JPH09206793A - Sewage treatment and sewage treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to prevent the stop of a treatment or the degradation in the quality of treated water in the event of emergency when sewage of the volume largely exceeding a designed water volume flows into the device while maintaining the advantages of a membrane sepn. method. SOLUTION: A membrane separating activated sludge vessel 23 is provided with a contact oxidation vessel 25 downstream thereof. The membrane permeated water 23b treated in this membrane separating activated sludge vessel 23 is normally admitted into this contact oxidation vessel 25 where the water is further treated by the activated sludge sticking to packing material layers. The sewage 21c exceeding the upper limit level in a flow rate regulating vessel 21 is admitted together with the membrane permeated water 23b into the contact oxidation vessel 25 in the event of emergency when the sewage of the volume largely exceeding the designed water volume flows into the device.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sewage treatment method and 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, sewage from which sand and contaminants have been removed is allowed to flow into the flow rate adjusting tank 1 and flow out at an appropriate flow rate, and sewage 2 flowing out of the flow rate adjusting tank 1 is sent to the activated sludge tank 3. A part 4 of the activated sludge mixed solution in the tank is sent to the settling tank 5 while being treated by the activated sludge introduced into the tank. And settling tank 5
After sending the supernatant 6 in the sterilization tank 7 to sterilize it, the treated water 8
Sludge 9 which has been discharged as sediment and settled in the sedimentation tank 5
Is appropriately extracted, sent to a concentration tank (not shown) for concentration, and then carried out for disposal.

Alternatively, as shown in FIG. 5, the sewage 2 flowing out of the flow rate adjusting tank 1 is made to flow into the membrane separation activated sludge tank 10 and treated by the activated sludge introduced into the tank while the activity in the tank is activated. The sludge mixed liquid is subjected to solid-liquid separation by a membrane separation device (not shown) installed by immersion in the tank, and the membrane permeated water 11 that has permeated the membrane surface of the membrane separation device is sent to the sterilization tank 7 and remains in the tank. The sludge 12 is appropriately pulled out. Such a treatment method in which the activated sludge method and the membrane separation method are combined can reduce the tank volume because the activated sludge having a high concentration can be maintained in the tank, as compared with the above-mentioned treatment method, and the sedimentation There is an advantage that the entire processing facility can be made compact by eliminating the need for a tank.

[0004]

However, the treatment method shown in FIG. 5 has the advantages as described above, but on the other hand, when a large amount of sewage that greatly exceeds the design water flows into the flow control tank 1. Since the sewage 2 overflowing from the flow rate adjusting tank 1 flows into the membrane-separating activated sludge tank 10, the membrane separation device for solid-liquid separation with a fixed treatment amount cannot cope with it, and the activated sludge mixed liquid overflows from the upper portion of the tank. However, there is a risk that the surroundings of the tank will be polluted or that the pump or blower installed outside the tank will be submerged and the processing of the entire facility will be stopped. In order to prevent these, the flow rate adjusting tank 1 must be enlarged or the membrane separation device must be designed with a margin.

In this respect, in the treatment method shown in FIG. 4, the wastewater flows to the flow rate adjusting tank 1, the activated sludge tank 3, the settling tank 5 and the sterilizing tank 7 in a natural flow-down manner, so that the design water amount is greatly increased. Even when a larger amount of dirty water flows into the flow rate adjusting tank 1, the processing 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 that should be settled in the settling tank 5 flows out without settling and the quality of treated water is deteriorated. Invite.

The present invention solves the above-mentioned problems, and while maintaining the advantages of the membrane separation method, even when an emergency situation occurs in which an amount of wastewater that greatly exceeds the design water amount flows into the treatment system,
It is an object of the present invention to provide a sewage treatment method and a sewage treatment apparatus capable of preventing treatment stoppage and deterioration of treated water quality.

[0007]

In order to solve the above problems, the method for treating sewage of the present invention is such that sewage such as domestic sewage is caused to flow into a flow rate adjusting tank and flow out at an appropriate flow rate to adjust the flow rate. The effluent flowing out of the tank is introduced into the membrane separation activated sludge tank and treated by the activated sludge, while the activated sludge mixed solution in the tank is solid-liquid separated by the membrane separator installed in the tank, In the sewage treatment method of taking out the membrane permeated water that has permeated the membrane surface to the outside of the tank, normally, the membrane permeated water is allowed to flow into the catalytic oxidation tank and further treated with the activated sludge supported on the carrier in the tank. When the sewage in the flow rate adjusting tank exceeds the upper limit water level, the sewage exceeding the upper limit water level is caused to overflow and flow into the contact oxidation tank together with the membrane permeated water.

The sewage treatment apparatus of the present invention is a membrane in which a waste water such as domestic sewage is made to flow into the inside and flows out at an appropriate flow rate, and a membrane in which activated sludge is introduced and a membrane separation device is installed by immersion. A separation activated sludge tank and a contact oxidation tank provided with a carrier for supporting activated sludge inside are arranged in this order, and communicated with the upper limit water level position of the flow rate adjustment tank and the inflow section of the contact oxidation tank, An overflow pipe is provided to guide sewage exceeding the upper limit water level in the adjusting tank to the catalytic oxidation tank.

Further, the sewage treatment apparatus of the present invention is provided with a sludge withdrawal pipe which communicates with the bottom of the catalytic oxidation tank and withdraws the activated sludge separated from the carrier and accumulated on the bottom of the inside of the tank. Further, the sewage treatment apparatus of the present invention comprises a contact oxidation tank, B
The OD volume load is 0.3 to 1.0 kg BOD / m ³ · day.

According to the sewage treatment method and the sewage treatment apparatus described above, normally, the membrane permeated water having a water quality sufficiently lower than the discharge standard through the biological treatment by the activated sludge and the solid-liquid separation treatment by the membrane separation device is obtained. Water is passed through the catalytic oxidation tank and further biologically treated by the activated sludge attached to the carrier in the catalytic oxidation tank. When a large amount of sewage exceeding the upper limit water level flows into the flow rate adjustment tank, the sewage water exceeding the upper limit water level flows into the catalytic oxidation tank through the overflow pipe, and the permeated water that has flowed in together and advanced treatment in the tank are also performed. It is diluted with water, biologically treated with activated sludge, and discharged with a water quality below the discharge standard.

Further, according to the sewage treatment apparatus in which the sludge drawing pipe is provided at the bottom of the catalytic oxidation tank, the activated sludge which is separated from the carrier and accumulated on the bottom of the tank can be directly drawn. In addition, the catalytic oxidation tank has a BOD volume load of 0.3 to 1.0k.
According to the sewage treatment apparatus configured to have a tank capacity of gBOD / m ³ · day, the sewage water that flows in from the flow adjustment tank through the overflow pipe is accommodated even though it is a relatively small contact oxidation tank. It can be discharged as water quality below the discharge standard.

[0012]

Embodiments of the present invention will be described below. In FIG. 1 and FIG. 2, the sewage treatment apparatus has a flow rate adjusting tank 21 which allows sewage such as domestic sewage to flow into the inside and to flow out at an appropriate flow rate, and activated sludge is put into the inside and a membrane separator 22 is immersed Installed membrane separation activated sludge tank 2
3, a contact oxidation tank 25 in which a carrier such as a filler layer 24 is provided, and a sterilization tank 26 are arranged in this order.

At the position of the upper limit water level HL of the flow rate adjusting tank 21, the overflow pipe 2 reaching the inflow portion of the catalytic oxidation tank 25.
7 are provided. The membrane separation activated sludge tank 23 comprises an anaerobic part 28 and an aerobic part 29.
The above-mentioned membrane separation device 22 is provided in the inside 9, and the activated sludge mixed liquid 23a in the tank is anaerobic part 28 and aerobic part 29.
It is provided with circulation pipes 30 and 31 and a sludge extraction pipe 32 that circulate over

The membrane separation device 22 includes a box-shaped casing 22.
A flat plate-shaped membrane cartridge 22b having organic filtration membranes on both sides is arranged in the upper part of a, and an aeration device 22c is provided below the membrane cartridge 22b.

The catalytic oxidation tank 25 has a BOD volume load of 0.
It is configured to have a tank capacity of ^{3 to} 1.0 kgBOD / m ³ · day, and a sludge drawing pipe 33 is provided at the bottom. A waste water supply pipe 34 is provided between the flow rate adjusting tank 21 and the membrane separation activated sludge tank 23, and a permeate water pipe 35 is provided between the membrane permeation side of the membrane separation device 22 and the contact oxidation tank 25.
A treated water pipe 36 is provided between the outflow portion of the contact oxidation tank 25 and the sterilization tank 26.

The operation of the above configuration will be described. At normal times when the amount of sewage equal to or less than the design water flows into the flow rate adjustment tank 21 and the sewage 21a in the tank is below the upper limit water level HL,
An appropriate flow rate of sewage 21b from the flow rate adjusting tank 21 is sent to the membrane separation activated sludge tank 23 and treated by the activated sludge, and the activated sludge mixed solution 23a in the tank is subjected to solid-liquid separation by the membrane separation device 22, and BOD etc. The membrane permeated water 23b having good water quality that is sufficiently lower than the discharge standard is taken out.

The membrane permeated water 23b taken out flows into the catalytic oxidation tank 25, is further treated by the activated sludge adhering to the filler layer 24, and flows out as highly treated water 25a having a BOD of 5 mg / L or less. .

On the other hand, in an emergency when a large amount of sewage that greatly exceeds the design water flows into the flow rate adjustment tank 21 and the sewage 21a in the tank exceeds the upper limit water level HL, the sewage 21c that exceeds the upper limit water level HL is overflow pipe. Contact oxidation tank 25 through 27
BOD of 20 mg / L after being diluted with the membrane permeated water 23b that has flowed into the inside of the tank and the treated water existing in the tank and that has been diluted with the activated sludge adhering to the filler layer 24.
The treated water 25a having the following discharge standard or less is discharged.

Treated water 25a flowing out from the catalytic oxidation tank 25
After being sent to the sterilization tank 26 and sterilized, the discharged water 26
Released as a. The filler layer 24 in the catalytic oxidation tank 25
The separated sludge 25b that has been further separated and accumulated on the bottom of the tank is regularly drawn out from the sludge drawing pipe 33 and returned to the flow rate adjusting tank 21 or the like. This is because the membrane permeated water 23b is normally only passed through, so the activated sludge has a small thickness and the amount of the generated sludge 25b is small. Therefore, a settling tank for settling and separating the separated sludge 25b is unnecessary.

The larger the tank capacity of the catalytic oxidation tank 25, the longer the emergency response time can be, but on the other hand, the increase of the tank capacity leads to a longer tank installation space and longer sewage retention time. BOD volume load is 0.3
By setting the tank capacity to be up to 1.0 kgBOD / m ³ · day, the wastewater 21b that flows in from the flow rate adjusting tank 21 is accommodated and treated to a water quality below the discharge standard, even though it is a relatively small tank. it can.

The method of calculating the required capacity of the catalytic oxidation tank 25 will be specifically described below. First, as shown in Table 1 below, in order to satisfy the overflow wastewater amount X (m ³ / day) that overflows from the flow rate adjustment tank and flows into the catalytic oxidation tank, and the BOD concentration of treated water of 20 mg / L or less, The relationship with the required BOD removal rate Y (%) in the catalytic oxidation tank is determined.

Here, the amount of overflow sewage X (m ³ /
(Day) and the BOD removal rate Y (%) in the catalytic oxidation tank are, for example, those in which sewage is normally processed by inflowing in a flow adjustment tank, a membrane separation activated sludge tank which is a combined purification tank, and a catalytic oxidation tank in this order. When the planned treated water amount is 100 m ³ / day, the BOD concentration of the inflowing wastewater is 200 mg / L, and the BOD concentration of the membrane separation water is 5 mg / L, it can be calculated by the following calculation formula.

(Planned amount of treated water x BOD concentration of membrane separation water +
Overflow wastewater x BOD concentration of inflow wastewater x (1-
BOD removal rate in catalytic oxidation tank / 100)) / (planned treated water amount + overflow sewage amount) = BOD concentration of treated water (100 × 5 + X × 200 × (1-Y / 100)) /
(100 + X) = 20

[0024]

[Table 1] From Table 1, in order to achieve the BOD concentration of 20 mg / L of treated water, when the overflow wastewater amount X is about 10 m ³ / day, the B in the catalytic oxidation tank is high because the dilution effect is high.
It can be seen that the OD removal rate Y may be about 15%, and when the overflow wastewater amount X is 50 m ³ / day or less, the BOD removal rate Y in the catalytic oxidation tank may be 15 to 75%.

Next, as shown in FIG. 3, BOD volume load (kgBOD / m ³ · day) and BO in the catalytic oxidation tank were measured.
The relationship with the D removal rate (%) is experimentally obtained. From FIG.
BOD volume load 0.3 to 1.0 (kgBOD / m ³ ·
It can be seen that a BOD removal rate of 80 to 20% can be expected in (day).

From these, when it is predicted that the amount of overflow wastewater is 30 m ³ / day or less, for example, Table 1
From overflowing sewage volume 30m ³ / day BO
A D removal rate of 65% was found, and for safety, a BOD removal rate of 70% was found. From FIG. 3, a BOD volume load of 0.5 kg BOD / m ³ · day corresponding to a BOD removal rate of 70% was found. And, the amount of overflow sewage 30 m ³ / day and the BOD concentration of inflow sewage 200 mg / L (= 200/100
0 (kg / m ³ )) and BOD volume load 0.5 kg / m
^{From 3} days, the required capacity 12 (m ³ ) of the catalytic oxidation tank is calculated as follows.

Required capacity (m ³ ) = (30 × 200/1000) /0.5=12

[0028]

As described above, according to the present invention, a contact oxidation tank is provided downstream of the membrane separation activated sludge tank so that the membrane permeated water treated in the membrane separation activated sludge tank is normally contacted further. In an emergency when a large amount of sewage flows into the oxidation tank and is treated with the activated sludge adhering to the carrier, and overflows the sewage water that exceeds the upper limit water level in the flow rate adjustment tank, along with the membrane permeate. By allowing the water to flow into the catalytic oxidation tank, it is possible to prevent the stop of the treatment and the pollution of the public water area even in an emergency while maintaining the advantages of the membrane separation method.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating an embodiment of a wastewater treatment method of the present invention.

FIG. 2 is an explanatory view showing an embodiment of the sewage treatment apparatus of the present invention.

FIG. 3 is a graph showing a relationship between a BOD volume load and a BOD removal rate in a catalytic oxidation tank constituting the same wastewater treatment apparatus.

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

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

[Explanation of symbols]

 21 Flow rate adjusting tank 21b Sewage 21c Sewage 22 Membrane separation device 23 Membrane separation activated sludge tank 23a Activated sludge mixture 23b Membrane permeate 24 Filler layer 25 Contact oxidation tank 25a Treated water 25b Exfoliated sludge 27 Overflow pipe 33 Sludge extraction pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C02F 1/44 C02F 1/44 K 3/12 3/12 S MH

Claims (4)

[Claims] 1. Sewage such as domestic sewage is made to flow into a flow rate adjusting tank to flow out at an appropriate flow rate, and wastewater discharged from the flow rate adjusting tank is made to flow into a membrane separation activated sludge tank and treated with activated sludge. Meanwhile, in the sewage treatment method in which the activated sludge mixed solution in the tank is subjected to solid-liquid separation by the membrane separator installed in the tank and the membrane permeated water that has permeated the membrane surface of the membrane separator is taken out of the tank, Means that the membrane permeated water is allowed to flow into the catalytic oxidation tank to be further treated by the activated sludge carried on the carrier in the tank, and when the wastewater in the flow rate adjusting tank exceeds the upper limit water level, the upper limit water level is changed. A method for treating sewage, characterized in that overflowed sewage is allowed to flow into the contact oxidation tank together with the membrane permeate. 2. A flow rate adjusting tank for inflowing sewage such as domestic sewage into the inside and flowing out at an appropriate flow rate, and a membrane separation activated sludge tank in which activated sludge is introduced and a membrane separation device is immersed and installed. A contact oxidation tank having a carrier for supporting activated sludge inside is arranged in this order, and the upper limit water level in the flow rate adjustment tank is communicated with the position of the upper limit water level of the flow rate adjustment tank and the inflow part of the contact oxidation tank. A sewage treatment apparatus comprising an overflow pipe that guides sewage that exceeds the limit to a contact oxidation tank. 3. The sewage treatment apparatus according to claim 2, further comprising a sludge extraction pipe communicating with the bottom of the catalytic oxidation tank for withdrawing the activated sludge separated from the carrier and accumulated on the bottom of the tank. . 4. A catalytic oxidation tank having a BOD volume load of 0.3.
The sewage treatment apparatus according to claim 2 or 3, wherein the sewage treatment apparatus has a tank capacity of about 1.0 kgBOD / m ³ · day.