JP2003053364A - Method for controlling activated sludge concentration of liquid mixture in aerator and waste water treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and efficiently perform control and management of the activated sludge concentration in the liquid mixture in an aerator without carrying out vexatious work in a process step of cleaning livestock waste water, etc. SOLUTION: The waste water treatment system A has a screen 2 for removing solids from the waste water, a mixing vessel 4 for mixing the waste water treated by the screen 2, an initial settling tank 5 for removing the residual solids of the waste water sent from the fixing vessel 4, the aerator 6 for subjecting the waste water sent from the initial settling tank 5 to aeration treatment and solid-liquid separation treatment by a separating membrane, a sludge storage tank 10 for subjecting the excess sludge sent from the aerator 6 and the precipitate sent from the initial settling tank 5 to aeration treatment and a filter press 11 for dewatering the sludge sent from the sludge storage tank 10. The aerator 6 is so controlled as to stop the aeration by each prescribed time, to settle the activated sludge by standing the sludge still for the prescribed time after the stoppage of the aeration, to withdraw the precipitated sludge allowing the prescribed amount thereof to remain and to repeat the process steps from the aeration to the withdrawal of the activated sludge.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and a wastewater treatment system for controlling the activated sludge concentration of a mixed liquid in an aeration tank. More specifically, the control and management of the activated sludge concentration of the mixed liquid in the aeration tank can be easily performed without complicated work.
And, it relates to something that can be done efficiently.

[0002]

2. Description of the Related Art For example, a batch type activated sludge method and a continuous activated sludge method are known as the activated sludge method used in the purification treatment of livestock wastewater and the like. In the batch activated sludge method, as shown in FIGS. 7 and 8, sedimentation and discharge in one tank,
Four cycles of inflow and aeration are repeated on a daily basis, and the supernatant water in the precipitation step is discharged as treated water.
As shown in FIG. 9, in the continuous activated sludge method, a settling tank is provided in addition to the aeration tank, the activated sludge is settled in the settling tank, and the supernatant water in the settling step is discharged as treated water.

By the way, in a ranch or the like having an intensive milking facility, a large amount of livestock wastewater including manure of dairy cows and washing water for washing dairy cows during milking is generated. This purification of livestock wastewater is usually carried out by a large-scale wastewater treatment system adopting the activated sludge method, which is constructed by constructing a sedimentation tank or an aeration tank from concrete. In such a wastewater treatment system, a separation membrane such as a hollow fiber membrane is generally used for the final solid-liquid separation after the aeration treatment. As a result, treated water at a level that can be discharged into rivers is obtained.

In the wastewater treatment by the activated sludge method, the efficiency of the activated sludge treatment can be improved by maintaining the activated sludge (MLSS) concentration of the mixed liquid in the aeration tank at a high concentration. In order to exert sufficient purification capacity by the activated sludge method, the activated sludge concentration is generally 5000 mg / L.
It is necessary to maintain above. As a method of maintaining a high concentration of activated sludge, conventionally, a method of separating the mixed liquid in the aeration tank into treated water and sludge by a separation membrane and returning the concentrated separated sludge to the aeration tank again has been adopted. Was there. In this method, there is no sludge that flows into the treated water because the sludge is separated into membranes, and it is concentrated by the separation membrane and returned to the aeration tank, so it is possible to maintain a high concentration of activated sludge in the aeration tank. .

[0005]

However, the conventional activated sludge method has the following problems. The batch type activated sludge method repeats four cycles of precipitation, discharge, inflow and aeration on a daily basis, and is not continuous treatment, so it takes a considerable amount of time for purification treatment and is inefficient. It was In the above continuous activated sludge method, a settling tank is attached to the aeration tank and the activated sludge is settled in the settling tank. Therefore, a device such as a settling tank or a returning sludge device is required and the operation is complicated. There is also a problem that an expensive settling tank and a large installation area are required. Also, the treated water discharged as the supernatant water of the sedimentation tank contains impurities even if it is the supernatant water, and depending on the quality of the decomposition treatment, a bad odor may adversely affect the surrounding environment. There was also.

Further, if the activated sludge concentration in the aeration tank is maintained at a high concentration, the membrane surface of the separation membrane is likely to be contaminated with sludge as the treatment amount increases. Therefore, the membrane surface needs to be constantly cleaned, and complicated work such as cleaning at a high flow rate on the membrane surface and frequent backwashing is required, which is not satisfactory in terms of management and cost.

Further, when treated at such a high concentration, the activated sludge sometimes becomes viscous, which has been pointed out to be a great resistance to the separation membrane, so that the membrane separation can be stabilized. To do so, conversely, the BOD load in the aeration tank must be as low as possible. That is, in the activated sludge method, the purification capacity is fully exerted,
Moreover, in order to perform the membrane separation stably, the sludge sedimentation rate (SV%) is separately measured by the method shown in FIG. 10 to obtain the amount of activated sludge (MLSS), and then the concentration of activated sludge is adjusted (extraction of excess sludge). It was necessary to perform complicated concentration control, such as adjusting the amount) to maintain the activated sludge concentration at a predetermined value.

(Object of the Invention) The object of the present invention is to easily and easily control and manage the concentration of the activated sludge of the mixed liquid in the aeration tank in the process of purifying livestock wastewater and the like without complicated work. It is to be able to do it efficiently.

[0009]

[Means for Solving the Problems] The means of the present invention taken to achieve the above object are as follows. The first invention is a method for controlling the activated sludge concentration of a mixed liquid in an aeration tank provided with a separation membrane in a wastewater treatment process by the activated sludge method, wherein aeration in the aeration tank is performed every predetermined time. It is characterized in that after stopping the aeration, after leaving the aeration, the activated sludge is allowed to settle for a predetermined period of time, the settled activated sludge is removed leaving a predetermined amount, and the steps from aeration to removal of the activated sludge are repeated. A method for controlling the activated sludge concentration of the mixed liquid in the aeration tank.

In the second aspect of the present invention, a removing means for removing solid matter from the wastewater, a stirring tank for stirring the wastewater treated by the removing means and diffusing the residual solid matter into the wastewater, and the stirring. Separation by an initial settling tank that removes residual solids of wastewater sent from the tank, an aeration tank that performs aeration processing of the wastewater sent from the initial precipitation tank and solid-liquid separation processing by a separation membrane, and a separation membrane of the aeration tank Means for treating the treated water, a sludge storage tank for aerating the mixed sludge containing the excess sludge sent from the aeration tank and the precipitate sent from the initial settling tank, and the sludge sent from the sludge storage tank Sludge dewatering means for dewatering and stopping aeration in the aeration tank at every predetermined time, after stopping the aeration, letting it stand for a predetermined time to precipitate the activated sludge, and withdrawing a predetermined amount of the precipitated activated sludge from the aeration Extraction of activated sludge Characterized in that it comprises a means for controlling so as to repeat the previous step, a wastewater treatment system.

According to a third aspect of the invention, the initial settling tank is provided with means for preventing the flow of livestock hair and hair-like substances in livestock. is there.

In the fourth invention, the wastewater treatment according to the second or third invention is provided with means for controlling the pH value of the treatment liquid in the stirring tank or the aeration tank. System.

In the fifth invention, when the treated water is sucked through the separation membrane, suction is started with a weaker suction force than the rated value, and the suction force is adjusted continuously or stepwise to obtain a required value. The wastewater treatment system according to the second, third or fourth aspect of the invention is characterized in that the suction is performed intermittently by this control.

In the sixth aspect of the invention, the wastewater treatment system according to the second, third, fourth or fifth aspect of the invention is characterized in that each of the tanks is united individually or in combination. Is.

(Operation) The wastewater treatment system according to the present invention operates as follows. In the raw water of the waste water, most of the solid matter is removed by the removing means. The wastewater treated by the removing means is sent to the stirring tank. The wastewater is agitated and the residual solids diffuse into the wastewater. This wastewater is sent to the initial settling tank.

In the initial settling tank, the residual solid matter is precipitated and separated. Wastewater is sent from the initial settling tank to the aeration tank. The wastewater is aerated, and activated sludge settles on the bottom of the aeration tank. In the aeration tank, a solid-liquid separation process using a separation membrane is performed. The treated water separated by the separation membrane is subjected to a predetermined treatment such as discharge to the river.

In the aeration tank, aeration is stopped after a preset time has elapsed, and the aeration tank is allowed to stand for a predetermined time. This causes activated sludge to settle in the aeration tank.
The settled activated sludge is withdrawn, leaving only a preset amount. Then, the steps of aeration, stopping aeration, leaving still, and extracting activated sludge are repeated. In this way, the activated sludge concentration of the mixed liquid in the aeration tank is maintained at a concentration at which the purification performance is sufficiently exerted and the membrane separation can be performed stably. In addition, since the aeration is stopped for a predetermined time each time a predetermined amount of wastewater is processed, it becomes an intermittent aeration process, and a denitrification and dephosphorization effect can be expected.

On the other hand, the excess sludge sent from the aeration tank and the mixed sludge containing the precipitate sent from the initial settling tank are sent to the sludge storage tank for aeration treatment. The sludge generated by the aeration process is sent to the sludge dewatering means and dehydrated.

Those in which the initial settling tank is provided with a means for preventing the hair and hair-like substances of livestock (for example, thin straw waste, lint waste, and human hair) from circulating in the treatment process are aeration of wastewater. When solid-liquid separation is performed using a separation membrane such as a hollow fiber membrane after the treatment, it is possible to prevent clogging of the separation membrane due to entanglement of body hair and hair-like substances. Also, since it is not necessary to add a polymer coagulant to the wastewater to remove hair and hair-like substances,
The polymer coagulant does not adversely affect the separation membrane. Therefore,
It is possible to reduce the time and labor required for maintenance such as back washing and immersion washing of the separation membrane. Further, the life of the separation membrane can be extended, the frequency of replacement can be reduced, and the maintenance cost can be reduced.

In a device provided with means for controlling the pH value of the treatment liquid in the stirring tank or the aeration tank, the pH values of the treatment liquid in the stirring tank and the aeration tank are monitored and controlled by the control means. . As a result, p due to the progress of nitrification in the aeration tank
It is possible to prevent an adverse effect on the activated sludge due to the extreme decrease in H. Further, the pH value of the discharged water discharged from the aeration tank is always kept constant. Furthermore, since the set value of pH value in the aeration tank can be changed according to the state of activated sludge, p
The H value can be finely adjusted automatically, and the activated sludge can be easily maintained and managed.

When the treated water is sucked through the separation membrane, suction is started with a weaker suction force than the rated value, and the suction force is controlled continuously or stepwise to reach the required value. The suction by means of intermittent suction has the following effects. That is, at the start of the treatment in the aeration tank, the flow rate through the separation membrane is small and the flow velocity is slow. As a result, it is difficult for the solid matter to be sucked into the filtration hole, and even if it is adsorbed to the filtration hole, there is no acceleration, so the degree of adhesion is weak. Therefore, the solid matter adsorbed in the filtration holes is likely to be separated from the separation membrane by aeration when the suction is stopped later. Further, finally, it is necessary to secure a predetermined integrated flow rate, so it is necessary to strengthen the suction force continuously or stepwise, but by controlling the suction force in this way at the start of suction, The separation membrane is less likely to be clogged and the life is extended.

In the case where each tank is used individually or in combination to form a unit, it can be constructed by transporting to a site a prefabricated factory and assembling it. Therefore,
High degree of freedom in design, short construction period, and low construction cost. In addition, relocation and expansion after construction can be done relatively easily.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail based on the embodiments shown in the drawings. FIG. 1 is a flow chart of a wastewater treatment system according to the present invention, FIG. 2 is an explanatory view showing a part of the structure of a unit tank in which a stirring tank and an initial settling tank are combined, and FIG. 3 shows the structure of an aeration tank. (A) is the front view which notched one part, (b) is a top view.

Reference numeral A is a wastewater treatment system, and in the present embodiment, a case where it is installed in a ranch having a central milking facility will be described as an example. The wastewater treatment system A includes a raw water tank 1, a screen 2, a flow rate adjusting tank 3, a stirring tank 4, an initial settling tank 5, an aeration tank 6, a separation membrane separating device 7, a flow controlling device 8,
It is composed of a pH control device 9, a sludge storage tank 10, and a filter press 11. Each of the above tanks, that is, the raw water tank 1, the flow rate adjusting tank 3, the stirring tank 4, the initial settling tank 5, the aeration tank 6, and the sludge storage tank 10 are unit tanks made of metal that are unitized individually or in combination. .

The raw water tank 1 is a tank for collecting livestock wastewater such as manure of dairy cows and dairy cow wash water during milking and temporarily storing the raw water. The raw water in the raw water tank 1 is sent to the flow rate adjusting tank 3 by the water intake pump P1. A screen 2 as a removing means is provided in the middle of the flow path. The screen 2 separates and removes relatively large dust such as straw and grass dust from the raw water. It should be noted that the screen 2 is not limited in installation location as long as it can remove solids contained in the raw water sent to the stirring tank 4. A predetermined amount of waste water in the flow rate adjusting tank 3 is sent to the stirring tank 4 by the water intake pump P2. The stirring tank 4 is
It is formed integrally with the initial settling tank 5 to form a unit (see FIG. 2).

Here, the structure of the unit tank U in which the stirring tank 4 and the initial settling tank 5 are integrated will be described. The unit tank U is made of metal (material: stainless steel, iron, etc.) and is formed in a rectangular box shape as a whole. Half of the unit tank U is the initial settling tank 5, and about half of the remaining portion is the stirring tank 4. The stirring tank 4 and the initial settling tank 5 are substantially partitioned by a partition wall 50. In the lower part of the partition wall 50, there is provided a water guiding port 51 which is a water guiding part communicating with the current changing part 42 of the stirring tank 4 described later.

The stirring tank 4 comprises a stirring section 40 and a current transformation section 42. The stirring unit 40 includes a blade 412 by a motor 411.
A stirrer 41 having a structure for rotating is provided. The stirring section 40 and the current transformation section 42 are substantially partitioned by a partition wall 43. A through hole 44 is provided below the partition wall 43. The current changing portion 42 is provided with a current changing wall 45. The upstream portion of the current-changing wall 45 is formed lower than the upper end portion of the partition wall 43 so that the waste water overflows. The overflowed wastewater is further introduced into the initial settling tank 5 from the water guiding port 51 of the partition wall 50.

In the upper part of the end of the initial settling tank 5 away from the water inlet 51, one side 520 of a water suction pipe 52 which is a water suction portion is horizontally provided. A plurality of water withdrawal ports 53 are provided on the upper side of the part of the water withdrawal pipe 52 located in the initial settling tank 5. The other side 521 of the water withdrawal pipe 52
Are extended to the aeration tank 6. In the initial settling tank 5,
A scum stopper 54 is provided near the water pipe 52. The upper end of the scum stopper 54 is set to be higher than the waste water surface, and the lower end is submerged in the waste water. Therefore, the distribution of scum floating on the surface of the wastewater can be prevented.

On the upper side of the initial settling tank 5, a plurality of inclined plates 55, which are means for preventing hair, are provided in parallel. The inclined plates 55 are provided at intervals such that the hair of livestock (dairy cows) is caught. The inclination angle of each inclined plate 55 is set to 45 ° in the present embodiment, but is not limited thereto. Further, the interval between the inclined plates 55 is 40 in this embodiment.
Although it is set to mm, it is not limited to this and can be set as appropriate.

In the present embodiment, the inclined plate 55 is used as the hair blocking means, but the present invention is not limited to this, and a net body is provided below the inclined plates provided at a slightly wide interval. , Those having other structures can also be adopted. The flow rate of the waste water flowing from the bottom to the top in the initial settling tank 5 is adjusted so as not to disturb the precipitation of solid matter. The wastewater treated in the initial settling tank 5 is sent to the aeration tank 6 by the feed pump P3.

The aeration tank 6 is a device for decomposing waste water from which body hair, fine straw waste, solid matter and the like have been removed by aerobic microorganisms. Note that, in FIG. 3, the aeration device 64 and the separation membrane separation device 7 provided inside are not shown. The aeration tank 6 is made of corrosion-resistant steel, but is made of stainless steel or FRP (fiber-reinfo).
Other materials such as corrosion resistant plastics such as rced plastics) can also be used. The aeration tank 6 has a body portion 60.
Is formed in a cylindrical shape. On the upper part of the aeration tank 6, a removable lid 61 is provided. A ladder 62 is provided on the side surface of the aeration tank 6.

A surplus sludge discharge port 65 is provided at a substantially central portion of the side surface of the aeration tank 6. This excess sludge discharge port 6
The installation height H of No. 5 was determined by calculating the remaining amount of the activated sludge precipitated based on the activated sludge concentration estimated from the sludge sedimentation rate (SV%) previously measured by the method shown in FIG. There is. A water conduit 67 is connected to the excess sludge discharge port 65, and an excess sludge discharge valve 66 is installed in the middle thereof. In addition, an excess sludge drawing pump may be installed in the middle of the water pipe 67, if necessary.

A hatch 63 for maintenance is provided on the lower part of the side surface of the aeration tank 6. An aeration device 64 for feeding air is arranged at the inner bottom of the aeration tank 6, and a separation membrane separation device 7 is provided above it. The separation membrane separation device 7 is a device that separates only clean water from the activated sludge in the aeration tank 6 through a hollow fiber membrane that is a separation membrane.
The suction of the treated water is performed by the feed pump P4 that constitutes the flow rate control device 8. The flow rate control device 8 includes a feed pump P4, a flow meter 80, a flow rate controller 81, and an opening adjustment valve 82.

Reference numeral 9 is a pH controller. The pH control device 9 includes a controller 90, pH sensors 91 and 92, and an acid / alkali supply device 93. pH sensor 9
1 is provided in the current changing section 42 of the stirring tank 4 and has a pH of
The sensor 92 is provided in the aeration tank 6. The pH control device 9 agitates an acidic liquid or an alkaline liquid from the acid-alkali supply device 93 based on the pH values of the activated sludge in the stirring tank 4 and the aeration tank 6 detected by the pH sensors 91 and 92. By injecting into the tank 4, the pH of the treatment liquid
Manage values. In addition, in the stirring tank 4, the pH value of the waste water is constantly stirred by the stirring device 41 in order to make the pH value of the waste water uniform, and the pH value of the waste water is adjusted to 5 to 7 by the pH control device 9.

Excess sludge discharged from the surplus sludge discharge port 65 provided at the substantially central portion of the side surface of the aeration tank 6 leaving the remaining amount of the settled activated sludge, and the settling from the bottom of the initial settling tank 5. The sludge is mixed by the sludge storage tank 10 and is temporarily stored. An aeration device 100 is provided at the bottom of the sludge storage tank 10, and aeration and agitation are performed every time both sludges are taken in. The sludge in the sludge storage tank 10 is fed by the feed pump P5.
Is sent to the filter press 11 which is a sludge dewatering means.

Then, the sludge is dehydrated by the filter press 11 and separated and discharged as a dehydrated cake having a water content of about 85%. The separated water is returned to the flow rate adjusting tank 3 or the raw water tank 1. In this embodiment, the filter press is used for dewatering the sludge, but the present invention is not limited to this, and various dewatering means such as a belt press and a centrifugal dewatering machine may be used.

(Operation) FIG. 4 is a graph showing the relationship between the operating activated sludge concentration and the excess sludge withdrawal amount in the treatment apparatus according to the present invention, FIG. 5 is the suction pattern diagram of the separation membrane, and FIG. 6 is the suction control pattern of the separation membrane. It is a figure. The operation of the wastewater treatment system A according to the present invention will be described with reference to FIGS. 1 to 6.

(1) Raw water of livestock wastewater is sent to the raw water tank 1 and temporarily stored. (2) Raw water is sent to the screen 2 and most of the solid matter is removed, but some fine fibrous things such as body hair pass through. (3) The wastewater treated by the screen 2 is temporarily stored in the flow rate adjusting tank 3.

(4) Waste water in the flow rate adjusting tank 3 is sent to the stirring tank 4. The waste water is stirred in the stirring tank 4, and the residual solid matter that has passed through the screen 2 diffuses into the waste water. This wastewater is sent to the initial settling tank 5 through the current transformer 42. (5) In the initial settling tank 5, wastewater is introduced from the water inlet 51 at the bottom of the tank. The waste water is drawn from the water drawing port 53 of the water drawing pipe 52 at the upper part of the tank. The flow rate of the waste water in the initial settling tank 5 is adjusted to a level that does not hinder the precipitation of solid matter.

(6) Due to the flow of the wastewater, the hair contained in the wastewater is light, and therefore, the hair tends to rise to the side of the water catchment pipe 52 at the upper part of the tank together with the wastewater, but the hair is caught on the lower part of the inclined plate 55 provided side by side. Furthermore, the trapped body hairs are laminated in a net-like shape, and act like a filter. As a result, the hair is prevented from being sent to the aeration tank 6 in the next step, and the hair of the dairy cow, thin straw waste, thread waste, human hair, etc. are almost removed, and then the separation membrane separation device 7 is used. Separation processing can be performed by.

As a result, it is possible to prevent the separation membrane from being clogged due to the entanglement of fibrous substances such as body hair. In addition, the solid matter contained in the wastewater in the initial settling tank 5 is efficiently settled because the settling area is wide due to the large number of inclined plates 55 arranged in parallel. In this way, the initial settling tank 5
Can further remove residual solids from the wastewater.
Furthermore, since it is not necessary to add a polymer coagulant for removing body hair to the wastewater, the polymer coagulant does not adversely affect the separation membrane.

(7) Waste water is sent from the initial settling tank 5 to the aeration tank 6. Every time the wastewater is aerated in the aeration tank 6 for a predetermined treatment time (for example, about 24 hours), if the aeration is stopped for a predetermined stop time and the aeration tank 6 is allowed to stand, the activated sludge settles on the bottom of the aeration tank 6. While the aeration is stopped, the entire system is also stopped, but a part of the system may be operated. The time for stopping this aeration is 30 minutes in this embodiment. The boundary position between the settled activated sludge and the supernatant water is SV% measured by the method shown in FIG.
Is almost the same as When the excess sludge is discharged by opening the excess sludge discharge valve 66 from the excess sludge discharge port 65 installed by this SV%, the residual amount of activated sludge is always a constant amount. The excess sludge is discharged from the aeration tank 6 by an excess sludge drawing pump (not shown) installed in the middle of the water conduit 67, or an underwater pump (not shown) hung up to the installation height H of the excess sludge discharge port 65. It may be discharged by such means.

(8) Close the excess sludge discharge valve 66,
When the feed pump P3 is operated to supply the wastewater raw water (the BOD of the wastewater becomes almost constant when the type of livestock is fixed), the activated sludge (MLSS) concentration in the aeration tank 6 is always a constant concentration ( (Approximately 15,000 mg / L in the present inventors' test)
Maintained at. The pH value of the waste water in the stirring tank 4 and the aeration tank 6 is monitored and controlled by the pH controller 9. As a result, it is possible to prevent the activated sludge from being adversely affected by the extreme decrease in pH due to the progress of nitrification in the aeration tank 6. Further, the pH of the discharged water discharged from the aeration tank 6 is always kept constant. Furthermore, since the pH set value of the aeration tank 6 can be changed according to the state of the activated sludge, the pH can be automatically finely adjusted, and the activated sludge can be easily maintained and managed.

(9) In the aeration tank 6, solid-liquid separation processing is performed by the separation membrane separation device 7. Then, when sucking the treated water through the separation membrane, the following flow rate control is performed. Please refer to FIG. 5 and FIG.

A) The intermittent suction operation is performed in a pattern in which treated water is sucked from the separation membrane of the separation membrane separation device 7 installed in the aeration tank 6 for a predetermined time and stopped for a predetermined time (see FIG. 5). A) During suction for a predetermined time, the flow rate is measured by the flow meter 80, and the electric opening adjustment valve 8 is based on the flow rate value for each unit time.
The opening degree 2 is adjusted, and the flow rate controller 81 controls the flow rate so that the separation membrane is less likely to be blocked. (See Figure 6)

C) The opening adjustment valve 8 while reading the flow meter 80
2 is adjusted, the opening of the electric valve that provides the rated flow rate is read, and the valve opening at the rated flow rate is determined. D) At the start of suction, start at a predetermined low flow rate (a valve opening degree of a predetermined low flow rate), and after a predetermined unit time, open the opening adjustment valve 82 to a predetermined rated opening degree so that the predetermined rated flow rate is reached (rated (Valve opening at flow rate) Aspirate.

E) The flow rate per unit time is constantly detected, and when the suction flow rate gradually decreases due to clogging of the separation membrane and falls below a predetermined rated flow rate, the opening is adjusted so as to reach the predetermined rated flow rate. Widen the opening of the valve 82. F) Such control operation is continued for a predetermined suction time. After a predetermined suction time, it stops for a predetermined stop time. (When suction is stopped, the opening adjustment valve 82 is fully closed)

(G) The next suction start flow rate is set to be slightly larger than the first suction start flow rate, and suction is started. If the flow rate in the next unit time is less than the predetermined rated flow rate, the opening degree of the opening degree adjusting valve 82 is calculated from the deviation amount, and the opening degree adjusting valve 82 is opened by the calculated value. (H) If the flow rate exceeds the rated flow rate for some reason during suction (Fig. 6 (e)), the opening degree of the opening adjustment valve 82 is calculated from the deviation amount, and the valve is opened by the calculated value. The degree adjusting valve 82 is closed. C) The suction control is repeated as described above, and the integrated flow rate is continuously controlled so as to reach a predetermined rated flow rate.

In this way, since suction through the separation membrane is started with a suction force weaker than the rated value, the flow rate is small and the flow rate is slow at the start of suction. Therefore, the solid matter is difficult to be sucked, and even if the filtration hole is closed, the solid matter is not accelerated, so that the adhesion is weak and the solid matter is easily aerated when the suction is stopped later. That is, the suction control of the treated water through the separation membrane is an intermittent operation in which it is stopped for a predetermined time after suction for a predetermined time, and the flow meter 80 constantly measures the flow rate during the predetermined suction time, and the opening degree is adjusted based on the value. Since the opening degree of the valve 82 is adjusted to control the flow rate so that the separation membrane is less likely to be clogged, the suction pressure of the separation membrane is not increased even after a long-term operation (there is no membrane clogging). ), The stable suction characteristic can be maintained.

Since it is necessary to secure a predetermined integrated flow rate in the end, it is necessary to increase the suction force continuously or stepwise. However, by initially controlling the suction force in this way, , The separation membrane is less likely to be clogged and the life is extended.

(10) The treated water separated by a separation membrane such as a hollow fiber membrane is subjected to a predetermined treatment such as discharge to a river. (11) On the other hand, the wastewater containing the precipitate sent from the initial settling tank 5 is sent to the sludge storage tank 10. This wastewater is aerated in the sludge storage tank 10. In this way, the initial settling tank 5
The settling wastewater discharged from the aeration tank 6 is mixed with the excess sludge discharged from the aeration tank 6 in the sludge storage tank 10 and is aerated.
It is possible to remove the strong odor of the wastewater discharged from the initial settling tank 5.

(12) Surplus sludge discharge port 65 after aeration treatment
The excess sludge drawn out from is sent to the filter press 11 through the sludge storage tank 10 and is pressed and dehydrated. The water that has been dewatered from the excess activated sludge is returned to the flow rate adjusting tank 3 or the raw water tank 1. Water squeezing BOD is also 30p
It can be lowered to pm or less and can be discharged directly to rivers. Further, by returning the squeezed water to the flow rate adjusting tank 3 or the raw water tank 1, the effect of diluting the waste water close to the raw water is obtained, and the efficiency of the purification treatment is improved. The SS component of the squeezed water in the dehydration treatment is 10 ppm or less, and the SS and BOD of the precipitation wastewater discharged from the initial precipitation tank 5 are both 6000 ppm or more.

The results of the test conducted by the present inventor are shown in "Table 1". That is, as the operating activated sludge concentration of the aeration tank 6 is increased, the average activated sludge concentration of the upper 20% of the aeration tank after 30 minutes of stopping is also increased. "Table 2"
Is the amount of extracted activated sludge (MLSS) when the volume of the aeration tank 6 is 15 m ³ based on the test results of "Table 1".
Amount) is a calculated value. FIG. 4 is a graph showing the state of the amount of activated sludge drawn out. In addition, the record of the activated sludge concentration for each month in the long-term operation is 14000 to 18000 mg / L as shown in "Table 3", which is maintained at a substantially constant concentration.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

In this apparatus, each of the above-mentioned tanks, that is, the raw water tank 1, the flow rate adjusting tank 3, the stirring tank 4, the initial settling tank 5, the aeration tank 6, and the sludge storage tank 10 are united individually or in combination. Since it is a unit tank made of metal, it can be constructed by transporting what was made in the factory in advance to the site. Therefore, the degree of freedom in design is high, the construction period is short, and the construction cost can be low. In addition, relocation and expansion after construction can be done relatively easily.

It should be noted that the terms and expressions used in the present specification are merely for the purpose of explanation and are not limiting, and terms equivalent to the above terms and expressions and expressions are not excluded. The present invention is not limited to the illustrated embodiment, and various modifications can be made within the scope of the technical idea.

[0059]

The present invention has the above-mentioned structure and has the following effects. (A) According to the present invention, in the aeration tank, aeration is stopped after a preset time has elapsed, the aeration tank is allowed to stand for a predetermined time, and the settled activated sludge is removed leaving a preset amount. Since this is repeated, the activated sludge concentration of the mixed liquid in the aeration tank can be maintained at a concentration that allows sufficient purification performance and stable membrane separation by simple control. can do. Further, since this control can be automatically controlled, the activated sludge concentration can be easily managed.

(B) Wastewater Each time a predetermined amount of raw water is treated,
Since the aeration is stopped for a predetermined period of time, intermittent aeration processing is performed, and the effect of denitrification and dephosphorization can be expected.

(C) The initial settling tank is equipped with a means for preventing the hair and hair-like substances of livestock from flowing in the treatment step, after the waste water is aerated, for example, a separation membrane such as a hollow fiber membrane. When solid-liquid separation is performed by using, it is possible to prevent clogging of the separation membrane due to entanglement of body hair and body hair-like substances. Further, since it is not necessary to add a polymer coagulant or the like to the wastewater in order to remove body hair and hair-like substances, the polymer coagulant does not adversely affect the separation membrane. Therefore, it is possible to reduce the time and labor required for maintenance such as back washing and immersion washing of the separation membrane. Further, the life of the separation membrane can be extended, the frequency of replacement can be reduced, and the maintenance cost can be reduced.

(D) In the case where the means for controlling the pH value of the treatment liquid in the stirring tank or the aeration tank is provided, the pH values of the treatment liquid in the stirring tank and the aeration tank are monitored and controlled by the control means. Has been done. As a result, it is possible to prevent the activated sludge from being adversely affected by the extreme decrease in pH due to the progress of nitrification in the aeration tank. Further, the pH value of the discharged water discharged from the aeration tank is always kept constant. Furthermore, since the set value of the pH value in the aeration tank can be changed according to the state of the activated sludge, the pH value can be automatically finely adjusted, and the activated sludge can be easily maintained and managed.

(E) When the treated water is sucked through the separation membrane, suction is started with a weaker suction force than the rated value, and the suction force is controlled continuously or stepwise to reach the required value. The suction which is intermittently performed by this control has the following action. That is, at the start of the treatment in the aeration tank, the flow rate through the separation membrane is small and the flow velocity is slow. As a result, it is difficult for the solid matter to be sucked into the filtration hole, and even if it is adsorbed to the filtration hole, there is no acceleration, so the degree of adhesion is weak. Therefore, the solid matter adsorbed in the filtration holes is likely to be separated from the separation membrane by aeration when the suction is stopped later. Further, finally, it is necessary to secure a predetermined integrated flow rate, so it is necessary to strengthen the suction force continuously or stepwise, but by controlling the suction force in this way at the start of suction, The separation membrane is less likely to be clogged and the life is extended.

(F) In the case where each tank is used individually or in combination to form a unit, it can be constructed by transporting to a site a prefabricated one and assembling it. Therefore, the degree of freedom in design is high, the construction period is short, and the construction cost can be low. In addition, relocation and expansion after construction can be done relatively easily.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of a livestock wastewater treatment system according to the present invention.

FIG. 2 is a partially transparent explanatory view showing the structure of a unit tank in which a stirring tank and an initial settling tank are combined.

3A and 3B show a structure of an aeration tank, where FIG. 3A is a partially cutaway front view and FIG. 3B is a plan view.

FIG. 4 is a graph showing the relationship between operating activated sludge concentration and excess sludge withdrawal amount in the treatment apparatus according to the present invention.

FIG. 5 is a suction pattern diagram of a separation membrane.

FIG. 6 is a suction control pattern diagram of a separation membrane.

FIG. 7 is an explanatory diagram of a batch activated sludge method.

FIG. 8 is a time chart of the batch activated sludge method.

FIG. 9 is a flowchart of a continuous activated sludge method.

FIG. 10 is an explanatory diagram showing a method for measuring an SV value, which is carried out by the activated sludge method.

[Explanation of symbols]

A Livestock wastewater treatment system 1 raw water P1 water intake pump 2 screen 3 Flow rate adjustment tank P2 intake pump U unit tank 4 stirring tanks 40 Stirrer 41 Stirrer 411 motor 412 feathers 42 Current transformer 43 partitions 44 way 45 Current transformation wall 5 Initial settling tank 50 partitions 51 Headrace 52 Water pipe 53 Inlet 54 scum stopper 55 inclined plate P3 feeding pump 6 aeration tank 60 torso 61 Lid 62 ladder 63 hatch 64 Aeration device 65 Excess sludge discharge port H Surplus sludge discharge port installation height 66 Excess sludge discharge valve 67 water conduit 7 Separation membrane separation device P4 feeding pump 8 Flow control device 80 flow meter 81 Flow controller 82 Opening control valve 9 pH controller 90 controller 91, 92 pH sensor 93 Acid-alkali feeder 10 Sludge storage tank 100 Aeration device P5 feeding pump 11 Filter press

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4D006 GA06 GA07 HA01 JA53A                       JA65A KA12 KC14 KE03Q                       KE14Q KE21Q KE24Q KE28Q                       MB02 PA01 PB08 PB24 PC64                 4D028 AA08 BC03 BC17 BC18 BD06                       BD16 BD17 BE08 CB08 CC05                       CD01 CD02                 4D059 AA05 BE08 BE16 BE19 BE51

Claims (6)

[Claims] 1. A method for controlling the activated sludge concentration of a mixed liquid in an aeration tank equipped with a separation membrane in a wastewater treatment step by the activated sludge method, which comprises stopping aeration in the aeration tank at predetermined intervals, After the aeration is stopped, the activated sludge is allowed to settle for a predetermined period of time, the activated sludge that has settled is removed with a specified amount left, and the process from aeration to removal of the activated sludge is repeated. Method for controlling the concentration of activated sludge in a mixed solution of. 2. A removing means for removing solid matter from the wastewater, a stirring tank for stirring the wastewater treated by the removing means and diffusing residual solid matter into the wastewater, and a residual wastewater sent from the stirring tank. The initial settling tank that removes solids, the aeration tank that aerates the waste water sent from the initial settling tank and the solid-liquid separation process using a separation membrane, and the treated water that is separated by the separation membrane of the aeration tank Means for performing, a sludge storage tank for aerating the mixed sludge containing the excess sludge sent from the aeration tank and the sediment sent from the initial settling tank, and a sludge dewatering means for dehydrating the sludge sent from the sludge storage tank , Aeration in the aeration tank is stopped every predetermined time, after the aeration is stopped, the activated sludge is allowed to settle for a predetermined time, and the settled activated sludge is removed leaving a predetermined amount, from aeration to removal of the activated sludge. Repeat Characterized in that it comprises means for controlling to return the waste water treatment system. 3. The wastewater treatment system according to claim 2, wherein the initial settling tank is provided with means for blocking the flow of the hair and the hair-like substance of the livestock. 4. The pH of the treatment liquid in the stirring tank or the aeration tank
The wastewater treatment system according to claim 2 or 3, further comprising means for controlling a value. 5. When sucking the treated water through the separation membrane,
The suction is started with a weaker suction force than the rated value, and the suction force is controlled continuously or stepwise to reach the required value, and suction by this control is performed intermittently. The wastewater treatment system according to claim 2, 3 or 4, which is characterized. 6. The wastewater treatment system according to claim 2, 3, 4 or 5, wherein each of the tanks is united individually or in combination.