , in the aerobic reaction tank 22 of the waterway W2, the intermittent aeration operation is performed in a _phase opposite to that of the waterway W1, that is, microaeration and aeration occur at the same timing as the aerobic reaction tank 21 at the cycle T _{/ 2} . This is repeated (see _FIG . 8(a) aerobic reaction tank 22). For example, when the blower 10 blows air at an air volume of "18", the other valve opening/closing driving means 13e2 of the control unit 13 of the water channel W2 _sets the air volume adjustment valve 112 to T/ ₂ at the _time of slight aeration. By maintaining the predetermined opening degree "3 (1 × 3)" for the period, the aerobic reaction tanks 2A ₂ to 2C ₂ are slightly aerated with air diffusion amounts "1", "1", and "1", respectively. is performed (see FIG. 8(a)), and after the above T/ ₂ has passed, the other valve opening/closing driving means 13e2 opens the valve opening, and for the subsequent period of T/2, a predetermined opening By maintaining "15 (5 × 3)", the aerobic reaction tanks 2A ₂ to 2C ₂ are aerated with air diffusion amounts of "5", "5", and "5", respectively. The intermittent aeration operation in the opposite _phase to the aerobic reaction tank 21, that is, the opening and closing operation of the air volume control valve 112 is repeated every cycle T/ ₂ (see FIG. 8(a)). Here, even in the aerobic reaction tank ₂₂ , even if the amount of air diffusion during slight aeration increases or decreases, the amount of air diffusion is always constant (in this embodiment, the amount of air diffusion "1") is maintained.

That is, the other valve opening/closing driving means _{13e 2 , 13e 4 , 13e 6 .} At the same timing as the aerobic reaction tank 21, the valve opening _{degrees of the air volume control valves 11 2 ,} 11 ₄ , 11 ₆ . . . When there is an instruction to increase or decrease the amount of air diffusion during aeration from the amount changing means 13t and an instruction to increase or decrease the period from the period determining means 13r (the air volume of the blower 10 is also increasing or decreasing), the above instructions Accordingly, by adjusting the valve opening degree and the valve opening degree time during aeration, the air diffusion amount and period during aeration are changed (see P14 or P16, P18 or P20 of FIG. 5). In addition, the other valve opening/closing driving means 13e ₂ , 13e ₄ , 13e ₆ . Air volume control valves 11 ₂ , 11 ₄ , 11 ₆ based on flow rates from air flow meters G ₂ , G ₄ , G ₆ . . . . . is adjusted (see P2 in FIG. 5).

In this way, the increase or decrease in the amount of air diffuser increases or decreases the air volume of the blower 10, and the valve opening/closing drive means 13e ₁ , 13e ₂ , etc. change the flow rate from the air flow meters G ₁ , G ₂ , etc. Based on this, the opening degree of each air volume adjustment valve 11 ₁ , 11 ₂ etc. is adjusted to increase or decrease the amount of air diffusion (for example, increase the amount of air diffusion from “5” to “6”, or Aeration amount is reduced from "5" to "4"). Then, the air volume of the fan 10 is increased or decreased by the fan drive means 13d, and control is performed to increase or decrease the air diffusion amount during this aeration. Without changing the air volume, control is performed to always maintain "1" by adjusting the opening degrees of the air volume control valves 11 ₁ and 11 ₂ . By performing such control, during the intermittent aeration operation, unless there is an instruction to increase or decrease the air volume, the air volume of the blower 10 is always a constant value (for example, in the case of FIG. 8A, a constant air volume "18") is maintained. It becomes possible to

The cycle comparison means 13m determines whether the current cycle recognized by the current cycle recognition means 13p is greater than the lower limit of the cycle or the upper limit of the cycle according to the comparison result of the load concentration comparison means 13h. If the load concentration tends to decrease (see P11 in FIG. 5) and the current cycle is greater than the cycle lower limit value, the cycle changing means 13q is instructed to decrease the cycle, and the load concentration If there is an increasing trend (see P12 in FIG. 5) and the current cycle is smaller than the cycle upper limit value, the cycle changing means 13q is commanded to increase the cycle (see FIG. 3 (2)).

The period changing means 13q (see FIG. 4) of the control unit 13 increases the current period (for example, 60 minutes) by one step (for example, 70 minutes) or decreases by one step (for example, 50 minutes), and the period determining means Notify 13r. The period determination means 13r increases or decreases the current period by one step, and notifies the determined period to one or the other valve opening/closing driving means 13e ₁ , 13e ₂ , 13e ₃ . . . _The valve opening/closing driving means 13e ₁ , _{13e 2} . By doing so, the cycle during aeration or slight aeration is changed (see P16 or P20 in FIG. 5).

The control unit 13 (one valve opening/closing driving means 13e ₁ ) (the same applies to each one valve opening/closing driving means corresponding to the odd-numbered water passage) recognizes the period instructed by the period determining means 13r, and (for example, 60 minutes), the air volume control valve 11 ₁ is, for example, open 15 (5×3) during the period of 1/2 cycle (30 minutes) (air diffusion of the aerobic reaction tanks 2A ₁ to 2C ₁ ). Each air volume is set to "5") to maintain the opening of the aeration, and the opening of the air volume control valve 11 is narrowed for the period of 1/2 cycle (30 minutes) after that, for example, the opening is set to "3 (1 x 3) ” (air diffusion amount of each of the aerobic reaction tanks 2A ₁ to 2C ₁ is “1”). Aeration operation) is repeated (see waterway W1 in FIG. 8( _a )).

The control unit 13 (the other valve opening/closing drive means 13e ₂ ) (the same applies to the other valve opening/closing drive means corresponding to even-numbered water passages) recognizes the period instructed by the period determining means 13r, (or one of the valve opening/closing driving means corresponding to the paired odd-numbered water passages) has the same timing and the same cycle as the valve opening/closing driving means 13e ₁ (or the odd-numbered water passage), but the one valve opening/closing driving means 13e ₁ (or the odd-numbered The intermittent aeration operation is performed in the opposite phase to the one valve opening/closing driving means corresponding to each water channel (see _FIG . 8(a) water channel W2).

That is, the other valve opening/closing driving means _13e2 recognizes the above cycle, and during the half cycle (30 minutes) of the cycle (60 minutes), for example, the opening degree of the air volume control valve 112 is " ₃ ". (1 × 3)” (air diffusion amount of each of the aerobic reaction tanks 2A ₂ to 2C ₂ is “1”) to maintain the opening of fine aeration, and the period of 1/2 cycle (30 minutes) after that is Open the opening of the air volume control valve 11 ₂ to maintain the opening of the aeration, for example, the opening of "15 (5 x 3)" (the air diffusion amount of the aerobic reaction tanks 2A ₂ to 2C ₂ is "5" each). Then, such microaeration and aeration opening/closing operation (intermittent aeration operation) are repeated every _1/2 cycle (see waterway W2 in FIG. 8(a)).

Then, one or the other of the valve opening/closing drive means 13e ₁ , 13e ₂ . to FIG. 8(c))) or decreased (air volume decreased from “18” to “15” (see FIG. 8(a) to FIG. 8(b))), that is, from the air volume changing means 13t to the aeration When there is an instruction to change the amount of air diffusion, the air diffusion amount at the time of aeration will be the predetermined air diffusion amount after the change instruction (for example, the amount of air diffusion "4" or "6" etc.) , while detecting the flow rate from the flow rate detection means _{13c 1} , _{13c 2} . . . of the corresponding water channels W ₁ , W ₂ . Adjust the degree of opening (open/close control).

However, the one or the other valve opening/closing drive means 13e ₁ , 13e ₂ . While detecting the flow rate from the flow rate detection means _{13c 1} , _{13c 2} . The opening is adjusted (see FIG. 8(a)).

Since the present invention is configured as described above, the operating procedure of the present invention will be described below with reference to the flow chart of FIG. Also, for the sake of simplification of explanation, the waterway W1 having the reference control tank shown in _FIG . ₁ and the waterway W2 having the subordinate control tank will be described. In the flow chart of FIG. 5, the fine adjustment operation based on the air magnification in steps P2' and P7' will be collectively described in the second half (correction operation based on the air magnification).

Drainage ₍ water to be treated) flows into _each of the water channels W1 and W2, and the water to be treated after sedimentation in the _primary sedimentation tanks ₁₁ and ₁₂ flows into the aerobic reaction tanks ₂₁ and 22, Intermittent aeration operations are performed by the diffusers 5A ₁ to 5C ₁ and 5A ₂ to 5C ₂ of the reaction tanks 2 ₁ and 2 ₂ . Under the control of the control unit 13 (diffusion adjustment valve driving means 13f), the diffusion adjustment valves 9A ₁ to 9C ₁ and 9A ₂ to 9C ₂ of the water passages W ₁ and W ₂ always maintain a constant degree of opening. shall be It is also assumed that the cycle storage means 13s in the control unit 13 stores a basic cycle T (60 minutes in this embodiment).

1. First Embodiment The control unit 13 (blower driving means 13d) drives the blower 10 at a predetermined air volume (here, the air volume is "18") (FIGS. 8A and 9C). reference). Then, air blowing from the blower 10 to the air pipe 8 ₁ of the water channel W ₁ and the air pipe 8 ₂ of the water channel W ₂ is started. FIG. 9(a) shows the positive phase intermittent aeration operation of _{one aerobic tank (for example, 2A 1 )} of the aerobic reaction tank 21, and _FIG . 9(b) shows one aerobic tank of the aerobic reaction tank 22. (For example, 2A ₂ ) shows each timing chart of the reverse phase intermittent aeration operation, and the figure (c) shows the total air volume of both aerobic tanks 2A ₁ and 2A ₂ , and in the figure (c), the numbers in parentheses (18, 15, 21) indicates the air volume of the blower 10 at that time.

(Aeration operation of aerobic reaction tank ₂₁ )
The control unit 13 (flow rate detection means 13c ₁ ) detects flow rate data from the air flow meter G ₁ , and the control unit 13 (one valve opening/closing drive means 13e ₁ ) detects the current data from the flow rate detection means 13c ₁ . Constantly receiving flow rate data. Therefore, the control unit 13 (valve opening/closing driving means 13e ₁ ) constantly detects the flow rate data, and adjusts the valve opening degree of the air volume adjustment valve 11 ₁ to the air diffusion amount of each of the aerobic tanks 2A ₁ to 2C ₁ . is adjusted to be "5" (valve opening degree "15" (5 x 3)), and as _a result, the air volume corresponding to the air pipe 81 of the waterway W1 (" ₁₅ ") is blown, and the same opening Aeration devices 5A ₁ , 5B ₁ , 5C of each aerobic tank 2A ₁ , 2B ₁ , 2C ₁ of aerobic reaction tank 2 ₁ (reference control tank) via air diffusion adjustment valves 9A ₁ to 9C _{1 1} , and the diffusers 5A ₁ to 5C ₁ spray air with air diffusion amounts of "5", "5", and "5" into the tank, and each aerobic tank 2A ₁ , 2B ₁ and 2C ₁ , "aeration" with an air diffusion amount of "5" is started (see FIG. 5P1, FIG. 8(a) K1, and FIG. 9(a)(b)).

In FIG. ₈ , "K1", "K2", . _' ' .

₍ Slight aeration operation of aerobic reaction tank 22)
At the same time, the control unit 13 (flow rate detection means 13c ₂ ) detects flow data from the air flow meter G ₂ , and the control unit 13 (the other valve opening/closing drive means 13e ₂ ) detects the flow rate data from the flow rate detection means 13c ₂ . Constantly receiving current flow rate data. Therefore, the control unit 13 (valve opening/closing driving means 13e ₂ ) constantly detects the flow rate data, and adjusts the valve opening degree of the air volume adjustment valve 11 ₂ to the air diffusion amount of each of the aerobic tanks 2A ₂ to 2C ₂ . , Adjusted so that the air diffusion amount of micro-aeration, which is in the opposite phase to the reference control tank, is "1" (valve opening "3" (1 x 3)), and as a result, the air pipe ₈ of the water channel W2 ₂ ("3") is blown, and each aerobic reaction tank 2 ₂ (subordinate control tank) of the water channel W ₂ is blown through the diffusion adjustment valves 9A ₂ to 9C ₂ with the same opening degree. Blowing air is evenly distributed to the diffusers 5A ₂ , 5B ₂ and 5C ₂ of the tanks 2A ₂ , 2B ₂ and 2C ₂ , and the diffusers 5A ₂ to 5C ₂ emit air with an air diffusion amount of “1”. In each aerobic tank 2A ₂ , 2B ₂ , 2C ₂ , the air diffusion amount of "1", "1", "1" in the opposite phase to the reference control tank "slight aeration" starts at the same timing (See FIG. 5P2, FIG. 8(a) K1′, FIG. 9(b) (b)).

(Period determination operation)
After that, the control unit 13 (cycle determining means 13r) determines whether the duration of aeration of the aerobic tanks 2A ₁ to 2C ₁ of the aerobic reaction tank 21 of the waterway W ₁ reaches T/ ₂ (30 minutes). is determined (see P4 in FIG. 5). During this time, the control unit 13 (load concentration detection means 13a) obtains load concentration data from the load concentration confirmation sensor A, and the control unit 13 (dissolved oxygen concentration detection means 13b) detects the dissolved oxygen concentration from the dissolved oxygen concentration confirmation sensor D. Acquire data (see P5 in FIG. 5).

Then, when the aeration time reaches T/2 (30 minutes) (YES in P4 of FIG. 5), the control unit 13 (cycle determining means 13r) causes the valve opening/closing driving means 13e ₁ and 13e ₂ of the water channels W ₁ and W ₂ to aerate or Notifies that the micro-aeration cycle has ended. After that, the control unit 13 (valve opening/closing driving means 13e ₁ , valve opening/closing driving means 13e ₂ ) _aerates the aerobic reaction tank ₂₁ of the waterway W1 and slightly _aerates the aerobic reaction tank ₂₂ of the waterway W2. After completion, the aeration of the aerobic reaction tank _2-1 of the waterway W1 and the aeration of the aerobic reaction tank _2-2 of the waterway W2 are started at the same timing (see P6 and P7 in _FIG . ₅ ).

(Slight aeration operation of aerobic reaction tank ₂₁ )
The control unit 13 (valve opening/closing driving means 13e ₁ on one side) detects the flow rate data from the flow rate detection means 13c ₁ , and adjusts the valve opening of the air volume control valve 11 ₁ to an air diffusion amount of “5” (valve opening). "15") to air diffusion amount " ₁ " (valve opening degree "3"), and as a result, the air volume (" ₃ ") corresponding to the air pipe 81 of the waterway W1 is blown. , air diffusion devices 5A ₁ and 5B of each aerobic tank 2A ₁ , 2B ₁ and 2C ₁ of the aerobic reaction tank 2 ₁ (reference control tank) via the diffusion adjustment valves 9A ₁ to 9C ₁ having the same degree of opening ₁ and 5C ₁ are evenly distributed, and the diffusers 5A ₁ to 5C ₁ jet out air with air diffusion amounts of "1", "1", and "1" to start "slight aeration". (See FIG. 5P6, FIG. 8(a) K2, and FIG. 9(a)(c)).

₍ Aeration operation of aerobic reaction tank 22)
At the same time, the control unit 13 (the other valve opening/closing drive means 13e ₂ ) detects the flow rate from the flow rate detection means 13c ₂ and adjusts the valve opening of the air volume control valve 11 ₂ to the air diffusion amount of "1" (valve opening "3") to an air diffusion amount of "5" (valve opening degree of "15"), and as a result, an air _volume corresponding to the air pipe 82 of the water channel W2 ₍ "15") is blown. , air diffusion devices 5A ₂ , 5B of each aerobic tank 2A ₂ , 2B ₂ , 2C ₂ of the aerobic reaction tank 2 ₂ (subordinate control tank) via the diffusion adjustment valves 9A ₂ to 9C ₂ with the same opening degree ₂ and 5C ₂ are evenly distributed, and the diffusers 5A ₂ to 5C ₂ inject air with air diffusion amounts of "5", "5", and "5" to start "aeration" ( 5P7, FIG. 8(a)K2', FIG. 9(b)(d)).

(Period determination operation)
After that, the control unit 13 (cycle determining means 13r) determines whether or not the micro _- aeration duration of the aerobic reaction tank 21 of the waterway W1 has reached T/ ₂ (30 minutes) (see P9 in FIG. 5). During this time, the control unit 13 (load concentration detection means 13a) acquires load concentration data from the load concentration confirmation sensor A, and the control unit 13 (dissolved oxygen concentration detection means 13b) acquires dissolved oxygen data from the dissolved oxygen concentration sensor D. is obtained (see P10 in FIG. 5).

When the micro-aeration time reaches T/2 (30 minutes) (YES in P9 of FIG. 5), the control unit 13 (cycle determining means 13r) notifies the valve opening/closing driving means 13e ₁ and 13e ₂ that the cycle has ended. At the same time, the control unit 13 performs the following control operations for the aerobic reaction tank 2 ₁ (reference control tank) of the waterway W ₁ .

(Constant control of air diffusion amount and period)
The control unit 13 (load concentration detection means 13a) detects the current load concentration data from the load concentration confirmation sensor A, and the control unit 13 (load concentration comparison means 13h) stores the data in the previous load concentration storage means 13g. The load concentration at the end of the previous micro-aeration is compared with the load concentration at the current micro-aeration, and the current load concentration data is greater than the load concentration at the end of the previous micro-aeration in the positive phase intermittent aeration operation. or smaller (see P11 and P12 in FIG. 5).

In this case, it is assumed that the load concentration is constant and does not change (or the fluctuation of the load concentration is the same as the previous load concentration and is substantially unchanged within a certain range) (NO, P12 in FIG. 5). . Then, the control unit 13 (load concentration comparing means 13h) causes the blower driving means 13d and the air amount changing means 13t to maintain the current air volume (see FIGS. 3 and 4 (3)), and the period determining means 13r. to maintain the current period T (see FIGS. 3 and 4 (1)). As a result, the air volume of the blower 10 and the period T are maintained, and the process returns to steps P1 and P2.

Therefore, in the reference control tank (one aerobic reaction tank 2 ₁ ), the process returns from step P12 to step P1, and the operations of steps P1, P4, P6, and P9 are repeated as long as the load concentrations are the same, and the control unit 13 (One valve opening/closing driving means 13e ₁ ) performs aeration (air diffusion amount “5”) for period T/2 (30 minutes), and then fine aeration for period T/2 (30 minutes) (air diffusion amount "1") valve opening and closing operation (air diffusion amount "5, 5, 5", "1, 1, 1", "5, 5, 5", "1, 1, 1" ...) repetition (positive phase intermittent aeration operation) is performed (see FIG. 8(a) K1, K2, K3, K4 . . . , FIG. 9(a) period S1).

On the other hand, in the dependent control tank (the other aerobic reaction tank 2 ₂ ), the process returns from step P12 to step P2. The unit 13 (the other valve opening/closing driving means 13e ₂ ) operates in the opposite phase at the same timing as the reference control tank, that is, the cycle T/2 (30 minutes) of slight aeration (air diffusion amount “1”), and then , operation of aeration (air diffusion amount "5") with period T/2 (30 minutes) (air diffusion amount "1,1,1", "5,5,5", "1,1,1" , "5, 5, 5" .

In this way, if the load concentration is constant (or within a certain range), the air diffusion amount during aeration is "5" and the air diffusion amount during slight aeration is "1". In one aerobic reaction tank 2 ₁ ), positive phase intermittent aeration operation is performed, and in the subordinate control tank (the other aerobic reaction tank 2 ₂ ), at the same period and at the same timing, the phase is opposite to that of the reference control tank. A reverse phase intermittent aeration operation is performed.

That is, if the load concentration data at the time of slight aeration detected by the load concentration confirmation sensor A is the same or substantially the same as the load concentration data at the end of the previous slight aeration, and the load concentration is constant or within a certain range, the wastewater Since the amount of ammonia nitrogen in the waterway W ₁ does not change substantially, and there is _no need to change the amount of air diffusion and the period T, the period T The intermittent aeration operation is repeated in the other aerobic reaction tank 2 ₂ (subordinate control tank) of the waterway W ₂ , and the intermittent aeration operation in the opposite phase of the period T is repeated (see FIG. 8(a)).

Therefore, in each of the aerobic tanks 2A ₁ to 2C ₁ of one of the aerobic reaction tanks 2 ₁ , which is the reference control tank, during aeration, the air diffusers 5A ₁ to 5C ₁ to the aerobic tanks 2A ₁ to 2C Since abundant air with an air diffusion amount of "5" is injected into each of ₁ , the nitrification reaction in which the nitrifying bacteria oxidize the ammonia nitrogen in the wastewater into nitrite nitrogen and nitrate nitrogen is caused by the above air. done. On the other hand, at the time of slight aeration, a small amount of air with an air diffusion amount of “1” is injected from the air diffusers 5A to 5C to each of the aerobic tanks 2A to 2C. Nitrite nitrogen and nitrite nitrogen are reduced to nitrogen gas by nitrate respiration or nitrite respiration by nitriding bacteria and released into the air. In this way, the intermittent aeration operation can remove nitrogen in the waste water.

In each of the aerobic tanks 2A ₂ to 2C ₂ of the other aerobic reaction tank 2 ₂ , which is the subordinate control tank, the nitrogen in the wastewater can be removed in the same way only by being in reverse phase with the reference control tank. can be done. By intermittently aerating the _one aerobic reaction tank 21 and the other aerobic reaction tank 22 in opposite _phases , the airflow from the blower 10 is kept constant during the intermittent aeration operation. The operation can be continued at an air volume (for example, an air volume of "18") (see period S1 in FIG. 9(c)). Since _each of the water channels W1 and W2 has _three aerobic tanks, the air volume of the blower 10 is "18" (6×3)).

(Air diffusion amount reduction, cycle reduction control)
Intermittent aeration operation with _one aerobic reaction tank 21 as the reference control tank of waterway W1 and the _other aerobic reaction tank ₂₂ as the slave control tank of waterway _W2 in reverse to the reference control tank. It is assumed that the phase intermittent aeration operation is continuously performed (see Figures 5P1 to 5P9).

The control unit 13 (load concentration comparing means 13h) determines in step P11 that the load concentration (ammonia concentration) at the end of the previous slight aeration is lower than the load concentration (ammonia concentration) at the end of the current slight aeration. If it is determined that the concentration of oxygen is present (YES in P11 in FIG. 5), the fact is notified to the dissolved oxygen concentration comparison means 13i in the next stage.

When the control unit 13 (dissolved oxygen concentration comparison means 13i) receives a report that the load concentration at the end of the current slight aeration is lower than the load concentration at the time of the previous slight aeration, the amount of air diffusion is sufficiently sufficient. Therefore, the following control is performed to reduce the period and the amount of air diffusion.

The control unit 13 (dissolved oxygen concentration comparison means 13i) compares the dissolved oxygen concentration at the time of the previous aeration obtained by the dissolved oxygen concentration detection means 13b and the DO lower limit (dissolved oxygen concentration) stored in the DO lower limit storage means 13k. lower limit of oxygen concentration) (see step P13 in FIG. 5), and if it is determined that the dissolved oxygen concentration at the time of the previous aeration has not reached the DO lower limit, reduce the air volume of the blower 10 (air volume "18 ” to, for example, an air volume of “15”), and the air volume changing means 13t also decreases the air diffusion amount during aeration (from an air diffusion amount of “5” to, for example, an air diffusion amount of "4") (see FIGS. 3 and 4 (3)). The control unit 13 (blower driving means 13d) performs control to reduce the air volume of the blower 10. FIG. In this case, the air volume of the blower 10 decreases from "18" to "15" (see P14 in FIG. 5 and FIG. 8B). In this case, the amount of decrease in the air volume of the blower 10 and the amount of decrease in the diffusion amount of each aerobic tank may be decreased by a predetermined constant amount when the load concentration is decreasing, or the load concentration It can also be configured to reduce the air volume and air diffusion in accordance with the amount of reduction (for example, proportionally).

In addition, the air amount changing means 13t reduces the air diffusion amount during aeration by one or the other valve opening/closing driving means _13e1 , _13e2 (for example, the air diffusion amount is reduced from "5" to "4"). command to As a result, the valve opening/closing driving means 13e ₁ and 13e ₂ adjust the valve opening to reduce the amount of air diffused during aeration (valve opening during aeration from "15" to "12" (4 x 3)) (see P14 of FIG. 5).

In addition, when the control unit 13 (dissolved oxygen concentration comparison means 13i) determines that the dissolved oxygen concentration at the time of the previous aeration has already reached the DO lower limit (NO in FIG. 5 P13), the air diffusion amount is not changed. Then return to step P1.

Further, the control unit 13 (dissolved oxygen amount comparison means 13i) notifies the period comparison means 13m of the next stage that the air diffusion amount has been decreased. The control unit 13 (period comparison means 13m) recognizes the current period T (60 minutes) by the current period recognition means 13p, and calculates the current period T and the period lower limit stored in the period lower limit storage means 13o. (eg T=20 minutes). Then, when the period comparing means 13m confirms that the current period is longer than the lower limit of the period, that is, the current period T has not reached the lower limit of the period (YES in P15 in FIG. 5), the period is changed to decrease the period. Command means 13q (see FIG. 3(2)). The control unit 13 (period changing means 13q) sets a period T' (=50 minutes) (T>T') slightly shorter than the current period T, and notifies the period determining means 13r of the reduced period T'. . In this case, when the load concentration is decreasing, the period T may be decreased by a predetermined constant amount, or the cycle may be changed according to (for example, in proportion to) the amount of decrease in the load concentration. It can also be configured to decrease.

When the control unit 13 (cycle comparison unit 13m) determines that the current cycle has reached the cycle lower limit (NO in P15 of FIG. 5), the cycle returns to step 1 without changing the cycle.

The period determination means 13r determines a period T' slightly shorter than the current period T (see P16 in FIG. 5), and sets a new period T' (50 minutes) to the _one valve opening/closing drive means _13e1 of the waterway W1 and the waterway W1. It is transmitted to the other valve opening/closing driving means _13c2 of W2 (see _FIG . 4).

Thereafter, the control unit 13 returns to step P1, and the control unit 13 (blower driving means 13d) operates the blower 10 at the reduced air volume of "15". Then, the blower 10 blows an air volume corresponding to each of the air pipe 8 ₁ of the water channel W ₁ and the air pipe 8 ₂ of the water channel W ₂ (see period S2 in FIG. 8(b) and FIG. 9(c)).

Since the controller 13 (valve opening/closing driving means 13e ₁ ) receives a command to decrease the air diffusion amount from the air amount changing means 13t, the air flow meter G ₁ (flow rate detecting means 13c ₁ ) While detecting the flow rate of , the valve opening during aeration of the air volume adjustment valve 11 ₁ is adjusted from "15" (5 x 3) to a reduced air diffusion amount of "4" (throttle), and the valve opening is adjusted to "12" (4 × 3), and as a result, the air volume ("12" (4 × 3)) corresponding to the air pipe 8 ₁ of the water channel W ₁ is blown, and the diffusion adjustment valves 9A 1 to 9A ₁ to Via 9C ₁ , the air is evenly distributed to the diffusers 5A ₁ , 5B ₁ and 5C ₁ of the aerobic tanks 2A ₁ , 2B ₁ and 2C ₁ of the aerobic reaction tank 2 (reference control tank). Air diffusers 5A ₁ to 5C ₁ inject air with air diffusion amounts of "4", "4", and "4" to start "aeration" (Fig. 5P1, Fig. 8(b) K5, Fig. 9 ( a) See (e)).

At the same time, the control unit 13 (the other valve opening/closing drive means 13e ₂ ) detects the flow rate from the air flow meter G ₂ (flow rate detection means 13c ₂ ) and adjusts the valve opening degree of the air volume control valve 11 ₂ to the air diffusion amount. Adjust the air diffusion amount from "5" to "1" (throttle), set the valve opening to "3" (1 × ₃ ), and as a result, the air _volume corresponding to the air pipe 82 of the water channel W2 ("3" (1 × 3)) is blown, and each aerobic tank 2A ₂ of the aerobic reaction tank 2 ₂ (subordinate control tank) through the diffusion adjustment valves 9A ₂ to 9C ₂ with the same opening degree The blown air is evenly dispersed in the air diffusers 5A ₂ , 5B ₂ and 5C ₂ of 2B ₂ and 2C ₂ , and the air diffusion amounts from the air diffusers 5A ₂ to 5C ₂ are "1", "1", and "1". of air is injected and "slight aeration" is started (see Fig. 5P2, Fig. 8(b) K5', Fig. 9(b) (to)).

After that, the control unit 13 (cycle determining means 13r) determines whether or not the aeration duration of the aerobic reaction tank 21 of the waterway W1 has decreased to T' _{/ 2} (25 minutes) (see P4 in FIG. 5). ). In the meantime, similarly, the control unit 13 (load concentration detection means 13a) and the control unit 13 (dissolved oxygen concentration detection means 13b) acquire load concentration data and dissolved oxygen data (see P5 in FIG. 5).

When the aeration time reaches T'/2 (25 minutes) (YES in P4 of FIG. 5), the control unit 13 (one valve opening/closing driving means 13e ₁ ) ends the aeration, and the aerobic reaction tank _{2 1 (} Start micro-aeration of the reference control tank (Fig. 5P6, Fig. 8(b) K6, Fig. 9(a)(g)).

That is, the control unit 13 (one valve opening/closing driving means 13e ₁ ) detects the flow rate from the air flow meter G ₁ and adjusts the valve opening of the air volume adjustment valve 11 ₁ from the air diffusion amount “4” to the air diffusion amount “4”. As a result, an air volume of “3” (1×3) corresponding to the air diffuser 8 ₁ of the waterway W ₁ is blown, and the aerobic reaction tank 2 _{1 of the waterway W 1 (} standard control Air diffusers 5A ₁ , 5B ₁ , 5C ₁ of each aerobic tank 2A ₁ , 2B ₁ , 2C ₁ of the tank) are injected with air diffusion amounts of “1”, “1”, and “1”, and “fine Aeration" is started (see Figure 5P6).

At the same time, the controller 13 (the other valve opening/closing driving means 13e ₂ ) reduces the air diffusion amount during aeration from the air flow rate changing means 13t (reduces the air diffusion amount from "5" to "4"). Since the command is received, the valve opening degree of the air _volume adjustment valve 112 is opened so that the air diffusion amount changes from "1" to " ₄ " while detecting the flow rate from the air flow meter G2. The air volume "12" (4 × 3) corresponding to the air pipe 8 ₂ of No. ₂ is blown, and each aerobic tank 2A ₂ , 2B ₂ , 2C ₂ of the aerobic reaction tank 2 ₂ (subordinate control tank) of the waterway W ₂ Air diffusers 5A ₂ , 5B ₂ , and 5C ₂ of the air diffusers 5A 2 , 5B 2 , and 5C 2 inject air with air diffusion amounts of “4”, “4”, and “4” to start “aeration” (Fig. 5P7, Fig. 8(b) K6 ', see FIG. 9(b)(h)).

After that, the control unit 13 (cycle determining means 13r) determines whether or not the micro _- aeration duration of the aerobic reaction tank 21 of the waterway W1 reaches T'/ ₂ (25 minutes) (see P9 in FIG. 5). . During this time, the control unit 13 (load concentration detecting means 13a) and the control unit 13 (dissolved oxygen concentration detecting means 13b) acquire load concentration data and dissolved oxygen data (see P10 in FIG. 5).

Then, when the micro-aeration time reaches T'/2 (25 minutes) (YES in P9 of FIG. 5), the control unit 13 (period determination means 13r) causes the valve opening/closing driving means 13e ₁ and 13e ₂ to perform micro-aeration or the aeration period. Along with notifying the completion, the control unit ₁₃ again performs the load concentration detection operation for the aerobic reaction tank _2-1 of the waterway W1.

Therefore, after that, the load concentration data at the time of slight aeration detected by the load concentration confirmation sensor A is the same as the load concentration data at the end of the previous slight aeration (or within a certain range), and the load concentration is constant (or substantially constant). Then, the aerobic reaction tank _{2 1 (} reference control tank) intermittent aeration operation (air diffusion amount "4, 4, 4", "1, 1, 1", "4, 4, 4", "1, 1, 1" ..., Fig. 8 ( _b ) _K7 , K8 . 1", "4,4,4", "1,1,1", "4,4,4" . . . , see FIG. 8(b) K7', K8' . 9 (a) and (b) period S2).

During this time, the blower 10 can be a large blower such as a turbo blower, for example, because it is sufficient to reduce the air volume from "18" (5 x 3 + 1 x 3) to "15" (4 x 3 + 1 x 3). (see FIG. 9(c), change from period S1 to S2).

Also, in step P11 of FIG. 5, the load concentration is lower than the load concentration at the end of the previous slight aeration, and if the air diffusion amount has not reached the DO lower limit value in step P13 of FIG. The air volume is reduced (for example, from "18" to "15"), and as _a result, in the aerobic reaction tank _2-1 as the reference control tank of the waterway W1, the air volume control valve _11-1 is opened. When the degree is aeration, the air diffusion amount decreases from "4" to "3", for example, until it reaches the lower limit. Alternatively, if the air diffusion amount has not reached the DO lower limit value in step P13 of FIG. Gradually decreased. In this case, when the load concentration decrease amount is large, the decrease amount of the air volume and/or the air diffusion amount of the fan 10 is also large, and when the load concentration decrease amount is small, the air volume and/or the air diffusion amount of the fan 10 is also increased. decreases. However, the air diffusion rate during slight aeration is always maintained at "1" (see FIGS. 8(a) and 8(b)). In addition, when the cycle has not reached the cycle lower limit (T = 20 minutes) in step P15 in Fig. 5, the cycle is also reduced step by step or gradually until it reaches the cycle lower limit, consisting of aeration and microaeration. The period of intermittent aeration is also reduced step by step (for example, T=50 minutes, 40 minutes, 30 minutes, 20 minutes) (see FIGS. 8 and 9). Alternatively, if the cycle has not reached the cycle lower limit (T = 20 minutes), it is gradually decreased (eg, T = 50 minutes, 48 minutes, 44 minutes) according to (eg, in proportion to) the load concentration decrease amount. , 38 minutes, even integer values in 2 minute increments). Therefore, in this case, when the amount of load concentration decrease is large, the amount of decrease in the cycle is also large, and when the amount of load concentration decrease is small, the amount of decrease in the cycle is also small.

_On the other hand, in the other aerobic reaction tank 22 as a subordinate control tank of the waterway W2, intermittent aeration operation in the opposite phase ₍ air diffusion amount during aeration) is performed at the same cycle and timing as the reference control tank is the same as the air volume during aeration of the standard control tank, and the air diffusion volume during micro-aeration is always "1"), and the cycle of intermittent reverse phase aeration consisting of aeration and micro-aeration at the same timing as the standard control tank also decreases step by step or gradually.

In this way, if the load concentration at the end of the current slight aeration is lower than the load concentration at the end of the previous slight aeration, it means that the amount of air diffusion is sufficient. The dissolved oxygen concentration decreases stepwise or gradually until it reaches the lower limit, and the cycle of the intermittent aeration operation also decreases stepwise or gradually until it reaches the lower limit of the cycle.

Therefore, the amount of air diffusion during aeration can be appropriately reduced in accordance with the decrease in load concentration, and even if the amount of air diffusion during aeration decreases, normal phase intermittent aeration operation and reverse With the intermittent aeration operation, a constant small amount of air diffusion can be maintained at all times, so a constant denitrification rate can be maintained at all times, and stable conversion to nitrogen gas can be performed.

In the aerobic tanks 2A to _2C of the other aerobic reaction tank 22, which is the subordinate control tank, the nitrogen in the waste water can be removed in the same way only by being in the opposite phase to the reference control tank. .
(Air volume increase, cycle increase control)
Similarly, the intermittent aeration operation in the aerobic reaction tank 21 on _{one side} of the waterway W1 and the intermittent aeration operation in the opposite _{phase on} the other aerobic reaction tank 22 in the waterway W2 are continuously performed. (see P1 to P9 in FIG. 5).

If the load concentration (ammonia concentration) at the end of the previous slight aeration is higher than the load concentration at the end of the current slight aeration (Fig. 5 P11 NO, P12 YES), the control unit 13 (load concentration comparison means 13h) This is notified to the dissolved oxygen concentration comparison means 13i in the next stage.

When the control unit 13 (dissolved oxygen concentration comparison means 13i) receives a report that the load concentration at the end of the current slight aeration is higher than the load concentration at the end of the previous slight aeration, the amount of air diffusion is insufficient. Then, the following control is performed to increase the air volume and the air diffusion volume.

That is, the control unit 13 (dissolved oxygen concentration comparison means 13i) compares the dissolved oxygen concentration at the time of the previous aeration obtained by the dissolved oxygen concentration detection means 13b and the DO upper limit stored in the DO upper limit storage means 13j. (Upper limit of dissolved oxygen concentration) (see FIG. 5P17), and if it is determined that the dissolved oxygen concentration at the time of the previous aeration has not reached the DO upper limit, the air volume of the blower 10 is increased. A command is issued to the driving means 13d (see FIG. 3(3)). The control unit 13 (blower driving means 13d) performs control so as to increase the air volume of the blower 10. FIG. In this case, assume that the air volume of the blower 10 has increased from "18" to "21" (6×3+1×3) (see P18 in FIG. 5, FIG. 8(c), and FIG. 9(c) period S3 to S4).

In addition, the control unit 13 (dissolved oxygen concentration comparison means 13i) determines that the dissolved oxygen concentration at the time of the previous aeration has already reached the DO upper limit value (Fig. 5 P17 NO), step without changing the air amount Return to P1.

In addition, the air amount changing means 13t commands one or the other valve opening/closing driving means _13e1 , _13e2 to increase the air diffusion amount during aeration. As a result, the valve opening/closing driving means 13e ₁ and 13e ₂ recognize to increase the amount of air diffused during aeration.

Further, the control unit 13 (dissolved oxygen amount comparison means 13i) notifies the period comparison means 13m of the next stage that the air diffusion amount has been increased. The control unit 13 (period comparison means 13m) recognizes the current period (60 minutes in this case) by the current period recognition means 13p, and the current period T and the period upper limit value storage means 13n are stored. Compare with the cycle upper limit (90 minutes). When the period comparison means 13m confirms that the current period (60 minutes) is shorter than the upper limit of period, that is, the current period T has not reached the upper limit of period (YES in P19 of FIG. 5), it increases the period. Therefore, the period changing means 13q is notified (see FIG. 3(2)). The control unit 13 (period changing means 13q) sets a period T″ (for example, 70 minutes) longer than the current period T (T<T″), and sets the increased period T″ (70 minutes) to the period determining means 13r. send to

When the control unit 13 (cycle comparison unit 13m) determines that the current cycle has reached the cycle upper limit value (NO in P19 in FIG. 5), the cycle returns to step P1 without changing the cycle.

The cycle determination means 13r determines a cycle T'' (70 minutes) longer than the current cycle T (see P20 in FIG. 5), and sets the new cycle T'' to the _one valve opening/closing driving means _13e1 of the water channel W1 and the water channel W. ₂ to the other valve opening/closing driving means _13c2 .

After that, the control unit 13 returns to step 1, and the control unit 13 (blower driving means 13d) drives the blower 10 from the previous air volume "18" to the air volume "21". Then, the blower 10 blows an air volume corresponding to the air pipe 8 ₁ of the water channel W ₁ and the air pipe 8 ₂ of the water channel W ₂ (see FIG. 8(c) and FIG. 9(c) period S4).

The controller 13 (one valve opening/closing driving means 13e ₁ ) is instructed by the air amount changing means 13t to increase the air amount during aeration, so the air amount is detected while detecting the flow rate from the air flow meter G ₁ The valve opening during aeration of the regulating valve 11 ₁ is adjusted (opened) from the previous valve opening of "15" (5 x 3) to the valve opening of "18" (6 x 3), and as a result, An air volume of "18" corresponding to the air pipe 8 ₁ of the water channel W ₁ is blown, and _each of the _one aerobic reaction tanks 2 (reference control tank) The blown air is evenly dispersed in the air diffusers 5A ₁ , 5B ₁ and 5C ₁ of the aerobic tanks 2A ₁ , 2B ₁ and 2C ₁ , and the air diffusion amounts from the air diffusers 5A ₁ to 5C ₁ are "6", "6" and "6" are injected to start "aeration" (see FIG. 5P1, FIG. 8(c) K9, and FIG. 9(a) (li)).

At the same time, the control unit 13 (the other valve opening/closing driving means 13e ₂ ) detects the flow rate from the air flow meter G ₂ and adjusts the valve opening degree of the air volume control valve 11 ₂ in the opposite phase to the reference control tank, in this case is adjusted so that the opening of the valve for slight aeration is "3" (1 x 3), and as a result, an air _volume of " ₃ " corresponding to the air pipe 82 of the waterway W2 is blown, and the dispersion with the same opening Air diffuser 5A ₂ , 5B ₂ , 5C ₂ of each aerobic tank 2A ₂ , 2B ₂ , 2C ₂ of the other aerobic reaction tank 2 ₂ (subordinate control tank) via air regulating valves 9A ₂ to 9C ₂ The air is evenly dispersed in the air diffusers 5A 2 to 5C 2, and air with air diffusion amounts of "1", "1", and "1" is injected from each air diffuser 5A ₂ to 5C ₂ to start "slight aeration" (Fig. 5P2, See FIG. 8(c) K9′ and FIG. 9(b) (J)).

After that, the control unit 13 (period determining means 13r) determines whether or not the aeration duration of the aerobic reaction tank ₂ in the waterway W1 has reached T″/2 (35 minutes) (see P4 in FIG. 5). During this time, the control unit 13 (load concentration detection means 13a) and the control unit 13 (dissolved oxygen concentration detection means 13b) acquire load concentration data and dissolved oxygen data (see P5 in FIG. 5).

Then, when the aeration time reaches T″/2 (35 minutes) (YES in P4 of FIG. 5), the aeration is terminated and microaeration of the aerobic reaction tank 2 ₁ (reference control tank) of the waterway W ₁ is started (P6 in FIG. 5, See FIG. 8(c) K10 and FIG. 9(a) (L)).

That is, the control unit 13 (one valve opening/closing driving means 13e ₁ ) detects the flow rate from the air flow meter G ₁ and adjusts the valve opening degree of the air volume adjustment valve 11 ₁ from the air diffusion amount “6” to the air diffusion amount “6”. Adjusted (throttling) so that the amount was "1", and as a result, the air volume "3" ( ₁ x ₃ ) corresponding to the air pipe 81 of the waterway W1 was blown, and the aerobic reaction tank ₂ of the waterway W1 was blown. ₁ (reference control tank) from each aerobic tank 2A ₁ , 2B ₁ , 2C ₁ air diffuser 5A ₁ , 5B ₁ , 5C ₁ of the air diffusion amount "1", "1", "1" air It is injected and "slight aeration" is started (see Fig. 5P6, Fig. 8(c) K10).

At the same time, the control unit 13 (the other valve opening/closing driving means 13e ₂ ) is instructed by the air amount changing means 13t to increase the air volume during aeration, so while detecting the flow rate from the air flow meter G ₂ The valve opening degree of the air volume adjustment valve 11 ₂ is adjusted (opened) from the air diffusion amount “1” to the air diffusion amount “6”, and as a result, the air volume corresponding to the air supply pipe 8 ₂ of the water channel W ₂ "18" (6 × 3) is blown, and the diffusers 5A ₂ , 5B ₂ of the aerobic tanks 2A ₂ , 2B ₂ , 2C ₂ of the aerobic reaction tank 2 ₂ (subordinate control tank) of the waterway W ₂ , Air with an air diffusion amount of "6", "6", "6" is injected from 5C ₂ and "aeration" is started (Fig. 5P7, Fig. 8(c) K10', Fig. 9(b) (o) reference).

After that, the control unit 13 (period determining means 13r) determines whether or not the micro-aeration continuation time of the aerobic reaction tank ₂ of the waterway W1 has reached T″/2 (35 minutes) (see P9 in FIG. 5). During this time, the control unit 13 (load concentration detecting means 13a) and the control unit 13 (dissolved oxygen concentration detecting means 13b) acquire load concentration data and dissolved oxygen data (see P10 in FIG. 5).

Then, when the micro-aeration time reaches T″/2 (35 minutes) (YES in P9 of FIG. 5), the control unit 13 (period determination means 13r) causes the valve opening/closing drive means 13e ₁ and 13e ₂ to perform micro-aeration or the aeration cycle. Along with notifying the completion, the control unit 13 performs the load concentration detection operation again for the aerobic reaction tank 2 ₁ (reference control tank) of the waterway W ₁ .

Therefore, after that, the load concentration data at the time of slight aeration detected by the load concentration confirmation sensor A is the same (or within a certain range) as the load concentration data at the end of the previous slight aeration, and the load concentration is constant (or substantially the same). Then, at the same air diffusion amount (“6” for aeration, “1” for slight aeration) and the same period T”, one aerobic reaction tank 2 ₁ (reference control tank) of the water channel W ₁ Intermittent aeration operation (air diffusion amount "6, 6, 6", "1, 1, 1", "6, 6, 6", "1, 1, 1" ..., Fig. 8 ( c ) K9, See K10, K11...), reverse phase intermittent aeration operation at the same timing in the other aerobic reaction tank 2 ₂ (subordinate control tank) of water channel W ₂ (air diffusion amount "1, 1, 1" , ``6, 6, 6'', ``1, 1, 1'', ` `6, 6, 6'' . .

During this time, the blower 10 can be a large blower such as a turbo blower, for example, because a small increase in the air flow from "18" (5×3+1×3) to "21" (6×3+1×3) is sufficient. can be dealt with without any problem (see the change from period S3 to S4 in FIG. 9(c)).

Also, if the load concentration has increased from the load concentration at the end of the previous slight aeration at step P12 in FIG. (For example, the air _volume is _{increased stepwise} or gradually from "18" to "21"). During aeration, the air diffusion rate increases from "5" to "6" until the air diffusion rate reaches the upper limit. Alternatively, if the air diffusion amount has not reached the DO upper limit value in step P17 in FIG. Increased. In this case, when the load concentration increase amount is large, the increase amount of the air volume and/or the air diffusion amount of the fan 10 is also large, and when the load concentration increase amount is small, the air volume and/or the air diffusion amount of the fan 10 is increased. The amount of increase in is also reduced. However, the air volume during slight aeration is always maintained at a constant air diffusion volume (for example, the air diffusion volume is "1").

In addition, when the cycle has not reached the cycle upper limit value in step P19 of FIG. The cycle of intermittent aeration consisting of air and microaeration also increases step by step or gradually. Alternatively, if the cycle has not reached the upper limit, it is gradually increased (for example, T = 70 minutes, 72 minutes, 80 minutes, etc. in 2-minute increments) according to the load concentration increase amount (for example, proportionally). even integer value). Therefore, in this case, when the amount of increase in load concentration is large, the amount of increase in the period is also large, and when the amount of increase in load concentration is small, the amount of increase in the period is also small.

_On the other hand, in the other aerobic reaction tank 22 as a subordinate control tank of the waterway W2, the intermittent aeration operation of the opposite phase is performed at the same period and at the same timing as the reference control tank ₍ the amount of aeration during aeration is , the same amount of air diffusion during aeration of the standard control tank, the air diffusion amount during micro-aeration is always "1"), and the intermittent aeration cycle consisting of aeration and micro-aeration is performed at the same timing as the standard control tank. increase step by step.

In this way, if the load concentration at the end of the current slight aeration is higher than the load concentration at the end of the previous slight aeration, the amount of air diffusion is insufficient, so the amount of air diffusion reaches the DO upper limit value. The cycle of the intermittent aeration operation also increases stepwise or gradually until it reaches the cycle upper limit, and this operation is repeated.

Therefore, it is possible to appropriately increase the amount of air diffusion during aeration according to the increase in the load concentration, and even if the amount of air diffusion during aeration increases, the normal phase intermittent aeration operation and the reverse In the intermittent aeration operation, a constant small amount of aeration can be maintained at all times, so a constant denitrification rate can be maintained at all times, and conversion to nitrogen gas can be stably performed.

Similarly, in the aerobic reaction tank ₂₂ as a subordinate control tank, an intermittent aeration operation of the opposite phase is performed at the same timing and in the same period as the reference control tank with an appropriate amount of air diffusion.

In this way, during aeration, the appropriate air with an air diffusion amount of "6" is injected from the air diffusers 5A ₁ to 5C ₁ to the aerobic tanks 2A ₁ to 2C ₁ , so that the nitrifying bacteria are killed by the air. A nitrification reaction is performed to oxidize ammonium nitrogen in wastewater into nitrite nitrogen and nitrate nitrogen. On the other hand, even if the air diffusion amount at the time of aeration changes, at the time of slight aeration, air with a constant air diffusion amount of "1" is injected from the air diffusers 5A to 5C into the aerobic tanks 2A to 2C. Therefore, almost anoxic conditions are established, and nitrite nitrogen and nitrite nitrogen are reduced to nitrogen gas by nitrate respiration or nitrite respiration by denitrifying bacteria and released into the air. In this way, the intermittent aeration operation can remove nitrogen in the waste water.

(Correction operation based on air magnification)
In this embodiment, in order to perform efficient processing without using a load concentration confirmation sensor and a dissolved oxygen concentration sensor in the subordinate control tank, as shown in FIG. _The air ratio (= air flow rate/inflow water flow rate) in the waterway W1 is calculated ₍ this is referred to as the “standard air ratio S”), and the air in the waterway _W2 is applied to the other waterway W2. Correct the amount of diffusion.

Specifically, after starting the subordinate control tank _2-2 in step P2 in FIG. ₅ , in step _P2 ' in FIG. ), and measure the flow rate _R1 (in this case, "10") of the air flow meter G1 at the time of aeration of the reference control tank 21, and obtain " _R1 /F1 = (10/5) = 2". Then, the reference air ratio S (=2) is calculated and stored in the reference air ratio storage means 13v (see P2' in FIG. 5).

After that, in step P7 in _FIG . 5, the control unit 13 (fine adjustment amount calculation means _{13y 2} ) starts aeration of the subordinate control tank 22, and in step P7′ in _FIG . In addition to measuring the flow rate F2 of the waterway W2 (in this case, it is set to "4.5"), the waterway W2 is adjusted so that the air ratio of the waterway W2 is the same as the reference air _ratio S ( _{= 2} ) of the waterway W1. finely adjust the opening degree of the air _volume control valve 11-2. Specifically, in the fine adjustment amount calculating means _13y2 , the finely adjusted air volume "R2 = reference air magnification S x inflow water volume F2 of water channel W2" is calculated (in this embodiment, ₂ x 4.5 =9= _R2 ), the other valve opening/closing driving means is adjusted so that the flow rate _R2 of the air flow meter G2 of the water channel W2 changes from the air flow rate before the fine adjustment of "10" to the air flow rate after the fine adjustment of "9". Command 13e ₂ .

_The other valve opening/closing driving means _13e2 of the water channel W2 _adjusts the opening of the air _volume control valve ₁₁₂ while detecting the flow rate from the air flow meter G2 with the flow rate detecting means _13c2 . The air flow rate is adjusted (corrected) to be "9" (in this case, the air flow rate is decreased). As _a result, corresponding to the difference between the inflow water _volume of the water channel W2 and the water inflow volume of the water channel W1 ( _5-4.5 =0.5), the air _ratio of the water channel W2 was changed to the same reference air as that of the water channel W1. A magnification of S is possible. In this way, it is only necessary to measure the standard air magnification factor S in the waterway W1, and for the _other waterway W2, it is only necessary to adjust the valve opening to match the above _- mentioned standard air magnification factor S. There is no need to use a load concentration confirmation sensor and a dissolved oxygen concentration sensor, and the air magnification can be adjusted efficiently.

(When there are 4 or more waterways W)
_The above description is for the case where _waterway W ₁ and _waterway W ₂ exist. ~ W ₁₀ ) may be present.

FIG. 6 shows the operation procedure when there are four or more water channels W. As shown in FIG. Compared to the operation procedure of FIG. 5, this operation procedure has the start of aeration of the subordinate control tank in the same phase (step P3 in FIG. 6) and the start of slight aeration of the subordinate control tank in the same phase (step P8 in FIG. 6). Other procedures are the same as in FIG. 5 except for additions.

In this case, the reference control tank is only the aerobic reaction tank 2 ₁ of the waterway W ₁ , and the aerobic reaction tanks 2 ₂ to 2 ₄ of the other waterways W ₂ to W ₄ are all subordinate. As for the control tank, two sets of water channels, _namely water channel W3 and water channel W4 ₍ water channel _W5 and water channel _W6 , etc.) are paired (see FIG. 10), and _each water channel W3 _, W4, . . . Air volume adjustment valves _{11 3} , 11 ₄ . . . and air flow meters G ₃ , G ₄ . ₄ . . . and flow rate detection means 13c _{3 ,} 13c ₄ . In the subordinate control tanks of W ₅ (aerobic reaction tanks 2 ₃ , 2 ₅ . The same phase intermittent aeration operation as the tank is performed, and the subordinate control tanks (aerobic reaction tanks _{2 4 , 2 6 .} . . In the other aerobic reaction tank), an intermittent aeration operation opposite to the reference control tank described above is performed.

That is, the control (command) from the control unit 13 to the aerobic reaction tanks on _one side of the odd-numbered water channel is the same as the command given to the aerobic reaction tank 21 on the _one side of the water channel W1. , in each one of the odd-numbered aerobic reaction tanks, the same phase intermittent aeration operation as in the _one aerobic reaction tank 21 is performed, and the controller 13 controls the other even-numbered aerobic reaction tanks. _The control (command) for the other aerobic reaction tank 22 of the waterway W2 is the same as the command given to the other aerobic reaction tank 22 of the waterway W2, and the other aerobic reaction tank of these even _- numbered waterway A reversed _- phase intermittent aeration operation similar to that of the aerobic reaction tank 22 is performed. Therefore, even if the number of water channels is increased by four or more, the aerobic reaction tanks 2 of a plurality of water channels can be controlled with exactly the same command from the control unit 13 .

Specifically, as shown in FIG. _{10 ,} the valve opening/closing drive means _13e3 corresponding to the water channel W3 detects the flow rate of the air flow meter G3 in order to perform the intermittent aeration operation in the same phase as the reference control tank. While detecting by the means _{13c3 ,} the valve opening/closing control of the air volume control valve 113 is performed, and the operation at the time of aeration (for example, the air diffusion amount is "5") and the operation at the time of slight aeration (air diffusion amount is "1") is repeated. Do ("5, 5, 5", "1, 1, 1", "5, 5, 5", "1, 1, 1"...). _In addition, the other valve opening/closing drive means _13e4 corresponding to the water channel W4 detects the flow rate of the air flow meter _G4 with the flow rate detection means _13c4 , and the air volume control valve 11 ₄ valve opening and closing control is performed, and the operation at the time of slight aeration (air diffusion amount "1") and at the time of aeration (for example, air diffusion amount "5") is repeated ("1, 1, 1", "5 , 5,5”, “1,1,1”, “5,5,5” . . . ). Of course, the one or the other valve opening/closing driving means 13e ₃ , 13e ₄ . , the valve opening during aeration is increased or decreased stepwise or continuously.

Therefore, as shown in FIG. 6, at step P1, the aeration of the reference control tank (one aerobic reaction tank 2 ₁ ) is started, and at step P2, the opposite phase slave control tanks (eg, the other even-numbered tanks) are simultaneously aerated. of the aerobic reaction tanks _{2 2} , _{2 4} . ) is started.

After that, after the cycle of aeration or micro-aeration is completed (see P4 in FIG. 6), micro-aeration of the reference control tank (one aerobic reaction tank 2 ₁ ) is started in step P6, and at the same time in step P7 Aeration of the dependent control tanks (for example, the other even-numbered aerobic reaction tanks 2 ₂ , 2 ₄ . Slight aeration of the gas reaction tanks 2 ₃ , 2 ₅ . . . ) is started.

After that, after the micro-aeration or aeration cycle is completed (see P9 in FIG. 6), in steps P11 to P20, the air diffusion amount and cycle increase/decrease control is performed by one reference control tank (one aerobic reaction tank 2 ₁ ) Based on the load concentration and dissolved oxygen concentration of the other tanks, the air diffusion amount and period of all other subordinate control tanks are controlled to increase or decrease.
(Correction operation based on air magnification)

As for the air ratio, in steps P3′ and P8′ of FIG. 6, the air ratio of _each of the water channels W ₂ , W ₃ . . . can be done.

At step P3' in FIG. 6, the control unit 13 (FIG. 18, air-magnification calculation means 13u) calculates the reference air _- magnification S of the reference control tank 21 of the waterway W1, and converts the reference air _- magnification S It is stored in the magnification storage means 13v (see FIG. 18). After that _, in step P8' of _FIG . ₆ , the inflow water amounts F2, F3 _, . ), the adjusted air flow rates R2, R3, . . . are calculated for each channel. Then, the fine adjustment amount calculation means 13y ₂ , 13y ₃ . . . send a fine adjustment command to the valve opening/closing control means 13e ₂ , 13e ₃ . . As a result, the valve opening/closing driving means _{13e 2 ,} 13e _{3 . . . of the water channels W 2 , W 3} .・By finely adjusting the air volume control valves _{11 2 , 11 3} . becomes.

In this way, _only the aerobic reaction tank 21 as the reference control tank is provided with the load concentration confirmation sensor A and the dissolved oxygen concentration sensor D, and based on the load concentration data and dissolved oxygen concentration data of the reference control tank, a single Since the control unit 13 can control the air diffusion amount and the intermittent aeration operation cycle during aeration of all the other subordinate control tanks including the reference control tank, there are a plurality of water channels W (4 or more water channels) It is possible to easily control the entire waterway.

Regarding the increase and decrease of the air diffusion amount, only the air diffusion amount during aeration is increased, and the air diffusion amount during slight aeration is a constant value for both the positive phase intermittent aeration operation and the negative phase intermittent aeration operation. Since a small amount of air (for example, air diffusion rate "1") is maintained, the denitrification rate can always be maintained constant, and stable denitrification can be achieved even if the air diffusion rate during aeration is increased or decreased. reaction can be realized.

In the intermittent aeration operation, switching between aeration and slight aeration of each water channel is performed by adjusting the valve opening of the air volume control valves 11 ₁ , 11 ₂ . . . provided for each water channel. By making the intermittent aeration operation of each other aerobic reaction tank of the other waterway (even-numbered waterway) opposite to the intermittent aeration operation of each one of the aerobic reaction tanks of the odd-numbered waterway), The total air volume of the aeration of the aerobic reaction tanks of the odd-numbered water channels and the micro-aeration of the other aerobic reaction tanks of the even-numbered channels, which are performed at the same time, Therefore, the air volume of the blower 10 can be kept constant as long as there is no instruction to increase or decrease the air volume.

Also, when increasing or decreasing the air diffusion amount, for example, the air diffusion amount at the time of aeration of the water channel W1 is " ₅ ", and the air diffusion amount at the time of the reverse phase water channel W2 is " ₁ ". The air volume is increased from the state (for example, in the case of 4 channels, the total air volume of the blower 10 is "36" (the air volume of 2 channels is "18" x ₂ )), and the air diffusion volume during aeration of the channel W1 is "6", even if the air diffusion amount at the _time of slight aeration in the water channel W2 becomes "1", the total air volume of the blower 10 will change from "36" to the air volume "42" (air volume of the two water channels "21" x 2). It should be increased by a small amount. Further, for example, from the state of air diffusion amount "5" during aeration in water channel W1 and air diffusion amount " ₁ " during slight aeration in water channel W2 ₍ air volume "36" state of blower 10), the air volume is changed to Even if the air diffusion amount during aeration in the waterway W1 becomes " ₄ " and the air diffusion amount during slight aeration in the waterway W2 becomes " ₁ ", the air volume of the blower 10 decreases from "36" to "30" (air volume of two channels "15" x 2).

Therefore, even existing large-scale blowers (for example, turbo-type blowers) used in large-scale sewage treatment plants, for example, can sufficiently cope with increases and decreases in air volume. It can be applied without problems in municipal sewage treatment plants.

In addition, even if there are four or more water channels, the configuration of FIG. 18 allows the air magnification of _each water channel W2 _, W3, . Even if there is a plurality of waterways, there is no need to use a load concentration confirmation sensor and a dissolved oxygen concentration sensor for each waterway, and the air magnification of multiple waterways can be efficiently adjusted to the reference air magnification.

2 Embodiment in Case of Constant Cycle (Second Embodiment)
In the above embodiment, the configuration was described in which the period of the intermittent aeration operation is increased or decreased together with the increase or decrease in the amount of air diffused during aeration. Here, an embodiment (second embodiment) in which the amount of air diffused during aeration is increased or decreased and the cycle is constant (for example, 60 minutes) will be described.

5 or 6, steps P15, P16 and steps P19, P20 do not exist, and an operation is performed to reduce the air diffusion amount in step P14, or an air diffusion amount is reduced in step P18. After performing the increasing operation, return to step P1 or step P2 to perform the aeration operation of the reference control tank, the minor aeration operation of the subordinate control tank in opposite phase, and the aeration operation of the subordinate control tank in phase.

After that, the period is determined in steps P4 and P9. In this case, the period T is always constant (T/2=30 minutes) and does not change with the increase or decrease of the air diffusion amount during aeration. . Also, the amount of air diffusion is increased or decreased only during "aeration", and the amount of air diffusion during "slight aeration" does not increase or decrease in the same manner as above, and is a constant value (for example, air volume "1"). ).

In this case, the control unit 13 includes current cycle recognition means 13p, cycle lower limit value storage means 13o, cycle upper limit value storage means 13n, cycle comparison means 13m (FIG. 3 ), and cycle change means. No configuration for 13 q (FIG. 4) is required.

Therefore, in steps P14 and P18, the dissolved oxygen concentration comparing means 13i instructs the blower driving means 13d to increase or decrease the air volume during aeration, and the air volume changing means 13t is instructed to increase or decrease the air diffusion amount during aeration. Alternatively, a decrease is instructed, and as a result, in the valve opening/closing driving means 13e ₁ and 13e ₂ of each one and each other, control is performed so that only the air diffusion amount during aeration is increased or decreased while the period is constant. (see FIGS. 11(a) and 11(b)).

In this way, the periodicity of the intermittent aeration operation is constant, and only the air diffusion rate during aeration is increased or decreased in response to the increase or decrease of the load concentration. By increasing or decreasing the amount of air diffusion according to the increase or decrease in concentration (increase or decrease in ammonia), the nitrification reaction can be appropriately promoted according to the load concentration.

3 When Dissolved Oxygen Concentration Sensor D is not Used (Third Embodiment) (See FIG. 7)
_In the above embodiment, the dissolved oxygen concentration sensor D is used to detect the current dissolved oxygen concentration of the aerobic reaction tank 21 as the reference control tank, and the control unit 13 (dissolved oxygen concentration comparison means 13i) It is detected whether or not the current dissolved oxygen concentration has reached the DO lower limit value or the DO upper limit value, and depending on the result, the air flow rate and the air diffusion rate are increased or decreased.

On the other hand, in this embodiment, control is realized without using the dissolved oxygen concentration sensor D. FIG. FIG. 7 shows the operation procedure of this embodiment. This operation procedure is characterized in that the current air diffusion amount is compared with the preset upper limit or lower limit of the air diffusion amount instead of the determination based on the dissolved oxygen concentration in steps P13 and P17. Other procedures are the same as those of the first or second embodiment, except for the difference.

In this embodiment, instead of the dissolved oxygen concentration detection means 13b, the DO lower limit value storage means 13k, the DO upper limit value storage means 13j, and the dissolved oxygen concentration comparison means 13i of FIG. Storage means 13b', air diffusion amount lower limit value storage means 13k', air diffusion amount upper limit value storage means 13j', and air diffusion amount comparison means 13i' are provided.

Then, the control unit 13 (load concentration comparison means 13h) determines that the load concentration during the current slight aeration is lower than the load concentration during the previous slight aeration (YES in step P11 in FIG. 7), and compares the amount of air diffuser to that effect. If the means 13i' is notified, in step P13, if the air diffusion amount comparing means 13i' determines that the previous air diffusion amount has not reached the air diffusion amount lower limit value, the blower driving means 13d is commanded to decrease the air volume during aeration, and the air volume changing means 13t (see FIG. 4) is commanded to decrease the air diffuser volume during aeration (see FIG. 7, step P14). ). In this case, the amount of air diffusion can be decreased in accordance with (eg proportionally) the amount of decrease in load concentration. From then on, through steps P15 and P16, the period is also reduced, returning to step P1, where the reference control tank is aerated with a smaller amount of air, and the subordinate control tank is aerated with a constant amount of air. Slight aeration is performed with an air diffusion amount (for example, an air diffusion amount of "1"), and thereafter the same processing as in the first embodiment is performed.

In addition, the control unit 13 (load concentration comparison means 13h) determines that the load concentration during the current slight aeration is higher than the load concentration during the previous slight aeration (YES in step P12 in FIG. 7), and informs the air diffusion amount comparison means. 13i', if the air diffusion amount comparison means 13i' determines that the previous air diffusion amount has not reached the air diffusion upper limit value in step P17, the blower driving means 13d command to increase the air volume during aeration, and command the air changing means 13t (see FIG. 4) to increase the air diffusion volume during aeration (see FIG. 7, step P18). In this case, the amount of air diffusion can be increased in accordance with (for example, in proportion to) the increase in load concentration. After that, through steps P19 and P20, the period is also increased, returning to step P1, the main control tank is aerated with a larger amount of air diffusion, and the subordinate control tank is aerated with a constant amount of air. Slight aeration is performed with an air diffusion amount (for example, an air diffusion amount of "1"), and thereafter the same processing as in the first embodiment is performed.

_In this case, the control unit ₁₃ (air diffusion amount comparison means 13i') determines that the previous air diffusion amount is, for example, the valve opening degree data (or 1/3 of the valve opening data, that is, the opening data corresponding to one of the three opportunity tanks), or the flow rate data of the previous aeration of the air flow meter G ₁ (or 1/3 of the flow rate data, That is, the flow rate data corresponding to one of the three opportunity tanks) is recognized, these data are stored by the control unit 13 (previous air diffusion amount detection means 13b'), and this is used as the previous air diffusion amount, It can be compared with the air diffusion amount upper limit value or the air diffusion amount lower limit value.

With this configuration, although the accuracy is slightly lowered, the dissolved oxygen concentration sensor D is not used, and the present invention can be realized with a lower-cost device configuration.
4 Fourth embodiment (see FIG. 13)
This embodiment has the same basic configuration as the first embodiment, but denitrification is provided upstream of the aerobic reaction tanks _{2 1} , _{2 2 .} . . _{Anoxic tanks 14 1} , _{14 2} . and the sludge return pipe 6 transfers part of the microbial flocs precipitated and separated in the final sedimentation tank 3 to the aerobic tanks 2A ₁ and 2A ₂ instead of the aerobic tanks 2A ₁ and 2A ₂ . It is configured to be returned to each of the anoxic tanks 14 ₁ , 14 ₂ . . .

The rest of the configuration is the same as in the _first embodiment, and aeration and Positive-phase intermittent aeration operation consisting of slight aeration is performed, and in the other aerobic reaction tanks 2 ₂ (and even-numbered subordinate control tanks) as subordinate control tanks, at the same timing and period as the reference control tank , anti-phase intermittent aeration operation consisting of micro-aeration and aeration in opposite phase to the reference control tank (or odd-numbered subordinate control tank).

The anoxic tank 14 is not provided with an air diffuser, but is provided with an agitator for agitating the waste water in the anoxic tank 14 . With this configuration, the intermittent aeration operation performed in the aerobic tanks 2A, 2B, and 2C reduces the amount of air diffusion during slight aeration, and the denitrifying reaction by the denitrifying bacteria releases nitrogen gas into the air. However, an anoxic tank 14 dedicated to denitrification reaction is provided upstream of the aerobic tank 2A, and the nitrifying liquid is returned to the anoxic tank 14 through the waste water circulation pipe 12, so that deoxidization is performed in the anoxic tank 14. Since the nitriding reaction is actively carried out, the denitrifying effect in each water channel W can be enhanced.

5 Fifth embodiment (see FIG. 14)
This embodiment has the same basic configuration as the _fourth embodiment, _{but a phosphorus} Anaerobic tanks 15 ₁ , 15 ₂ . Instead of the oxygen tank 14, the anaerobic tanks _15.sub.1 , _15.sub.2 , . . .

The anaerobic tank 15 is not provided with an air diffuser, but is provided with a stirrer for stirring the waste water in the anaerobic tank 15 . With this configuration, the treated water from the primary sedimentation tank 1 is sent to the anaerobic tank 15. In the anaerobic tank 15, phosphorus-accumulating bacteria in the returned sludge from the final sedimentation tank accumulate acetic acid-based organic matter in their bodies. and releases (exhales) phosphate. This phosphoric acid is sent to the aerobic tanks 2A to 2C via the anoxic tank 14, and in these aerobic tanks 2A to 2C, phosphorus is absorbed into the activated sludge, thereby removing phosphorus. can be done.

Therefore, by providing the anaerobic tank 15 on the upstream side of the anoxic tank 14, it is possible to remove not only nitrogen but also phosphorus in the waste water.

6 Sixth embodiment (see FIG. 15)
This embodiment has the same basic configuration as the _first embodiment, but phosphorus is discharged upstream of the _aerobic reaction tanks ₂₁ , ₂₂ , . _anaerobic tanks 15 ₁ , _{15 2} . It is configured to be returned to each of the anaerobic tanks 15 ₁ , 15 ₂ . . . The anaerobic tank 15 is not provided with an air diffuser, but is provided with a stirrer for stirring the waste water in the anaerobic tank 15 .

With this configuration, nitrogen removal is performed by intermittent aeration operation of the aerobic tanks 2A to 2C, and the phosphoric acid released (exhaled) by the anaerobic tank 15 is transferred into the activated sludge of the aerobic tanks 2A to 2C. By being absorbed, phosphorus can be removed while removing nitrogen in the aerobic tanks 2A to 2C.

In the above embodiment, the ammonia sensor is used as the load confirmation means, but it is not necessarily limited to this. Nicotinamide, adenine, dinucleotide, which is one of the coenzymes that are involved in this process, can be measured, and the dissolved oxygen sensor can be used because the change in load can be confirmed by calculating the rate of decrease in DO concentration during microaeration, that is, the respiration rate. It is possible. In addition, an oxidation-reduction potential meter (ORP meter), a UV meter, etc. are also applicable.

In the above embodiment, the aerobic tanks 2A, 2B and 2C of the aerobic reaction tank 21 are _all aerated, and the aerobic tanks 2A, 2B and _2C of the aerobic reaction tank 22 are microaerated. However, as shown in FIG. 16, for example, both the aerobic reaction tanks 2 ₁ and 2 ₂ are divided into five tanks (2A to 2E), and the diffusers 5A to 5E are separated for each tank. Aeration (marked with circles in FIG. 16) and microaeration (marked with triangles in _FIG . 16) are alternately performed in _five tanks in the aerobic reaction tank 21, and the other aerobic reaction tank 22 performs the opposite phase and the same It is also possible to perform periodic and intermittent aeration with the same timing. In this case, switching between aeration and slight aeration can be performed by means of the aeration control valves 9A to 9E provided for each of the aeration devices 5A to 5E.

Further, in the above description, the configuration in which the blowers 10 are provided in the air pipes 8 ₁ , 8 ₂ . A plurality of air blowers 10 (for example, two air blowers 10) may be provided for the entire water passages (for example, 10 water passages).

Further, in the above embodiment, the opening degrees of the air diffusion adjusting valves 9A, 9B, and 9C are assumed to be equal. The degree of opening of > 9C" is set in advance, and on the other hand, at the time of slight aeration, the even degree of opening is set to "the degree of opening of 9A = the degree of opening of 9B = the degree of opening of 9C". The diffusion rate is set with a gradient (for example, the air diffusion rate of each aerobic tank 2A, 2B, 2C is "7, 5, 3" (total "15"), and the diffusion rate at the time of slight aeration is "1, 1, 1". In this case, the controller 13 (diffusion adjustment valve drive means 13f) opens the diffusion adjustment valves 9A, 9B, and 9C in accordance with the cycle T of aeration and slight aeration. The operation of switching the opening degree between the inclined opening degree during the aeration and the uniform opening degree during the slight aeration is repeatedly performed. It is possible to realize a so-called tapered aeration system in which the air diffusion amount is increased at the inflow end of the gas reaction tank where the oxygen demand is high and the air diffusion amount is decreased at the outflow end where the oxygen demand is low. Since it is possible to appropriately respond to the oxygen demand along the , it is possible to realize an intermittent aeration system that is more efficient than uniform aeration.

Further, in the above embodiment, for the sake of simplicity of explanation, the air diffusion amount during aeration is set to "4", "5", and "6", the air diffusion amount during slight aeration is set to "1", and the air volume of the blower is set to Although expressed as "15", "18", "21", etc., these are numbers that indicate the directionality of increase and decrease, and the air volume and air diffusion volume are not limited to these, and are not limited to integers. . For example ^, the air flow rate measured by the air flow meters ^G ₁ ^, G ₂ . . . m ³ /min, and so on.

In the above embodiment, the shortest period T is 20 minutes and the longest period T is 90 minutes based on the hypothetical experiment shown in FIG. 17, but the lower limit and upper limit of the period are not limited to this.

As described above, the present invention performs positive phase intermittent aeration operation in _one aerobic reaction tank ₂₁ and reverse operation in the other aerobic reaction tank 22 without setting the air volume of microaeration in the intermittent aeration operation to zero. By performing the intermittent aeration operation, it is possible to continue the operation at a predetermined air volume (for example, a constant air volume) without stopping the air volume of the fan 10 during the intermittent aeration operation. In urban large-scale sewage treatment plants currently in operation, change to high-performance wastewater treatment facilities that can remove nitrogen through intermittent aeration treatment without significantly changing the configuration of aerobic reaction tanks, air diffusers, etc. It can be realized at relatively low cost.

Also, for example, even in a large-scale urban sewage treatment plant with multiple waterways (for example, 4 or more waterways), change to a high-performance wastewater treatment facility that can remove nitrogen by intermittent aeration operation at a relatively low cost. becomes possible.

In addition, by simply installing the load concentration confirmation sensor A and the dissolved oxygen concentration sensor D in any one of the aerobic reaction tanks 2 ₁ , all the aerobic reaction tanks 2 ₁ , 2 ₂ . An aerobic reaction tank that can control the increase or decrease of the air diffusion amount and period during aeration, and can appropriately change the air diffusion amount and period in response to the increase or decrease of the load concentration, for all water channels. It becomes possible to realize in

Also, the aerobic reaction tanks 2 ₁ , 2 ₃ . . . on one side and the aerobic reaction tanks 2 ₂ , 2 ₄ . Even if there is, the increase or decrease in the air volume of the blower 10 can be minimized, and for example, a wastewater treatment device and wastewater that can be applied to a large-scale urban sewage treatment plant using a large turbo blower A processing method may be implemented.

In addition, while the cycle is always maintained at a constant value, only the air diffusion amount can be increased or decreased according to the increase or decrease of the load concentration. It is possible to realize a wastewater treatment apparatus and a wastewater treatment method that are applicable to large-scale wastewater treatment facilities that enable nitrogen removal by aeration operation.

In addition, without using the dissolved oxygen concentration sensor D, it is possible to realize a wastewater treatment facility that can remove nitrogen by intermittent aeration. A wastewater treatment device and a wastewater treatment method can be realized.

In addition, by providing the anoxic tank 14, in addition to the function of nitrogen removal by intermittent aeration operation in the aerobic reaction tank, the denitrification reaction is actively performed in the upstream anoxic tank 14, so it is more effective. Nitrogen removal can be performed immediately.

Further, by providing the anaerobic tank 15 upstream of the anaerobic tank 14, phosphorus can be removed in addition to the function of removing nitrogen by the anaerobic tank 14 and the aerobic reaction tank.

Further, by providing the anaerobic tank 15 on the upstream side of the aerobic reaction tank, nitrogen can be removed by the intermittent aeration operation of the aerobic reaction tank, and phosphorus can also be removed.

Further, when there are a plurality of water channels, the air ratio of the aerobic reaction tank of each water channel can be matched with the standard air ratio S by a simple configuration.

According to the wastewater treatment apparatus and the wastewater treatment method according to the present invention, the wastewater treatment facility to which the standard activated sludge method is applied, such as a large-scale municipal sewage treatment plant, can be highly functionalized to enable nitrogen removal by the intermittent aeration method. The wastewater treatment facility can be modified at a low cost, and can be widely applied to large-scale sewage treatment plants.

2 ₁ , 2 ₂ ... Aerobic reaction tanks 3 ₁ , 3 ₂ ... Final sedimentation tanks 5A, 5B, 5C Air diffuser 6 Return sludge pipes 8 ₁ , 8 ₂ ... Air pipes 11 ₁ , 11 ₂ ... Air volume control valve 12 Waste water circulation means 13 Control unit 13a Load concentration detection means 13b Dissolved oxygen concentration detection means 13b' Air diffusion amount storage means 13d Blower driving means 13e ₁ , 13e ₂ ... Valve opening/closing driving means 13c ₁ , 13c ₂ . Flow rate detection means 13c' Air diffusion amount comparison means 13h Load concentration comparison means 13i Dissolved oxygen concentration comparison means 13m Period comparison means 13t Air amount change means 13q Period change means 13u Air magnification calculation means 13v Reference air magnification storage means 13y ₁ , 13y ₂ ... Fine adjustment amount calculation means 14 Anoxic tank 15 Anaerobic tank _A Load concentration confirmation sensor D Dissolved oxygen concentration sensor W1, _W2 ... Water channel

Claims (16)

Sludge return for returning sludge from each final sedimentation tank on the downstream side of each aerobic reaction tank to the upstream side of each aerobic reaction tank. In wastewater treatment equipment provided with means,
The aerobic reaction tank of each water channel includes an air diffuser provided in each tank, an air pipe for sending air to each air diffuser, and the air diffuser provided in the air pipe. An aeration adjustment unit comprising an air volume adjustment valve for adjusting the amount of air diffused to the air means and an air flow meter capable of measuring the air flow rate of each of the air pipes is provided,
A common blower is provided in each water channel for sending air into each air pipe,
A control unit for controlling the opening and closing of each of the air volume control valves is provided,
The control unit is provided with valve opening/closing drive means for each air volume adjustment valve of each aeration adjustment unit, which can adjust the air diffusion amount to the air diffusion means while detecting the flow rate of each air flow meter. be
In a state in which air is being blown from the blower to the air pipes of the water channels, in the pair of aerobic reaction tanks, in one of the aerobic reaction tanks, one of the valve opening/closing driving means corresponding to the one of the aerobic reaction tanks is supported. By controlling the opening and closing of the air volume adjustment valve, a positive phase intermittent aeration operation is performed in which aeration with a large amount of air diffusion and fine aeration with a small amount of air diffusion are repeated in the same cycle,
In the other aerobic reaction tank, the corresponding valve opening/closing driving means controls opening/closing of the corresponding air volume control valve, so that slight aeration is performed during aeration of the one aerobic reaction tank, and during slight aeration is a wastewater treatment apparatus which performs reverse phase intermittent aeration operation in the same period and at the same timing as the above positive phase intermittent aeration operation consisting of aeration. In addition to the above two water channels, at least two or more even number of water channels are added, and each added water channel is the above-mentioned preferred sludge return means including the above-mentioned final sedimentation tank and the above-mentioned aeration adjustment unit. each provided with an aerobic reaction tank,
The blower is provided in common to each waterway for sending air to each airpipe,
The control unit includes valve opening/closing driving means capable of adjusting the amount of air diffusion to the air diffusion means while detecting the flow rate of each air flow meter for each of the air volume adjustment valves of the added water channel. is provided,
In a pair of aerobic reaction tanks in a plurality of additional aerobic reaction tanks that are separate from the pair of aerobic reaction tanks,
In one of the aerobic reaction tanks, the positive phase intermittent aeration operation is performed by controlling the opening and closing of the corresponding air volume control valve by the corresponding valve opening/closing drive means, and in the other aerobic reaction tank, 2. A waste water treatment apparatus according to claim 1, wherein said other valve opening/closing drive means corresponding thereto controls opening/closing of said corresponding air volume control valve to perform said reverse phase intermittent aeration operation. A load concentration confirmation sensor and a dissolved oxygen concentration sensor are provided in any one of the plurality of aerobic reaction tanks,
The control unit can detect data from each sensor and can control the air volume of the blower,
The control unit includes load concentration comparing means for comparing the measured value of the load concentration confirmation sensor with the measured value of the previous measurement, blower driving means for instructing an increase or decrease in the air volume of the blower, and the measured value of the dissolved oxygen concentration sensor being the upper limit. Dissolved oxygen concentration comparison means for detecting whether the value or the lower limit has been reached, and period comparison means for detecting whether the period has reached the upper limit or the lower limit,
In the one aerobic reaction tank that performs the positive phase intermittent aeration operation,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is lower than the previous load concentration, the blower driving means instructs the blower to decrease the air volume of the blower, and the dissolved Until the measured value of the dissolved oxygen concentration sensor and the period reach the lower limit based on the comparison by the oxygen concentration comparing means and the period comparing means, the one valve opening/closing driving means operates the one aerobic reaction tank. The air volume control valve is instructed to decrease the above period and the air diffusion amount during aeration, and to maintain the air diffusion amount during slight aeration at a constant value,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor has increased from the previous load concentration, the blower driving means instructs the blower to increase the air volume of the blower, and the dissolved Until the measured value of the dissolved oxygen concentration sensor and the period reach the upper limit based on the comparison by the oxygen concentration comparing means and the period comparing means, the one valve opening/closing driving means operates the one aerobic reaction tank. The air volume control valve is instructed to increase the above period and the air diffusion amount during aeration, and to maintain the above constant value for the air diffusion amount during slight aeration,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration, the blower driving means maintains the air volume of the blower and the one valve The open/close driving means instructs the air volume control valves of the one aerobic reaction tank to maintain the period and the air diffusion volume,
In the other aerobic reaction tank that performs the reversed-phase intermittent aeration operation,
The other valve opening/closing drive means is the above-mentioned period and air diffusion amount increased or decreased after the change in the positive phase intermittent aeration operation at the time of aeration, and the air diffusion amount at the time of slight aeration maintains the above-mentioned constant value. 3. The waste water treatment apparatus according to claim 1 or 2, which controls the A load concentration confirmation sensor and a dissolved oxygen concentration sensor are provided in any one of the plurality of aerobic reaction tanks,
The control unit can detect data from each sensor and can control the air volume of the blower,
The control unit includes load concentration comparing means for comparing the measured value of the load concentration confirmation sensor with the measured value of the previous measurement, blower driving means for instructing an increase or decrease in the air volume of the blower, and the measured value of the dissolved oxygen concentration sensor being the upper limit. Dissolved oxygen concentration comparison means for detecting whether the value or lower limit has been reached,
In the one aerobic reaction tank that performs the positive phase intermittent aeration operation,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is lower than the previous load concentration, the blower driving means instructs the blower to decrease the air volume of the blower, and the dissolved Until the measured value of the dissolved oxygen concentration sensor reaches the lower limit based on the comparison by the oxygen concentration comparing means, the one valve opening/closing drive means operates the air volume control valves of the one aerobic reaction tank. While the period remains the same, only the air diffusion amount during aeration is reduced, and the air diffusion amount during slight aeration is instructed to be maintained at a constant value,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor has increased from the previous load concentration, the blower driving means instructs the blower to increase the air volume of the blower, and the dissolved Until the measured value of the dissolved oxygen concentration sensor reaches the upper limit based on the comparison by the oxygen concentration comparison means, the one valve opening/closing driving means operates the air volume control valve of the one aerobic reaction tank in the above cycle. is to increase only the amount of air diffusion during aeration while maintaining the same, and to maintain the above constant value for the amount of air diffusion during slight aeration,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration, the blower driving means maintains the air volume of the blower and the one valve The open/close driving means instructs each air volume control valve of the one aerobic reaction tank to maintain the above cycle and air diffusion volume,
In the other aerobic reaction tank that performs the reversed-phase intermittent aeration operation,
The other valve opening/closing drive means controls the air diffusion amount increased or decreased after the change in the normal phase intermittent aeration operation during aeration, and the air diffusion amount during slight aeration maintains the above constant value. 3. The wastewater treatment system according to claim 1 or 2, wherein A load concentration confirmation sensor is provided in any one of the plurality of aerobic reaction tanks,
The control unit includes load concentration comparing means for comparing the measured value of the load concentration confirmation sensor with the measured value at the time of the previous measurement, blower driving means for instructing an increase or decrease in the air volume of the blower, and an upper limit value or a lower limit value for the amount of air diffusion. air diffusion amount comparison means for detecting whether or not the period has reached the upper limit value or the lower limit value;
In the one aerobic reaction tank that performs the positive phase intermittent aeration operation,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is lower than the previous load concentration, the blower driving means instructs the blower to reduce the air volume, Until the air diffusion amount and the period reach the lower limit based on the comparison by the air diffusion amount comparison means and the period comparison means, the one valve opening/closing driving means operates the air volume control valves of the one aerobic reaction tank. , the above period and the air diffusion amount during aeration are decreased, and the air diffusion amount during slight aeration is to be maintained at a constant value,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is higher than the previous load concentration, the blower driving means instructs the blower to increase the air volume, Until the air diffusion amount and period reach the upper limit based on the comparison by the air diffusion amount comparison means and the period comparison means, the one valve opening/closing drive means operates the air volume adjustment valves of the one aerobic reaction tank. On the other hand, it is instructed to increase the period and the air diffusion amount during aeration, and to maintain the above constant value for the air diffusion amount during slight aeration,
When the load concentration comparing means determines that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration, the blower driving means maintains the air volume of the blower and the one valve The open/close driving means instructs each air volume control valve of the one aerobic reaction tank to maintain the cycle and the air diffusion volume,
In the other aerobic reaction tank that performs the reversed-phase intermittent aeration operation,
The other valve opening/closing drive means is the above-mentioned period and air diffusion amount increased or decreased after the change in the positive phase intermittent aeration operation at the time of aeration, and the air diffusion amount at the time of slight aeration maintains the above-mentioned constant value. 3. The waste water treatment apparatus according to claim 1 or 2, which controls the An anoxic tank for denitrification is provided upstream of each aerobic reaction tank in each water channel,
A waste water circulation means is provided for supplying a part of the waste water existing downstream of each aerobic reaction tank in each water channel to the anoxic tank,
6. A waste water treatment apparatus according to any one of claims 1 to 5, wherein said return sludge means of said water channels return said sludge to said anoxic tank instead of said aerobic reaction tank. An anaerobic tank for discharging phosphorus is provided upstream of each anoxic tank in each water channel,
7. A waste water treatment apparatus according to claim 6, wherein said sludge returning means returns said sludge to said anaerobic tank instead of said anoxic tank. An anaerobic tank for discharging phosphorus is provided upstream of the aerobic reaction tank in each water channel,
6. The wastewater treatment apparatus according to claim 1, wherein said sludge returning means returns said sludge to said anaerobic tank instead of said aerobic reaction tank. The waste water treatment apparatus according to any one of claims 1 to 8, wherein the period is 20 minutes to 90 minutes. An inflow water meter for measuring the amount of water flowing into each waterway is provided for each waterway,
The control unit is provided with the water volume of the inflow water meter of the water channel corresponding to the one aerobic reaction tank performing the positive phase intermittent aeration operation, and the air flow rate of the air flow meter corresponding to the one aerobic reaction tank. an air ratio calculation storage means for obtaining an air ratio from the air ratio and storing the air ratio as a reference air ratio;
In addition, in order to match the air ratio of the aerobic reaction tank of the other channel with the reference air ratio, the air volume of the aerobic reaction tank of the other channel is adjusted based on the inflow water volume of the inflow water meter of the other channel. Fine adjustment amount calculation means for calculating is provided,
The control unit finely adjusts the air volume control valves of the other water passages based on the air volume after fine adjustment calculated by the fine adjustment amount calculation means so as to match the air volume after fine adjustment. The wastewater treatment device according to any one of claims 1 to 9, which is a Sludge returning means for returning sludge from each final sedimentation tank on the downstream side of each of the aerobic reaction tanks to the upstream side of each of the aerobic reaction tanks. A wastewater treatment method in a wastewater treatment apparatus provided with
The aerobic reaction tank of each water channel includes an air diffuser provided in each tank, an air pipe for sending air to each air diffuser, and the air diffuser provided in the air pipe. An aeration adjustment unit comprising an air volume adjustment valve for adjusting the amount of air diffused to be blown to the air means and an air flow meter capable of measuring the air flow rate of each air pipe,
A common blower is provided in each water channel for sending air into each air pipe,
a control unit capable of adjusting the amount of air diffused to the air diffusion means by controlling the opening and closing of each of the air volume control valves while detecting the flow rate of each of the air flow meters;
The control unit controls opening and closing of the air volume control valves when air is being blown from the air blower to the air pipes of the water channels, so that one of the aerobic reaction tanks in the pair of aerobic reaction tanks In the aerobic reaction tank, positive-phase intermittent aeration is performed in which aeration with a large amount of air diffusion and fine aeration with a small amount of air diffusion are repeated in the same cycle,
In the other aerobic reaction tank, the negative phase intermittent aeration operation is performed in the same period and at the same timing as the positive phase intermittent aeration operation, which consists of slight aeration during aeration of the one aerobic reaction tank and aeration during slight aeration. Wastewater treatment method in wastewater treatment equipment. In addition to the two waterways, an even number of at least two waterways are added, and each additional waterway is equipped with the sludge return means including the final sedimentation tank and the aeration adjustment unit. Provide each reaction tank,
The blower is provided in common to each waterway for sending air to each airpipe,
The control unit adjusts the amount of air diffused to each of the air diffusion means by controlling the opening and closing of each of the air volume control valves while detecting the flow rate of each of the air flow meters in the added water channel. ,
In a pair of aerobic reaction tanks in a plurality of aerobic reaction tanks that are added separately from the pair of aerobic reaction tanks,
By controlling the opening and closing of the air volume control valve, the control unit performs the positive phase intermittent aeration operation in one of the aerobic reaction tanks and the reverse phase intermittent aeration operation in the other aerobic reaction tank. The wastewater treatment method in a wastewater treatment apparatus according to claim 11, wherein A load concentration confirmation sensor and a dissolved oxygen concentration sensor are provided in any one of the plurality of aerobic reaction tanks,
The control unit can detect data from each sensor and control the air volume of the blower,
In the one aerobic reaction tank that performs the positive phase intermittent aeration operation,
When determining that the measured value of the load concentration confirmation sensor is lower than the previous load concentration, the control unit instructs to decrease the air volume of the blower, and the dissolved oxygen concentration sensor measured value and Until the cycle reaches the lower limit, for each of the air volume control valves of the one aerobic reaction tank, the cycle and the air diffusion amount during aeration are decreased, and the air diffusion amount during slight aeration is constant. instructed to keep
When it is determined that the measured value of the load concentration confirmation sensor is higher than the previous load concentration, an instruction to increase the air volume of the blower is given, and the measured value of the dissolved oxygen concentration sensor and the period are the upper limit values. Up to, for each air volume control valve of the one aerobic reaction tank, increase the period and the air diffusion amount during aeration, and maintain the above constant value for the air diffusion amount during slight aeration. and
When it is determined that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration, the air volume of the blower is maintained, and the air volume adjustment valve of the one aerobic reaction tank is instructed to maintain period and air sparge,
In the other aerobic reaction tank that performs the reversed-phase intermittent aeration operation,
During aeration, the control unit controls the cycle and the air diffusion amount that have been increased or decreased after the change in the positive phase intermittent aeration operation, and controls the air diffusion amount during slight aeration to maintain the above constant value. A wastewater treatment method in a wastewater treatment apparatus according to claim 11 or 12. A load concentration confirmation sensor and a dissolved oxygen concentration sensor are provided in any one of the plurality of aerobic reaction tanks,
The control unit can detect data from each sensor and control the air volume of the blower,
In the one aerobic reaction tank that performs the positive phase intermittent aeration operation,
When determining that the measured value of the load concentration confirmation sensor is lower than the previous load concentration, the control unit instructs to decrease the air volume of the blower, and the measured value of the dissolved oxygen concentration sensor increases. Until the lower limit value is reached, for each air volume control valve of one of the aerobic reaction tanks, only the air diffusion volume during aeration is reduced while the cycle remains the same, and the air diffusion volume during slight aeration is instructed to maintain a constant value,
When it is determined that the measured value of the load concentration confirmation sensor is higher than the previous load concentration, an instruction is given to increase the air volume of the blower, and the measured value of the dissolved oxygen concentration sensor reaches the upper limit. , for each of the air volume control valves of the one aerobic reaction tank, only the air diffusion volume during aeration is increased while the cycle remains the same, and the air diffusion volume during slight aeration is maintained at the above constant value. and
When it is determined that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration, the air volume of the blower is maintained, and for each air volume adjustment valve of the one aerobic reaction tank, Instruct to maintain the above period and air diffusion rate,
In the other aerobic reaction tank that performs the reversed-phase intermittent aeration operation,
11. The control unit controls the air diffusion amount increased or decreased after the change in the normal phase intermittent aeration operation at the time of aeration, and controls the air diffusion amount at the time of slight aeration to maintain the above constant value. Or the wastewater treatment method in the wastewater treatment equipment according to 12. A load concentration confirmation sensor is provided in any one of the plurality of aerobic reaction tanks,
The control unit detects data from the sensor, controls the air volume of the blower, and is provided with air diffusion amount storage means for storing the current air diffusion amount,
In the one aerobic reaction tank that performs the positive phase intermittent aeration operation,
When it is determined that the measured value of the load concentration confirmation sensor is lower than the previous load concentration, the control unit instructs to decrease the air volume of the blower, and stores the period and the air diffusion amount. Decrease the period and the air diffusion amount during aeration for each of the air volume control valves of the one aerobic reaction tank until the previous air diffusion amount stored in the means reaches the lower limit, Instructed to maintain a constant value for air diffusion during micro-aeration,
When it is determined that the measured value of the load concentration confirmation sensor is higher than the previous load concentration, an instruction to increase the air volume of the blower is given, and the period and air diffusion amount are stored in the storage means. Until the previous air diffusion amount reaches the upper limit, increase the period and the air diffusion amount at the time of aeration for each of the air volume adjustment valves of each of the above-mentioned aerobic reaction tanks. Instruct the air diffusion rate to maintain the above constant value,
When it is determined that the measured value of the load concentration confirmation sensor is equivalent to the previous load concentration, the air volume of the blower is maintained, and the air volume adjustment valve of the one aerobic reaction tank is instructed to maintain period and air sparge,
In the other aerobic reaction tank that performs the reversed-phase intermittent aeration operation,
During aeration, the control unit controls the cycle and the air diffusion amount that have been increased or decreased after the change in the positive phase intermittent aeration operation, and controls the air diffusion amount during slight aeration to maintain the above constant value. A wastewater treatment method in a wastewater treatment apparatus according to claim 11 or 12. An inflow water meter for measuring the amount of water flowing into each waterway is provided for each waterway,
The control unit is provided with the water volume of the inflow water meter of the water channel corresponding to the one aerobic reaction tank performing the positive phase intermittent aeration operation, and the air flow rate of the air flow meter corresponding to the one aerobic reaction tank. an air ratio calculation storage means for obtaining an air ratio from the air ratio and storing the air ratio as a reference air ratio;
In addition, in order to match the air ratio of the aerobic reaction tank of the other channel with the reference air ratio, the air volume of the aerobic reaction tank of the other channel is adjusted based on the inflow water volume of the inflow water meter of the other channel. Provide fine adjustment amount calculation means for calculating,
Based on the air volume after fine adjustment calculated by the fine adjustment amount calculating means, the control unit finely adjusts the air volume adjustment valves of the other water passages so as to match the air volume after fine adjustment. The wastewater treatment method in a wastewater treatment apparatus according to any one of claims 11 to 15.

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