JP3257946B2 - Sewage treatment method and sewage treatment apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sewage treatment method and a sewage treatment apparatus for treating sewage such as domestic sewage by an activated sludge method and a membrane separation method.

[0002]

2. Description of the Related Art Conventionally, sewage such as domestic sewage is treated by the following treatment flow. For example, as shown in FIG. 4, the sewage from which sand and impurities are removed flows into the flow control tank 1 and flows out at an appropriate flow rate, and the sewage 2 flowing out of the flow control tank 1 flows into the activated sludge tank 3. A part 4 of the activated sludge mixed liquid in the tank is sent to the sedimentation tank 5, and the supernatant 6 in the sedimentation tank 5 is sent to the sterilization tank 7 while being treated by the activated sludge introduced into the tank. After disinfection, it is discharged as treated water 8. The sludge 9 settled in the sedimentation tank 5 is appropriately extracted, sent to a concentration tank (not shown), concentrated, and then subjected to a treatment such as removal.

[0005] Alternatively, as shown in FIG. 5, sewage 2 flowing out of a flow control tank 1 flows into a membrane-separated activated sludge tank 10, and is treated with activated sludge introduced into the tank. The mixed sludge solution is solid-liquid separated by a membrane separation device (not shown) immersed and installed in the tank, and the membrane permeated water 11 that has passed through the membrane surface of the membrane separation device is sent to the sterilization tank 7 for disinfection and then treated water 8 And the sludge 12 remaining in the tank is appropriately pulled out. Such a treatment method that combines the activated sludge method and the membrane separation method can maintain a high concentration of activated sludge in the tank and can reduce the tank capacity, and can reduce the sedimentation, as compared with the above-described treatment method. There is an advantage that the entire treatment facility can be made compact, for example, no tank is required.

[0004]

However, the treatment method shown in FIG. 5 has the above-mentioned advantages, but when the amount of sewage which greatly exceeds the design water amount flows into the flow control tank 1, the treatment method shown in FIG. Since a larger amount of wastewater 2 flows into the membrane separation activated sludge tank 10 than the flow rate adjustment tank 1, the activated sludge mixed liquid overflows from the upper part of the tank, which cannot be handled by a membrane separation apparatus which performs solid-liquid separation with a fixed treatment amount. There is a possibility that the surroundings of the tank may be soiled, or a pump or a blower disposed outside the tank may be flooded, thereby stopping the processing of the entire facility. To prevent these,
It is necessary to increase the size of the flow control tank 1 or design the membrane separation apparatus with a margin.

In this regard, in the treatment method shown in FIG. 4, the wastewater flows naturally to the flow control tank 1, the activated sludge tank 3, the sedimentation tank 5, and the sterilization tank 7 sequentially, so that the design water amount is greatly reduced. Even when an excess amount of sewage flows into the flow control tank 1, the treatment does not stop. However, in such a case, not only the activated sludge treatment is not sufficiently performed in the activated sludge tank 3, but also the activated sludge to be settled in the settling tank 5 flows out without settling, and the quality of the treated water deteriorates. Invite.

[0006] The present invention solves the above-mentioned problems, and while maintaining the advantages of the membrane separation method, even in the event of an emergency in which sewage inflows in a much larger amount than the designed amount of water, the treatment can be stopped or treated. It is an object of the present invention to provide a sewage treatment method and a sewage treatment apparatus that can prevent deterioration of water quality.

[0007]

In order to solve the above-mentioned problems, a method for treating sewage according to the present invention comprises the steps of flowing sewage such as domestic sewage into a flow control tank and discharging it at an appropriate flow rate. The sewage discharged from the tank flows into the membrane separation activated sludge tank and is treated with activated sludge, while the activated sludge mixed liquid in the tank is solid-liquid separated by the membrane separation apparatus immersed and installed in the tank. In the sewage treatment method for removing the permeated water permeated through the membrane surface to the outside of the tank, usually, the permeated water was further flowed into the contact oxidation tank and treated with activated sludge carried on the carrier in the tank. After that, it is sent to the next treatment system such as a sterilization tank, and when the sewage in the flow rate adjustment tank exceeds the upper limit water level, the membrane permeated water is sent directly to the next treatment system such as the sterilization tank, and exceeds the upper limit water level. Sewage overflows into contact oxidation tank ON Toe, after processing by supported activated sludge to carrier in the tank, in which the send next processing system, such as a sterilization chamber.

[0008] The sewage treatment apparatus of the present invention comprises:
In the sewage treatment apparatus in which activated sludge is charged inside and a membrane separation device is immersed and installed, and a contact oxidation tank provided with a carrier for supporting activated sludge therein are arranged in this order. An overflow means is provided to allow the wastewater exceeding the upper limit water level in the regulating tank to flow into the contact oxidation tank, a pipe for sending the membrane permeated water permeated through the membrane separation device to the contact oxidation tank, a sterilization tank or the like to a next treatment system. A branch pipe is provided via a switching valve.

Further, the wastewater treatment apparatus of the present invention is provided with a sludge extraction pipe communicating with the bottom of the contact oxidation tank and extracting activated sludge separated from the carrier and deposited on the bottom of the tank. Further, in the sewage treatment apparatus of the present invention,
It has a tank capacity with an OD volume load of 0.3 to 1.0 kg BOD / m ³ · day.

According to the sewage treatment method and the sewage treatment apparatus described above, the membrane permeated water having a water quality sufficiently lower than the discharge standard through the biological treatment with the activated sludge and the solid-liquid separation treatment with the membrane separation apparatus is usually used. Then, the water is passed through the contact oxidation tank, is further biologically treated by activated sludge attached to the carrier in the tank, and is discharged through the next treatment system such as a sterilization tank.

When a large amount of wastewater exceeding the upper limit water level flows into the flow control tank, the membrane permeated water having a water quality sufficiently lower than the discharge standard is sent directly to the next treatment system such as a sterilization tank and the upper limit water level is reduced. The excess sewage is passed through the overflow means to the contact oxidation tank, where it is biologically treated by activated sludge attached to the carrier in the tank while staying in the tank for a sufficient time. After being sent to the system, it is released. As the overflow means, an overflow pipe or an overflow weir is provided.

Further, according to the sewage treatment apparatus provided with a sludge extraction pipe at the bottom of the contact oxidation tank, the activated sludge that has been separated from the carrier and deposited on the bottom of the tank can be directly extracted. Further, the contact oxidizing tank is required to have a BOD volume load of 0.3 to 1.0 k.
According to the sewage treatment apparatus configured to have a tank capacity of gBOD / m ³ · day, the sewage flowing from the flow control tank through the overflow means is accommodated while being a relatively small contact oxidation tank. , And can be discharged as water quality below the discharge standard.

[0013]

Embodiments of the present invention will be described below. In FIGS. 1 and 2, the sewage treatment apparatus includes a flow rate adjusting tank 21 for inflowing sewage such as domestic sewage and flowing out at an appropriate flow rate, and immersing activated sludge therein and immersing a membrane separation device 22 therein. Installed membrane separation activated sludge tank 2
3, a contact oxidation tank 25 in which a carrier such as a filler 24 is provided, and a sterilization tank 26 are arranged in this order.

The flow control tank 21 is provided with a sewage supply pipe 27 for supplying the sewage 21a in the tank to the membrane separation activated sludge tank 23, and the overflow reaches the inflow portion of the contact oxidation tank 25 at the position of the upper limit water level HL. A tube 28 is provided.

The membrane separation activated sludge tank 23 is composed of an anaerobic section 29 and an aerobic section 30. The above-mentioned membrane separation device 22 is provided in the aerobic section 30. Circulation pipes 31 and 32 for circulating 23 a between the anaerobic section 29 and the aerobic section 30 and a sludge extraction pipe 33 are provided.

The membrane separation device 22 includes a box-shaped casing 22.
A flat membrane cartridge 22b provided with an organic filtration membrane on both sides is arranged in the upper part of a, and an aeration device 22c is provided below the membrane cartridge 22b. A permeated water pipe 34 communicating with the membrane permeation side of each membrane cartridge 22b is led to the inflow portion of the contact oxidation tank 25, and a branch pipe 36 provided in the middle of the permeated water pipe 35 via a switching valve 35 is connected to the sterilization tank 26. Is led to.

The contact oxidation tank 25 has a BOD volume load of 0.1.
It has a tank capacity of ^{3 to} 1.0 kg BOD / m ³ · day, and a treatment water pipe 37 reaching the sterilization tank 26 is provided at the outflow portion, and a sludge extraction pipe 38 is provided at the bottom. I have.

The operation of the above configuration will be described. Normally when the sewage below the design water volume flows into the flow control tank 21 and the sewage 21a in the tank is below the upper limit water level HL,
An appropriate flow rate of the sewage 21b is sent from the flow control tank 21 to the membrane separation activated sludge tank 23 and treated by the activated sludge in the tank 23, and the activated sludge mixed liquid 23a in the tank is solid-liquid separated by the membrane separation device 22. Then, the membrane permeated water 23b having good water quality whose BOD or the like is sufficiently lower than the discharge standard is taken out.

The removed membrane permeated water 23b flows into the contact oxidation tank 25 and is further treated by the activated sludge attached to the filler 24 to become highly treated water 25a having a BOD of 5 mg / L or less. It is sent to the sterilization tank 26.

On the other hand, a large amount of sewage greatly exceeding the design water amount flows into the flow control tank 21, and in an emergency when the sewage 21a in the tank exceeds the upper limit water level HL, the switching valve 35 is switched, and the membrane separation device 22 is turned on. The membrane permeated water 23b taken out is sent directly to the sterilization tank 26 through the branch pipe 36.

The sewage 21c exceeding the upper limit water level HL flows into the contact oxidation tank 25 through the overflow pipe 28, and stays in the tank for a time sufficient for being treated by the activated sludge attached to the filler 24, The treated water 25a having a BOD of 20 mg / L or less and a discharge standard or less is sent to the sterilization tank 26 through the treated water pipe 37.

The permeated water 23b and the treated water 25a are supplied to the sterilization tank 2
6 and are discharged together as effluent water 26a. Excess sludge 23c in the membrane separation activated sludge tank 23 is appropriately drawn through a sludge drawing pipe 33.

The separated sludge 25b separated from the filler 24 in the contact oxidation tank 25 and deposited on the bottom of the tank is supplied to a sludge extraction pipe 38.
, And is returned to the flow rate adjusting tank 21 or the like. This is because only the membrane permeated water 23b is normally passed therethrough, so that the activated sludge has a small thickness and the separated sludge 25
This is because the amount of b generated is small. Therefore, a sedimentation tank for settling and separating the separated sludge 25b is unnecessary.

The response time in an emergency can be extended by increasing the tank capacity of the contact oxidation tank 25. On the other hand, an increase in the tank capacity leads to a longer tank installation space and a longer sewage retention time. The BOD volume load is 0.3
By setting the tank capacity to be ~ 1.0 kgBOD / m ³ · day, it is a relatively small tank, but accommodates the sewage 21c flowing from the flow control tank 21 and treats it to a water quality below the discharge standard. it can.

[0025]

As described above, according to the present invention, the contact oxidation tank is provided downstream of the membrane separation activated sludge tank, and the membrane permeated water treated in the membrane separation activated sludge tank is usually contact oxidized. After flowing into the tank, it is further treated by activated sludge adhering to the carrier in the tank.In the event of an emergency when a larger volume of wastewater flows in, the membrane permeated water is sent directly to a sterilization tank, etc. The wastewater exceeding the upper limit water level is allowed to flow into the contact oxidation tank, and treated by activated sludge attached to the carrier in the tank. It can prevent the stoppage of treatment and the pollution of public waters.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a normal processing flow in a sewage treatment method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an emergency process flow in the wastewater treatment method.

FIG. 3 is an explanatory view showing one embodiment of a sewage treatment apparatus of the present invention.

FIG. 4 is a flowchart illustrating a conventional sewage treatment method.

FIG. 5 is a flowchart illustrating another conventional wastewater treatment method.

[Explanation of symbols]

 21 Flow control tank 21b Sewage 21c Sewage 22 Membrane separation device 23 Membrane separation activated sludge tank 23a Activated sludge mixture 23b Membrane permeate 24 Filler 25 Contact oxidation tank 25a Treated water 25b Separation sludge 26 Sterilization tank 28 Overflow pipe 35 Switching valve 36 Branch pipe 38 Sludge extraction pipe

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-155758 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 1/44, 3/12, 3 / 06

Claims (4)

(57) [Claims] 1. Sewage such as domestic sewage flows into a flow control tank and flows out at an appropriate flow rate. Sewage flowing from the flow control tank flows into a membrane separation activated sludge tank and is treated with activated sludge. In the sewage treatment method, the activated sludge mixed liquid in the tank is separated into solid and liquid by a membrane separator immersed and installed in the tank, and the permeated water that has passed through the membrane surface of the membrane separator is taken out of the tank. After further flowing the membrane permeated water into the contact oxidation tank and treating it with the activated sludge carried on the carrier in the tank, it is sent to the next treatment system such as a sterilization tank, and the wastewater in the flow rate adjustment tank is When the water level exceeds the upper limit, the membrane permeated water is sent directly to the next treatment system such as a sterilization tank, and the wastewater that has exceeded the upper limit water level overflows and flows into the contact oxidation tank, and is transferred to the carrier in the tank. After treatment with the supported activated sludge, sterilization tank A sewage treatment method characterized by sending the wastewater to the next treatment system. 2. A flow rate regulating tank, a membrane separation activated sludge tank into which activated sludge is charged and a membrane separation device is immersed and installed, and a contact oxidation tank provided with a carrier for carrying activated sludge inside. In the sewage treatment apparatus arranged in order, an overflow means is provided for allowing sewage exceeding the upper limit water level in the flow rate adjusting tank to flow into the contact oxidation tank, and a pipe for sending membrane permeated water having passed through the membrane separation apparatus to the contact oxidation tank. A sewage treatment apparatus, wherein a branch pipe for a next treatment system such as a sterilization tank is provided via a switching valve. 3. A sewage treatment apparatus according to claim 2, further comprising a sludge withdrawing pipe which communicates with the bottom of the contact oxidation tank and removes activated sludge separated from the carrier and deposited on the bottom of the tank. . 4. The method according to claim 1, wherein the contact oxidation tank has a BOD volume load of 0.3.
The sewage treatment apparatus according to claim 2, wherein the sewage treatment apparatus has a tank capacity of 1.0 kgBOD / m ³ · day.