JPH05192688A - Anaerobic-aerobic activated sludge treating device using buffer tank - Google Patents

Abstract

PURPOSE:To provide the anaerobic-aerobic activated sludge treating device which removes the org. matter and nitrogen in waste water with high efficiency and takes the remedy for the load fluctuation arising from an increase in the inflow rate of the waste water into consideration as well. CONSTITUTION:The buffer tank 11 is provided in combination with an anaeration tank 2 and the waste water 9 is shunted to the buffer tank 11 and the anaeration tank 2 of the anaerobic-aerobic activated sludge treating device including a stage for denitrifying the waste water, such as sewage, by denitrifying bacteria in the anaeration tank 2, a stage for nitrifying ammonia nitrogen by nitrifying bacteria in an aeration tank 3, a stage for separating solid from the liquid in a final settling basin 4 and a stage for accelerating a denitrifying reaction by returning a part of the nitrifying liquid in the aeration tank 3 to the anaeration tank 2. On the other hand, an oxygen utilizing speedometer 18 and an oxygen utilizing speedometer 19 subtracting the oxygen utilizing speed by nitrification are installed in the aeration tank 3. A control means 14 which judges the progressing condition of the nitrification reaction of the aeration tank 3 by these two speedometers 18, 19 and determines the shunting ratio of the waste water to the buffer tank 11 and the anaeration tank 2 from the results of the judgment is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to anaerobic use of a buffer tank.
The present invention relates to an aerobic activated sludge treatment device, and more particularly to a device that takes into consideration measures against load fluctuations.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed for efficiently removing organic substances in wastewater such as sewage and removing nitrogen and phosphorus which are considered to be the causative substances of eutrophication. This eutrophication refers to an increase in the concentration of nutrient salts such as N and 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.

Physicochemical and biological methods have been proposed as means for removing nitrogen and phosphorus, which are the causative substances of eutrophication, from wastewater, but the physicochemical method is costly. The current situation is that it has not spread. For example, a phosphorus removal method that has been put into practical use as a physicochemical method includes a coagulation precipitation method and a crystallization method, but this method has drawbacks in terms of cost and maintenance.

On the other hand, an anaerobic-aerobic activated sludge method has attracted attention as a method for biologically removing nitrogen and phosphorus simultaneously as a modification of the conventional standard activated sludge method. (For example, Water Pollution Research, Volume 12, No. 441-448, 1989.
See. ) This anaerobic-aerobic activated sludge method is, for example, as shown in FIG.
It is divided into an anaerobic tank 2 in which O is abbreviated) and an aerobic tank 3 in which DO is present, and this anaerobic tank 2 denitrifies the inflowing wastewater 9 by denitrifying bacteria in activated sludge under anoxic conditions. Then, by supplying air from the blower 7 to the air diffuser 6 arranged inside the aerobic tank 3, oxidative decomposition of organic matter by activated sludge and nitrification of ammonia by nitrifying bacteria in the presence of oxygen by aeration. To do. Next, the nitrification solution at the end of the aerobic tank 3 is fed into the anaerobic tank 2 using the nitrification solution circulation pump 5, whereby the denitrification effect of the anaerobic tank 2 is promoted.

The above-mentioned denitrifying bacteria refer to bacteria that reduce 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 wastewater is released in the anaerobic tank 2 and taken into the activated sludge in the aerobic tank 3 to be removed. The supernatant 8 of the final settling basin 4 is discharged after passing through a disinfection tank or the like not shown in the figure, and a part of the sludge settled in the final settling basin 4 is treated as excess sludge in an excess sludge treatment device not shown in the figure. It is sent and processed.

By using such an anaerobic-aerobic activated sludge treatment device, an effect comparable to the organic substance removal effect achieved by the usual 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.

[0007]

However, in the means for removing organic matter and nitrogen in wastewater using such a conventional anaerobic-aerobic activated sludge treatment device, the control of the anaerobic-aerobic activated sludge treatment device is performed. It cannot be said that it has been established, and there is a problem that measures against load fluctuation are not sufficient.

That is, in order to efficiently remove nitrogen by the anaerobic-aerobic activated sludge treatment device, 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 affected by the nitrification step, it is necessary that the nitrification step is performed well in order to perform good nitrogen removal. In addition, when the amount of wastewater flowing into the biological reaction tank 1 suddenly increases,
When the substrate concentration of wastewater rises, the load on the bioreactor 1 increases sharply, and accordingly the wastewater flows out without being completely treated, or the sludge expands due to the high load (bulking). ), There is a fear that the sludge outflow phenomenon from the final settling tank 1 will occur.

Under the present circumstances, no drastic measures have been taken to cope with such load fluctuations. In addition to the establishment of the operating conditions of the anaerobic tank 2 and the aerobic tank 3, there are problems in wastewater treatment. Is becoming

The present invention has been made in view of the above circumstances, and provides an anaerobic-aerobic activated sludge treatment device that facilitates the above-mentioned denitrification process and nitrification process and also takes into consideration measures against load fluctuations. The purpose is to do.

[0011]

In order to achieve the above object, the present invention provides a step of denitrifying wastewater such as sewage in an anaerobic tank with denitrifying bacteria, and ammonia nitrogen with nitrifying bacteria in an aerobic tank. Anaerobic process, which includes the step of performing nitrification of the solution, the step of solid-liquid separation in the settling tank, and the step of returning the nitrification solution in the aerobic tank and part of the sludge in the settling tank to the anaerobic tank to promote the denitrification reaction -In the aerobic activated sludge treatment device, a buffer tank is provided side by side with the anaerobic tank to divide wastewater into the buffer tank and the anaerobic tank, while the aerobic tank is provided with an oxygen utilization rate meter and an oxygen utilization rate by nitrification. With the oxygen utilization rate meter subtracted, the progress of the nitrification reaction of the aerobic tank along with the progress of anaerobic-aerobic activated sludge treatment is judged by both speed meters, and the judgment results for the buffer tank and the anaerobic tank Anaerobic-aerobic activated sludge with control means for determining the split ratio of wastewater Are you on the configuration of the management apparatus.

[0012]

[Operation] According to the anaerobic-aerobic activated sludge treatment device,
The wastewater is divided into a buffer tank and an anaerobic tank, the wastewater flowing into the anaerobic tank is denitrified based on the action of denitrifying bacteria, and aeration is performed in the aerobic tank. Nitrification is performed. The discharged liquid from the aerobic tank flows into the precipitation tank for solid-liquid separation, and the supernatant of the precipitation tank is discharged. or,
The wastewater flowing into the buffer tank aerobically acts on the microorganisms contained in the wastewater and naturally occurring microorganisms by the air emitted from the air diffuser, and the organic matter in the wastewater is based on the action of these microorganisms. Is decomposed to some extent and then introduced into the aerobic tank.

Then, the progress of the nitrification reaction in the aerobic tank is judged based on the data obtained from the oxygen utilization speed meter attached to the aerobic tank and the oxygen utilization speed meter subtracting the oxygen utilization rate from nitrification. Based on the result, the control means determines the diversion ratio of the waste water to the buffer tank and the anaerobic tank. Along with this, the denitrification process and the nitrification process are facilitated, and the presence of the buffer tank reduces the load on the activated sludge and prevents bulking.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an anaerobic-aerobic activated sludge treatment apparatus using a buffer tank according to the present invention will be described below with reference to FIG. Will be described in detail.

Reference numeral 11 in FIG. 1 denotes a buffer tank, and an air diffuser 12 is disposed inside the buffer tank 11.
The air is supplied from the blower 7 provided outside. 2 is an anaerobic tank without dissolved oxygen (DO), 3 is D
It is an aerobic tank in which O exists, and diffusers 6, 6, 6 are arranged inside the aerobic tank 3, and air is supplied from the blower 7.

4 is a final settling tank as a settling tank, 5 is a nitrification solution circulation pump for returning a part of the nitrification solution in the aerobic tank 3 to the anaerobic tank 2, and 13 is sludge settling in the final settling tank 4. It is a sludge return pump that returns a part to the anaerobic tank 2.

Reference numeral 14 is a controller as a control means, and the inflow amount data detected by a flowmeter 15 disposed in the middle of the inflow conduit of wastewater 9 such as sewage is the controller 14 described above.
Has been entered in. Further, a pipe line 16 is branched from a branch point a of the inflow pipe line of the wastewater 9, a flow rate adjusting valve 17 is arranged in the middle of the pipe line 16, and the other end portion of the pipe line 16 has an anaerobic tank 2 Are connected to.

To summarize the above construction, the buffer tank 11 and the anaerobic tank 2 are provided side by side, and the waste water 9 is divided into the buffer tank 11 and the anaerobic tank 2 from the branch point a. This diversion ratio is determined by appropriately adjusting the opening degree of the flow rate adjusting valve 17 arranged in the conduit 16 by the output signal from the controller 14.

Further, the aerobic tank 3 has an oxygen utilization speed meter 18
And (r _r meter), the oxygen utilization rate meter 19 minus the oxygen utilization rate by nitrification (ATU-r _r gauge) is attached, the detected signal of each speedometer 18 and 19 are input to the controller 14.

The operation of this embodiment will be described below. First, the basic operation will be described. After the flow rate of the waste water 9 is detected by the flow meter 15, a part of the waste water is branched into the pipe line 16 at the branch point a. Then, the wastewater that has flowed into the anaerobic tank 2 from the pipe 16 via the flow rate adjusting valve 17 is converted into N _{2 of} NO ₃ -N and NO ₂ -N ions based on the action of the denitrifying bacteria in the anaerobic tank 2. Reduction, ie denitrification, takes place. At this time, phosphorus in the wastewater is released in the anaerobic tank 2, and in the aerobic tank 3 in the next stage, the amount larger than that released in the preceding stage is taken in and removed by the activated sludge.

On the other hand, the wastewater 9 that has flowed into the buffer tank 11 is aerobically acted upon by the air diffused by the air diffuser 12 so that the microorganisms and the naturally occurring microorganisms originally contained in the wastewater are aerated. Organic matter in wastewater is decomposed based on the action of microorganisms. Since the nitrification solution from the aerobic tank 3 and the sludge in the final settling tank 4 are not recirculated to the buffer tank 11, the activated sludge is not exposed to a high-concentration substrate and the bulking is suppressed. The effect is obtained.

Next, the water to be treated in the buffer tank 11 is supplied to the conduit 2
1 is sent to the aerobic tank 3 together with the water to be treated in the anaerobic tank 2 through the 1, and aeration is performed by the aeration from the diffuser pipe 6 as the blower 7 is driven. In the presence of oxygen based on the action of nitrifying bacteria. And ammoniacal nitrogen NH ₄ --N NO _3-
Oxidation to N, that is, nitrification is performed. Therefore, a nitrification solution containing nitrate nitrogen (NO ₃ —N) is obtained in the aerobic tank 3. A part of the nitrification liquid in the aerobic tank 3 is returned to the anaerobic tank 2 by the nitrification liquid circulation pump 5, and denitrification is performed in the anaerobic tank 2.

The remaining water to be treated in the aerobic tank 3 is transferred to the final settling tank 4 for solid-liquid separation, and a part of the sludge settled in the final settling tank 4 is returned to the anaerobic tank 2 by the sludge return pump 13. As a result, MLSS (mixed liqu
or suspended solid) can be increased. The remaining sludge is sent as surplus sludge to a surplus sludge treatment device (not shown) for treatment, and the supernatant 8 of the final settling tank 4 is discharged as treated water.

During such an operation, an oxygen utilization speed meter 18 (r _r meter) attached to the aerobic tank 3 as an index and an oxygen utilization speed meter 19 obtained by subtracting the oxygen utilization speed due to nitrification.
Data obtained from (ATU-r _r total) are input to the controller 14 as control means, the controller 14
The progress of the nitrification reaction is judged by. Based on this determination result, the opening degree of the flow rate adjusting valve 17 is automatically controlled by the output signal of the controller 14, and the inflow amount of the waste water flowing into the anaerobic tank 2 via the pipe line 16 is determined.

That is, the progress of the nitrification reaction in the aerobic tank 3 is determined by the oxygen utilization rate respir.
cation, hereinafter abbreviated as r _r ) and a nitrification inhibitor N-allylthiourea (chemical formula C ₄ H ₈ N ₂ S, hereinafter abbreviated as ATU) were added to measure the oxygen utilization rate (hereinafter ATU-
(abbreviated as r _r ), in other words, it can be obtained from the difference between the oxygen utilization rate obtained by subtracting the oxygen utilization rate due to nitrification.

[0026] When the difference between the between [N], [N] = [r _r] - a [ATU-r _r] .......... (1).

The oxygen utilization rate r _r is the oxygen concentration used per unit time (mgO ₂ / l · hr), and when the aeration of the ordinary aerobic tank 3 becomes excessive, the sludge is fragmented and the aeration is insufficient. If so, phenomena such as organic matter remaining in the treated water and spoilage of sewage occur, and the purification performance deteriorates. Therefore, in order to optimally manage the activated sludge, it is necessary to supply oxygen at the oxygen utilization rate of the activated sludge or at a rate higher than that, which is used as an index of aeration.

An increase or decrease in the nitrification rate of the aerobic tank 3 can be detected by the value of the above [N]. When the nitrification rate is high, the flow rate of the nitrification solution from the aerobic tank 3 to the anaerobic tank 2 based on the action of the nitrification solution circulation pump 5 is increased, and as a result, it is necessary for the denitrification reaction in the anaerobic tank 2. Since the number of hydrogen donors increases, the opening degree of the flow rate adjusting valve 17 is increased to increase the flow rate of the waste water flowing into the anaerobic tank 2 via the conduit 16.

When the nitrification rate of the aerobic tank 3 is small, the hydrogen donor required for the denitrification reaction in the anaerobic tank 2 is also small. In this case, the opening of the flow rate adjusting valve 17 is small. Then, the flow rate of the wastewater flowing into the anaerobic tank 2 is reduced.

As described above, in this embodiment, since the wastewater 9 is divided into the buffer tank 11 and the anaerobic tank 2 in accordance with the nitrification rate of the aerobic tank 3, the denitrification process and the nitrification process are smoothly performed. The presence of the buffer tank 11 reduces the load on the activated sludge, and the activated sludge does not come into direct contact with the high-concentration substrate, so that bulking is prevented.

[0031]

As described in detail above, according to the anaerobic-aerobic activated sludge treatment apparatus using the buffer tank according to the present invention, the wastewater is divided into the anaerobic tank and the buffer tank and attached to the aerobic tank. The progress status of the nitrification reaction in the aerobic tank is judged based on the data obtained from the oxygen utilization rate meter that has been used and the oxygen utilization rate meter from which the oxygen utilization rate from nitrification is subtracted, and the diversion ratio of the wastewater is determined based on this determination result. Since the decision was made, the denitrification process and the nitrification process can be facilitated, and even if the inflow of wastewater suddenly increases or the substrate concentration of wastewater rises, the anaerobic tank and aerobic tank Therefore, it is possible to prevent the wastewater from flowing out untreated and the sludge outflow due to the expansion of the sludge (bulking) caused by the high load.

Therefore, according to the present invention, the anaerobic condition in which the operation condition is established and the countermeasure against the load variation is sufficiently taken into consideration-
An aerobic activated sludge treatment device can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a conventional anaerobic-aerobic activated sludge treatment device.

[Explanation of symbols]

2 ... Anaerobic tank, 3 ... Aerobic tank, 4 ... Final sedimentation tank (sedimentation tank),
5 ... Nitrification solution circulation pump, 6, 12 ... Air diffuser, 7 ... Blower, 9 ... Waste water, 11 ... Buffer tank, 13 ... Sludge return pump,
14 ... Controller (control means), 15 ... Flowmeter, 1
6, 21 ... Pipe line, 18 ... Oxygen utilization speedometer, 19 ... ATU
-R _r total.

Claims (2)

[Claims] 1. A step of denitrifying wastewater such as sewage with denitrifying bacteria in an anaerobic tank, a step of nitrifying ammoniacal nitrogen with nitrifying bacteria in an aerobic tank, and a step of solid-liquid separation in a precipitation tank. In the anaerobic-aerobic activated sludge treatment device, which includes a step of refluxing a nitrification solution in the aerobic tank and a part of the sludge in the precipitation tank to the anaerobic tank to accelerate the denitrification reaction, a buffer tank is provided in the anaerobic tank. Along with it, the wastewater is divided into the buffer tank and the anaerobic tank, while the aerobic tank is provided with an oxygen utilization speed meter and an oxygen utilization speedometer subtracting the oxygen utilization rate due to nitrification. It is characterized by comprising a control means for judging the progress of the nitrification reaction of the aerobic tank with the progress of the aerobic activated sludge treatment and determining the diversion ratio of the waste water to the buffer tank and the anaerobic tank from the judgment result. , Anaerobic-aerobic activated sludge treatment device using a buffer tank. 2. The anaerobic-aerobic activated sludge treatment device using a buffer tank according to claim 1, wherein the buffer tank is an aerobic tank in which air is diffused from an air diffuser arranged inside.