JPH0724493A - Method for controlling operation of activated sludge circulation modified method - Google Patents

Abstract

PURPOSE:To provide the method for controlling operation of an activated sludge circulation modified method capable of improving nitrification efficiency in an aeration tank and enhancing denitrification effect in an anaeration tank according thereto. CONSTITUTION:This activated sludge circulation modified method treatment includes a stage for denitrifying raw water 3 by clenitrifying bacteria in the anaeration tank 1a, a stage for nitrifying the raw water in plural stages of aeration tanks 2a, 2b, 2c, 2d and a stage for subjecting the water to a sepn. of solid from liquid in a settling vessel 7. The aeration tanks are respectively arranged with pH meters 13a, 13b, 13c, 13d to measure the pH of the samples separately sampled from the respective aeration tanks. Whether the nitrification reaction is under progression or not or is already ended or not is judged. A controller 16 outputs control signals to properly control driving of a blower 5 and the opening degrees of respective blast rate regulating valves 15a, 15b, 15c, 15d from the results of the judgment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control method for highly efficiently removing organic matter and nitrogen in wastewater by using a modified anaerobic-aerobic activated sludge circulation method.

[0002]

2. Description of the Related Art Various methods have conventionally been proposed for efficiently removing organic matter in wastewater such as sewage and removing nitrogen and phosphorus which are considered to be the causative agents of eutrophication in closed water areas. . This eutrophication refers to an increase in the concentration of nutrient salts such as N, P in the water area, which activates biological activities using these nutrients as nutrients and changes the ecosystem. In particular, it is known that the above-mentioned eutrophication rapidly progresses when a large amount of domestic wastewater or industrial wastewater flows into lakes and the like.

Recently, it has been required to increase the removal rate of nitrogen, and it is expected that the regulations on nitrogen will be stricter. Therefore, the number of facilities adopting an advanced treatment process capable of removing this will increase. it is conceivable that.

Although physicochemical methods and biological methods have been proposed as means for removing nitrogen and phosphorus in wastewater, physicochemical methods are not widely used because of the high cost. For example, a phosphorus removal method which has been put into practical use as a physicochemical method includes a coagulation precipitation method and a crystallization method, but this method has a drawback in terms of cost and maintenance.

On the other hand, as a method for biologically removing nitrogen and phosphorus simultaneously, the conventional activated sludge circulation modification method is anaerobic-
The aerobic activated sludge method is drawing attention. (See, for example, Water Pollution Research, Vol. 12, No. 7, 441-448, 1989.) This anaerobic-aerobic activated sludge method is, for example, as shown in FIG. (Abbreviated as DO)
Anaerobic tank 1a in which DO does not exist and aerobic tank 2a in which DO exists,
Partitioned into 2b, 2c, 2d, and by this anaerobic tank 1a,
The inflowing raw water 3 is agitated by an agitation mechanism 10 under anoxic conditions to denitrify by denitrifying bacteria in the activated sludge, and then each of the scatterers placed inside the aerobic tanks 2a, 2b, 2c, 2d. By supplying air from the blower 5 to the trachea 4, oxidative decomposition of organic matter by activated sludge and nitrification of ammonia by nitrifying bacteria are performed in the presence of oxygen by aeration. Then, the nitrification solution in the last-stage aerobic tank 2d is sent to the anaerobic tank 1a by using the nitrification solution circulation pump 6, whereby the denitrification effect of the anaerobic tank 1a is promoted.

The above-mentioned denitrifying bacterium refers to a bacterium that reduces N0 ₂ -N and N0 ₃ -N to N ₂ and NO ₂ by respiration of nitric acid under anaerobic conditions. Further, phosphorus in the raw water is released in the anaerobic tank 1a, and is taken in and removed by the activated sludge in the aerobic tanks 2a, 2b, 2c, 2d. Reference numeral 7 denotes a final settling basin, and the supernatant of the final settling basin 7 is discharged after passing through a disinfecting tank not shown in the figure, and a part of the sludge settled in the final settling basin 7 is a sludge return pump. Other sludge is returned to the anaerobic tank 1a by 8 and is sent from the excess sludge drawing pump 9 to an excess sludge treatment device (not shown) for treatment.

By using such an anaerobic-aerobic activated sludge treatment method, an effect comparable to the organic substance removal effect achieved by the ordinary standard activated sludge method can be obtained, and nitrogen and phosphorus are more effective than the activated sludge method. A high removal rate is achieved.

[0008]

However, in the case of such a conventional anaerobic-aerobic activated sludge treatment method, it is difficult to establish an efficient operation control method, and in particular, the nitrification efficiency in the aerobic tank and the accompanying There was a problem that it was difficult to carry out monitoring to sufficiently enhance the denitrification effect in the anaerobic tank.

That is, the operating modes in the anaerobic-aerobic activated sludge method are the denitrification reaction in the anaerobic tank 1a and the aerobic tank 2
It can be roughly divided into nitrification reactions in a, 2b, 2c and 2d, but the latter, that is, the nitrification reaction, is the rate-determining reaction.

In particular, in order to efficiently remove nitrogen by the anaerobic-aerobic activated sludge treatment method, it is required to maintain denitrification in the anaerobic tank and nitrification in the aerobic tank under optimum operating conditions. Since the nitrogen removal process is highly influenced by the nitrification process, it is necessary that the nitrification process is performed well in order to perform good nitrogen removal. This nitrification reaction is caused by nitrifying bacteria as described above,
It is known that the activity of this nitrifying bacterium is easily affected by subtle changes such as pH and water temperature. Nitrification reaction is oxidation of ammonium nitrogen by nitrifying bacteria, nitrification rate decreasing speed or NO _X -N ammoniacal nitrogen (NO ₂
It can be expressed as an increasing rate of −N + NO ₃ −N).

The other denitrification reaction can be expressed as 2NO ₃ ⁻ +5 (H ₂ ) → N ₂ ↑ + 2OH ⁻ + 2H ₂ O.

When the nitrification progresses satisfactorily, the quality of the denitrification reaction affects the nitrogen removal rate. Therefore, in order to maintain a high nitrogen removal rate, a good balance between the nitrification reaction and the denitrification reaction should be maintained. Required to do so.

On the other hand, it is known that nitrification of ammoniacal nitrogen by the above nitrifying bacteria is greatly affected by DO concentration in the nitrification tank. Therefore, it is necessary to increase the DO concentration to promote the nitrification reaction, but on the other hand, when a part of the nitrification solution is circulated from the nitrification tank to the denitrification tank to carry out the denitrification reaction, DO should not exist. There is a problem of being good. Therefore, considering that the denitrification reaction is hindered by the introduction of DO due to the circulation of the nitrification solution, it is important to manage the DO concentration in the nitrification tank so that it does not become higher than necessary.

From the above points, it is an important technical element to monitor the nitrification reaction in order to establish an efficient operation method by the modified activated sludge circulation method. No monitoring means has been established, and it is difficult to say that control is performed to sufficiently enhance both the nitrification efficiency in the aerobic tank and the denitrifying effect in the anaerobic tank.

Therefore, the present invention solves the problems of such anaerobic-aerobic activated sludge treatment, and in particular, by monitoring the progress of the nitrification reaction among the above control factors, By simply determining the end point of the nitrification reaction and controlling the amount of air blown from the blower, it is possible to enhance the nitrification efficiency and suppress the increase of the excess DO concentration, and accordingly enhance the denitrification effect in the anaerobic tank. It is an object of the present invention to provide an operation control method of a modified activated sludge circulation method.

[0016]

In order to achieve the above-mentioned object, the present invention comprises a step of denitrifying raw water by denitrifying bacteria in an anaerobic tank, and aeration and nitrifying bacteria in a plurality of aerobic tanks. In the modified activated sludge circulation process including the step of performing nitrification by means of the step of: and separating the solid-liquid separation in the settling tank and discharging the supernatant as treated water, first, according to claim 1, Each of the aerobic tanks is equipped with a pH meter, and the pH of the sample separately sampled from each aerobic tank is measured to determine whether the nitrification reaction is in progress or has ended. Provided is an operation control method of a modified activated sludge circulation method, in which the amount of air blown to the air is controlled appropriately.

Further, according to the second aspect, a pH meter is arranged in each of the plurality of aerobic tanks, the pH of the sample sampled separately from each aerobic tank is measured, and the controller is based on the measured value. Provided is an operation control method of a modified activated sludge circulation method, which judges the nitrification characteristics of each aerobic tank and outputs a control signal for appropriately controlling the opening of a blower for aeration and each air flow rate adjusting valve. .

The anaerobic-aerobic tank is constructed by partitioning the same biological reaction tank with a partition plate, and the aerobic tank has at least three.
It is divided into more than partitions.

[0019]

[Operation] According to the operation control method of the modified activated sludge circulation method, raw water is denitrified in the anaerobic tank, aeration in the aerobic tank and nitrification based on the action of nitrifying bacteria are performed, while The pH of the sampled sample is separately measured by a pH meter, and based on the measured value of each pH meter, the controller determines whether the nitrification reaction is in progress or is completed, and the controller blows the blower. A drive control signal is output to the drive and air flow rate adjusting valve, and the air flow rate from the blower to each aerobic tank is appropriately controlled.

Therefore, the progress of the nitrification reaction can be grasped by monitoring the change in the pH value in each aerobic tank, and by controlling the air flow rate, the nitrification efficiency in the aerobic tank can be increased, and accordingly. As a result, the effect of increasing the denitrification effect in the anaerobic tank can be obtained.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the operation control method of the modified activated sludge circulation method according to the present invention will be described in detail below with reference to the drawings, in which the same components as those of the conventional components are designated by the same reference numerals. . FIG. 1 is a schematic view showing an overall anaerobic-aerobic activated sludge system adopting an operation control method according to the present invention, in which 1a is an anaerobic tank for denitrifying wastewater, 2a, 2b,
2c and 2d are multi-stage aerobic tanks for nitrification,
The anaerobic tank 1a and the aerobic tanks 2a, 2b, 2c and 2d are configured by dividing the same biological reaction tank by a partition plate 12.

A stirring mechanism 10 is provided inside the anaerobic tank 1a.
Are arranged in the aerobic tanks 2a, 2b, 2c, 2d, and air diffusers 4, 4, 4, 4 serving as air blowing mechanisms are arranged in the aerobic tanks 2a, 2b, 2c, 2d, and air is supplied to the air diffusers 4, 4, 4, 4 outside. The blower 5 for supplying is provided. And, in the middle of the pipeline connecting the blower 5 and each of the diffusers 4, 4, 4, 4.
Valves 15a, 15b, 15c, 15 whose degree of opening and closing can be adjusted
d is deployed.

In the present embodiment, the aerobic tanks 2a, 2b, 2
pH meter 13a, 13b, 13c, 13d on c and 2d, respectively
Is installed, and the measured value of each pH meter is the controller 1
It has been entered in 6. The output signal of the controller 16 is transmitted to the blower 5 and the valves 15a, 15b, 15
It is input to c and 15d. 6 is a nitrification solution circulation pump,
7 is a final settling tank, 8 is a sludge return pump, and 9 is an excess sludge drawing pump.

The basic operation of such a device is as follows. As shown in FIG. 1, first, raw water 3 as waste flows into the anaerobic tank 1a, based on the stirring action and the action of denitrifying bacteria stirring mechanism 10 in the water, NO ₃ -N, NO ₂ - N
The reduction of the ions to N ₂ is performed, that is, denitrification.

Next, the raw water is a multi-stage aerobic tank 2a, 2b, 2
c, 2d, and the aeration by aeration from the diffusers 4, 4, 4 and 4 is performed as the blower 5 is driven, and the ammonia nitrogen NH 3 is generated based on the action of nitrifying bacteria.
Oxidation of _4- N to NO ₂ -N or NO ₃ -N, that is, nitrification is performed.

During the above operation, the aerobic tanks 2a, 2a
p of samples sampled separately from b, 2c and 2d
H is measured by each of the pH meters 13a, 13b, 13c, 13d, and based on the measured value of each pH meter, the controller 16 determines whether the nitrification reaction is in progress or has ended. , The controller 16
From the blower 5 and the valves 15a, 15b, 15
A drive control signal is output to c, 15d, and the blower 5 appropriately controls the amount of air blown to the aerobic tanks 2a, 2b, 2c, 2d.

FIG. 2 shows an anaerobic tank 1a and aerobic tanks 2a, 2b,
2c, pH value in the 2d and NO _X -N concentration (mg /
1), that is, a graph plotting nitrification characteristics, in this example, NO _X − in each of the aerobic tanks 2a, 2b, 2c, 2d.
The value of N is increasing, which means that the nitrification reaction is not completed even in the aerobic tank 2d. Then, it was observed that the measured values of the respective pH meters 13a, 13b, 13c, 13d at this time gradually decreased from the aerobic tank 2a toward the aerobic tanks 2b, 2c, 2d.

On the other hand, FIG. 3 shows the results of measuring the pH and NO _X -N in the same manner as above, by advancing the nitrification reaction under different nitrification conditions from FIG. 2, and in this example, the stage of the aerobic tank 2c. The nitrification reaction has almost finished. And the measured value by each pH meter is pH 7.2 in the aerobic tank 2b and pH in the aerobic tank 2c.
7.2, pH was 7.3 in aerobic tank 2d.

As can be seen from FIG. 3, when the nitrification reaction is completed while the raw water 3 is sequentially flowing in the aerobic tanks 2a, 2b, 2c, 2d, the pH value becomes substantially constant or slightly. It is rising. From such measurement results, it was found that the progress of the nitrification reaction can be grasped by monitoring the pH value in each aerobic tank 2a, 2b, 2c, 2d.

Further, in FIG. 1, the nitrification solution in the aerobic tank 2d is fed into the anaerobic tank 1a by using the nitrification solution circulation pump 6, whereby the denitrification effect in the anaerobic tank 1a is promoted.
Particularly, phosphorus in the wastewater is released in the anaerobic tank 1a and the aerobic tank 2
It is taken into and removed by the activated sludge in a, 2b, 2c and 2d.

Further, a part of the sludge settled in the final settling basin 7 is returned to the anaerobic tank 1a by the sludge return pump 8, and the other sludge is sent to the surplus sludge treatment device (not shown) by the surplus sludge drawing pump 9. Will be processed. The supernatant of the final settling tank 7 is discharged as treated water 11 after passing through a disinfection tank (not shown).

In the above embodiment, an example in which a total of 4 aerobic tanks are provided has been described, but in consideration of the characteristic method of this embodiment of monitoring the pH value in a plurality of stages of aerobic tanks, it is preferable. It is necessary to provide at least three air tanks.

As described above, according to the operation control method of the modified activated sludge circulation method according to this embodiment, each aerobic tank 2
The end time of the nitrification reaction in the aerobic tank is determined by monitoring with a pH meter disposed in a, 2b, 2c, 2d, and the blower 5 and each valve 15a, 1
By adjusting the openings of 5b, 15c and 15d, the nitrification efficiency is increased and the increase of the excess DO concentration is suppressed,
It is characterized by enhancing the denitrification effect in the anaerobic tank.

[0034]

As described above in detail, according to the operation control method of the modified activated sludge circulation method according to the present invention, the raw water is denitrified in the anaerobic tank, and the aeration and the action of nitrifying bacteria in the aerobic tank are performed. While nitrification is performed based on, it is possible to determine whether the nitrification reaction is in progress or completed by separately measuring the pH of the sample sampled from each tank. The nitrification efficiency in the aerobic tank can be enhanced and the denitrification effect in the anaerobic tank can be enhanced by controlling the opening of the drive and air flow adjusting valve.

Particularly, in order to remove nitrogen efficiently by the anaerobic-aerobic activated sludge treatment method, it is required to maintain denitrification in the anaerobic tank and nitrification in the aerobic tank under optimum operating conditions. Since the nitrogen removal step is highly influenced by the nitrification step, it is required to maintain a good balance between the nitrification reaction and the denitrification reaction in order to maintain a high nitrogen removal rate. By monitoring the nitrification reaction, the DO concentration in the aerobic tank will be controlled so that it will not be higher than necessary, and the anaerobic tank will circulate the nitrification solution by bringing in the DO during nitrification of ammonia nitrogen by nitrifying bacteria. It is possible to obtain the effect that the denitrification reaction in step 2 is not hindered, and an efficient operation control method for anaerobic-aerobic activated sludge treatment can be established.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an operation control method of a modified activated sludge circulation method according to the present invention.

FIG. 2 is a graph showing the correlation between the pH value and nitrification characteristics of each aerobic tank in this example.

FIG. 3 is a graph showing the correlation between the pH value of each aerobic tank and nitrification characteristics under other nitrification conditions of this example.

FIG. 4 is a schematic diagram showing an example of conventional anaerobic-aerobic activated sludge treatment.

[Explanation of symbols]

 1a ... Anaerobic tank 2a, 2b, 2c, 2d ... Aerobic tank 4 ... Diffuser pipe 5 ... Blower 6 ... Nitrification liquid circulation pump 7 ... Final sedimentation tank 8 ... Sludge return pump 9 ... Excess sludge extraction pump 10 ... Stirring mechanism 12 ... Partition plate 13a, 13b, 13c, 13d ... pH meter 15a, 15b, 15c, 15d ... Valve 16 ... Controller

Claims (3)

[Claims] 1. A step of denitrifying raw water by denitrifying bacteria in an anaerobic tank, a step of nitrifying by aeration and action of nitrifying bacteria in a plurality of aerobic tanks, and solid-liquid separation in a precipitation tank. In a modified activated sludge circulation process including a step of discharging a clear liquid as treated water, pH meters are respectively arranged in the aerobic tanks of the above-mentioned stages, and the pH of a sample sampled separately from each aerobic tank is measured. It is judged whether the nitrification reaction is in progress or has ended, and the amount of air blown to each aerobic tank is appropriately controlled based on this judgment result. Control method. 2. A step of denitrifying raw water by denitrifying bacteria in an anaerobic tank, a step of nitrifying by the action of aeration and nitrifying bacteria in a plurality of aerobic tanks, and solid-liquid separation in a precipitation tank. In a modified activated sludge circulation process including a step of discharging a clear liquid as treated water, pH meters are respectively arranged in the aerobic tanks of the above-mentioned stages, and the pH of a sample sampled separately from each aerobic tank is measured. Then, the controller determines the nitrification characteristics of each aerobic tank based on this measurement value and outputs a control signal that appropriately controls the opening of the blower for aeration and each air flow rate adjusting valve. A method for controlling the operation of the modified activated sludge circulation method. 3. The activated sludge circulation according to claim 1, wherein the anaerobic-aerobic tank is constructed by partitioning the same biological reaction tank with a partition plate, and the aerobic tank is divided into at least three compartments. Modified operation control method.