JP7247713B2 - Biological treatment equipment for organic wastewater - Google Patents

Description

The present invention relates to a biological treatment apparatus suitable for biologically treating organic wastewater containing volatile substances and odor-generating substances, and more particularly to a biological treatment apparatus for organic wastewater employing a microbial power generator.

When bio-treating organic wastewater containing volatile or odor-producing substances, a fully mixed reactor is usually used to prevent odors. However, since the reaction rate is extremely low in a completely mixed reactor, a large reactor with a long residence time is required. In addition, even in a completely mixed reaction tank, it is difficult to completely prevent the volatilization of odorous substances due to the one-sided flow of water and the difference in partial aeration intensity.
In order to increase the reaction rate and reduce the tank volume, a multi-stage reaction tank or the like in which a plurality of reaction tanks are connected in series is used. However, in this case, since the decomposition of the odorant has not been completed in the first reaction tank, part of the remaining odorant volatilizes due to aeration, generating an odor and volatilizing toxic substances. . The same applies to plug flow type reactors.

As a power generating device using microorganisms, Patent Documents 1 to 3 disclose that a conductive filler that retains microorganisms is present throughout the anode chamber, and a non-conductive membrane that separates the anode chamber and the cathode chamber is provided in the anode chamber. A microbial power generator in intimate contact with electrodes respectively placed in the cathode compartment is described.

JP 2009-152091 A JP 2010-33823 A JP 2009-224128 A

It is an object of the present invention to provide a biological treatment apparatus for organic wastewater that can treat even organic wastewater containing volatile substances and odor-generating substances without generating odors or volatilizing harmful substances. aim.

A biological treatment apparatus for organic wastewater according to the present invention includes first to n-th (n is 2 or more) biological treatment tanks connected in series, wherein treatment is performed in each tank. , at least the first biological treatment tank is separated from an anode chamber to which raw water containing organic matter that retains microorganisms and is an electron donor is supplied, and the anode chamber is separated via a non-conductive membrane having ion permeability. , a cathode chamber supplied with an electron acceptor, wherein at least the final biological treatment tank is an aerobic biological treatment tank.

In one aspect of the present invention, the organic wastewater is organic wastewater containing volatile substances or odor-generating substances.

In one aspect of the present invention, the biological treatment tank other than the microbial power generator is a sludge floating reaction tank or a carrier flow reaction tank.

In one aspect of the present invention, there is provided means for returning part of the treated water and/or sludge from the aerobic biological treatment tank to the microbial power generator.

In one aspect of the present invention, there is provided means for supplying at least part of the exhaust gas containing oxygen from the aerobic biological treatment tank to the cathode chamber of the microbial power generation device.

In one aspect of the present invention, the microbial power generation device includes an air cathode and means for supplying at least a portion of oxygen-containing exhaust gas from the cathode chamber to the aerobic biological treatment tank.

Since the microbial power generator can treat the organic wastewater in a sealed anode chamber without aeration, volatile substances do not volatilize into the exhaust gas from the microbial power generator. Volatile substances, odor-causing substances, or odorous substances originating from the water to be treated or generated by biological reactions are oxidatively decomposed in the microbial power generator and decomposed into substances that do not contain at least volatile substances, odor-causing substances, or odorous substances. Therefore, it is not discharged outside the system as exhaust gas.

Since the microbial power generator that treats with the biofilm formed on the electrode surface is not suitable for removing BOD at extremely low concentrations, installing the microbial power generator in the final tank of the multi-stage biological treatment tank requires a large reaction tank. It becomes necessary and disadvantageous in terms of location and cost. In consideration of these points, in the present invention, the final biological treatment tank is an aerobic treatment tank. This enables efficient biological treatment without odor generation and volatilization of volatile substances.

According to the biological treatment apparatus of the present invention, even organic wastewater containing volatile substances or odor-generating substances can be treated without generating odors or volatilizing harmful substances.

1 is a schematic diagram of a biological treatment apparatus for organic waste water according to an embodiment; FIG. 1 is a schematic diagram of a biological treatment apparatus for organic waste water according to an embodiment; FIG. 1 is a schematic vertical cross-sectional view of a microbial power generation device used in a biological treatment device for organic waste water according to an embodiment; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a biological treatment apparatus for organic wastewater according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a biological treatment apparatus for organic waste water according to a first embodiment.

This biological treatment apparatus for organic waste water has a first microbial power generation device 11 and a second microbial power generation device 12 , an aerobic biological treatment tank 13 and a sedimentation tank 14 .

Raw water is supplied to the anode chamber 4 of the first microbial power generation device 11 through the raw water pipe 10, and is subjected to biological treatment by the power-generating microorganisms to obtain the first treated water, which is passed through the pipe 15. It is supplied to the anode chamber 4 of the second microbial power generator 12 . The second treated water obtained by the second microbial power generator 12 is supplied to the aerobic biological treatment tank 13 through the pipe 16, and aerated through the air diffusion pipe 13a to be aerobic biologically treated. The aerobic biologically treated water passes through the screen 13b provided in the aerobic biological treatment tank 13 and flows out to the pipe 17, and part of it is returned to the raw water pipe 10 via the pipe 18. The rest of the aerobic biologically treated water is introduced into the sedimentation tank 14 through the pipe 17, and the supernatant water flows out as treated water. The sludge settled in the sedimentation tank 14 is discharged from the bottom of the sedimentation tank 14 as excess sludge.

Air is supplied to the cathode chamber 3 of each of the microbial power generators 11 and 12 through a pipe 7 . Exhaust air from the cathode chamber 3 exits through the pipe 8 .

In FIG. 1, the aerobic biological treatment tank 13 is a carrier flow reactor and is filled with carriers 13c. When the aerobic biological treatment tank 13 is a carrier fluidized bed, it is preferable that a carrier such as a sponge is charged to 30 to 50% of the volume, and a screen 13b for preventing carrier outflow is provided at the outflow part of the reaction tank. .

In FIG. 2, the aerobic biological treatment tank 13 is a sludge flotation reaction tank and is not filled with carriers 13c. The entire amount of the effluent from the aerobic biological treatment tank 13 is supplied to the sedimentation tank 14 through the pipe 17, the supernatant water is taken out as treated water, and part of it is returned to the raw water pipe 10 through the pipe 18. be. A part of the settled sludge is returned to the aerobic biological treatment tank 13 through the return pipe 19, and the remainder is discharged out of the system as excess sludge.

Other configurations of the biological treatment apparatus for organic wastewater in FIG. 2 are the same as in FIG. 1, and the same reference numerals denote the same parts.

In FIGS. 1 and 2, the biological treatment apparatus for organic wastewater is composed of the microbial power generators 11 and 12 and the aerobic biological treatment tank 13, but other treatment tanks may be provided.

If all or most of the organic substances are volatile substances, it is desirable that the biological treatment tanks other than the final biological treatment tank be microbial power generators.

When the proportion of volatile components in the organic matter is small, it is desirable that about half of the front half be the microbial power generator and about half of the rear half be the non-microbial power generator. For example, in the case of four tanks in total, it is desirable that the first two tanks are microbial power generators and the latter two tanks are not microbial power generators.

If the organic matter concentration in the raw water is high (for example, the BOD concentration is 200 mg/L or more, preferably 1,000 mg/L or more), the microbial power generator is effective. In the latter reaction tank where the treatment progresses and the concentration is low (for example, the BOD concentration is 20 to 2,000 mg/L, preferably 50 to 1,000 mg/L), biofilm formation is difficult to proceed, so aeration is required. It is more effective to use a floating method with high contact efficiency or a carrier method such as a fluidized bed.

In addition, since the microbial power generator takes out the energy of organic matter as electrical energy, sludge is less likely to grow than in aerobic treatment. Therefore, it is desirable to return part of the sludge in the final biological treatment tank or the treated water containing SS as an inoculum to the microbial power generator at the time of start-up.

Examples of raw water include, but are not limited to, organic wastewater such as sewage and food factory wastewater.

In the above embodiment, air is supplied to the cathode chamber, but pure oxygen, oxygen-enriched air, aerated exhaust gas from the aerobic biological treatment tank 13, or the like can also be used. Alternatively, a liquid containing an electron acceptor other than oxygen, such as potassium hexacyanoferrate (III) (potassium ferricyanide) may be supplied.

Next, the configuration of the microbial power generators 11 and 12 will be described with reference to FIG.

FIG. 3 is a schematic cross-sectional view showing a schematic configuration of the microbial power generator.

A plurality of ion-permeable non-conductive membranes 2 are arranged in parallel in the tank body 1 to alternately partition cathode chambers 3 and anode chambers 4 . A positive electrode 5 is arranged in each cathode chamber 3 so as to be in contact with the ion-permeable non-conductive membrane 2 .

Although FIG. 3 shows a multi-cell type microbial power generator in which a plurality of anode chambers 4 and cathode chambers 3 are installed, a single cell may be used.

The positive electrode (cathode) 5 is a three-dimensional body made of a conductive material (graphite, titanium, stainless steel, etc.). The material constituting the positive electrode may be appropriately selected according to the type of electron acceptor. When oxygen is used as an electron acceptor, it is preferable to use an oxygen reduction catalyst such as platinum. For example, graphite felt may be used as a base material to support platinum.

A three-dimensional negative electrode 6 made of a conductive material (graphite, titanium, stainless steel, etc.) is arranged in each anode chamber 4 . Power-generating microorganisms are held in the anode chamber 4 .

In this embodiment, the inside of the cathode chamber 3 is empty, air is introduced through the gas inlet pipe 7 and exhaust gas is discharged through the gas outlet pipe 8 .

As the ion-permeable non-conductive film 2 for partitioning the cathode chamber 3 and the anode chamber 4, almost any material can be used as long as it is non-conductive and ion-permeable. Ion-exchange membranes, paper, woven fabrics, non-woven fabrics, so-called organic membranes (microfiltration membranes), honeycomb molded bodies, grid-like molded bodies, and the like can be used. In order to allow ions to easily pass through, the thickness is preferably as thin as 10 μm to 1 mm, particularly 30 to 100 μm.

A pH adjuster such as an aqueous sodium hydroxide solution is added to the raw water or the first treated water as necessary to adjust the pH to 6 to 9, preferably 6.5 to 7.5. is more preferred. The temperature condition of the anode chamber is preferably from room temperature to middle to high temperature, specifically about 10 to 70°C.

An oxygen-free gas such as nitrogen gas may be continuously or intermittently supplied to the anode chamber 4 . A shearing force is applied to the negative electrode surface by the gas, and in addition to increasing the effect of preventing clogging due to excessive adhesion of biofilm, especially when oxygen is used as an electron acceptor in the cathode chamber 3, aerobic slime grows. It also has the effect of removing oxygen permeating from the cathode chamber 3 to the anode chamber 4, which leads to deterioration in performance.

Due to the electromotive force generated between the positive electrode 5 and the negative electrode 6, current flows through terminals 20 and 21 to an external resistor (not shown).

By passing the oxygen-containing gas through the cathode chamber 3 and circulating the negative electrode solution, in the anode chamber 4,
(Organic matter) + H ₂ O→CO ₂ + H ⁺ +e ⁻
reaction proceeds. This electron e ⁻ flows through the negative electrode 6 , the terminal 21 , the external resistor, and the terminal 20 to the positive electrode 5 .

When the ion-permeable non-conductive membrane 2 is a cation exchange membrane, the protons H 2 ⁺ generated in the above reaction move to the positive electrode 5 through the cation exchange membrane. At the positive electrode 5,
O ₂ +4H ⁺ +4e ⁻ →2H ₂ O
reaction proceeds. H ₂ O generated by this positive electrode reaction is discharged together with the cathode exhaust gas.

When an anion exchange membrane is used as the ion permeable non-conductive membrane 2, the positive electrode 5 is
O ₂ +2H ₂ O+4e ⁻ →4OH ⁻
reaction proceeds. OH ⁻ generated by this positive electrode reaction permeates the anion exchange membrane as the ion-permeable non-conductive membrane 2 .

In the present invention, the microorganism that is held in the anode chamber and that produces electrical energy is not particularly limited as long as it has the function of donating electrons to the electrode. For example, Saccharomyces, Hansenula, Candida, Micrococcus, Staphylococcus, Streptococcus, Leuconostoa, Lactobacillus, Corynebacterium, Arthrobacter, Bacillus, Clostridium, Neisseria, Escherichia, Enterobacter, Serratia, Achromobacter, Alcaligenes, Flavobacterium, Acetobacter, Moraxella, Nitrosomonas, Nitorobacter, Thiobacobacter, Bacteria belonging to the genera Gluconobacter, Pseudomonas, Xanthomonas, Vibrio, Comamonas, Proteus (Proteus vulgaris), Shewannell and Geobacter, filamentous fungi, yeast and the like can be mentioned. As sludge containing such microorganisms, activated sludge obtained from biological treatment tanks for treating organic matter-containing water such as sewage, microorganisms contained in effluent from primary sedimentation tanks of sewage, anaerobic digestion sludge, etc. are used as inoculum for the anode. A chamber can be supplied to retain the microorganisms on the negative electrode. In order to increase power generation efficiency, it is preferable that the amount of microorganisms retained in the anode chamber is high, for example, the concentration of microorganisms is preferably 1 to 50 g/L.

REFERENCE SIGNS LIST 1 tank body 2 ion-permeable non-conductive membrane 3 cathode chamber 4 anode chamber 5 positive electrode 6 negative electrode 11, 12 microbial power generator 13 aerobic biological treatment tank 14 sedimentation tank

Claims (6)

A biological treatment apparatus for organic wastewater comprising first to n-th (n is 2 or more) biological treatment tanks connected in series, and performing treatment in each tank,
At least the first biological treatment tank is separated from an anode chamber to which raw water containing organic matter that retains microorganisms and is an electron donor is supplied and the anode chamber is separated by a non-conductive membrane having ion permeability, a cathode chamber to which an electron acceptor is supplied; and
A biological treatment apparatus for organic wastewater, wherein at least the final biological treatment tank is an aerobic biological treatment tank, and the system comprises means for returning part of the treated water of the aerobic biological treatment tank to the microbial power generation apparatus. 2. A biological treatment apparatus for organic wastewater according to claim 1, wherein said organic wastewater is organic wastewater containing volatile substances or odor-generating substances. 3. The biological treatment apparatus for organic wastewater according to claim 1, wherein the biological treatment tank other than the microbial power generation apparatus is a sludge floating reaction tank or a carrier flow reaction tank. The microbial power generator includes a first microbial power generator (11) and a second microbial power generator (12) to which the first treated water from the anode chamber of the first microbial power generator is supplied to the anode chamber. cage,
4. A biological treatment apparatus for organic waste water according to any one of claims 1 to 3 , wherein part of the treated water in said aerobic biological treatment tank is returned to said first microbial power generator (11). 5. A biological treatment apparatus for organic wastewater according to claim 1, further comprising means for supplying at least part of exhaust gas containing oxygen from said aerobic biological treatment tank to a cathode chamber of said microbial power generation apparatus. 6. Organic wastewater treatment according to any one of claims 1 to 5, wherein said microbial power generation device is equipped with an air cathode and means for supplying at least part of exhaust gas containing oxygen from a cathode chamber to said aerobic biological treatment tank. biological treatment equipment.

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