JPH0232038B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an anaerobic wastewater treatment method, and particularly to a wastewater treatment method for treating wastewater such as domestic wastewater and organic industrial wastewater using an anaerobic fluidized bed formed deep underground. BACKGROUND ART Anaerobic treatment methods for organic wastewater using anaerobic microorganisms do not require the aeration equipment used in aerobic treatment methods, making it possible to reduce the construction and operating costs of wastewater treatment facilities. For example, JP-A-57-7297 discloses a floating method of anaerobic treatment in which anaerobic sludge and anaerobic decomposition reaction product gas are flowed downward in a mixed phase state through a circulation path that includes a downward flow path and an upward flow path connected to the downward flow path. is taught. However, floating-type anaerobic treatment has the disadvantage that it takes a long time to treat pollutants, and it may take several days to several tens of days to carry out practical wastewater treatment. As a method for shortening wastewater treatment time in an anaerobic treatment method, a fluidized bed method is known in which anaerobic microorganisms are immobilized on a fluidized carrier and fluidized in a treatment tank. According to the fluidized bed method, the concentration of anaerobic microorganisms that come into contact with wastewater is increased and the processing speed is improved. However, conventional fluidized beds have the following drawbacks: (a) It is difficult to scale up the fluidized bed due to economic and technical limitations on the height of the fluidized bed and the occurrence of uneven flow in large-diameter tanks;
(b) Winter heat retention is necessary; (c) when the height of the fluidized bed is high above ground, the power required to circulate wastewater increases; and (d) management of a fluidized bed with high height above ground is troublesome. There are drawbacks such as: Problems to be solved by the invention Therefore, the problems to be solved by the invention are as follows:
The aim is to increase the scale of the anaerobic fluidized bed, simplify heat retention and maintenance in the anaerobic fluidized bed, and reduce wastewater supply circulation power. Means for Solving the Problems Referring to FIG. 1, according to the present invention, a treatment tank 3 consisting of an inner tube 1 and an outer tube 2 concentrically arranged and communicating with each other at their lower ends is formed underground. Wastewater is supplied downward through the inner pipe 1, and an upward flow U of wastewater is formed between the inner and outer pipes upward from the lower end of the outer pipe.
Particles of a carrier 4 having a specific gravity of 1.0-3.0 and an average particle diameter of 0.1-1.0 mm are mixed in the upward flow 4, anaerobic microorganisms are fixed on the surface of the carrier 4, and an anaerobic fluidized bed 5 is formed in the inner tube. 1 and the outer tube 2 is formed in the above-mentioned upward flow U. Function The anaerobic fluidized bed 5 formed in the underground treatment tank 3 has a large effective surface area due to the particulate carrier 4 having a specific gravity and average particle size within the above range, and a large amount of anaerobic microorganisms can Adheres to its surface. Therefore, this fluidized bed 5 comes into contact with the upward flow U of wastewater with a high concentration of microorganisms, and treats pollutants in the wastewater with high efficiency. Furthermore, since the scale of the fluidized bed 5 can be increased by deepening the underground treatment tank 3, it is easy to realize this. Furthermore, since the fluidized bed 5 is constructed underground, there is no need for special heat insulation equipment even in winter.
There is no need for maintenance like in the case of wastewater treatment facilities with high ground clearance. In addition, since the action of gravity from the ground surface to the underground can be used to supply wastewater to the fluidized bed 5, a large amount of power for pushing up and circulating wastewater is not required, unlike when using ground equipment with a high ground clearance. . EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples shown in the accompanying drawings. In Figure 1, wastewater is
The water is poured from the supply channel 6 into the sedimentation tank 7, and its supernatant is sent to the raw water pump tank 8, and further sent out as a downward flow D of the inner pipe 1 by the pump 9, and sent to the bottom of the underground treatment tank 3. The wastewater at the bottom of treatment tank 3 is transferred to inner pipe 1.
It passes through the fluidized bed 5 formed in the upward flow U between the outer tube 2 and the outer tube 2, and rises to reach the upper part 10 thereof. In the fluidized bed 5, the wastewater is subjected to anaerobic treatment to decompose organic matter contained in the wastewater. The methane generated in this case is recovered by a gas collector (not shown). Solids contained in the water subjected to anaerobic treatment settle in the upper part 10 of the treatment tank 3 and are taken out as surplus sludge 11 to the outside. The supernatant in the upper part 10 of the treatment tank 3 overflows into the circulation pump tank 12 and is further discharged as treated water through the outflow path 13 or sent to the next treatment process (not shown). A portion of the water in the circulation pump tank 12 is returned to the treatment tank 3 by the pump 14, mixed with wastewater from the settling area 7, and cyclically treated by anaerobic microorganisms in the fluidized bed 5. This circulation process is performed as necessary to increase the overall processing efficiency of the processing device. Figure 2 shows how wastewater from the supply channel 6 is transferred to the flow rate regulating pond 1.
5 is temporarily stored, and an appropriate amount of wastewater is supplied by a pump 9 through a screen 16 from a flow rate regulating pond 15 to a treatment tank 3. The other parts of this embodiment are similar to the embodiment of FIG. In any of the above embodiments, in order to form the required fluidized bed 5 with the carrier 4 and achieve good anaerobic treatment, it is necessary to appropriately set the following factors in particular. Specific gravity and particle size of carrier 4 It can be appropriately selected within the range of specific gravity 1.0-3.0 and average particle size 0.1-1.0 mm. Diameter and depth of underground treatment tank 3 The underground depth can be selected from 20 to 150 meters, and the inner diameter can be selected from several tens of centimeters to several meters. The filling rate of carrier 4 is preferably selected to be 70-90% of the effective capacity of the anaerobic tank. Input amount of raw water and return water When the amount of raw water fluctuates, if the amount of water supplied to the treatment tank 3 is always constant by providing a flow rate adjustment tank or adjusting the amount of return water, the fluidized bed 5 will be stabilized. It is possible to aim for Expansion rate Select an appropriate upward flow rate according to the particle size and specific gravity of the carrier, and operate so that the expansion rate is approximately 1.1-1.3. Experimental Example The effectiveness of the treatment method shown in FIG. 1 was confirmed through experiments. An underground treatment tank with a diameter of 1.65 m and a depth of 30 m was constructed, and the carrier shown in Table 1 was filled between the upright inner pipe and the upright outer pipe. After acclimating anaerobic microorganisms in the tank using the raw water shown in the same table, operation was performed under the conditions shown in the table. For reference, an above-ground anaerobic fluidized bed experiment using the conventional method was conducted under the conditions shown in the same table. The experimental results are shown in Table 1.

[Table] ** Dimensions of the conventional method are width x length x height As is clear from Table 1, the method of the present invention can achieve sufficient sewage treatment effects with equipment that requires a small installation surface area and a small amount of operating power. has been proven. Effects of the Invention As explained above, the wastewater treatment method of the present invention provides the following effects because the anaerobic fluidized bed is provided in an underground treatment tank, particularly a deep underground treatment tank. (b) A large capacity wastewater treatment facility can be constructed within a relatively small land area. (b) The amount of microorganisms per unit volume of the treatment tank can be increased to enable high-load operation. (c) It has good heat retention and can perform stable treatment of wastewater. (d) There is no need for power to push up wastewater as in facilities with high ground clearance. (f) Methane can be recovered as a product of anaerobic digestion and used as a heat or power source. Also, because the surface area is small, the cover required for methane recovery can be made smaller.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the wastewater treatment method according to the present invention,
FIG. 2 is an explanatory diagram of another embodiment. 1... Inner tube, 2... Outer tube, 3... Processing tank, 4... Carrier,
5... Fluidized bed, 6... Supply path, 7... Sedimentation tank, 8... Raw water pump tank, 9, 14... Pump, 10... Upper part, 11
...excess sludge, 12...circulation pump tank, 13...outflow channel, 15...flow rate adjustment pond, 16...screen.

Claims (1)

[Claims] 1. A treatment tank consisting of an inner pipe and an outer pipe concentrically arranged and communicating with each other at the lower end is formed underground, and wastewater is supplied downward through the inner pipe, and from the lower end of the outer pipe. An upward flow of waste water is formed between the inner and outer tubes, a carrier with a specific gravity of 1.0-3.0 and an average particle size of 0.1-1.0 mm is mixed into the upward flow, and anaerobic microorganisms are placed on the surface of the carrier. A wastewater treatment method comprising: forming an anaerobic fluidized bed in an upward flow between the inner pipe and the outer pipe. 2. The wastewater treatment method according to claim 1, wherein the carrier is pumice particles with an average particle size of 0.1-0.7 mm.