JPH0243996A - Scum crushing type anaerobic bioreactor - Google Patents

Abstract

PURPOSE:To make treatment of scum easy by providing a sludge return path which communicates with both the bottom part of a scum stripper and an anaerobic reaction cylinder and crushing scum by shock at a time when scum falls to the aperture of the scum stripper. CONSTITUTION:Inflow water 2 fed near to the lower end of an anaerobic reaction cylinder 1 is made to an upward flow and raised in a sludge bed 20. When slow agitation is performed by an agitator 4, raw water is brought into contact with anaerobic sludge and decomposing reaction is promoted. The gas being a reaction product is stuck on one part of anaerobic sludge as gas foams according to progress of decomposing reaction and gas sticking sludge 21a is formed and raised to form a sludge ppt. part. Large parts of gas sticking sludge 21a are separated from gas foams and settled as anaerobic sludge to maintain sludge and blanket of the sludge bed 20. Scum 30 falls through a falling port 31 and is crushed. Thereby scum can be crushed and energy consumption can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anaerobic bioreactor for wastewater treatment, and in particular to a method for treating sewage, etc. by crushing the floating scum in the anaerobic bioreactor and using it as returned sludge to increase the concentration of microorganisms. This paper relates to a scum crushing anaerobic bioreactor that enables anaerobic biological treatment of low-concentration organic wastewater.

Anaerobic wastewater treatment, which uses aerobic microorganisms to treat wastewater, does not require aeration, so not only does it require no equipment or energy, but it also recovers energy from the methane gas generated during the process of digesting organic matter. It is extremely economical. Conventional aerated wastewater treatment has targeted concentrated organic wastewater that can maintain a high growth rate of anaerobic microorganisms, sewage sludge with a solids concentration of 2-7%, and the like. Third
Referring to Figure A, in the standard digestion method using anaerobic wastewater treatment, inflow water 2 is sent to the anaerobic reactor 1, and treated water 3 decomposed by anaerobic microorganisms is taken out.A stirrer is installed in the anaerobic reactor 1. 4 is provided, and the gas produced by the reaction is recovered from the top of the reaction column 1.

Biochemical oxygen demand BOD 1,000 rag/Q
The following organic wastewater (hereinafter referred to as low-concentration organic wastewater)
When treating with the anaerobic reactor 1 of the standard digestion method described above, the woody retention time HRT (Hydraulic reaction time
If the ten-tion time is selected within a relatively short practical range, anaerobic microorganisms with extremely low growth rates will be washed out, making it impossible to ensure the microorganism concentration necessary for purification. In order to solve this problem and increase the concentration of microorganisms inside the reactor, the following various improvement methods are being studied, but related technologies such as those for setting optimal operating conditions have not yet been fully established. .

That is, FIG. 3B shows the anaerobic activated sludge method, in which a settling tank 5 is provided after the anaerobic reactor 1, and the sludge settled there is returned to the anaerobic reactor l as return sludge 6 to increase the microbial concentration and remove excess When sludge is generated, it is taken out of the system as surplus sludge 7. FIG. 3C shows an anaerobic filter bed method in which a filter bed 8 is used, and FIG. 3D shows an aerobic fluidized bed method in which a portion of the water from the anaerobic reactor 1 is returned as circulating water 9. In FIG. 3E, the inflow water 2 is sent upward from the lower end of the anaerobic reactor 1, an anaerobic reaction zone 11 and a precipitation zone 12 are formed in the anaerobic reactor 1, and the reaction product gas is recovered by the gas recovery device 13. This shows the anaerobic sludge bed method.

The anaerobic sludge bed method is one of the improved methods mentioned above.

The anaerobic activated sludge method is attracting attention as a treatment method that simplifies the process by omitting the settling tank, and is characterized by the use of a device that separates scum or flocs with gas bubbles into sludge, treated water, and gas. . This method focuses on the phenomenon that when the gas bubbles attached to the flocs are removed, the anaerobic sludge exhibits its original good settling ability and settles, increasing the microbial concentration in the sludge bed in the anaerobic reaction zone 11.

FIG. 4 shows an example of an apparatus for separating the sludge, treated water, and gas. The flow of the sludge mixture after anaerobic fermentation that enters the first sludge separation device 15 as shown by arrow a is first roughly separated at the inverted conical portion, and the separated sludge sinks. The sludge with unseparated adhered gas continues to float and is efficiently separated from the adhered gas in the thin tube 1B forming the second sludge separator, and the separated sludge sinks as shown by the arrow. The treated water is taken out from above the outside of the capillary tube 16 as shown by arrow C, and the separated gas is collected at the upper end of the capillary tube 16 as shown by arrow d.

FIG. 5 shows an example of the configuration of a scale equipment for realizing the anaerobic sludge bed method. A sludge bed 20 is formed at the bottom of the equipment, and a gas-adhering sludge mixture 21 after the decomposition reaction is formed on the sludge bed 20. Ru. A gas recovery tank 22 covers the mixed liquid 21, and a sludge separation tank 23 is formed with a small gap from the gas recovery tank 22, and is settled at the top of the device! A B tank 24 is provided.

However, even with the equipment shown in Figures 4 and 5 that separates sludge, treated water, and gas, it is difficult to form a high-concentration sludge bed for low-concentration organic wastewater, and anaerobic The reality is that the application of the sludge bed method is limited to thick wastewater.
The reason why the concentration of sludge bed becomes low when the raw water to be decomposed, that is, the inflow water is low-concentration organic wastewater, is thought to be due to the following reason.

(a) If high concentration organic wastewater is raw water.

The anaerobic sludge grows in the form of granules, has very good sedimentation properties, and has very low bacterial cell wash out from the reaction tube.
) are very few. However, if the raw water is low-concentration organic wastewater such as ordinary sewage, the granulation of anaerobic sludge is insufficient, and unless special measures are taken, bacterial cells will flow out and high-concentration sludge will enter the reaction tube. Not formed.

(b) Although the sedimentation property of anaerobic sludge is not small, if gas bubbles adhere to it during the reaction, the sedimentation property becomes extremely poor and bacterial cells easily flow out.

(C) In the anaerobic sludge bed method, it is essential to form a clear sludge bed (sludge blanket), but for low-concentration organic wastewater, it is necessary to circulate the generated gas by pumping as in the case of high-concentration organic wastewater. Reactor agitation by 200°C does not form the required well-defined sludge bed.

Therefore, the problem to be solved by the present invention is to provide an anaerobic bioreactor that can form a well-defined aerobic sludge bed even for low-concentration organic wastewater.

Referring to a longitudinal cross-sectional view of an embodiment of the present invention in FIG. 1 and a plan view thereof in FIG. Opening 33 into which the scum 30 from the drop opening 31 falls
A scum removing device 32 having a It has a structure made by crushing scum.

Preferably, the anaerobic reaction tube l is vertically elongated, and the stirrer 4 is provided inside the anaerobic reaction tube l.

Referring to FIG. 1, the sludge that has completed the decomposition reaction on the sludge bed 2° of the anaerobic reactor 1 rises in the gas-adhered sludge mixture 21 as gas-adhered sludge 21a and floats to the water surface at the top. It becomes scum 30. This scum 30 passes through the drop port 31 of the anaerobic reactor 1 and falls into the opening 30 of the scum removal device 32. Scum 30 that has fallen into the scum removal device 32
The leading scum 30 floats on the water surface of the opening 33 due to the buoyancy of the attached gas bubbles.Since the attached gas bubbles of the leading scum 30 are lighter than water, there is a high possibility that they will float upward.

Subsequent scum 30 then falls into this opening 33.
When the scum 30 collides with the water surface of the opening 33, the impact crushes the scum 30, especially the attached gas bubbles, and the anaerobic sludge is released from the attached gas bubbles. The impact upon this collision not only acts directly on the scum 30 that collided with it, but also indirectly acts on the preceding scum 3o near the water surface. Further, the above-mentioned collision not only directly crushes the adhered gas bubbles, but also a case in which the scum 3o is crushed by the collision, and at that time, the adhered gas bubbles are indirectly separated from the anaerobic sludge. The anaerobic sludge released and separated from the attached gas bubbles settles at the bottom of the gas removal device 32 due to its inherent good sedimentation properties.

The sludge return path 34 serves as a path for returning the anaerobic sludge deposited at the bottom of the gas removal device 32 to the sludge bed 1 in the anaerobic reaction column 1. The returned anaerobic sludge makes it possible to maintain the sludge plancher in the sludge bed 20.

In this way, the problem to be solved by the present invention is achieved, namely, the provision of an anaerobic bioreactor that makes it possible to form a clear anaerobic sludge bed even during the treatment of low-temperature organic wastewater.

Furthermore, the present inventors made the anaerobic reaction cylinder l vertically long,
When the stirrer 4 is installed in the anaerobic reactor 1 and the rotational speed of the stirrer 4 is set appropriately, a sludge settling part with only a gentle uniform upward flow, that is, a gas-adhered sludge mixture, is created in the anaerobic reactor 1. It has been experimentally found that the portion 21 and the gently rotating sludge bed 20 are clearly separated and formed.

Figures 1 and 2 show conceptual diagrams of an anaerobic bioreactor that is an embodiment of the present invention.

The anaerobic reactor l in the illustrated example is vertically long and has a motor 4a inside.
A stirrer 4 is provided which is driven by.

Inflow water 2 as raw water to be treated is supplied to the vicinity of the lower end of the anaerobic reaction tube 1 by a pump 39 for raw water into the reaction tube 1. Before the raw water flows, for example, sewage digested sludge is added as seed sludge at a predetermined concentration. Add the mixture and stir gently using the stirrer 4. After several hours, a sludge blanket is formed as shown in Figure 1, and the contents of the reaction tube 1 are a sludge bed 20 and a gas-adhered sludge mixture 2.
It is divided into a sludge settling part consisting of 1.

The height of the top surface of the sludge bed 20 is detected by a sludge interface meter (not shown) inserted from the upper opening of the anaerobic reaction cylinder l. When the height of the sludge bed 20 is above a predetermined value, the excess sludge 7 is taken out to the outside by the pump 4o for removing excess sludge, and its height is adjusted.

Raw water, ie, inflow water 2, supplied to the vicinity of the lower end of the anaerobic reaction tube becomes an upward flow and quietly rises in the sludge bed 2o.

At this time, if the agitator 4 is used to gently stir the raw water, the raw water will come into contact with the anaerobic sludge and the decomposition reaction will be promoted. 0 As the decomposition reaction progresses, gas, which is a reaction product, will form gas bubbles in some of the anaerobic sludge. This adheres to form gas-adhered sludge 21a, which rises to constitute the sludge settling section, that is, the gas-adhered sludge mixed liquid 21 in FIG. However, most of the gas-adhering sludge 21a that has risen to the sludge settling section is separated from the gas bubbles and settles as anaerobic sludge, maintaining the sludge fist blanket on the sludge bed 2o.

Gas-adhering sludge 21 that continues to float without being separated from the gas bubbles
A becomes scum 30 and floats on the water surface at the top of the anaerobic reactor 1. This scum 30 naturally falls vertically from the drop port 31 as part of the water flowing out from the reactor reactor 1, and passes through the opening of the scum removing device 32. Enter 33.

The reaction tube outflow water hits the water surface at the opening 33 of the scum removal device 32, and the impact separates gas bubbles from the gas-adhered sludge 21a in the reaction tube outflow water and the preceding scum 30 floating in the opening 33. The anaerobic sludge released from the gas bubbles exhibits its original good settling ability and settles at the lower end of the scum removal device 32.

In this way, clean treated water 3 is obtained, and the scum removal device 32
The treated water 3 flows out from the treated water outlet 35.

In the illustrated example, the opening 33, which is the entrance to the scum removing device 32, is made small so that the scum 3o is always floating on the water surface of this opening 33. This allows the residual scum 3o in the scum removal device 32 to be kept floating in the opening 33 even if the gas separation from the scum 3o is insufficient with just one free fall of the water flowing out of the reaction tube. This is to ensure sufficient gas separation in addition to the repeated impact of free fall.

An important feature of the present invention is that the anaerobic sludge settled at the lower end of the scum removal device 32 is returned to the sludge bed 20 of the anaerobic reactor 1 via the sludge return path 34, preferably by a sludge return pump 41. The anaerobic sludge returned in this way is
To ensure a stable sludge bed 20 even when treating low turbidity organic wastewater.

As explained in detail above, the scum crushing type anaerobic bioreactor according to the present invention comprises: an anaerobic reactor having a scum drop port, a scum removal device having an opening into which scum from the L-shaped drop port falls; A sludge return path is provided that communicates the bottom of the scum removal device with the anaerobic reactor, and the scum is crushed by the impact when it falls into the opening of the scum removal device, so the following effects are achieved.

(a) The use of the bioreactor of the present invention makes it possible to treat low-turbidity organic wastewater such as sewage using the anaerobic sludge bed method, which was previously considered impossible.

(b) Since the reaction tube can be designed vertically, space can be saved.

(c) Since the top surface of the sludge blanket can be detected with an interface detector, it is possible to manage the excess sludge extraction operation and remove the sludge.
It is easy to control the height of the blanket.

(d) Since the bioreactor uses an anaerobic sludge bed method, it is economical because no carrier is required for immobilizing anaerobic bacteria in the reaction cylinder.

(e) The structure is simple and maintenance is easy.

(f) Since VJ does not require care, it is resource-saving and energy-saving.

(g) The amount of surplus sludge is very small because the treatment uses anaerobic sludge with a low bacterial yield.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the scum crushing type anaerobic bioreactor according to the present invention, FIG. 2 is a plan view thereof, and FIGS.
The figures up to E are explanatory diagrams of the conventional anaerobic biological treatment method, and FIGS. 4 and 5 are explanatory diagrams of the conventional anaerobic sludge bed method. Water, 4... Stirrer, 5.24... Sedimentation tank,
6... Returned sludge, 7... Excess sludge, 8.
... Filter bed 9 ... Circulating water, 11 ... Anaerobic reaction zone, 12 ... Sedimentation zone, 13 ... Gas recovery device, 15 ... First sludge separation device, 16 ... Thin tube,
17...Outer pipe, 2o...Sludge bed, 21...
Gas adhering sludge mixed liquid, 22... gas recovery tank, 3
0... Scum, 31... Falling port, 32... Scum removal device, 33... Opening, 34... Sludge return path, 35... Treated water outlet, 39.4o, 41
···pump. Patent applicant: Kajima Corporation Patent application agent: Patent attorney: Tsugube Ichito 1...Anaerobic reactor, ? ... Inflow water, 3... Treatment 35 Meji JllL & Outlet Figure 2 Figure 3A Figure 3E

Claims (2)

[Claims] (1) comprising an anaerobic reaction tube having a scum fall port, a scum removal device having an opening into which scum from the fall port falls, and a sludge return path communicating the bottom of the scum removal device and the anaerobic reaction tube; A scum crushing type anaerobic bioreactor in which scum is crushed by the impact when it falls into the opening of the scum removal device. (2) The anaerobic bioreactor according to claim 1, wherein the anaerobic reaction column is vertically elongated and a stirrer is provided in the anaerobic reaction column.