JPH0780493A - Anaerobic treating device for waste water and operating method thereof - Google Patents

Abstract

PURPOSE:To provide such an anaerobic treating device for waste water wherein a start-up can be effected in a short period and the concentration of bacteria in a reaction part is highly maintained by preventing outflow of a fungus body and separation of gas, liquid and solid is efficiently performed and treatment of load higher than in a conventional process is enabled and to provide an operating method thereof. CONSTITUTION:A methane fermentation tank 1 is partitioned in order of a reaction part 3, a deaeration part 6, a separation part 7 and a stabilization part 10. Suspended solid 15 stuck to bubbles 14 generated in the reaction part 3 is separated from bubbles 14 in the deaeration part 6 and the separation part 7. Floating sludge recovered from the vicinity of the water surface of the separation part 7 is sprayed on the liquid of the reaction part 3 and the deaeration part 6 by a floating sludge spraying means 16 and separation of gas, solid and liquid is promoted. Sludge is recovered from the bottom of the separation part 7 and returned to the reaction part 3 by a return means 18 of settling sludge. Treated water is returned to the reaction part 3 by a return means 18a of treated water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater anaerobic treatment apparatus for treating medium-concentration organic wastewater and a method for operating the same.

[0002]

2. Description of the Related Art Treatment of medium-concentration organic wastewater with a BOD of 5000 mg / L or less is carried out by using a self-granulating methane bacterium, UASB (upflow anaerobic sludge blanket) reactor Anaerobic treatment with a bed reactor is the mainstream, and aerobic treatment is performed in the subsequent stage.

However, in the UASB reactor, it takes time to form granular bacterial cells of methane bacteria, it takes about 3 months to start up, the selectivity of waste water that can be treated is strong, and high load cannot be applied (BOD load 10 kg. / m ³ · day or less), the process is unstable due to bacterial outflow,
There are problems such as high cost of alkaline chemicals for pH adjustment, high cost of gas-liquid separation equipment, and large-scaled equipment. Further, in the case of one fixed bed reactor, there are problems that the cost of the carrier is high and the carrier may be clogged.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, can be started up in a short period of time, can prevent the outflow of bacterial cells and can maintain a high bacterial concentration in the reaction part, and The purpose of the present invention is to provide an anaerobic treatment device for wastewater that can reduce the cost of alkaline chemicals required for adjustment, can perform gas-solid separation efficiently, and can perform treatment with a higher load than before, and its operating method. It is a thing.

[0005]

In the wastewater anaerobic treatment apparatus of the present invention made to solve the above problems, a methane fermentation tank is divided into a reaction section, a deaeration section, a separation section and a stabilization section in this order. The raw water supply means for supplying the raw water to the reaction part and the treated water discharge means for discharging the treated water from the stabilizing part are provided, and the reaction part, the degassing part and the separating part have a hermetically sealed structure and the generated gas A means for collecting gas is provided, and flotation sludge spraying means for spraying the floating sludge collected from the separation part to the liquid surface of the reaction part and the degassing part is provided, and the settled sludge collected from the bottom of the separation part is returned. It is characterized in that a settling sludge returning means and a settling sludge discharging means for discharging the settling sludge are provided. Further, the operating method of the anaerobic treatment apparatus for wastewater of the present invention,
Raw water supplied to the reaction section of the methane fermentation tank of the anaerobic treatment apparatus for wastewater described above is floated with gas bubbles produced by anaerobically treating the floating sludge and the settling sludge collected in the separation section. Floating sludge collected in the separation unit is sprayed on the suspended particles coming in and degassed, and then sent to the separation unit.
It is characterized in that the flotation sludge and the sedimentation sludge are collected in the separation part, and then fed into the stable part, and further solid-liquid separated to obtain a clear treatment liquid. Another method of operating the wastewater anaerobic treatment apparatus of the present invention is to pressurize the reaction part, the degassing part, and the separation part, which have a sealed structure, and utilize the pressure drop in the stable part, which is open to the atmosphere. Is raised to crystallize metal salts such as calcium and magnesium, and the settled sludge containing the recovered crystallization product and part of the treated water having an increased pH are returned to the reaction section.

[0006]

In order to treat the medium-concentration organic wastewater with the anaerobic treatment apparatus of the present invention, first, raw water is introduced into the reaction section by the raw water supply means, and methane fermentation is carried out together with the flotation sludge and sedimentation sludge recovered in the separation section. To perform. At this time, bubbles of methane gas adhere to the bacterial cells, which are suspended particles in the reaction part liquid, and float up.The suspended particles are separated from the gas in the degassing part partitioned by the current plate. Settles in the separation section.
Then, the floating sludge floating in this part is recovered from the separation part by the floating sludge spraying means and sprayed on the liquid surfaces of the reaction part and the degassing part, so that the impact further promotes the gas separation from the suspended particles. To be done. The suspended particles separated from the gas in this way settle in the separation section, and the supernatant water is sent to the subsequent step as a treatment liquid. Further, since the settled settled sludge is returned to the reaction section by the settling sludge returning means, the microbial cells are prevented from flowing out, and the microbial cell concentration can be maintained high.

Moreover, if pressure is applied to the reaction section to the separation section, which have a sealed structure, the pressure is lowered in the stable section, which is open to the atmosphere, and the carbon dioxide gas dissolved in the liquid is released, so that the pH is maintained. To rise. As a result, crystallization of metal salts such as calcium and magnesium occurs, so if these crystallized substances are returned to the reaction section by the settling sludge returning means, they act as nuclei for the self-granulation of the methane bacteria. Promotes the granulation action of. For this reason, the wastewater anaerobic treatment apparatus of the present invention can significantly shorten the start-up period as compared with the conventional case. Furthermore, by returning part of the treated water whose pH has increased to the reaction section by means of the treated water returning means,
It is possible to suppress the decrease in pH of the reaction part due to the accumulation of volatile organic acids generated in the methane fermentation process, and to reduce the consumption amount of alkaline chemicals for pH adjustment.

[0008]

The present invention will be described below in more detail with reference to the illustrated embodiments. FIG. 1 shows a first embodiment, in which 1 is a methane fermentation tank, the inside of which is composed of a first partition plate 2 with a reaction part 3 of 60% by volume and a gas volume of 40% by volume. It is partitioned into a solid-liquid separation section 4. The gas-solid separating section 4 is composed of a degassing section 6, a separating section 7 and a stabilizing section 10. The first partition plate 2 extends from the bottom of the tank to a height of 90% of the water depth. In addition, the gas-solid separating section 4 has a second partition plate 5
Is divided into a deaeration part 6 and a separation part 7, and a lower part thereof is a sedimentation part 8 communicating with the bottom of the separation part 7, and a stabilizing part 10 is formed by a third partition plate 9. Second
Partition plate 5 extends about 10% of the water depth above the water surface,
% Extends below the surface of the water. A baffle plate 11 is provided close to the lower end of the third partition plate 9 so that only the supernatant water flows into the stabilizing portion 10. Further, the reaction part 3, the degassing part 6 and the separating part 7 are provided with roofs to form a hermetically sealed structure, and a gas recovery means 20 for recovering the generated gas is provided above the roof, but the stabilizing part 10 is the atmosphere. It is an open system.

In order to carry out an appropriate methane fermentation treatment, it is preferable that the volume of the reaction section 3 is set to about 50 to 70% of the methane fermentation tank 1. In addition, when methane fermentation treatment of organic wastewater,
It is more preferable to be able to change the volume ratio between the reaction section 3 and the gas-solid separation section 4 in the methane fermentation tank 1 depending on the type, temperature, concentration of the inflowing wastewater, the target concentration of the treated water, the properties, and the like.

In the reaction section 3, there are granular bacterial cells 12 by the above-mentioned self-granulating methane bacterium, and anaerobically the organic matter in the medium-concentration organic wastewater which is the raw water flowing in from the raw water inflow pipe 13. To process. As a result, the methane gas is generated as bubbles 14 and adheres to the suspended substance 15 in the reaction liquid to levitate it as shown in the figure.

The suspended matter 15 that has floated is collected in the first partition plate 2.
Flows into the degassing section 6 from the upper end of the air bubble, receives the impact from the floating sludge spraying means 16, and separates the bubbles 14. The suspended substance 15 after the air bubble separation settles in the settling section 8 below the separating section 7. Also,
The floating sludge becomes floating sludge in the separation unit 7 and floats on the surface of the water, and the float-like suction port 17 of the floating sludge spraying unit 16 sucks the sludge, and a nozzle is directed toward the water surface of the reaction unit 3 and the degassing unit 6. Spray from 17a. Due to this impact, the bubbles 14 are separated from the suspended matter 15, and the gas-solid separation of the floating sludge itself is promoted, so that the sludge settles in the settling section 8 below the separation section 7. Then, the settled sludge is returned to the reaction section 3 by the settling sludge returning means 18, whereby the decrease of the bacterial cell concentration is prevented, and the surplus is discharged by the settling sludge discharging means 19. The treatment liquid in which the gas and the suspended particles are separated in this way enters the stabilizing portion 10 from the lower end of the third partition plate 9 and is taken out as the treatment liquid. Further, the generated gas is recovered by the gas recovery means 20 via the pressurizing means 20a.

Further, as described above, the reaction section 3 and the degassing section 6
Since the separating part 7 is provided with a roof and has a sealed structure, it is preferable to operate this part by applying a pressure of about 100 to 300 mmAq by the pressurizing means 20a. As a result,
A large amount of carbon dioxide gas generated by methane fermentation is dissolved in the liquid, and the pressure is reduced in the stable portion 10 which is an open system to the atmosphere, and carbon dioxide gas is released. The removal of carbon dioxide gas in the liquid raises the pH of the treatment liquid, and as a result, crystallization of metal salts such as calcium and magnesium occurs, and the crystallized substance settles in the sedimentation section 8 together with the sludge. When the settled sludge containing this crystal substance is returned to the reaction section 3 by the settling sludge return means 18, the crystal substance acts as a nucleus when the bacterial cells are self-granulated, and promotes the granulation action of methane bacteria. Further, the treated liquid having an increased pH is taken out from the stabilizing part 10 as treated water, and a part of the treated water is treated by the treated water returning means 18a.
If it is returned to the reactor, it is possible to suppress the decrease in pH of the reaction solution due to the accumulation of volatile organic acids generated in the methane fermentation process in the reaction section 3 and reduce the consumption amount of the alkaline chemical for pH adjustment.

In the second embodiment shown in FIG. 2, a carrier for immobilization of methane bacteria 21 is used instead of the reaction section 3 filled with the granular bacterial cells 12 by the self-granulating methane bacteria in the first embodiment. The reaction part 3 filled with is used. However, in this case as well, the structure and operational effects are the same as those of the first embodiment shown in FIG.

In the third embodiment shown in FIG. 3, the reaction section 3 and the gas-solid separation section 4 are separated, and in addition to this, a stationary section 24 is provided. In this embodiment, the liquid flowing out from the reaction section 3 flows into the degassing section 6 of the gas-solid separation section 4 through the flow path 22. Further, the treated water flowing out from the stabilizing part 10 flows into the stationary part 24 through the flow path 23. In this embodiment, the reaction part 3 and the gas-liquid separation part 4 have a sealed structure,
Since the crystallization of the metal salt such as calcium and magnesium described above occurs in the stationary section 24 which is open to the atmosphere, the treated water returning means 18a is provided between the stationary section 24 and the reaction section 3 which are separate bodies. And, it is returned from the bottom of the stationary section 24 to the pull-out reaction section 3. However, the basic structure and operational effects are the same as those of the first embodiment.

[0015]

As described above in detail, according to the wastewater anaerobic treatment apparatus of the present invention, it is possible to prevent the outflow of bacterial cells and maintain a high bacterial concentration in the reaction section, and the floating sludge spraying means. The gas-solid separation can be efficiently performed, and a higher load can be achieved than in the past. Further, according to the operating method of the anaerobic treatment apparatus for wastewater of the present invention, by crystallizing a metal salt such as calcium or magnesium, it is possible to promote the granulation action of granular bacterial cells, and the period required for start-up can be increased. It can be shortened. Further, by returning the treated water to the reaction section, it is possible to reduce the consumption amount of the alkaline chemicals for pH adjustment.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

1 methane fermentation tank, 3 reaction section, 6 degassing section, 7 separation section, 8 sedimentation section, 10 stabilization section, 16 floating sludge spraying means, 18
Settling sludge returning means, 20 gas recovery means, 20a pressurizing means, 24 stationary part of the third embodiment

Claims (6)

[Claims] 1. A methane fermentation tank is divided into a reaction section, a deaeration section, a separation section and a stabilization section in this order, and a raw water supply means for supplying raw water to the reaction section and a treatment for discharging treated water from the stabilization section. A water discharge means is provided, and a gas recovery means for recovering the generated gas is provided on the upper part of the reaction section, the degassing section, and the separation section in a sealed structure, and the floating sludge collected from the separation section is connected to the reaction section and the degassing section. Wastewater characterized by being provided with floating sludge spraying means for spraying on the liquid surface, and also provided with settling sludge returning means for returning settling sludge collected from the bottom of the separation section and settling sludge discharging means for discharging settling sludge. Anaerobic treatment equipment. 2. The anaerobic treatment apparatus for wastewater according to claim 1, further comprising a pressurizing means for pressurizing the reaction section, the degassing section, and the separating section, which have a sealed structure. 3. A settling sludge returning means for returning the settled sludge obtained in the separation section, and a treated water returning section for returning a part of the treated water discharged from the stabilizing section to the reaction section.
Or the anaerobic treatment apparatus for wastewater according to 2. 4. The volume ratio between the reaction section of the methane fermentation tank and the gas-liquid separation section composed of the degassing section, separation section and stabilizing section of the methane fermentation tank can be changed. An anaerobic treatment apparatus for wastewater according to any one of claims. 5. The method for operating the anaerobic treatment apparatus for wastewater according to claim 1, wherein the raw water supplied to the reaction section of the methane fermentation tank is used as floating sludge recovered in the separation section. The suspended sludge collected in the separation unit is sprinkled with the floating sludge collected by the anaerobic treatment together with the settling sludge and floating on the suspended particles. A method for operating an anaerobic treatment apparatus for wastewater, comprising collecting floating sludge and settling sludge in a section, feeding them into a stable section, and further separating them into solid and liquid to obtain a clear treatment liquid. 6. The method of operating the anaerobic treatment apparatus for wastewater according to claim 2, wherein the reaction section, the deaeration section and the separation section, which have a sealed structure, are pressurized to stabilize the atmosphere in a stable section. Utilizing the pressure reduction, the pH is increased to crystallize metal salts such as calcium and magnesium, and the settled sludge containing the recovered crystallization product and a part of the treated water having an increased pH are returned to the reaction section. Method for operating wastewater anaerobic treatment equipment.