JPH06277689A - Purifying tank and purifying process - Google Patents

Abstract

PURPOSE:To treat combined drainage of high BOD by carrying out the solid- liquid separation of liquid to be treated in a biological treatment tank in which active sludge is floated, feeding concentrated liquid into a sludge digestion tank and permeated liquid into a disinfection tank respectively and disposing properly. CONSTITUTION:When liquid to be treated which is the combined drainage of bath drainage, washing drainage, excrement, kitchen drainage and the like is treated, first the liquid to be treated is fed into biological tanks S1 and S2 through an introduction pipe 5 in which intermittent aeration is carried out and anaerobic treatment and aerobic treatment are repeated. Then the liquid to be treated coming out of the biological treatment tank S1 is fed to a film separation device 10 and solid-liquid separation is carried out, and the permeated liquid is fed to a disinfection tank S5 through a storage tank S6, disinfected and discharged. On the other hand, concentrated liquid containing active sludge is fed into a sludge digestion tank and organic matters such as sluge are turned into methane or carbon dioxide gas by means of anaerobic digestion and discharged or exhausted outside the system. The digested liquid (supernatant) in the digestion tank is returned to the biological tank S1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a septic tank and a purifying method for purifying wastewater from a toilet, a washroom, a bath, a kitchen or the like.

[0002]

2. Description of the Related Art Conventionally, it has been practiced to purify wastewater from a toilet or the like by using activated sludge mainly composed of aerobic bacteria and anaerobic bacteria and then discharge the wastewater. In the above-mentioned purification, the activated sludge is separated from the waste water by the sedimentation separation tank, and the activated sludge is returned to the anaerobic or aerobic treatment tank so that continuous treatment is possible.

However, the separation in the sedimentation separation tank is inefficient because sludge does not settle quickly, and scum and the like may float on the surface, so that only the supernatant liquid may not be taken out well. Therefore, JP-A-1-15
Japanese Patent Laid-Open No. Hei 4-222696 or 1995 discloses a septic tank using a membrane separator as a solid-liquid separator, that is, an apparatus replacing a sedimentation tank.

The apparatus disclosed in Japanese Patent Laid-Open No. 1-151995 discloses that after aeration treatment (aerobic treatment) in an aeration tank in which activated sludge floats, the aeration is stopped and the activated sludge is allowed to settle, and the supernatant liquid is removed. The liquid is taken out to a separate supernatant liquid tank, and the liquid having a small dissolved amount of activated sludge taken out to the supernatant liquid tank is sent to a membrane treatment device for solid-liquid separation. In this way, solid-liquid separation of a liquid having a small dissolved amount of activated sludge can reduce the load on the membrane separation device.

Further, the apparatus disclosed in Japanese Patent Laid-Open No. 4-222696 etc. is provided with an air diffuser having an air diffusing function and a filtering function in a treatment tank in which activated sludge floats, and performs aerobic treatment during air diffusing. When stopped, anaerobic treatment is carried out, activated sludge is filtered on the air diffusion surface, and the permeated liquid is drawn out of the system.

[0006]

All of the above-mentioned conventional apparatuses have one tank, that is, the apparatus disclosed in Japanese Patent Laid-Open No. 1-151995 has an aeration tank, and Japanese Patent Laid-Open No. 4-222 does.
In the apparatus disclosed in Japanese Patent No. 696, etc., anaerobic treatment cannot be performed while the aeration tank is performing aerobic treatment, and there is a problem in terms of purification capacity.

Further, in the conventional apparatus, since the excess sludge is collected as it is, that is, it is collected and discarded as a solid, the difficult problem of the disposal place, the disposal method, etc. is not solved.

[0008]

In order to solve the above problems, a septic tank according to the present invention comprises a biological treatment tank in which activated sludge floats, and a membrane separation device for solid-liquid separating the liquid to be treated in the biological treatment tank. A sludge digestion tank into which the concentrated liquid from the membrane separation device or sludge in the biological treatment tank flows in, and a disinfection tank into which the permeated liquid from the membrane separation device flows.

Further, in the purification method according to the present invention, the liquid to be treated which has been treated in the biological treatment tank in which the activated sludge is suspended is sent to the membrane separation device, and part or all of the concentrated liquid discharged from the membrane separation device or The sludge in the biological treatment tank was sent to the sludge digestion tank, where it was digested and gasified.

[0010]

The liquid to be treated introduced into the biological treatment tank is denitrified by oxidative decomposition of ammonia nitrogen and undecomposed organic matter by the activated sludge, or is taken into the activated sludge. On the other hand, in the sludge digestion tank, digestion (volume reduction) of sludge is performed by anaerobic digestion, that is, gasification (CO ₂ , CH ₄ ) of organic matter by methane fermentation.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a vertical cross-sectional view of the septic tank according to the present invention, and FIG. 2 is a view as seen from the direction of arrow AA in FIG. It is divided into a floating first biological treatment tank S1, a second biological treatment tank S2, a sedimentation tank S3 for causing activated sludge to settle, and a sludge digestion tank S4,
The second treatment tank S2 and the sedimentation tank S3 communicate with each other at the bottom, and the disinfection tank S5 is provided above the sedimentation tank S3.
1 is provided with an introduction pipe 5, the partition walls 2 and 4 are provided with communication passages 6 and 7, and the disinfection tank S5 is provided with a discharge pipe 8.

A membrane separation device 10 is arranged on the upper surface of the main body 1. This membrane separation device 10 has a tubular separation membrane 11
And a pump 12, and a suction pipe 13 for the liquid to be treated, which is connected to the pump 12, faces the upper part of the settling tank S3.
2 through the supply pipe 14 for the liquid to be treated, the separation membrane 1
1 is connected to the primary side, and the secondary side of the separation membrane 11 is connected to a permeate pipe 15 for taking out the permeate, and the tip of the permeate pipe 15 is provided in the disinfection tank S5 during backwashing. It faces the storage tank S6 to be used. This storage tank S
The permeated liquid from 6 overflows into the disinfection tank S5. The reason why the permeate in the storage tank S6 is used during the backwash is to use the permeate that has not yet been mixed with the disinfectant and may not kill the bacteria.

From the primary side of the separation membrane 11, there is led out a concentrated liquid pipe 16 for taking out a concentrated liquid containing a high concentration of activated sludge. An ejector 17 is connected in the middle of the concentrated liquid pipe 16, and a diffuser pipe 19 is attached to the tip of a gas-liquid introduction pipe 18 extending from the ejector 17.

Further, a branch pipe 16a is provided in the middle of the concentrated liquid pipe 16, and a valve 20 provided in the branch pipe 16a.
Is opened so that part of the concentrated liquid containing a high concentration of activated sludge is sent to the sludge digestion tank S4.

FIG. 3 is a vertical sectional view of a septic tank according to another embodiment,
FIG. 4 is a view taken in the direction of arrows BB in FIG. 3, and in this embodiment, the membrane separation device 30 is different from the membrane separation device 10 of the above-mentioned embodiment. That is, the membrane separation device 30 is the membrane unit 3
1, a blower 32 for supplying air and a pump 33, the membrane unit 31 accommodates a hollow fiber-shaped separation membrane 35 and an air diffusing pipe 36 in a cylindrical body 34, and an air feeding pipe 37 extending from the blower 32 is provided in the diffusing pipe 36. The permeate pipe 38 connected and led out from the secondary side of the separation membrane 35 is connected to the pump 33, and the permeate pipe 38 downstream of the pump 33 faces the disinfection tank S5. A storage tank S6 similar to the above is provided in the disinfection tank S5.

The membrane separation device 30 does not have a mechanism for sending the concentrated liquid to the sludge digestion tank S4. Instead, in this embodiment, the sludge transportation pump 40 is provided in the second biological treatment tank S2. The sludge accumulated in the first biological treatment tank S1 and the second biological treatment tank S2 is sent to the sludge digestion tank S4.

A method for purifying the liquid to be treated using the septic tank having the above-described structure will be described with reference to FIGS. 5 and 6.
The septic tank will be described based on the one in which sludge is fed from the membrane separation device to the sludge digestion tank as shown in FIGS. 1 and 2.

In the method shown in FIG. 5, the combined waste water including bath waste water, wash waste water, laundry waste water, night soil, kitchen waste water and kitchen waste water is sent to the biological treatment tank S1 as the liquid to be treated, and this merger is performed. The effluent is subjected to intermittent aeration and anaerobic treatment and aerobic treatment are repeated.

In the anaerobic treatment, the organic matter in the wastewater combined with the acid-producing bacteria contained in the activated sludge becomes acetic acid (CH ₃ COO).
H) and propionic acid (CH ₃ CH ₂ COOH), etc. are reduced to low molecular weight, and these organic acids are further decomposed and methane (CH 4) and carbon dioxide (CO ₂ )
Converted to gas. In addition, ammonia nitrogen (NH ₄ ⁺ ) which is a decomposition product of nitrogen components such as protein and urea is generated. Further, in the aerobic treatment, the ammonia nitrogen blown by the aeration is used to convert the ammonia nitrogen (NH ₄ ⁺ ) into nitrate nitrogen (NO ₃ ⁻ ) or nitrite nitrogen (NO ₂ ) by nitrifying bacteria contained in activated sludge. ^- ) Is oxidatively decomposed, and undecomposed organic matter is incorporated into activated sludge.

The combined wastewater that has been treated in the biological treatment tank is sent to the membrane separation device 10 where it is subjected to solid-liquid separation. In other words, the permeated liquid of the membrane separation device is sent to the disinfection tank S5 via the storage tank S6, discharged after the disinfection, and the concentration of the concentrated liquid containing the activated sludge in which the organic matter of the soluble component in the wastewater is converted is less than a certain amount. Is supplied to the sludge digestion tank S4, and when the amount exceeds a certain amount, the rest is returned to the biological treatment tank S1. This is because if a large amount of concentrated liquid is supplied to the sludge digestion tank S4 at one time, the residence time in the sludge digestion tank S4 becomes shorter and sufficient digestion cannot be performed. Regarding the inflow of activated sludge into the sludge digestion tank S4, the biological treatment tanks S1 and S
It may be performed during the anaerobic treatment in 2.

In the sludge digestion tank S4, organic matter such as activated sludge is anaerobically digested and converted into methane (CH ₄ ) or carbon dioxide (CO ₂ ) gas, which is removed outside the system, and in the sludge digestion tank S4. Digestion liquid (supernatant liquid) is biological treatment tank S
Set back to 1.

On the other hand, in the method shown in FIG. 6, the wastewater sent to the biological treatment tank S1 is bath wastewater, washroom drainage,
Wastewater with a relatively low biochemical oxygen demand (BOD) such as laundry drainage and night soil (single drainage), which contains a large amount of SS components (floating components) such as kitchen drainage and kitchen waste drainage (biochemical oxygen demand ( Wastewater having a relatively high BOD) is sent to the sludge digestion tank S4, subjected to anaerobic treatment in the sludge digestion tank S4, and then sent to the biological treatment tank S1. By sending the wastewater having a relatively high BOD to the sludge digestion tank S4 in this manner, the sludge concentration in the sludge digestion tank S4 is higher than that in the biological treatment tank S1, and before the aerobic treatment is performed in the biological treatment tank, By performing anaerobic treatment in the digestion tank and decomposing a large amount of SS components that are difficult to progress in aerobic treatment,
High BOD wastewater can be treated efficiently.

Incidentally, since human waste (single drainage) has a much lower BOD than kitchen drainage and kitchen wastewater, and the amount thereof is large, it is made to flow into the biological treatment tank S1 together with the low BOD drainage. Since it contains more SS components than the other low BOD wastewater, it can be treated by flowing into the sludge digestion tank S4 together with the high BOD wastewater. In this case, it is necessary to make the residence time in the sludge digestion tank S4 longer than in the case of treating with the low BOD wastewater.

In the septic tank of the embodiment, the biological treatment tank, the sedimentation tank, the sludge digestion tank, the disinfection tank and the membrane separation device are integrally incorporated, but they may be separated separately. . Further, the storage tank S6 may be arranged outside the disinfection tank.

[0025]

As described above, according to the present invention, a part of the concentrated liquid from the membrane separator containing a large amount of activated sludge is sent to the sludge digestion tank, and excess sludge is converted into methane gas in the sludge digestion tank. Since it is decomposed and removed to the outside of the system, the trouble of regularly collecting and removing excess sludge as a solid is eliminated, and maintainability is greatly improved.

Further, even kitchen wastewater and kitchen wastewater containing a high BOD source which cannot be treated by the biological treatment tank alone, can be anaerobically treated in the sludge digestion tank and then aerobically treated in the biological treatment tank. It will be possible.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a septic tank according to the present invention.

FIG. 2 is a view on arrow AA of FIG.

FIG. 3 is a vertical sectional view of a septic tank according to another embodiment.

FIG. 4 is a view taken in the direction of arrow BB in FIG.

FIG. 5 is a block diagram illustrating a purification method according to the present invention.

FIG. 6 is a block diagram illustrating a purification method according to another embodiment.

[Explanation of symbols]

1 ... Septic tank main body, 2, 3, 4 ... Partition wall, 10, 30 ... Membrane separation device, 11, 25 ... Separation membrane, 17 ... Ejector, 1
9, 36 ... Air diffuser, S1, S2 ... Biological treatment tank, S3 ... Sedimentation tank, S4 ... Sludge digestion tank, S5 ... Disinfection tank.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Katsumi Nishimura, Inventor Katsumi Nishimura 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture Totoki Kikai Co., Ltd. (72) Isao Miura 2 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka 1st-1st Totoki Equipment Co., Ltd.

Claims (4)

[Claims] 1. A biological treatment tank in which activated sludge floats, and a membrane separation device for solid-liquid separating the liquid to be treated in the biological treatment tank.
A sludge digestion tank into which the concentrated liquid from this membrane separator flows,
A septic tank comprising a disinfecting tank into which the permeated liquid from the membrane separator flows. 2. A biological treatment tank in which activated sludge floats, and a membrane separation device for solid-liquid separating the liquid to be treated in the biological treatment tank.
A septic tank comprising: a sludge digestion tank into which sludge in the biological treatment tank flows, and a disinfection tank into which permeate from the membrane separation device flows. 3. A liquid to be treated, which has been treated in a biological treatment tank in which activated sludge floats, is sent to a membrane separation device, and part or all of the concentrated liquid taken out from the membrane separation device or sludge in the biological treatment tank is sludge. A purification method characterized in that the sludge is sent to a digestion tank, where it is digested and gasified. 4. The biochemical oxygen demand (BO) of the liquid to be treated such as bath drainage, wash drainage, laundry drainage or night soil.
Wastewater with a relatively low D) is sent to the biological treatment tank, and wastewater with a relatively high biochemical oxygen demand (BOD) such as kitchen wastewater or kitchen wastewater is sent to the sludge digestion tank and the supernatant of the sludge digestion tank is sent. The purification method according to claim 3, wherein the liquid is sent to the biological treatment tank.