JPH08103795A - Anaerobic treatment device - Google Patents

Abstract

PURPOSE: To provide an anaerobic treatment device which can restore precipitating properties of sludge having reduced specific gravity thereby to maintain the precipitating properties of the sludge of an anaerobic reactor so that the sludge can be prevented from being lifted up, and keep the concentration of the sludge in the reactor higher, effecting thereby an anaerobic treatment at high processing efficiency. CONSTITUTION: A reaction zone 11 is formed, in an anaerobic processing reactor 1 of UASB system, to have a solid-liquid separation section 9 and a gas collecting section 10 in the upper section of the reactor and a sludge blanket 13 in the lower section, the sections being separated by solid-liquid separation members 8a, 8b, and sludge taken out of the reaction zone 11 is separated into a sludge having higher specific gravity and a sludge having a lower specific gravity in a sludge separation device 20 by means of an upward flow and the sludge having a higher specific gravity is returned as it is to the reactor 1, while the sludge having a lower specific gravity is crushed at a crushing device 30 and returned to the reactor 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention uses organic waste liquid UASB.
The present invention relates to an anaerobic treatment device for anaerobic treatment by the (upstream sludge blanket) method.

[0002]

2. Description of the Related Art As a method of anaerobic treatment of organic waste liquid, a granular sludge having a high density and a large sedimentation property is formed, and an organic waste liquid containing soluble BOD is upwardly flowed to form a sludge blanket. The UASB method is employed in which the high-load and high-speed processing is performed by bringing them into contact with each other in the formed state. In this method, solid organic matter with a slow digestion rate is separated and treated separately, and only soluble organic matter with a fast digestion rate is treated at high speed with high load by anaerobic treatment using granulated sludge with high anaerobic microorganism density. It is a method and is distinguished from the traditional anaerobic treatment.

The conventional anaerobic digestion method is a method in which an organic waste liquid containing a solid organic matter and a soluble organic matter is directly introduced into a digestion tank for anaerobic digestion, which is a long process in the step of solubilizing the solid organic matter. Since it takes time, 20-4 as a whole
A long residence time of 0 days is required, and a large processing device is required. On the other hand, since the UASB method uses granule-like sludge in which highly active anaerobic microorganisms are accumulated and has a large settling property, solid-liquid separation is improved even at high flow rates, and a large amount of sludge is retained in the tank. However, the sludge concentration in the tank can be maintained high, and thus 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, and thus the produced gas adheres to the surface to form a scum, but in the UASB method, the sludge is granulated and has a good sedimentation property. Since the sludge does not normally float up with the digestive gas to form scum as in the anaerobic digestion method, it is not necessary to crush the scum and return it to the reaction section. Is also said to be easy.

However, among the UASB type anaerobic treatment apparatuses, a BOD load of 10 kg / m ³ ·
In a device that performs high-load treatment of d or more, a phenomenon in which the granular sludge floats up to form scum, the floating sludge flows out into the treated water, and the sludge holding amount in the anaerobic reaction tank decreases is observed. . When this sludge floats or flows out, the treatment becomes insufficient, making it difficult to perform high-load operation, which is a characteristic of the UASB system, and anaerobic sludge flows into the activated sludge treatment device that is the post-treatment of the UASB system. The DO of the aeration tank is significantly reduced, and the treatment performance of the activated sludge treatment device is reduced.

Most of the granular sludge floating in the UASB type anaerobic reaction tank has a small specific gravity because the gas generated by the anaerobic reaction is contained inside the granular sludge. There are many cases where Therefore, by crushing the granular sludge enclosing the gas, it is possible to release the gas in the encapsulated state and form a blanket, which is the original existing form of the granular sludge. Therefore, in a UASB-type anaerobic treatment device, 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 crushable pump, mixer, homogenizer, etc. Attempts have been made to return the film to the reaction tank in an exposed state (for example, JP-A-6-182382).

[0007]

However, the recent anaerobic treatment device has a completely closed structure from the viewpoint of odor control, and it is difficult to efficiently collect the sludge floating in the reaction tank. In many cases, the floating granulated sludge is left in the reaction tank for a long period of time. Therefore, the floating sludge flows out together with the treatment liquid, and the retained amount of the granulated sludge forming a good blanket in the reaction tank gradually decreases, which makes normal anaerobic treatment difficult. Even when a sludge collecting device such as a gas injection nozzle on the liquid surface of the solid-liquid separation unit is provided as in the above publication, it is difficult to efficiently take out the floating sludge because the operating condition cannot be confirmed in the reaction tank having a closed structure. There is a problem that is.

In order to solve the above problems in the UASB method, an object of the present invention is to take out sludge in the reaction section and separate it into sludge having a small specific gravity and sludge having a large specific gravity and crushing the sludge having a small specific gravity. The anaerobic treatment device that recovers the sedimentation property of the sludge and prevents the sludge from floating, thereby maintaining a high sludge concentration in the tank and performing the treatment with high treatment efficiency. Is to provide.

[0009]

The present invention is the following anaerobic treatment apparatus. (1) Anaerobic with a reaction part in which a sludge blanket made of granulated sludge containing anaerobic microorganisms is formed, a liquid to be treated inflow part at the bottom, and a solid-liquid separation part and a gas collection part at the top Separation with a sludge separator that separates sludge extracted from the reaction tank and anaerobic reaction tank into sludge with high specific gravity and sludge with low specific gravity, and returns sludge with high specific gravity to the anaerobic reaction tank. An anaerobic treatment device, comprising: a crushing device for crushing the sludge having a small specific gravity and returning it to the anaerobic reaction tank. (2) The device according to (1) above, wherein the sludge separating device develops the sludge in an upward flow and separates it into sludge having a large specific gravity and sludge having a small specific gravity due to a difference in specific gravity. (3) The device according to (1) above, wherein the sludge separating device separates a sludge having a small particle size and a large specific gravity by a screen and a sludge having a large particle size and a small specific gravity.

Although the growth process of the granulated sludge in the UASB method is not clear, anaerobic microorganisms are present on the surface of fine inorganic SS having a particle diameter of about 0.1 mm and the surface of scale components containing calcium and magnesium. When attached, new anaerobic microorganisms grow and attach in an annual ring shape with the minute SS and scale as the nucleus, and when it takes several months or more to grow into granular sludge with a particle size of 0.5 to 1 mm. Has been done. It is said that the grown granular sludge is crushed by the flow of water and gas generated in the reaction tank, and the crushed fine particles and fragments serve as 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 hollow, and the gas generated by the methanogenic reaction is accumulated in the hollow, and the specific gravity of the granulated sludge is reduced by the enclosed gas, and as a result, the granular sludge floats up and flows out. Conceivable.

When the load amount in the UASB method is low,
The growth of granulated sludge and the rate of crushing of the grown sludge are balanced, so the proportion of granulated sludge that grows to a large particle size and contains gas is small, and the sludge floats, The outflow phenomenon is not remarkable. On the other hand, when the treatment is performed at a high BOD load of 10 to 15 kg / m ³ · d, the growth rate of the granulated sludge is
The rate is much higher than the rate of shredding, and sludge floating and runoff phenomena increase. Therefore, when the UASB system operates under high load, scale components with a high specific gravity and inorganic SS
Unless sludge is constantly supplied, the floating phenomenon of granulated sludge occurs.

When the granular sludge floats in the anaerobic reaction tank in this manner, it is difficult to take it out. Therefore, in the present invention, the sludge in the reaction section is taken out and separated into sludge having a large specific gravity and sludge having a small specific gravity. By crushing sludge with a small specific gravity and returning it, the settling property is restored, thereby preventing the sludge from floating and maintaining a high sludge concentration in the tank. As a method for separating sludge with a large specific gravity and sludge with a small specific gravity, it is common to develop sludge by an upward flow and separate sludge with a large specific gravity and sludge with a small specific gravity due to the difference in specific gravity. Since small particles have a large particle size and particles with a large specific gravity have a small particle size, a screen is used.Sludge with a small particle size and a large specific gravity and sludge with a large particle size and a small specific gravity are used according to the size of the particle size. Can also be separated into

When sludge is separated by an upward flow velocity, the sludge separating device divides the opening into a high-speed passage and a low-speed passage by a partition wall that can be adjusted, and sludge having a large specific gravity separated in the low-speed passage. It can be configured to return to the high speed flow path through the opening. It is preferable that the low-speed flow passage has an LV of 1 to 3 m / hr, and the high-speed flow passage has an LV of 3 to 5 m / hr. However, when the inorganic substance adheres and the specific gravity becomes large as a whole, each can be shifted to a higher level. it can. The flow velocity (LV) of the high-speed flow passage is preferably 3 to 5 times that of the low-speed flow passage. In this case, it is preferable to determine the flow rate so that sludge having a particle size of 0.7 mm or more can be separated.

When sludge is separated by a screen,
As a sludge separating device, a screen having an opening of 0.7 to 3 mm may be immersed in a liquid in a state of being inclined at 30 to 60 ° with respect to a horizontal plane, and sludge may be passed in an upward flow to be separated. it can. If the separation is performed in the upward flow, the chance of contact with air can be reduced, but in the case of the closed type, the downward flow may be used. The sludge to be separated here preferably has a particle size of 1 mm or more. In this case, a screen having an opening of 1 to 1.5 mm can be used to separate particles having a particle size of 1 mm or more. As the screen, a wedge wire type screen in which thin metal rods are arranged side by side in a certain direction is preferable, and it is particularly preferable that the screen is inclined so that the slits face in the vertical direction.

The crushing device is for crushing the separated sludge having a small specific gravity, and a pump having a crushing mechanism such as a grinder pump, a mixer, a homogenizer or the like can be used. A pump or the like is used as a means for removing the sludge from the anaerobic reaction tank, but it is preferable to use a pump or the like that does not crush the sludge here.

[0017]

In the method for anaerobic treatment using the anaerobic treatment apparatus of the present invention, first, the granulated sludge containing anaerobic microorganisms granulated by utilizing the self-granulating property of the anaerobic microorganisms is stored in the anaerobic reaction tank. It is charged into the reaction part, and the organic drainage is introduced from the treated liquid inflow part provided in the bottom part, and is passed in the upward flow to form a sludge blanket, which is contacted under anaerobic conditions. As a result, the soluble organic matter in the effluent is decomposed into methane and carbon dioxide by the action of the anaerobic microorganisms through the acid producing step and the methane producing step.

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

Under normal operating conditions when the load is relatively low, the granular sludge does not float up, and the sludge that has flowed into the solid-liquid separation section settles back to the reaction section as it is, but when operating under high load, Alternatively, when the operation is continued for a long period of time, the apparent specific gravity of the granule sludge becomes small and it becomes easy to float.

In the present invention, such sludge is taken out from the reaction section and separated into a sludge having a large specific gravity and a sludge having a small specific gravity by a sludge separating device. When expanding and separating in the upward flow,
Separated by the difference in specific gravity. When the particles are separated by a screen, they are separated (sieved) according to the particle size and separated into sludge having a small particle size and a large specific gravity and sludge having a large particle size and a small specific gravity.

The separated sludge having a large specific gravity is returned to the anaerobic reaction tank as it is, and the sludge having a small specific gravity is introduced into a crushing device to be crushed. Since sludge with a small specific gravity has a cavitation inside, if crushed so that this cavitation is exposed on the surface, the granulated sludge returns to its original high specific gravity and the sedimentation property is restored. . Regarding the degree of crushing at this time, most of the crushed sludge has a particle size of 0.2 to 1 m.
m, preferably 0.3 to 0.7 mm. If the particle size of the crushed sludge is less than 0.2 mm, it tends to flow out together with the treatment liquid, and if it exceeds 1 mm, the hollow portion is not exposed and the sedimentation property is not recovered in many cases, which is not preferable.

When crushing with a pump having a sludge crushing mechanism, a special pump having a vortex system or a foreign matter crushing mechanism is used to check the crushing degree in advance, and the rotation speed suitable for the appropriate crushing situation. It is preferable to operate at a flow rate of or. The proper crushing condition can be checked and adjusted by measuring the particle size of crushed sludge. Even when a mixer, a homogenizer or the like is used for crushing, it is preferable to adjust the stirring strength while checking the crushing condition.

If the treatment is continued without separating and crushing such sludge, the sludge having a small specific gravity floats up and flows out together with the treated water to reduce the sludge amount and the treatment efficiency, but By crushing small sludge and returning it to the reaction section, the sludge is prevented from floating and the sludge concentration in the tank (amount of sludge in the tank / volume of reaction section) is maintained high. Sludge concentration in the tank is 10
It can be maintained at 000 mg / l or more. The organic waste liquid to be treated in the present invention is a waste liquid containing a soluble organic substance, and may contain some solid organic substance. When a large amount of solid organic matter is contained, the solid organic matter removed in advance by solid-liquid separation is subjected to treatment.

Although the present invention is applied to a high load anaerobic treatment apparatus by the UASB method, it does not depend on the operating temperature of the UASB apparatus and the treatable temperature is from 20 ° C to 45 ° C.
The present invention can be applied to either the intermediate temperature treatment which is between 0 ° C or the high temperature treatment which has a temperature range capable of being treated at 45 ° C or higher. The upward flow velocity of the drainage in the anaerobic reaction tank is 0.5 to
2 m / hr, preferably 1 to 1.5 m / hr, sludge blanket development rate 5 to 20%, preferably 10 to 1
5% and a residence time of 4 to 48 hours, preferably 6 to 24 hours are suitable.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments of the drawings. FIG. 1 is a sectional view of a UASB type anaerobic treatment apparatus according to an embodiment. In FIG. 1, reference numeral 1 is an anaerobic reaction tank, which is composed of a rectangular parallelepiped-shaped container and has a processing liquid inflow portion 2 at the bottom thereof.
Are evenly provided and communicate with the liquid introducing passage 3.
An 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 is provided on the top thereof.
Is in contact.

A liquid chamber 7 is formed below the gas chamber 5 in the anaerobic reaction tank 1, and a solid gas composed of first and second partition plates inclined in opposite directions is formed above the liquid chamber 7. Separation members 8a, 8
b is arranged, and a solid-liquid separating section 9 is partitioned inside the upper part, a gas collecting section 10 is partitioned outside the upper part, and a reaction section 11 is partitioned below. The lower ends of the solid-gas separating members 8a and 8b are isolated from each other to form a communication path 12, and one lower end covers the lower side of the other lower end so that the floating gas can flow from the communicating path 12 into the solid-liquid separation section 9a. It is structured to prevent entry.

The organic waste liquid is introduced into the liquid chamber 7 in the anaerobic reaction tank 1, and the sludge blanket 13 is formed in the reaction section 11. An overflow type treatment liquid take-out portion 14 is provided above the solid-liquid separation portion 9 and communicates with a treatment liquid take-out passage 15. Reference numeral 16 is a sludge extraction tank, and a sludge extraction passage 17 communicates with the reaction section 11 of the anaerobic reaction tank 1,
A sludge supply path 19 having a pump 18 is connected to the lower part of the sludge separation device 20.

The sludge separating device 20 is composed of a vertically long cylindrical tank, and a partition 22 which can be moved up and down makes a high-speed flow passage 21.
a and the low-speed flow passage 21b. Both channels 21
Apertures 22a are formed at the base points of a and 21b.
The opening can be adjusted by raising or lowering 2. A transfer liquid path 24 having a pump 23 is connected to the lower part of the sludge separation device 20. The sludge return passage 25 communicates with the reaction part 11 of the anaerobic reaction tank 1 from the upper part of the high-speed flow passage 21a, and the communication passage 26 communicates with the crushing device 30 from the upper part of the low-speed flow passage 21b.

The crushing device 30 is provided with a crushing pump 31, and the sludge return passage 25a communicates with the reaction section 11 of the anaerobic reaction tank 1. The crushing strength of the crushing pump 31 is adjustable, and the particle size of the crushed sludge is adjusted to 0.3 to 0.5 mm. When the particle size of the crushed sludge during operation is out of the above range, Can be corrected.

In the anaerobic treatment method using the above anaerobic treatment apparatus, first, a granular sludge containing anaerobic microorganisms granulated by utilizing the self-granulating property of anaerobic microorganisms is used as a reaction part of the anaerobic reaction tank 1. Put in 11. Then, the organic waste liquid is introduced from the liquid to be treated introduction passage 3 into the liquid to be treated 2 provided at the bottom of the anaerobic reaction tank 1, and the sludge blanket 13 is formed by passing the liquid in an upward flow to form an anaerobic gas. The anaerobic reaction is carried out by contacting under sex. As a result, the soluble organic matter in the effluent is decomposed into methane and carbon dioxide by the action of the anaerobic microorganisms through the acid producing step and the methane producing step.

Since the granular sludge has a high density and an excellent settling property, a uniform sludge blanket 13 is formed by passing the waste liquid in an upward flow, and is retained in the reaction section 11. The organic waste liquid that has passed through the sludge blanket 13 enters the solid-liquid separation unit 9 from the communication passage 12, and is separated into solid-liquid there, and the separated liquid overflows from the processing liquid take-out unit 14 and becomes a processing liquid take-out path 15 as a processing liquid. Taken out. The separated sludge settles down, and the reaction passage 1 passes through the communication passage 12.
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. It is taken out from the gas chamber 5 to the gas take-out path 6.

In a normal operating condition with a low load, the granular sludge does not float on the liquid surface, and the sludge that has flowed 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 granulated sludge becomes small and the sludge comes to float.

Then, an operation is carried out to take out the granular sludge from the anaerobic reaction tank 1 to separate the floating sludge and recover the sedimentation property. For this reason, the sludge extraction path 17 from the reaction section 11
The sludge is taken out to the sludge taking-out tank 16 through. At this time, it is preferable to remove the sludge without crushing it as much as possible, and when using a pump, a snake type, a tube type and the like are preferable.

The sludge taken out from the sludge take-out tank 16 is supplied to the lower part of the sludge separating device 20 by a pump 18 through a sludge supply passage 19, while a part of the treated liquid is pumped as a transfer liquid by a pump 23.
The liquid is supplied from the transfer liquid passage 24 to be mixed, and the liquid is passed in an upward flow. At this time, the partition wall 22 is moved up and down to adjust the opening degree of the opening 22a so that the flow velocity (LV) of the high-speed flow passage 21a is 3 to 5 m.
/ Hr, and the low-speed flow passage 21b is adjusted to 1 to 2 m / hr.

Of the sludge that has entered the sludge separator 20, particles having a large specific gravity that have entered the high-speed flow passage 21a ascend in the high-speed flow passage 21a as they are, and flow from the sludge return passage 25 to the reaction section 11 of the anaerobic reaction tank 1. Will be returned. On the other hand, since the sludge entering the low speed flow path 21b through the opening 22a has a low flow velocity,
The particles having a large specific gravity settle, return to the high-speed flow passage 21a, rise in the high-speed flow passage 21a, and are returned to the anaerobic reaction tank 1.
Particles having a small specific gravity that float in the low-speed flow passage 21b are sent to the crushing device 30 from the communication passage 26.

In the crushing apparatus 30, the sludge having a small specific gravity introduced is crushed by the crushing pump 31 and the sludge return passage 2
It is returned to the reaction part 11 from 5a. Since sludge with a small specific gravity has a large particle size and a hollow portion is formed inside,
By crushing so that the hollow portion is exposed on the surface, the original state of high specific gravity is restored, and the sedimentation property is restored.
By performing the anaerobic reaction while crushing the sludge having a small specific gravity and returning the sludge to the reaction section 11, the sludge in the reaction section 11 is kept in a large specific gravity state, thereby preventing the sludge from flowing out due to floating. At the same time, the sludge concentration in the tank is kept high and the treatment efficiency is kept high.

FIG. 2 is a sectional view of an anaerobic treatment apparatus of another embodiment. In this embodiment, the sludge separating device 20 has a screen 27 arranged in a slanting shape inside, and a lower side thereof is divided into a large particle size chamber 21c and an upper side thereof is divided into a small particle size chamber 21d.
The sludge supply path 19 communicates with the lower part of the large particle size chamber 21c, and the sludge return path 25 extends from the upper part of the small particle size chamber 21d to the anaerobic reaction tank 1.
The communication path 26 communicates with the crushing device 30 from the upper part of the large particle size chamber 21c. A cleaning liquid passage 35 is connected to the upper portion of the small particle size chamber 21d, and a cleaning drainage passage 37 having a valve 36 is connected to the lower portion of the large particle size chamber 21c. As the screen 27, a wedge wire screen has slits arranged in the vertical direction and is arranged at an angle of 30 to 60 ° with respect to the horizontal plane. Other configurations are the same as those in FIG.

In the above apparatus, the basic operation of the anaerobic treatment is performed in the same manner as in FIG. The sludge removed from the anaerobic reaction tank 1 is transferred from the sludge extraction tank 16 to the sludge supply path 1
The sludge having a small particle size passes through the screen 27 and enters the small particle size chamber 21d by being introduced into the large particle size chamber 21c of the sludge separating device 20 through 9 and flowing upward. The upward flow velocity at this time is a flow velocity at which sludge does not settle, for example, 1 m / h.
r or more.

Since sludge having a small particle size has a large specific gravity, it is returned to the anaerobic reaction tank 1 through the sludge return passage 25 as it is.
The sludge with a large particle size that does not pass through the screen 27 is a sludge with a small specific gravity, and it rises in the large particle size chamber 21c and is introduced into the crushing device 30 from the communication path 26 to be crushed to recover the sedimentation property and to undergo an anaerobic reaction Return to tank 1.

When the screen 27 is clogged, a part of the processing liquid is introduced as a cleaning liquid from the cleaning liquid passage 35,
By discharging from the cleaning drainage channel 37, the screen 2
7 is backwashed and restores its separating ability.

The test results will be described below. Test Example 1 As the sludge separation device 20 in FIG. 1, the upper portion is 30 cm.
X 50 cm, bottom 30 cm x 10 cm, overall height is 1
50 cm, an area ratio of the high-speed flow passage 21a and the low-speed flow passage 21b is 1: 4, an upward flow velocity of the high-speed flow passage 21a is about 4 m / hr, and an upward flow velocity of the low-speed flow passage 21b is 1 m / hr. Tap water was mixed with granulated sludge having a particle size of 0.2 to 3 mm to give a sludge concentration of 3000 to 5000 mg / l, and the sludge was separated from the lower part of the sludge separation device 20 by flowing in an upward flow of 5 m / hr,
The sludge flowing out from the high-speed channel 21a was recirculated and separated.

A blanket was formed in the low-speed flow passage 21b at the time when the liquid passing state became stable, and the interface was located 22% above the liquid depth from the lower end of the partition wall. In this state, sludge with a small specific gravity flowed out from the upper part of the low-speed flow passage 21b, the sludge concentration was 300 to 500 mg / l, and the sludge particle size was 2 mm or more. When this runoff sludge was crushed by a spiral crushing pump 31 at a rotational speed of 1500 to 2000 rpm, a particle size of 0.3 to 0.5 mm was 78%,
Less than 0.3 mm was 10%, and more than 0.5 mm was 12%.

Test Example 2 As the sludge separation device 20 in FIG.
m, height 150 cm, inside the wedge wire type screen of 2.5 mm opening, slits are arranged in the vertical direction, using an apparatus in which the slits are arranged at an angle of 60 ° with respect to the horizontal plane, and used in Test Example 1. The sludge thus separated was passed at an upward flow rate of 2.5 m / hr to separate the sludge.

As a result, 87% of the sludge that passed the screen had a particle size of less than 2 mm, and 80% of the sludge that did not pass the screen had a particle size of 2 mm or more. Sludge that does not pass through the screen was rotated at a rotation speed of 150 as in Test Example 1.
When crushed at 0-2000 rpm, particle size 0.3-
67% for 0.5 mm, 12% for less than 0.3 mm, 0.5
mm exceeded 21%. At a rotation speed of 3000 rpm, 50% or more had a particle size of less than 0.3 mm.

By taking out the sludge from the reaction section 11 and separating and crushing it as described above, it is possible to maintain the sedimentation property of the sludge and prevent the flotation of the sludge.
It is difficult to circulate to the reaction part 11 if
By providing a floating sludge take-out means near the liquid surface of the solid-liquid separation section 9,
The floating sludge can be taken out to the sludge taking-out tank 16.

The sludge separating device 20 is not limited to the one shown in the embodiment, and may be a device for separating large and small sludge having a specific gravity by another method. In the case of FIG. 1, the sludge supply passage 19 is connected to the lower portion of the high speed passage 21a in the embodiment, but may be connected to the low speed passage 21b. Further, although the high-speed flow path and the low-speed flow path are provided in FIG. 1, sludge having a small specific gravity may be taken out from the upper part of one ascending flow path and sludge having a large specific gravity may be taken out from the lower part. In the case of FIG. 2, the screen 27
If a wedge wire type is arranged so that the slits are oriented vertically, clogging is reduced, but it may be arranged in other directions, or a mesh screen may be used.

[0047]

As described above, according to the present invention, the sludge taken out from the anaerobic reaction tank is separated into a sludge having a large specific gravity and a sludge having a small specific gravity, and the sludge having a small specific gravity is crushed and returned. Therefore, it is possible to recover the settling property of sludge with reduced specific gravity and maintain the settling property of sludge in the anaerobic reaction tank, which prevents the sludge from floating and maintains a high sludge concentration in the tank. Therefore, anaerobic treatment can be performed with high treatment efficiency.

When sludge is separated by utilizing the difference in specific gravity by upward flow, sludge can be separated efficiently without causing clogging or the like. Further, when sludge is separated by a screen with a difference in particle size, it is possible to perform separation with a small amount of sludge without using a transfer liquid.

[Brief description of drawings]

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

FIG. 2 is a sectional view of an anaerobic treatment apparatus of another embodiment.

[Explanation of symbols]

 1 Anaerobic reaction tank 2 Treatment liquid inflow portion 3 Treatment liquid introduction passage 4 Cover 5 Gas chamber 6 Gas extraction passage 7 Liquid chamber 8a, 8b Solid-gas separation member 9 Solid-liquid separation portion 10 Gas collection portion 11 Reaction portion 12 Continuous Passage 13 Sludge blanket 14 Treatment liquid take-out part 15 Treatment liquid take-out route 16 Sludge take-out tank 17 Sludge take-out route 18,23 Pump 19 Sludge supply route 20 Sludge separator 21a High-speed flow passage 21b Low-speed flow passage 21c Large particle size chamber 21d Small particles Diameter chamber 22 Partition wall 22a Opening 24 Transfer liquid passage 25, 25a Sludge return passage 26 Connecting passage 27 Screen 30 Crushing device 31 Crushing pump 35 Washing liquid passage 36 Valve 37 Washing discharging passage

Claims (3)

[Claims] 1. A reaction part in which a sludge blanket made of granulated sludge containing anaerobic microorganisms is formed, a liquid to be treated inflow part at a bottom part, and a solid-liquid separation part and a gas collection part at an upper part. An anaerobic reaction tank, a sludge separator that separates the sludge extracted from the anaerobic reaction tank into sludge with a large specific gravity and sludge with a small specific gravity, and returns the sludge with a large specific gravity to the anaerobic reaction tank, and a sludge separation device An anaerobic treatment device, comprising: a crushing device for crushing sludge having a small specific gravity separated in step 1 and returning it to the anaerobic reaction tank. 2. The device according to claim 1, wherein the sludge separating device develops the sludge in an upward flow and separates it into sludge having a large specific gravity and sludge having a small specific gravity due to a difference in specific gravity. 3. The device according to claim 1, wherein the sludge separating device separates a sludge having a small particle size and a large specific gravity by a screen and a sludge having a large particle size and a small specific gravity.