JP4563121B2 - Wastewater treatment method - Google Patents

Description

The present invention relates to a method of treating wastewater, particularly, it relates to a method of processing sewage that can be utilized for biological treatment system wastewater containing organic matter.

Conventionally, many biological treatment methods using activated sludge microorganisms have been introduced as a treatment method for wastewater containing organic substances.
That is, by introducing sewage containing organic substances into the biological reaction tank holding the activated sludge microorganisms, and agitating them or aeration as necessary, the activated sludge microorganisms are brought into contact with the organic substance, and metabolism and utilization by the activated sludge microorganisms. The process is used to decompose and treat organic substances in sewage.

In the process of metabolism and assimilation, activated sludge microorganisms acquire energy by oxidizing and reducing organic or inorganic substances, and using the acquired energy to assimilate organic substances and synthesize new cells, that is, grow. .
In the acquisition of energy, a substance called ATP (adenosine triphosphate) is first synthesized, which is produced in one of the metabolic systems (called electron transport system) in which microbial enzymes and the like act. It is related to oxidation / reduction reactions between organic or inorganic substances, that is, transfer of electrons.
The ATP synthesized here is decomposed into ADP (adenosine diphosphate) in vivo, but at the same time, energy is generated, which is used as an energy source for cell synthesis.

On the other hand, in the biological treatment of sewage, the activated sludge microorganisms are retained in the biological reaction tank as described above, and the organic functions of the sewage are decomposed using the metabolic function, but good treatment performance is maintained. Therefore, it is necessary to keep the amount of microorganisms retained within a certain range.
In other words, microorganisms grown in the process of metabolism and assimilation of organic matter must be appropriately discharged out of the biological reaction tank.
For this reason, even in actual wastewater treatment facilities, in order to keep the sludge concentration in the biological reaction tank holding the activated sludge microorganisms within a certain range, a certain amount of sludge is discharged out of the system for treatment and disposal.

  In this way, in the process of treating sewage, activated sludge microorganisms grow with the decomposition and removal of organic substances in the water. Sludge needs to be properly treated and disposed of, and not only does the cost of the treatment and disposal become a problem, but there is also a problem that the number of disposal sites where the treated sludge is landed is decreasing year by year.

In view of the problems of the above-described conventional sewage treatment methods, the present invention provides a sewage treatment method capable of decomposing organic matter in sewage with microorganisms and appropriately treating wastewater while keeping the amount of generated sludge low. The purpose is to provide.

In order to achieve the above object, the wastewater treatment method of the present invention, when decomposing organic matter in wastewater by microorganisms, takes out electrons from microorganisms that metabolize organic matter by means of an electron transfer agent, and prevents cell synthesis by inhibiting cell synthesis. In a method for treating sewage in which growth is suppressed , sewage is caused to flow into an anaerobic tank coated with an electron transfer agent and loaded with a carrier supporting microorganisms, thereby supporting organic substances in the sewage on the carrier. After being decomposed by microorganisms, sewage from which organic substances have been removed is introduced into an aerobic tank, and a carrier containing an electron transfer agent that has received electrons from microorganisms that have metabolized organic substances is removed from the anaerobic tank and brought into contact with an oxidizing agent. It is characterized by being played back by sending and receiving electrons .

According to the sewage treatment method of the present invention, when organic matter in sewage is decomposed by microorganisms, electrons are extracted from the microorganisms that metabolize the organic matter with an electron transfer agent, and cell synthesis is inhibited to inhibit the growth of the microorganisms. Therefore, organic matter in the sewage can be decomposed while suppressing the growth of activated sludge microorganisms, which reduces the amount of sludge treatment / disposal required after the wastewater treatment and simplifies the treatment / disposal. Not only can this cost be reduced.

And an electron transfer agent and microorganisms can be efficiently thrown into a biological reaction tank by holding an electron transfer agent on a carrier and putting it in a biological reaction tank, or carrying a microorganism on this carrier.

Hereinafter, the embodiments of the process how the sewage of the present invention will be described with reference to the drawings.

The present embodiment proposes a wastewater treatment method and treatment apparatus in which microorganisms cannot synthesize or inhibit new cells in order to decompose organic matter in wastewater while suppressing the growth of activated sludge microorganisms.
That is, in this embodiment, the acquisition of energy necessary for cell synthesis of microorganisms is inhibited, that is, the electron transport system of microorganisms is interrupted so that ATP cannot be synthesized.

In order to cut off the electron transfer system of microorganisms, it is necessary to take electrons from microorganisms. However, since microorganisms are usually protected by cell membranes, they do not emit electrons outside the body.
However, some organic substances containing pigments such as neutral red and methylene blue can take electrons from microorganisms inside the cell or through the cell membrane surface, and these are called electron transfer agents.
Therefore, by putting such an electron transfer agent or a carrier holding the electron transfer agent into a biological reaction tank and bringing it into contact with activated sludge microorganisms, it is possible to deprive electrons from the microorganisms and inhibit energy acquisition necessary for cell synthesis. .

An outline of the mechanism using this mechanism as a microbial fuel cell is shown in FIG.
The microbial fuel cell includes a negative electrode 2 and a positive electrode 3, an external circuit 4 connecting them, and a diaphragm 5 that separates the negative electrode side and the positive electrode side.
Microorganisms 6 are held on the negative electrode side and metabolize using organic substances 7 to generate metabolites 8 and electrons 9.
In addition, the electron transfer agent 10 is also held on the negative electrode side at the same time, and this takes away the electrons 9 generated in the microorganism and becomes a reduced electron transfer agent 11.
During this time, the microorganism 6 normally obtains energy by using the electrons 9 obtained by metabolism and synthesizes new cells. However, since the electrons are deprived by the electron transfer agent 10, cell synthesis is performed. I can't.

On the other hand, the reduced electron transfer agent 11 delivers the electrons 9 in the negative electrode 2, changes again to the electron transfer agent 10, and is used for acquiring electrons from the microorganism 6. The reaction on the negative electrode side is performed under so-called anaerobic conditions in which no molecular oxygen is present. Under anaerobic conditions, there are hydrogen ions as the metabolite 8, which moves to the positive electrode side through the diaphragm 5 due to a concentration gradient. Therefore, a hydrogen permeable membrane or a cation exchange membrane is used as the diaphragm 5.
The electrons 9 transferred to the negative electrode 2 move to the positive electrode 3 through the external circuit 4. An oxidant 12 is introduced on the positive electrode side, receives electrons 9 on the positive electrode 3, and changes to a reduced oxidant 13. Note that oxygen is often used as the oxidant 12, which is reduced and combined with the hydrogen ions that have moved from the negative electrode side to change to water.

FIG. 1 is a flowchart showing a processing apparatus of a reference example.
The sewage A that has flowed into the treatment plant is first guided to the settling basin 14, but the first settling basin effluent B in which most of the contaminants have been removed and solid matter has been reduced by staying for a certain period of time is transferred to the negative electrode chamber 15. Flows in.
In the negative electrode chamber 15, the negative electrode 2 is installed and microorganisms are held, and are first mixed and stirred with the sedimentation basin effluent B. As the negative electrode 2, an electrode plate coated with an electron transfer agent (not shown) is used. As an example of the combination, a carbon cloth coated with neutral red, which is one of the electron transfer agents, can be considered. However, this combination is an example and does not limit the present invention.

The microorganisms held in the negative electrode chamber 15 first take in organic substances contained in the sedimentation basin effluent B and generate electrons for metabolism, that is, acquisition of energy, but are included in the negative electrode 2 by being in contact with the negative electrode 2. Electrons are taken away by an electron transfer agent (not shown).
Electrons taken into the negative electrode 2 reach the positive electrode 3 through the external circuit 4, but the positive electrode chamber 16 in which the positive electrode 3 is installed is in contact with the negative electrode chamber 15 across the diaphragm 5. Examples of the positive electrode 3 include, but are not limited to, electrodes made of graphite containing platinum.
The positive chamber 16 is provided with an air diffuser 17 through which air C is introduced, and oxygen contained in the air receives electrons on the surface of the positive electrode 3 and combines with hydrogen ions to form water. .
On the other hand, in the negative electrode chamber 15, the organic matter is decomposed and removed by the metabolism of microorganisms, but after staying for a certain time, it flows out as a mixed solution D and is led to the final sedimentation tank 18. In the final sedimentation basin 18, solid-liquid separation is performed by standing for a certain time, and the supernatant is discharged out of the system as treated water E, and a small part of the solid is discharged as surplus sludge F, but most of it is returned. The sludge G is returned to the negative electrode chamber 15.

FIG. 2 is a flowchart showing a treatment apparatus of one embodiment to which the wastewater treatment method of the present invention is applied.
In the sewage treatment apparatus, as in the above-described reference example, the sewage A that has flowed into the treatment plant passes through the first settling basin 14 to remove impurities, and flows into the anaerobic tank 19 as the first settling basin effluent B. .
The anaerobic tank 19 is coated with an electron transfer agent (not shown) and a carrier 20 having microorganisms attached to the surface thereof is held, and is first mixed and stirred with the settling basin effluent B.
At first, the organic matter in the sedimentation basin effluent B is taken up by microorganisms adhering to the carrier 20 and used for its metabolism, but the electrons generated by the microorganisms in the metabolic process are taken away by the electron transfer agent. It cannot be used to synthesize new cells. For this reason, the microorganisms attached to the carrier hardly grow.
The carrier 20 containing the electron transfer agent that has received the electrons may be deteriorated in performance over time. However, the carrier 20 may be taken out at regular intervals and contacted with an oxidizing agent to exchange electrons. Can be played.
On the other hand, the sewage from which some organic matter has been removed is guided to the aerobic tank 21, but the carrier 20 remains in the anaerobic tank 19.

In the aerobic tank 21, air C is introduced through the air diffuser 17, and the remaining organic matter is further decomposed and removed by microorganisms.
Microorganisms grow in this process, but the amount of growth is very small due to the small amount of remaining organic matter.
In the aerobic tank 21, after a certain residence time has elapsed, it flows into the final sedimentation basin 18 as a mixed solution D, solid-liquid separation is performed, and the supernatant is discharged out of the system as treated water E.
On the other hand, a part of the solid content is discharged out of the system as surplus sludge F, but the amount thereof is very small, and most of it is returned to the aerobic tank 21 as return sludge G.

Above, with the wastewater treatment method of the present invention have been described based on the example of its, the present invention is not limited to the configuration described in the above embodiment, combining the configurations described in Reference Example appropriately For example, the configuration can be changed as appropriate without departing from the spirit of the invention.

Method of processing sewage of the present invention, the active while suppressing the growth of sludge microorganisms since it also has the property of decomposing organic matter in sewage, the sewage treatment, including sludge, including sewage treatment applications Can be suitably used.

It is a flowchart which shows the processing apparatus of a reference example. It is a flowchart which shows the processing apparatus of one Example to which the processing method of the sewage of this invention is applied. It is a conceptual diagram of a microbial fuel cell.

DESCRIPTION OF SYMBOLS 1 Container 2 Negative electrode 3 Positive electrode 4 External circuit 5 Diaphragm 6 Microorganism 7 Organic substance 8 Metabolite 9 Electron 10 Electron transfer agent 11 Reduction type electron transfer agent 12 Oxidant 13 Reduction type oxidant 14 First sedimentation tank 15 Negative electrode chamber 16 Positive electrode chamber 17 Scattering Air device 18 Final sedimentation basin 19 Anaerobic tank 20 Carrier 21 Aerobic tank A Sewage B First sedimentation basin effluent C Air D Mixed liquid E Treated water F Surplus sludge G Return sludge

Claims (1)

The organic matter in the sewage when decomposed by microorganisms, organic matter is taken out electrons by electron transfer agent from metabolism microorganisms and the processing method to inhibit cell synthesis and for inhibiting the growth of microorganisms sewage, sewage, After flowing into an anaerobic tank coated with an electron transfer agent and loaded with a carrier carrying microorganisms, the organic matter in the sewage is decomposed by the microorganisms carried on the carrier, and then the sewage from which the organic matter has been removed is aerobic. Wastewater that is introduced into the tank and regenerated by removing the carrier containing the electron transfer agent that has received electrons from the microorganisms that metabolized organic matter from the anaerobic tank and bringing it into contact with an oxidant to exchange electrons. Processing method.

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