JPS63315196A - Anaerobic bioreactor - Google Patents

Abstract

PURPOSE:To carry out good agitation securely and digestive reaction sufficiently without making sludge fine pieces by providing a vertically long agitating screw encircled with an inner cylinder in a vertically low airtight digestion tank. CONSTITUTION:A vertically long agitation screw 3 encircled with an inner cylinder 2 is installed in a vertically long airtight digestion tank 1. As a result, good agitation can be carried out securely without making sludge into fine pieces in a digestion tank for methane fermentation. The speed of waste water treatment by means of methane fermentation process to be completed in a single digestion tank, therefore, can be increased. In other words, agitation effect and treatment speed can be increased without providing a precipitation separating device for sludge.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bioreactor for wastewater treatment, and particularly to an anaerobic bioreactor used for wastewater treatment using anaerobic microorganisms.

So-called methane fermentation, which uses anaerobic microorganisms to treat wastewater, is extremely economical because it not only requires less surplus sludge but also recovers energy from the methane gas generated during the process of digesting organic matter. It is true. In the early stages of the development of methane fermentation technology, septic tanks and settling tanks and digesters were used, but these tanks have become obsolete and are rarely used in new equipment.

The currently used wastewater treatment facilities for methane fermentation are mainly single-purpose digestion tanks and two-stage digestion tanks. A single-purpose digester is a single tank, so the equipment is for general use, but unless the raw material supply sludge and the microorganisms in the tank are forcibly mixed, the reaction rate is slow because there is insufficient contact between the two. If raw material supply sludge and microorganisms in the tank were simply mixed together in order to increase the reaction rate, the sludge would become extremely fine, and a separate settling device would be required to separate the suspended sludge, resulting in increased equipment and costs. invite.

As shown in Figure 3, the two-stage digestion tank requires two tanks: a mixing tank 21 for organic matter digestion and a standing tank 21 for sludge sedimentation and separation, so all treatment can be carried out in a single tank. The cost is higher than that of the method.

The methane fermentation methods currently under development include the anaerobic fixed bed treatment method in which sludge is supported in a matrix or fluidized fixed bed, and the anaerobic method in which a sludge blanket is formed at the bottom of the reaction treatment tank and wastewater is passed upward through it. There is an upflow sludge blanket (UASB) method. Both the aerobic fixed bed treatment method and the UASB method complete wastewater treatment using a single digestion tank, but it is necessary to bring the wastewater to be treated into sufficient contact with the microorganisms in the digestion tank. It is said that the quality of agitation has the greatest influence on the performance of a digester. There have been reports of dead spaces (parts not involved in reactions) exceeding 50% As in existing facilities.
There is an urgent need to improve the stirring effect.

Conventional stirring methods include (1) mechanical stirring using rotary blades, (2) stirring by recirculating the liquid in the digestion tank, and (3) stirring by recirculating the digestion gas (injection into the liquid). ■ etc. Of the various types of stirring impellers used for mechanical stirring (1), Fig. 4 shows a paddle type agitator, Fig. 5 shows a single turbine type, and Fig. 6 shows a large propeller type.

In the paddle-type agitator shown in Fig. 4, (a) is a flat stirring blade 20 in the digestion tank, (b) is an example of the structure of the flat stirring blade 20, (c) is a shelf-shaped stirring blade 20, (d ) is a multi-stage stirring blade 20, (e) is a combination of a multi-stage stirring blade 20 and a protrusion on the inner wall of the digestion tank, (f) is a semicircular stirring blade 20, (g) is a modified U-shaped stirring blade 20, (h) shows a flat stirring blade 20 with a guide frame.

Among the single turbine type stirring blades 20 shown in FIG.
(a) is a fan turbine, (b) is a flat blade turbine, (
C) is an angle turbine, (d) is an arrowhead turbine, (e
) is a curved flat blade turbine, (f) is a turbine with a disc, (
g) respectively show those in a pull margin type turbine.

In Figure 6, (a) is a standard three-blade propeller-1 (
b) shows a propeller with a guide cylinder 1 (C) shows a stirring blade 20 in a serrated propeller.

In any mechanical stirring method using rotary vane type stirring blades 20, the stirring force is strong near the blade plate, so the horizontal rotational flow shown in Figure 7(a) and the radial flow shown in Figure 7(c) are dominant in the digestion tank. The sludge in the tank is destroyed and made fine. Since this atomization has an adverse effect on the sedimentation separation of sludge, as shown in FIG. 3, a standing tank 22 as a sedimentation separation device is required in addition to the mixing tank 21 for reaction and digestion. Separately installed sedimentation separation equipment complicates the equipment and increases costs.

FIG. 8 shows an anaerobic stirring tank using a conventional circulation pump 25 as an example of (2) agitation by recirculating the liquid.

In this case, it is very difficult to control the flow rate of the circulation pump to maintain the sludge in a suspended state, and the power consumption is also large.

Figure 9 (a), (b), and (c) show examples of the above (3) agitation by recirculation of digestion gas, which is currently most commonly used, when the digestion tank has a floating cover. The case where the digester has a fixed cover and the case where the digester is connected to a heating boiler are shown respectively.

In the figure, 30 represents a gas pump, 31 represents a baffle, and 32 represents a boiler. If sufficient agitation is performed even in the case of agitation by recirculating the digestion gas, the inconvenience of requiring a separate sedimentation and separation device arises, as in the case of mechanical agitation using rotary blades.

Therefore, the problem to be solved by the present invention is to improve the stirring of sludge in so-called methane fermentation.

5 Hands for Divination Referring to FIG. 1, the anaerobic bioreactor according to the present invention has a configuration in which a vertically long stirring screw 3 surrounded by an inner cylinder 2 is provided in a vertically long airtight digestion tank 1. use

m'' Referring to FIG. 2, the vertically long stirring screw 3 surrounded by the inner cylinder 2 generates a uniform upward flow inside the inner cylinder 2, and raises the sludge 12 without applying shear force. While stirring, the mixture is brought into contact with the waste water 11.

In response to this upward flow, a downward flow is generated outside the inner cylinder 2, and the sludge 12 is also stirred in this downward flow, and good contact between the sludge 12 and the wastewater 11 is realized.

Therefore, the sludge 12 is efficiently stirred with the wastewater 11 without becoming fine, and the digestion reaction is sufficiently carried out.

Embodiment 1 In FIG. 1 showing an embodiment of the anaerobic bioreactor according to the present invention, the digestion tank 1 has a vertically long cylindrical shape and has a sludge concentration section IA and a digestion reaction section IB. Preferably, after the upper end of the digestion reaction section IB is once reduced in diameter, a clarification section IC having a larger diameter than the digestion reaction section 1B is formed above it. A vertically long stirring screw 3 surrounded by an inner cylinder 2 is arranged in the digestion reaction section IB. The lower end of the stirring screw 3 is pivotally supported by a screw support 3A that is integrated with the bottom wall of the digestion tank 1. A drive motor 5 is attached to a motor support 4 formed at the top of the digestion tank 1, and the stirring screw 3 is reversibly rotated by the drive motor 5 as shown by arrows R and S.

The sludge thickening section IA at the bottom of the digestion tank 1 contains wastewater 1 to be treated.
A wastewater inlet 6 is provided for introducing 1. The top of the digestion tank 1 is hermetically closed by a lid ID having a gas discharge lower, and a gas guide cylinder 8 is provided below the gas discharge lower. In the illustrated example, a treated water outlet 9 is formed in the lower part of the lid ID near the upper end of the clarifier IC, but this treated water outlet 9 is always filled with treated water 13, and the inside of the digestion tank 1 is cut off from the air. Surplus sludge 1 as needed
5, an excess sludge discharge port 10 is provided at the bottom of the digestion tank 1.

The operation will be explained with reference to FIG. The wastewater 11 flows through the wastewater inlet 6 into the inner cylinder 2 at the lower part of the reaction tank, that is, the digestion tank 1.
will be supplied to. In the figure, the flow of wastewater 11 and treated water 13 is indicated by arrow W. The supplied wastewater 11 rises inside the inner cylinder 2 according to the rotation of the stirring screw 3, comes into contact with the sludge 12, and the digestion reaction proceeds. The waste water 11 that has reached the upper part of the inner cylinder 2 flows out of the inner cylinder 2 and flows downward toward the lower part of the digestion tank 1, but even in this downward flow, the digestion reaction further progresses due to contact with the sludge 12.

A part of the wastewater 11 that has risen through the inner cylinder 2 flows into the clarification section IC, which has a larger cross-sectional area than the digestion reaction section IB, and its rising speed is slowed down, and the sludge 12 is separated by sedimentation. The sludge 12 that has started to settle in the clarification section IC falls to the digestion reaction section IB due to its own weight, and further reaches the sludge concentration section IA. The reduced sludge 12 is discharged to the outside as surplus sludge 15 through the surplus sludge discharge port 10 at any time. Furthermore, the treated clear water, that is, the treated water 13, is led to the outside from the treated water outlet 9.

Methane gas 14 generated as a result of the digestion reaction is collected by a gas guide tube 8 whose lower end is widened, moves to the second part so as not to impede sedimentation separation, and is finally released to the outside from the gas release lower. . In the figure, the flow of methane gas 14 is indicated by a dotted arrow G.

The speed of the drive motor 5 that rotates the stirring screw 3 is freely controllable, and the rotation speed is controlled to an appropriate speed depending on the degree of sedimentation of the sludge 12. Preferably, the drive motor 5 is reversible.

As explained in detail above, the anaerobic bioreactor according to the present invention uses a configuration in which a vertically long stirring screw surrounded by an inner cylinder is provided in a vertically long airtight digestion tank, so that the following effects can be achieved. play.

(a) It is possible to reliably perform good agitation without making the sludge fine in the digestion tank for methane fermentation treatment.

(b) Therefore, the processing speed of wastewater treatment by methane fermentation that can be completed in a single digestion tank can be improved. In other words, the stirring effect can be enhanced and the processing speed can be improved without providing a sludge sedimentation and separation device.

(c) Since sludge is not refined, sludge with relatively large particle size can be formed.

(d) If applied to the so-called squirting layer method that uses biofilm-adhered particles, that is, microorganism-immobilized carriers, and if the appropriate density of the immobilized carrier and rotation speed of the stirring screw are selected, good immobilized carriers can be obtained. Body layers can be easily fluidized.

(e) Even when the USAB method, which does not use a microorganism immobilization carrier, is applied to the self-immobilization method, self-immobilization (granulation) of microorganisms is promoted due to the rolling movement of the sludge.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the structure of one embodiment of the anaerobic bioreactor according to the present invention, Figure 2 is an explanatory diagram of its operation, Figure 3 is an explanatory diagram of the conventional two-tank wastewater treatment system, and Figure 4 Figures up to Figure 6 are explanatory diagrams of the stirring blades, Figure 7 is an explanatory diagram of the liquid flow in the tank, Figure 8 is an explanatory diagram of the conventional liquid recirculation system, and Figure 9 is an explanatory diagram of the conventional gas recirculation system. It is. DESCRIPTION OF SYMBOLS 1... Digestion tank, 2... Inner cylinder, 3... Stirring screw, 4... Motor support stand, 5...
Drive motor, 6... Wastewater inlet, 7... Gas discharge port, 8... Gas guide tube, 9... Processing outlet,
10... Surplus sludge discharge port, 11... Waste water,
12...Sludge, 13...Treated water, 14...
Methane gas, 15... Surplus sludge, 20... Stirring blade, 21... Mixing tank, 22... Stilling tank, 25
...Circulation pump, 30...Gas pressure feeder, 31.
...Baffle, 32...Boiler. Patent Applicant Kajima Corporation Patent Application Agent Patent Attorney Tsugube Ichito Figure 2 Figure 3 Figure 4 (e) (f) (9)
(h) Figure 5 (d) (e)
(Z) -6; -17.

Claims (1)

[Claims] An anaerobic bioreactor consisting of a vertical stirring screw surrounded by an inner cylinder inside a vertically airtight digestion tank.