JP3358322B2 - Anaerobic treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a UASB
The present invention relates to an anaerobic treatment apparatus for performing anaerobic treatment by the (upflow sludge blanket) method.

[0002]

2. Description of the Related Art As an anaerobic treatment method for organic wastewater, a granular sludge having high density and large sedimentation is formed, and an organic wastewater containing soluble BOD is circulated upward to form a sludge blanket. The UASB method of performing high-load high-speed processing by making contact in the formed state has been adopted. In this method, solid organic substances having a low digestion rate are separated and separately treated, and only soluble organic substances having a high digestion rate are subjected to high-speed anaerobic treatment at a high load by anaerobic treatment using granular sludge having a high anaerobic microorganism density. Method and is distinguished from traditional anaerobic treatment.

The conventional anaerobic digestion method is a method in which an organic effluent containing a solid organic substance and a soluble organic substance is directly introduced into a digestion tank to perform anaerobic digestion. Since it takes time, 20 to 4
A long residence time of 0 days is required, and a large processing apparatus is required. On the other hand, the UASB method uses highly sedimentable granular sludge in which highly active anaerobic microorganisms are accumulated, so that even at a high flow rate, solid-liquid separation is improved and a large amount of sludge is retained in the tank. In addition, the sludge concentration in the tank is kept high, whereby the anaerobic treatment can be performed with high treatment efficiency, and the treatment can be efficiently performed using a small apparatus.

[0004] In the anaerobic digestion method, sludge is fine and light, so it floats up due to the adhesion of generated gas and forms scum on the liquid surface. However, when the scum is crushed by stirring and the sludge and gas are separated, Sludge settles and scum formation is prevented. On the other hand, in the UASB method, since the sludge that has been granulated and has good sedimentation properties is used, the sludge does not normally float with the digestion gas to form scum unlike the anaerobic digestion method. There is no need to perform operations such as crushing and returning to the reaction section, and the driving operation is said to be simple.

However, some UASB anaerobic treatment apparatuses have a BOD load of 10 kg / m ³ ···
In a device that performs high-load treatment of d or more, a phenomenon is seen in which the granular sludge floats and turns into scum, and the floating sludge flows out into the treated water, and the amount of sludge retained in the anaerobic reaction tank decreases. . If this sludge floats or flows out, the treatment becomes insufficient, and high load operation, which is a characteristic of the UASB method, becomes difficult. In addition, anaerobic sludge flows into the activated sludge treatment device, which is a post-treatment of the UASB method, The DO of the aeration tank is greatly reduced, and the processing performance of the activated sludge treatment device is reduced. The floating of the above-mentioned sludge is phenomenologically similar to the floating of scum in the conventional anaerobic digestion method.However, unlike the floating of the sludge accompanying gas adhering like scum, the granular sludge itself This is because the specific gravity becomes small, and the sedimentation property is not recovered only by removing the gas attached to the outside as in the conventional scum breaker.

[0006] Most of the granular sludge floating in the UASB anaerobic reaction tank contains gas generated by the anaerobic reaction inside the granular sludge, and the specific gravity of the sludge is light. There are many examples. Therefore, by crushing the granular sludge containing the gas, the gas in the encapsulated state is released, and it is possible to form a blanket which is the original form of the granular sludge. Therefore, in the anaerobic treatment device of the UASB type, the granular sludge floating in the reaction tank is appropriately discharged to the outside of the reaction tank, and the discharged sludge is crushed using a pump, a mixer, a homogenizer, or the like capable of crushing the sludge. Attempts have been made to return the product in a state where it has been exposed (for example, JP-A-6-182382).

[0007]

However, recent anaerobic treatment apparatuses have a completely hermetic structure from the viewpoint of odor control, and it is difficult to efficiently recover the sludge floating in the reaction tank. In some cases, the granulated sludge that has floated is often left in a reaction tank for a long period of time. As a result, the floating sludge flows out together with the processing liquid, and the amount of granular sludge forming a good blanket in the reaction tank gradually decreases, making normal anaerobic treatment difficult. Even if a sludge collection device such as a gas injection nozzle is provided at the liquid surface of the solid-liquid separation unit as described in the above-mentioned publication, it is difficult to efficiently remove floating sludge because the operation status cannot be checked in a reaction tank having a closed structure. There is a problem that is.

[0008] An object of the present invention is to solve the above-mentioned problems in the UASB method. Even when granulated sludge floats, the sludge is efficiently taken out, the sedimentation property is restored, and the sludge is returned to the reaction section. An object of the present invention is to provide an anaerobic treatment apparatus capable of performing treatment with high treatment efficiency while maintaining a high sludge concentration in a tank.

[0009]

According to the present invention, there is provided an anaerobic reaction tank having a reaction section in which a sludge blanket made of granular sludge containing anaerobic microorganisms is formed, and a bottom section having an inflow section of a liquid to be treated. And, a solid-gas separation member that is arranged at an inclination to separate the solid-liquid separation part and the gas collection part at the upper part of the reaction part, and a communication path that communicates the reaction part with the lower part of the solid-liquid separation part, An overflow type floating sludge take-out part provided in a solid-liquid separation part near the upper part of the communication passage,
An overflow-type processing liquid extraction unit provided in the solid-liquid separation unit at a position away from the upper part of the communication passage, and a baffle provided near the liquid level between the processing liquid extraction unit and the floating sludge extraction unit, An anaerobic treatment device comprising a crushing device for crushing the granular sludge taken out from the floating sludge take-out portion and returning it to the reaction portion.

Although the growth process of granular sludge in the UASB method is not clear, anaerobic microorganisms are present on the surface of minute inorganic SS with a particle size of about 0.1 mm and the surface of scale components containing calcium and magnesium. When new anaerobic microorganisms grow and adhere in the form of annual rings with the fine SS and scale as nuclei attached, and it takes several months or more to grow into granular sludge with a particle size of 0.5 to 1 mm. Have been. It is said that the grown granular sludge is crushed by a flow caused by the flow of water or gas in the reaction tank, and the crushed fine particles and debris become nuclei to grow the next granular sludge.

When the grown granular sludge is not crushed, or when the crushed ratio or degree is small, as the sludge continues to grow and the particle size becomes 1 mm or more, the inside of the granular sludge becomes larger. Anaerobic microorganisms and organic SS components self-decompose. Then, after self-decomposition, it becomes a cavity, the gas generated by the methane generation reaction is accumulated in the cavity, the specific gravity of the granular sludge is reduced by the contained gas, and as a result, the granular sludge rises and flows out Conceivable.

When the load in the UASB method is low,
The growth of granulated sludge and the rate of crushing of the grown sludge are balanced, so the existence rate of granulated sludge that grows to a large particle size and contains gas is small, The outflow phenomenon is not significant. In contrast, when the treatment is performed at a high load of 10 to 15 kg / m ³ · d as the BOD load, the growth rate of the granular sludge becomes
It is much higher than the crushing rate, and the floating and runoff of sludge increases. Therefore, when the UASB method performs a high-load operation, the scale component having a high specific gravity or inorganic SS is contained in the sludge.
Unless water is continuously supplied, a floating phenomenon of granular sludge occurs.

Therefore, according to the present invention, the floating sludge is efficiently taken out and crushed appropriately, thereby reducing the average particle diameter of the floating sludge and, at the same time, exposing the internal hollow portion to the outer surface to recover the sedimentation property. , And is configured to maintain the sludge concentration in the tank high. The anaerobic reaction tank in the UASB method is used as a countermeasure against odorous gases such as generated organic acids and sulfur compounds.
In order to efficiently remove the floating sludge from the anaerobic reaction tank having such a closed structure, in the present invention, the sludge overflows to the solid-liquid separation section near the upper part of the communication passage between the solid-liquid separation section and the reaction section. A floating sludge take-out section is provided, an overflow-type treatment liquid take-out section is provided at a solid-liquid separation section at a position distant from the upper part of the communication passage, and a baffle is provided near a liquid surface between the two take-out sections.

It is preferable that the floating sludge take-out part is opened at a position lower than the treatment liquid take-out part. As the crushing device, a pump having a crushing mechanism such as a grinder pump, a mixer, a homogenizer, or the like can be used. It is preferable that the crushing device is disposed at a position lower than the floating sludge take-out section, and the floating sludge is configured to move down.

[0015]

In the anaerobic treatment method using the anaerobic treatment apparatus of the present invention, first, granulated sludge containing anaerobic microorganisms granulated by utilizing the self-granulating property of anaerobic microorganisms is supplied to an anaerobic reaction tank. The solution is charged into the reaction section, and an organic waste liquid is introduced from the inflow section of the liquid to be treated provided at the bottom, and the liquid is passed upward to form a sludge blanket, which is brought into contact under anaerobic conditions. Thereby, the soluble organic matter in the wastewater is decomposed into methane and carbon dioxide by the action of the anaerobic microorganism through the acid generation step and the methane generation step.

Since the granular sludge has a high density and an excellent sedimentation property, a uniform sludge blanket is formed by passing the discharged liquid in an upward flow, and is held in the reaction section. The waste liquid that has passed through the sludge blanket enters the solid-liquid separation section through the communication passage, where it is separated into solid and liquid, and the separated liquid is taken out as a treatment liquid from the treatment liquid take-out section. The separated sludge settles and returns to the reaction section from the communication passage. Gas such as methane generated in the reaction section rises in the reaction section, but is blocked by the solid-gas separation member, does not flow into the solid-liquid separation section, and is taken out from the gas collection section.

In a normal operation state where the load is relatively low, there is no floating of the granular sludge, and the sludge flowing into the solid-liquid separation section settles as it is and returns to the reaction section. Alternatively, when the operation is continued for a long period of time, the apparent specific gravity of the granular sludge becomes small and floats, and floats on the liquid surface of the gas collecting part or the solid-liquid separating part. In the gas collecting section, since the liquid level is disturbed by the generated gas, even if the specific gravity of the granular sludge is small, it is easy to circulate to the reaction section as it is.

In the present invention, the anaerobic reaction is carried out while the floating sludge floating in the solid-liquid separation section is taken out from the floating sludge take-out section, crushed by the crushing device and returned to the reaction section. Floating sludge is blocked by the baffle and does not flow out of the processing liquid outlet. As the floating sludge has a hollow part formed inside, if it is crushed so that this hollow part is exposed on the surface,
Granular sludge returns to its original state of higher specific gravity, and sedimentation is restored. The degree of crushing at this time is such that most of the crushed sludge has a particle size of 0.2 to 1 mm, preferably 0.3 to 0.
It is appropriate to set it to about 7 mm. If the particle size of the crushed sludge is less than 0.2 mm, it easily flows out together with the treatment liquid, and if it exceeds 1 mm, the hollow portion is not exposed,
It is not preferable because the sedimentability often does not recover.

When crushing with a pump having a sludge crushing mechanism, the degree of crushing is checked in advance using a special pump having a vortex type or a foreign matter crushing mechanism, and the number of rotations suitable for an appropriate crushing situation is determined. It is preferable to operate with a constant flow rate. The appropriate crushing situation can be confirmed and adjusted by measuring the particle size of the crushed sludge. When using a mixer or a homogenizer for crushing, it is preferable to adjust the stirring intensity while checking the crushing status.

If the treatment is continued without crushing the floating sludge, the floating sludge flows out together with the treated water, and the amount of the sludge decreases, thereby reducing the treatment efficiency. By returning, the sludge concentration in the tank (the amount of sludge in the tank /
Reaction volume) is kept high. Sludge concentration in the tank is 100
It can be maintained at 00 mg / l or more. The organic effluent to be treated in the present invention is an effluent containing a soluble organic substance, and may contain some solid organic substances. When a large amount of solid organic matter is contained, the solid organic matter that has been removed by solid-liquid separation in advance is subjected to the treatment.

Although the present invention is applied to a high-load anaerobic treatment apparatus using the UASB method, it does not depend on the operating temperature of the UASB apparatus.
The present invention can be applied to a medium-temperature treatment at a temperature between ℃ and a high-temperature treatment having a temperature range of 45 ° C. or more. The upward flow rate of the drainage in the anaerobic reaction tank is 0.5 to
2 m / hr, preferably 1 to 1.5 m / hr, and the residence time is 4 to 48 hours, preferably about 6 to 24 hours.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a sectional view of a UASB type anaerobic treatment apparatus according to an embodiment. In the figure, 1 is an anaerobic reaction tank,
It is formed of a rectangular parallelepiped container, and the to-be-processed liquid inflow portion 2 is uniformly provided at the bottom, and communicates with the to-be-processed liquid introduction passage 3. The upper part of the anaerobic reaction tank 1 is covered with a cover 4 to form a gas chamber 5 having a closed structure, and a gas extraction path 6 communicates with the top.

A liquid chamber 7 is formed below the gas chamber 5 in the anaerobic reaction tank 1, and a solid gas formed by first and second partition plates inclined in opposite directions is formed above the liquid chamber 7. Separating members 8a, 8
b, a solid-liquid separation section 9 is defined inside the upper part, a gas collecting section 10 is defined outside the upper part, and a reaction part 11 is defined below the lower part. The lower ends of the solid-gas separation members 8a and 8b are separated to form a communication passage 12, and one lower end covers the lower side of the other lower end. It is designed to prevent entry.

An organic effluent is introduced into the liquid chamber 7 in the anaerobic reaction tank 1, and a sludge blanket 13 is formed in the reaction section 11. An overflow-type floating sludge take-out section 14 is provided at a liquid level near the upper portion of the communication passage 12 above the solid-liquid separation section 9 and communicates with a floating sludge take-out path 15. Further, an overflow-type processing liquid take-out unit 16 is provided on the solid-gas separation members 8a and 8b located at a position away from the vicinity of the upper portion of the communication passage 12 above the solid-liquid separation unit 9,
It is connected to the processing liquid take-out path 17. Floating sludge removal part 14
Is provided at a position 1 to 5 cm lower than the processing liquid take-out section 16, and a baffle 18 is provided near the liquid surface between the two take-out sections 14 and 16 in the vicinity of the processing liquid take-out section 16.

Numeral 21 denotes a crushing device, in which a gas chamber 5a is formed in the upper part and a liquid chamber 7a is formed in the lower part. The gas chamber 5a communicates with the pressure equalizing pipe 22 from the gas chamber 5 of the anaerobic reaction tank 1. 7a
Is connected to the rising sludge removal path 15. The liquid chamber 7a
Is provided with a crushing pump 23, and a sludge return path 24 communicates with the liquid chamber 7 of the anaerobic reaction tank 1. The crushing strength of the crushing pump 23 can be adjusted by adjusting the number of revolutions and the flow rate of the crushing sludge, and the crushing sludge is adjusted to have a particle size of 0.3 to 0.7 mm. If the particle diameter of the particles is out of the above range, it can be corrected.

In the anaerobic treatment method using the anaerobic treatment apparatus described above, first, granule-like sludge containing anaerobic microorganisms granulated by utilizing the self-granulating properties of anaerobic microorganisms is reacted in the reaction section of the anaerobic reaction tank 1. Put into 11. Then, an organic wastewater is introduced from the liquid-to-be-processed introduction path 3 to the liquid-to-be-processed inflow section 2 provided at the bottom of the anaerobic reaction tank 1, and is passed upward to form a sludge blanket 13. An anaerobic reaction is performed by contacting under sexual conditions. Thereby, the soluble organic matter in the wastewater is decomposed into methane and carbon dioxide by the action of the anaerobic microorganism through the acid generation step and the methane generation step.

Since the granular sludge has a high density and an excellent sedimentation property, a uniform sludge blanket 13 is formed by passing the discharged liquid in an upward flow, and the sludge blanket 13 is held in the reaction section 11. The organic effluent that has passed through the sludge blanket 13 enters the solid-liquid separation section 9 through the communication path 12, where it is separated into solid and liquid. The separated liquid overflows from the processing liquid extraction section 16 and becomes a processing liquid as a processing liquid. Is taken out. The separated sludge is settled, and the reaction section 1
Return to 1. Gas such as methane generated in the reaction section 11 rises in the reaction section 11, but is blocked by the solid-gas separation members 8a and 8b and does not flow into the solid-liquid separation section 9, but is collected in the gas collection section 10, The gas is extracted from the gas chamber 5 to the gas extraction path 6.

In a normal operation state with a low load, the granular sludge does not float on the liquid surface, and the sludge flowing into the solid-liquid separation section 9 settles as it is and returns to the reaction section 11.
When the operation is performed under a high load, or when the operation is continued for a long period of time, the apparent specific gravity of the granular sludge becomes small and floats, and floats on the liquid surface of the solid-liquid separation section 9.

In this case, the buoyant sludge that has entered the solid-liquid separation unit 9 from the communication passage 12 rises up as it is, and is taken out by overflowing from the buoyant sludge removal unit 14 near the upper right part of the communication passage 12, and the floating sludge is removed. It is introduced into the crushing device 21 from the extraction path 15.

Since the floating sludge is blocked by the baffle 18 and does not reach the processing liquid extracting section 16, it does not flow out to the processing liquid extracting passage 17. Since the gas chambers 5 and 5a are maintained at an equal pressure by the equalizing pipe 22, and the floating sludge take-out part 14 is opened at a position lower than the treatment liquid take-out part 16, the floating sludge is transferred to the crusher 21 at a substantially constant flow rate. Is done.

In the crushing device 21, the introduced floating sludge is crushed by the crushing pump 23 and returned to the reaction section 11 from the sludge return path 24. The floating sludge has a hollow part formed inside, so by crushing this hollow part to be exposed on the surface, it returns to the original state with a large specific gravity,
Sedimentation recovers. By performing the anaerobic reaction while crushing the floating sludge and returning it to the reaction section 11 in this manner, the sludge concentration in the tank is maintained at a high level, and the treatment efficiency is maintained at a high state.

In the above-described apparatus, the floating sludge take-out section 14 is provided near the upper portion of the communication path 12.
The floating sludge that has passed through 2 is directly lifted as it is and is taken out from the floating sludge take-out section 14. Further, since the processing liquid take-out section 16 is disposed at a position away from the upper part of the communication passage 12 and a baffle 18 is provided between the floating sludge take-out section 14 and the processing liquid take-out section 16, the floating sludge is taken together with the processing liquid. Outflow is prevented.

The floating sludge take-out section 14 is a processing liquid take-out section 1
Since the floating sludge is opened at a position lower than 6, the floating sludge is taken out by a fixed amount, and is prevented from staying in the solid-liquid separation section 9.
In addition, the crushing device 21 crushes the floating sludge flowing in a fixed amount at a time, so that it can be easily crushed to a constant particle size, thereby recovering the settling property of the sludge and performing an efficient anaerobic treatment. . The buoyant sludge floating in the gas collecting part 10 is easily circulated to the reaction part 11 by stirring by the release of gas, and finally flows into the solid-liquid separation part 9 from the communication passage 12 and is taken out from the floating sludge take-out part 14. The gas collection unit 1
0 may be provided with a floating sludge take-out part 14.

[0034]

As described above, according to the present invention, a floating sludge take-out part is provided near the upper part of the communication passage between the reaction part of the anaerobic reaction tank and the solid-liquid separation part, and is located at a position away from the upper part of the communication passage. A treatment liquid take-out section is provided and a baffle is provided between the two, so that the floating sludge is efficiently taken out and crushed, the sedimentation property is restored, and the sludge is returned to the reaction section, thereby preventing sludge from flowing out. Anaerobic treatment can be performed efficiently by increasing the concentration.

[Brief description of the drawings]

FIG. 1 is a sectional view of an anaerobic treatment device according to an embodiment.

[Explanation of symbols]

 Reference Signs List 1 anaerobic reaction tank 2 liquid to be treated 3 inlet for liquid to be treated 4 cover 5, 5a gas chamber 6 gas extraction path 7, 7a liquid chamber 8a, 8b solid-gas separation member 9 solid-liquid separation unit 10 gas collection unit 11 Reaction unit 12 Communication passage 13 Sludge blanket 14 Floating sludge take-out unit 15 Floating sludge take-out passage 16 Treatment liquid take-out unit 17 Treatment liquid take-out passage 18 Baffle 21 Crusher 22 Equalizing tube 23 Crush pump 24 Sludge return passage

Continuation of front page (72) Inventor Hideki Nakayama 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Kogyo Co., Ltd. (56) References JP-A-8-103793 (JP, A) JP-A-7- 328687 (JP, A) JP-A-6-182382 (JP, A) JP-A-5-115709 (JP, A) Japanese Utility Model Application Sho 55-88895 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3/28

Claims (1)

(57) [Claims] An anaerobic reaction tank having a reaction section in which a sludge blanket made of granular sludge containing anaerobic microorganisms is formed, and an inflow section for a liquid to be treated at a bottom portion, and an upper portion of the reaction section. A solid-gas separation member inclined to separate the solid-liquid separation section and the gas collection section, a communication path communicating a lower part of the solid-liquid separation section with a reaction section, and a solid passage near an upper part of the communication path. An overflow-type floating sludge take-out section provided in the liquid separation section; an overflow-type processing liquid take-out section provided in the solid-liquid separation section at a position away from the upper part of the communication passage; An anaerobic treatment comprising: a baffle provided in the vicinity of a liquid level between sludge discharge units; and a crushing device for crushing granular sludge taken out from the floating sludge discharge unit and returning the sludge to the reaction unit. apparatus.