JP7015117B2 - Organic wastewater treatment method and organic wastewater treatment system - Google Patents

Description

The present invention relates to an organic wastewater treatment method and an organic wastewater treatment system.

As shown in FIG. 4, Patent Document 1 describes equipment for treating nitrogen-containing wastewater using activated sludge, which is an oxygen-free tank A (A1 to An) and an aerobic tank O (O1 to On). A plurality of oxygen-free tanks A and aerobic tanks O are alternately coupled in series in order, and nitrogen-containing drainage DW is supplied to the oxygen-free tank A1 in the first stage and at least one oxygen-free tanks A2 and An in the second and subsequent stages. The last-stage aerobic tank On is equipped with a dipping-type separation device M for separating activated sludge to obtain treated water, and the last-stage aerobic tank On is equipped with a front-end oxygen-free tank. Disclosed is a treatment facility for oxygen-containing wastewater, which comprises a route R for circulating and returning activated sludge liquid to A1. Reference numeral P is a suction pump for membrane separation, and reference numeral P1 is a sludge return pump.

Japanese Unexamined Patent Publication No. 2000-140886

According to the treatment equipment adopting the above-mentioned method, it is possible to realize a treatment equipment for nitrogen-containing wastewater DW having a nitrogen removal rate of 90% or more. Piping etc. will become larger.

In addition, it is necessary to periodically inject a carbon source such as methanol into the oxygen-free tank in order to promote the denitrification process, and if the injection amount is incorrect due to a failure of the sensing device, etc., it will be discharged after the process. There was a risk that the TN concentration of water would increase.

Therefore, as shown in FIG. 5, a circulation type membrane separation activated sludge method (hereinafter referred to as a sludge method) in which an immersion type membrane separation device M is provided not only in the final aerobic tank On but also in all the aerobic tanks O (O1 to On). , "Step inflow type MBR". MBR is an abbreviation for Membrane Bio Reactor.) Has been proposed.

According to this method, for example, an oxygen-free tank and an aerobic tank are connected in series in three stages each, and the activated sludge in the final-stage aerobic tank is returned to the top-level oxygen-free tank, which is unrealistic until now. The 9Q circulation (setting the circulation amount to be 9 times the inflow amount Q of sludge) can be easily realized, the above-mentioned power equipment and sensing equipment can be miniaturized, and the number of points can be reduced.

However, when the step inflow type MBR is adopted, since the nitrifying liquid is membrane-separated in the aerobic tank O, residual TN such as nitrate nitrogen flows out to the membrane permeation liquid, and TN. There was a limit to the reduction of concentration.

Therefore, the TN concentration of organic wastewater with a TN concentration of 50 mg / L, such as inland sewage with low rainfall and low tap water usage, is purified to, for example, 3 mg / L or less, which is an environmental standard. It was difficult to handle.

In addition, when removing phosphorus contained in wastewater by biological treatment with a step inflow type MBR, a high dephosphorization effect is achieved only when some membrane separation devices are stopped and the aerobic tank is transferred to an anaerobic state. However, since the membrane permeate as treated water is usually taken out in the process of excessive intake of phosphorus by microorganisms in the aerobic tank, it is said that a part of T-P flows out into the membrane permeate. There was also a problem.

Further, there is also a problem that the equipment for deodorizing a large amount of aerated air for cleaning the separation membrane and releasing it to the atmosphere becomes large.

In view of the above-mentioned problems, an object of the present invention is to provide an organic wastewater treatment method and an organic wastewater treatment apparatus capable of effectively obtaining treated water having a low TN concentration with respect to organic wastewater containing nitrogen. It is in the point of providing.

In order to achieve the above object, the first characteristic configuration of the organic wastewater treatment method according to the present invention is an organic wastewater treatment method for biologically treating organic wastewater containing nitrogen in active sludge, which is preferable to an anaerobic tank. The air tank and the membrane separation tank for anoxic treatment are provided with a plurality of biological treatment units arranged in this order along the flow of active sludge, and the biological treatment unit on the upstream side to the biological treatment unit on the downstream side. Multiple biological treatment units are connected in series so that active sludge flows into the anaerobic tank, and the organic wastewater is divided and supplied to the anaerobic tank of each biological treatment unit, and the inside of the membrane separation tank of each biological treatment unit. The point is that the membrane permeation liquid obtained by solid-liquid separation of the active sludge in the above is taken out as treated water.

A membrane in which organic wastewater divided and supplied to the most upstream anaerobic tank of each biological treatment unit is guided to an aerobic tank, ammoniacal nitrogen is nitrified into nitrate nitrogen, etc., and further downstream anoxic treatment is performed. Since the treated water is taken out by undergoing an endogenous denitrification action in the separation tank and being denitrified, the value of the TN concentration contained in the treated water can be kept low. The trace amount of nitrate nitrogen remaining in the membrane separation tank is also almost completely denitrified in the anaerobic tank by using the organic wastewater supplied to the anaerobic tank of the next-stage biological treatment unit as a carbon source. Further, since the phosphorus exhaled from the microorganism in the anaerobic tank is overdose by the microorganism in the aerobic tank and then solid-liquid separated in the anoxic membrane separation tank, T contained in the membrane permeate which is the treated water. The value of -P concentration can also be kept low.

In addition to the above-mentioned first feature configuration, the second feature configuration is active in the anaerobic tank of the biological treatment unit located in the most upstream portion from the membrane separation tank of the biological treatment unit located in the most downstream portion. The point is to return the sludge.

By circulating the activated sludge in a plurality of biological treatment units connected in series, a sufficient circulation amount of the activated sludge can be ensured.

The third characteristic configuration is that, in addition to the above -mentioned first or second characteristic configuration, the membrane permeate obtained by solid-liquid separation by the membrane separation device is aerated in an aeration tank.

Even when the membrane permeate of the membrane separation device, which has been solid-liquid separated by the membrane separation device in an oxygen-free state, is discharged to a river, etc., the amount of dissolved oxygen is adjusted to a level that does not affect the environment by aeration treatment. You will be able to.

In the fourth characteristic configuration, in addition to any of the above -mentioned first to third characteristic configurations, the gas phase portion at the upper part of the membrane separation tank forms a closed space and activates the gas in the gas phase portion. The point is that it is circulated so as to dissipate air from the lower part of the membrane separation device arranged by immersing it in sludge.

The gas recovered from the gas phase part of the membrane separation tank, which is a closed space, is circulated so as to be dissipated from the lower part of the membrane separation device immersed in the membrane separation tank. There is no need to install deodorizing equipment. Further, it is not necessary to replace the gas in the gas phase portion of the membrane separation tank with an inert gas such as nitrogen gas at the start of operation. This is because even if the gas phase portion is air, oxygen contained in the air is consumed in a short period at the initial stage.

The first characteristic configuration of the organic wastewater treatment system according to the present invention is an organic wastewater treatment system that biologically treats organic wastewater containing nitrogen in active sludge, and has an anaerobic tank, an aerobic tank, and anoxic treatment. The membrane separation tank to be performed is equipped with a plurality of biological treatment units arranged in this order along the flow of the active sludge, and the active sludge is generated from the membrane separation tank of the upstream biological treatment unit to the anaerobic tank of the downstream biological treatment unit. A biological treatment unit connector in which a plurality of biological treatment units are connected in series so as to flow, a raw water supply path for dividing and supplying the organic wastewater to the anaerobic tank of each biological treatment unit, and a membrane of each biological treatment unit. It is equipped with a membrane separation device that separates the active sludge in the separation tank into solid and liquid and takes out the membrane permeation liquid as treated water.

In addition to the above-mentioned first feature configuration, the second feature configuration includes organisms arranged in the most upstream portion from the membrane separation tank of the biological treatment unit located in the most downstream portion of the biological treatment unit connection. The point is that the anaerobic tank of the treatment unit is equipped with a sludge return path for returning activated sludge.

The third feature configuration is that, in addition to the first feature configuration described above , the biological treatment unit connector is configured by connecting the plurality of biological treatment units in a ring shape.

The fourth characteristic configuration is that, in addition to any of the above -mentioned first to third characteristic configurations, an aeration tank for aerating the membrane permeate obtained from the membrane separation device is provided.

In the fifth characteristic configuration, in addition to any of the above -mentioned first to fourth characteristic configurations, the gas phase portion at the upper part of the membrane separation tank forms a closed space and activates the gas in the gas phase portion. The point is that it is equipped with a circulating air dispersal mechanism that circulates air from the lower part of the membrane separation device arranged by immersing it in sludge.

As described above, according to the present invention, there is provided an organic wastewater treatment method and an organic wastewater treatment apparatus capable of effectively obtaining treated water having a low TN concentration for organic wastewater containing nitrogen. You can now do it.

(A) is an explanatory diagram of the wastewater treatment apparatus according to the present invention, and (b) is an explanatory diagram of a membrane separation tank. Layout explanatory view of wastewater treatment apparatus by this invention Other layout explanatory drawing of wastewater treatment apparatus by this invention Explanatory drawing of conventional wastewater treatment equipment Explanatory diagram of wastewater treatment equipment adopting conventional step inflow type MBR

Hereinafter, embodiments of a wastewater treatment method and a wastewater treatment system according to the present invention will be described.
FIG. 1A shows an organic wastewater treatment system 1 according to the present invention. The organic wastewater treatment system 1 is an organic wastewater treatment system 1 that biologically treats organic wastewater DW containing nitrogen in activated sludge, and is connected in series in a plurality of stages along the flow of activated sludge and is an anaerobic tank AN. Biological treatment units U (U1 to Un) in which (AN1 to ANn), aerobic tanks O (O1 to On), and membrane separation tanks (A1 to An) that separate solid and liquid in anoxic state are arranged in order, and each. The raw water supply channel S for dividing and supplying the organic waste DW to the anaerobic tank AN of the biological treatment units U (U1 to Un) and the membrane separation tanks A (A1 to An) of each biological treatment unit U (U1 to Un). It is provided with a membrane separation device M for solid-liquid separation of the activated sludge inside and taking out a membrane permeation liquid TW as treated water. Note that n is a positive integer. That is, a biological processing unit connector is configured by a plurality of biological processing units U (U1 to Un) connected in series.

Then, sludge that returns activated sludge from the membrane separation tank An of the biological treatment unit Un arranged in the most downstream part to the anaerobic tank AN1 of the biological treatment unit U1 arranged in the most upstream part in the biological treatment unit connection body. It has a return route R. By circulating the activated sludge in a multi-stage biological treatment unit U connected in series along the flow of the activated sludge, it is possible to secure a sufficient circulation amount of the activated sludge and perform efficient denitrification treatment. can.

At the bottom of each aerobic tank O (O1 to On), an air diffuser that discharges fine bubbles to promote aerobic treatment is arranged, and air is supplied from a blower B connected to each air diffuser. ..

Further, as shown in FIG. 1 (b), the membrane separation apparatus M in which the gas phase portion of the membrane separation tanks A (A1 to An) is closed and the gas in the gas phase portion is immersed in activated sludge. It is equipped with a circulating aeration mechanism CA that circulates so as to dissipate air from the lower part.

The circulating aeration mechanism CA is a blower B1 that sucks gas from the gas phase portion of each membrane separation tank A (A1 to An), and an air diffuser that arranges the gas sucked by the blower B1 under the membrane separation device M. It is equipped with a guiding pipe and a check valve V provided for the suction side pipe. Air is preferably used as the circulating gas. Oxygen contained in the air is taken up by microorganisms in a short period of time at the initial stage, and the oxygen concentration is rapidly lowered, so that an oxygen-free state can be realized. Further, since the check valve V is configured to supply a small amount of air when the pressure is reduced due to the consumption of oxygen, the gas circulation amount is maintained almost constant.

That is, the gas recovered from the gas phase portion of the membrane separation tank A configured as a closed space is dissipated from the lower part of the membrane separation device M immersed and arranged in the membrane separation tank A, and the dissipated gas is the membrane. After cleaning the separation membrane surface of the separation device M, it reaches the gas phase portion and is circulated. Since the gas in the gas phase is not released to the atmosphere under normal operating conditions, it is not necessary to install a large deodorizing facility. Further, in order to maintain the oxygen-free state of the membrane separation tank A, it is also possible to use air as the circulating gas without using a special gas. This is because the oxygen contained in the air is consumed in a short period of time at the beginning.

The organic wastewater containing nitrogen is separately supplied to the most upstream anaerobic tank A of each biological treatment unit U. In the anaerobic tank A, the organic component contained in the organic wastewater functions as a hydrogen donor, and the nitrate nitrogen contained in the circulating sludge from the biological treatment unit U on the upstream side is reduced to nitrogen and denitrified. Later, it flows into the aerobic tank O.

In the aerobic tank O, aerobic treatment is promoted, and the ammoniacal nitrogen contained in the organic wastewater is nitrified into nitrite nitrogen, and then endogenous in the oxygen-free membrane separation tank A on the downstream side. It undergoes denitrification and is denitrified to be separated into solid and liquid.

The membrane separation tank A functions as a substantially oxygen-free tank, and the concentration of nitrate nitrogen in the tank decreases due to the denitrification treatment. The value is kept extremely low. The trace amount of nitrate nitrogen remaining in the membrane separation tank A is also almost completely denitrified by the organic wastewater as a hydrogen donor in the anaerobic tank AN of the biological treatment unit U in the next stage.

Further, since phosphorus is excessively ingested by microorganisms in the aerobic tank O and then solid-liquid separated in the anoxic membrane separation tank A, the value of the T-P concentration contained in the separated water can be kept low.

The above-mentioned organic wastewater treatment system 1 is further provided with an aeration tank AE for aerating the membrane permeate TW obtained by solid-liquid separation by the membrane separation device M. Even when the membrane permeate that has been solid-liquid separated by the membrane separation device M in an oxygen-free state is discharged into a river or the like, the amount of dissolved oxygen can be adjusted to a level that does not affect the environment by aeration treatment. become able to.

The organic wastewater treatment method of the present invention is executed in the above-mentioned organic wastewater treatment system 1, and the biological treatment unit U in which the anaerobic tank AN, the aerobic tank O, and the membrane separation tank A for performing anoxic treatment are arranged in order. Is connected in series along the flow of activated sludge, and organic wastewater is divided and supplied to the anaerobic tank AN of each biological treatment unit U, and the activated sludge in the membrane separation tank A of each biological treatment unit U is supplied. The membrane permeation liquid obtained by solid-liquid separation by the membrane separation device M is configured to be taken out as treated water.

Further, the activated sludge is configured to be returned from the membrane separation tank An of the biological treatment unit Un located in the most downstream portion to the anaerobic tank AN1 of the biological treatment unit U1 arranged in the most upstream portion, and is configured by the membrane separation device M. The membrane permeate obtained by solid-liquid separation is configured to be aerated in the aeration tank AE.

Hereinafter, another embodiment will be described. In the above-described embodiment, the anaerobic tank AN, the aerobic tank O, the membrane separation tank AN, and the plurality of biological treatment units U constituting the biological treatment unit U are all physically arranged linearly along the flow of activated sludge. It goes without saying that the arrangement of the anaerobic tank AN, the aerobic tank O, and the membrane separation tank AN is not limited to the linear shape, and the arrangement of the plurality of biological treatment units U is not limited to the linear shape. Needless to say.

In the example shown in FIG. 2, although the plurality of biological treatment units U are arranged in a straight line, each biological treatment unit U has an anaerobic tank AN and an aerobic tank O adjacent to the membrane separation tank AN. It is arranged along the meandering flow path of activated sludge.

In the example shown in FIG. 3, an annular flow path through which organic wastewater circulates is formed, and each biological treatment unit U is arranged along the annular flow path. That is, the anaerobic tank of the biological treatment unit U on the downstream side is adjacently arranged so as to be adjacent to the membrane separation tank of each biological treatment unit U, and the biological treatment unit connection body is configured. Therefore, as in the examples shown in FIGS. 1 and 2, it is not necessary to configure the path R for circulating and returning the activated sludge liquid with a long pipe, and therefore it is not necessary to use a large pump facility having a large amount of water to be sent.

In the example of FIG. 3, for example, an air lift pump is provided on the anaerobic tank A side facing the partition wall between the anaerobic tank A and the aerobic tank O, and organic wastewater is sent from the anaerobic tank A to the aerobic tank O. It may be configured as follows.

In any of the examples of FIGS. 2 and 3, the number of stages of the biological processing unit U is composed of four stages. The inflow amount of organic sludge per unit time is Q, the inflow amount of organic sludge into the anaerobic tank AN of each biological treatment unit U is Q / 4, and the total amount of membrane permeation liquid from each membrane separation device M is Q. When the treated water of the above is drawn out and the activated sludge of the most downstream membrane separation tank A is returned to the most upstream anaerobic tank AN via the sludge return route R, the substantial circulation ratio of the sludge is Is 3 × 4, and a high circulation ratio of 12Q can be realized, and the capacity of the tank can be reduced while maintaining the actual sludge residence time SRT of each tank at a sufficient value.

As the membrane element incorporated in the immersion type membrane separation device M, a membrane element having a porous organic polymer membrane on the surface of the non-woven fabric and having a pore diameter of about 0.4 μm at the maximum is preferably used. However, it is possible to use any kind of separation membrane and any form of membrane element (hollow yarn membrane element, tubular membrane element, monolithic membrane element, etc.).

In the above-described embodiment, an example in which the membrane separation device M is immersed and arranged in the membrane separation tank A has been described, but the membrane separation device M according to the present invention is not limited to the embodiment in which the membrane separation device M is immersed and arranged in the membrane separation tank A. A mode may be used in which cross-flow filtration is performed by a membrane separation device M installed outside A. A part of the activated sludge separated at this time may be returned to the membrane separation tank A or the anaerobic tank A in the next stage.

The number of biological treatment units U is not particularly limited, but is preferably in the range of 3 to 5. Generally, increasing the number tends to improve the quality of treated water, but conversely, because the actual HRT is shortened, the amount of fouling substances generated in the membrane separation tank increases and membrane clogging is likely to occur, resulting in water quality. It causes a decline. Therefore, it is necessary to set an appropriately balanced number.

According to the organic wastewater treatment method according to the present invention, the TN concentration of organic wastewater having a TN concentration of 50 mg / L, for example, while denitrifying without adding a separate carbon source as a hydrogen donor. Can be purified to 3 mg / L or less. Further, since no separate carbon source is input, the amount of excess sludge generated can be reduced.

The above-described embodiment is an example of the present invention, and the description thereof does not limit the present invention, and the specific configuration of each part can be appropriately modified and designed within the range in which the action and effect of the present invention are exhibited. Needless to say.

1: Wastewater treatment device AN: Anaerobic tank A: Membrane separation tank DW: Organic wastewater M: Membrane separation device O: Aerobic tank R: Sludge return path S: Raw water supply path U: Biological treatment unit

Claims (9)

It is an organic wastewater treatment method that biologically treats organic wastewater containing nitrogen in activated sludge.
The anaerobic tank, the aerobic tank, and the membrane separation tank for anoxic treatment are provided with a plurality of biological treatment units arranged in this order along the flow of activated sludge, and the upstream biological treatment unit is downstream from the membrane separation tank. Multiple biological treatment units are connected in series so that activated sludge can flow into the anaerobic tank of the biological treatment unit.
The organic wastewater is divided and supplied to the anaerobic tank of each biological treatment unit.
An organic wastewater treatment method characterized by taking out a membrane permeation liquid obtained by solid-liquid separation of activated sludge in a membrane separation tank of each biological treatment unit with a membrane separation device as treated water. The organic wastewater treatment according to claim 1, wherein the activated sludge is returned from the membrane separation tank of the biological treatment unit arranged in the most downstream part to the anaerobic tank of the biological treatment unit arranged in the most upstream part. Method. The organic wastewater treatment method according to claim 1 or 2, wherein the membrane permeate obtained by solid-liquid separation by the membrane separation device is aerated in an aeration tank. The gas phase portion at the upper part of the membrane separation tank forms a closed space, and the gas in the gas phase portion is immersed in activated sludge and circulated so as to dissipate from the lower part of the arranged membrane separation device. The organic wastewater treatment method according to any one of claims 1 to 3. An organic wastewater treatment system that biologically treats organic wastewater containing nitrogen in activated sludge.
The anaerobic tank, the aerobic tank, and the membrane separation tank for anoxic treatment are provided with a plurality of biological treatment units arranged in this order along the flow of activated sludge, and the upstream biological treatment unit is downstream from the membrane separation tank. A biological treatment unit connector in which multiple biological treatment units are connected in series so that activated sludge flows into the anaerobic tank of the biological treatment unit.
The raw water supply channel that divides and supplies the organic wastewater to the anaerobic tank of each biological treatment unit,
A membrane separation device that separates activated sludge in the membrane separation tank of each biological treatment unit into solid and liquid and takes out the membrane permeation liquid as treated water.
It features an organic wastewater treatment system. It is provided with a sludge return path for returning activated sludge from the membrane separation tank of the biological treatment unit arranged at the most downstream part of the biological treatment unit connection to the anaerobic tank of the biological treatment unit arranged at the most upstream part. The organic wastewater treatment system according to claim 5. The organic wastewater treatment system according to claim 5, wherein the biological treatment unit connector is configured by connecting the plurality of biological treatment units in a ring shape. The organic wastewater treatment system according to any one of claims 5 to 7, further comprising an aeration tank for aerating the membrane permeate obtained from the membrane separation device. A circulating air dispersal mechanism in which the gas phase portion at the upper part of the membrane separation tank forms a closed space, and the gas in the gas phase portion is immersed in activated sludge and circulated so as to dissipate air from the lower part of the membrane separation device arranged. The organic wastewater treatment system according to any one of claims 5 to 8, wherein the organic wastewater treatment system comprises.

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