JP2018161620A - Sludge treatment apparatus, water treatment system using the same, sludge treatment method and water treatment method - Google Patents

Abstract

A sludge treatment apparatus capable of efficiently treating sludge with a high concentration, a water treatment system using the sludge treatment apparatus, a sludge treatment method, and a water treatment method are obtained. A sludge treatment apparatus 100 retains anaerobic microorganisms that decompose organic sludge, anaerobic tank 10 that anaerobically treats organic sludge contained in sludge-containing treated water, and anaerobic treatment process. The negative electrode chamber 21 in which the negative electrode 211 for holding the electricity-producing bacteria that decomposes the low-molecular organic acid generated in step 1 and emits electrons and collects the electrons released to the electricity-producing bacteria is inserted, and the electrons collected in the negative electrode 211 The microbial fuel cell 20 having the positive electrode 221 to which is supplied, the anaerobic tank 10 and the negative electrode chamber 21 of the microbial fuel cell 20 are connected, and sludge is contained between the anaerobic tank 10 and the negative electrode chamber 21 of the microbial fuel cell 20. And a circulation means 30 for circulating the treated water. [Selection] Figure 1

Description

  The present invention relates to a sludge treatment apparatus for reducing the volume of sludge generated during treatment of wastewater, a water treatment system using the sludge treatment apparatus, a sludge treatment method, and a water treatment method.

  As a method for treating waste water containing organic matter, a treatment method using microorganisms such as a standard activated sludge method is widely used. In the treatment method using microorganisms, microorganisms are introduced into organic sludge to treat wastewater, and microorganisms in the organic sludge proliferate with the treatment of wastewater. In this treatment method, microorganisms may proliferate excessively, and excess sludge can be generated by the excessively proliferating microorganisms. Excess sludge is unnecessary for water treatment and is discharged outside the wastewater treatment system. It is incinerated, landfilled as industrial waste, or fermented under anaerobic conditions. Since energy, cost, and land are required, it is required to reduce the amount of surplus sludge generated.

An anaerobic digestion method using anaerobic microorganisms is known as one method for reducing the amount of excess sludge generated. In this anaerobic digestion method, surplus sludge containing aerobic microorganisms or the like is supplied to an anaerobic tank and decomposed by anaerobic microorganisms to reduce the volume of surplus sludge. Anaerobic digestion consists of multiple processes with multiple types of anaerobic microorganisms. Each type of anaerobic microorganisms consists of a chain system that decomposes excess sludge while relaying decomposition by-products generated in each process. Yes. In such a chain system, first, excess sludge is decomposed by acid-producing bacteria to produce low-molecular organic acids such as propionic acid, butyric acid, and acetic acid. Next, the low molecular organic acid is decomposed by the methane producing bacteria to produce methane and carbon dioxide. In the anaerobic digestion method, the concentration of anaerobic microorganisms in the anaerobic tank is increased, and excess sludge containing aerobic microorganisms is added to increase the amount of excess sludge decomposed by anaerobic microorganisms per unit mass. Higher efficiency is achieved by concentrating and producing concentrated sludge.
On the other hand, in the decomposition process of excess sludge in the anaerobic digestion method, the production rate of low molecular organic acids is faster than the production rate of methane and the like. For this reason, when the amount of excess sludge supplied to the anaerobic tank is increased and the load on the anaerobic microorganism is increased, the low-molecular organic acid may not be sufficiently decomposed and accumulated in the anaerobic tank. Moreover, accumulation of low-molecular organic acids leads to a decrease in pH in the anaerobic tank, and the activity of methanogens decreases when the pH is low. For this reason, there exists a possibility that the vicious circle of the fall of pH by accumulation | storage of a low molecular organic acid and the further accumulation | storage of low molecular organic acid by the activity fall of the methanogen accompanying this may occur.

Thus, a system combining an anaerobic tank and a microbial fuel cell has been proposed as a method for suppressing the accumulation of low-molecular organic acids in an anaerobic digestion method. A microbial fuel cell is one that obtains electrical energy using electricity-producing bacteria. The electricity-producing bacteria are microorganisms that adhere to the surface of a conductor electrode and grow by assimilating low-molecular organic acids. In a microbial fuel cell, energy released by decomposing a low-molecular organic acid by an oxidation-reduction reaction of electricity-producing bacteria is recovered as electric energy.
As a system combining an anaerobic tank and a microbial fuel cell, for example, as disclosed in Patent Document 1, a negative electrode of a microbial fuel cell is attached to a medium of an anaerobic culture tank (equivalent to an anaerobic tank) in which methane fermentation treatment is performed. By inserting, there is a hybrid system combining a methane fermentation process and a microbial fuel cell. In this hybrid system, microorganisms attached to the negative electrode coexist with acid producing bacteria in an anaerobic environment, and acid producing bacteria obtain methane and electric energy by decomposing low molecular organic acids produced from excess sludge, Generation of hydrogen gas and accumulation of low molecular organic acids in an anaerobic culture tank are suppressed.
In addition, as disclosed in Patent Document 2, for example, a microbial fuel cell tank equipped with an anode for holding power generation microorganisms is installed at the rear stage of an anaerobic tank that holds sludge containing anaerobic microorganisms and performs anaerobic treatment of wastewater. In addition, there is a microbial fuel cell system in which a substrate contained in wastewater is oxidatively decomposed into power-generating microorganisms, and electrons generated in the process of oxidative decomposition are collected to collect power.

JP 2007-227216 A Japanese Unexamined Patent Publication No. 2016-31778

  However, Patent Document 1 only describes that an organic substance is introduced together with an acid-producing microorganism and a methanogenic microorganism into an anaerobic culture tank in which a negative electrode is inserted. It is not specifically disclosed whether organic substances are supplied to the anaerobic culture tank and excess sludge is discharged from the anaerobic culture tank. Patent Document 2 describes that wastewater containing organic substances and from which suspended substances are removed via a sedimentation basin or the like is introduced into an anaerobic tank, and after anaerobic treatment, transferred to a microbial battery tank. However, when the excess sludge is reduced by the anaerobic digestion method in the system of Patent Document 2, there is a problem that the sludge treatment efficiency may be reduced. That is, in the anaerobic digestion method, as described above, the concentration of anaerobic microorganisms in the anaerobic tank is increased, and excess sludge containing aerobic microorganisms to be treated is concentrated to obtain concentrated sludge. Although high efficiency is achieved, the concentrated sludge treated with a high concentration of anaerobic microorganisms itself contains a high concentration of anaerobic microorganisms, and is a highly viscous sludge. Since such a high-viscosity sludge has poor fluidity, when it is transferred to the microbial fuel cell tank, the contact between the sludge and the negative electrode becomes non-uniform and the contact efficiency decreases. When the contact efficiency between the sludge and the negative electrode is lowered, the low-molecular organic acid is not sufficiently decomposed and the accumulation of the low-molecular organic acid cannot be suppressed, so that the efficiency of the entire sludge treatment is also deteriorated. Although it is conceivable to make up the negative electrode or increase the number of negative electrodes to compensate for the decrease in contact efficiency, such an increase in the size causes an increase in initial cost and maintenance cost.

  The present invention has been made to solve the above-described problems, and is a sludge treatment apparatus capable of efficiently treating high-concentration sludge, a water treatment system using the same, a sludge treatment method, and water. A processing method is obtained.

  The sludge treatment apparatus of the present invention holds anaerobic microorganisms that decompose organic sludge, an anaerobic tank that anaerobically treats organic sludge contained in a sludge-containing liquid, and a low molecular weight produced in the process of anaerobic treatment An electrode chamber in which a negative electrode for holding an electron-producing bacterium that decomposes organic acids and emits electrons and that collects electrons released by the electricity-producing bacterium is inserted, and a positive electrode to which the collected electrons are supplied to the negative electrode. The microbial fuel cell has a circulation means for connecting the anaerobic tank and the electrode chamber and circulating the sludge-containing liquid between the anaerobic tank and the electrode chamber.

  The sludge treatment method of the present invention is an anaerobic treatment step for decomposing organic sludge contained in the sludge-containing liquid in an anaerobic tank holding anaerobic microorganisms that decompose organic sludge, and an anaerobic treatment step. Power generation process in which low-molecular organic acids generated in the process of microbial fuel cells are decomposed into electricity-producing bacteria in the electrode chamber of the microbial fuel cell to generate electricity, and the sludge-containing liquid is circulated between the anaerobic tank and the electrode chamber. The treatment process and the power generation process are performed in parallel.

According to this invention, sludge is contained between an anaerobic tank for anaerobically treating organic sludge and a microbial fuel cell that generates electricity by decomposing a low-molecular organic acid generated in the course of anaerobic treatment by an electricity-producing bacterium. Since the circulation means for circulating the liquid is provided, high-concentration sludge can be treated efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows the sludge processing apparatus and water treatment system in Embodiment 1 of this invention. It is a flowchart which shows the water treatment process by the water treatment system in Embodiment 1 of this invention. It is a flowchart which shows the sludge process by the sludge processing apparatus in Embodiment 1 of this invention. It is a whole block diagram which shows the sludge processing apparatus and water treatment system in Embodiment 2 of this invention. It is a whole block diagram which shows the sludge processing apparatus and water treatment system in Embodiment 3 of this invention. It is a whole block diagram which shows the sludge processing apparatus and water treatment system in Embodiment 4 of this invention. It is a whole block diagram which shows the sludge processing apparatus and water treatment system in Embodiment 5 of this invention.

Hereinafter, embodiments of a sludge treatment apparatus and a water treatment method, a sludge treatment method, and a water treatment method using the same will be described in detail with reference to the accompanying drawings. In the following, “treated water” represents water to be treated.
Embodiment 1 FIG.
FIG. 1 is an overall configuration diagram showing a sludge treatment apparatus and a water treatment system according to Embodiment 1 of the present invention. Equipment configuration, control system configuration, and flow system configuration of the sludge treatment apparatus and water treatment system according to Embodiment 1 Is shown. The water treatment system 1000 stores the wastewater F1 and aerobically treats it, and the wastewater F1 aerobically treated in the aeration tank 1 is separated into treated water F2 and sludge containing treated water, that is, sludge containing liquid. The liquid separation tank 4 and the sludge processing apparatus 100 which processes the sludge contained in the sludge containing treated water separated from the waste water F1 in the solid-liquid separation tank 4 are provided. The wastewater F1 is an example of water to be treated, and more specifically, any wastewater F1 may be used as long as it contains an organic substance to be treated, such as household or industrial wastewater.

  The aeration tank 1 is an aggregate of aerobic bacteria and microorganisms, and holds activated sludge (not shown) for aerobically treating the wastewater F1 under aerobic conditions. Further, the aeration tank 1 is provided with an aeration device 2 that supplies air from the air supply device 3 into the aeration tank 1 to make the inside of the aeration tank 1 an aerobic condition. As the air supply device 3, a blower, a compressor, a pump, or the like is used according to the air supply amount necessary to make the inside of the aeration tank 1 an aerobic condition.

  The solid-liquid separation tank 4 is connected downstream of the aeration tank 1 and separates waste water F1 discharged from the aeration tank 1 into treated water F2 and sludge-containing treated water. The solid-liquid separation tank 4 may be a precipitation tank or a membrane separation tank. In the case of a membrane separation tank, a membrane module used in the membrane separation activation method is used. The solid-liquid separation of the wastewater F1 by membrane separation is not limited to the outside type in which a separate solid-liquid separation tank 4 is provided as shown in FIG. 1, but a tank in which a solid-liquid separation membrane module is submerged in the aeration tank 1 Internal membrane separation may be employed.

The sludge treatment apparatus 100 is connected to the solid-liquid separation tank 4 via the extraction pipe 5, and a sludge concentration unit 41 for concentrating organic sludge contained in the sludge-containing treated water supplied from the solid-liquid separation tank 4, An anaerobic tank 10 connected to the sludge concentration unit 41 via the anaerobic tank inlet pipe 42 and anaerobically treating the sludge concentrated in the sludge concentration unit 41 with anaerobic microorganisms, and generated in the process of anaerobic treatment in the anaerobic tank 10 A microbial fuel cell 20 that generates electricity by decomposing low-molecular organic acid produced by electricity-producing bacteria, and a circulation means 30 that circulates sludge-containing treated water between the anaerobic tank 10 and the microbial fuel cell 20. .

  The sludge concentration part 41 concentrates the organic sludge contained in sludge containing treated water, and makes the density | concentration of an aerobic microorganism etc. a high density | concentration. As the sludge concentration unit 41, a known dehydrator or concentrator may be used. Examples of the dehydrator include a rotary screw type centrifugal dehydrator that uses centrifugal force, and a belt press dehydrator that performs dehydration by filtration. Examples of the concentrator include a normal-pressure levitation concentrator that attaches sludge to bubbles and floats and separates, and a granulation concentrator that granulates and aggregates by adding a flocculant to the sludge. The sludge concentrated in the sludge concentration unit 41 is sent to the anaerobic tank 10 through the anaerobic tank inlet pipe 42. In addition, a tank for storing an inorganic flocculant or an organic polymer flocculant that enlarges the flocs (lumps) of the sludge is provided in the previous stage of the sludge concentrator 41, and the sludge-containing treated water before being introduced into the sludge concentrator 41 You may add these flocculants to. The flocculant used here is not particularly limited as long as it does not inhibit or kill the growth of anaerobic microorganisms in the anaerobic tank 10 or the electricity producing bacteria in the negative electrode chamber 21 of the microbial fuel cell 20. .

  The inside of the anaerobic tank 10 is maintained under anaerobic conditions, and holds a high concentration of anaerobic microorganisms (not shown). Anaerobic microorganisms held in the anaerobic tank 10 are acid-producing bacteria that decompose organic sludge contained in sludge-containing treated water to produce low-molecular organic acids such as propionic acid, butyric acid, and acetic acid, and acid-producing bacteria. Includes methanogens that further decompose the generated low molecular organic acids to produce methane and carbon dioxide. The anaerobic tank 10 has a first inflow portion 11 and a first outflow portion 12. The first inflow part is connected to the anaerobic tank inlet pipe 42, and the first outflow part 12 is connected to the anaerobic tank outlet pipe 51.

  The anaerobic tank 10 is configured to circulate the sludge-containing treated water with the negative electrode chamber 21 of the microbial fuel cell 20 described later by the circulation means 30. The circulation means 30 is connected to the second outflow part 14, connected to the forward piping 31 that sends the sludge-containing treated water from the anaerobic tank 10 to the negative electrode chamber 21, and to the second inflow part 13, and is connected to the anaerobic tank from the negative electrode chamber 21. 10 and a return pipe 32 for returning the sludge-containing treated water. The forward piping 31 is connected to the lower surface of the negative electrode chamber 21, and the return piping 32 is connected to the upper surface of the negative electrode chamber 21. A circulation pump 33 is provided on the outward piping 31.

  The microbial fuel cell 20 is a two-tank type microbial fuel cell having two electrode chambers, and includes a negative electrode chamber 21 into which a negative electrode 211 is inserted, a positive electrode chamber 22 into which a positive electrode 221 is inserted, a negative electrode chamber 21, and a positive electrode chamber 22. A proton exchange membrane 23 is provided between them. The proton exchange membrane 23 prevents the inflow of sludge-containing treated water from the negative electrode chamber 21 to the positive electrode chamber 22 and the electrolyte solution from the positive electrode chamber 22 to the negative electrode chamber 21 across the negative electrode chamber 21 and the positive electrode chamber 22. Protons can move from the chamber 21 to the positive electrode chamber 22.

The negative electrode chamber 21 holds electricity producing bacteria (not shown) in a state where the inside is maintained under anaerobic conditions. The electricity producing bacteria are retained in the negative electrode chamber 21 by adhering to the surface of the negative electrode 211 inserted into the negative electrode chamber 21, and the low-molecular organic acid contained in the sludge-containing treated water from the anaerobic tank 10 is removed. As a substrate. Electricity producing bacteria decompose this low-molecular organic acid by an oxidation-reduction reaction, and emit electrons during the decomposition process. Electrons released to the electricity-producing bacteria are collected by the negative electrode 211 and sent to the positive electrode 221 via an external circuit.
In the positive electrode chamber 22, the positive electrode 221 is inserted, and an electron acceptor (not shown) that receives the electrons sent to the positive electrode 221 is held together with the electrolytic solution. The electrolytic solution is not particularly limited as long as it has conductivity and does not corrode the positive electrode 221. For example, a known electrolytic solution such as a sodium nitrate solution or a potassium ferricyanide solution can be used.
In the first embodiment, a two tank type microbial fuel cell is used, but a one tank type microbial fuel cell may be used. In the case of a one-cell type microbial fuel cell, a negative electrode with electricity-producing bacteria attached is inserted into one electrode chamber provided with an air cathode as a positive electrode on one side surface.

The material of the negative electrode 211 is not particularly limited as long as it is a conductive material, and a known material can be adopted. From the viewpoint of durability, it is preferable that the material is not easily decomposed by microorganisms and has good biocompatibility. For example, carbon materials such as carbon rods, carbon brushes, carbon paper, carbon felt, and metals such as gold and iron oxide It is preferable to use a material. In addition, from the viewpoint of efficient recovery of electrons produced by the electricity producing bacteria, it is more preferable if the material is highly adherent to the electricity producing bacteria. The structure of the negative electrode 211 is not particularly limited, and a known structure such as a sheet shape or a cylindrical shape can be employed. From the viewpoint of stable recovery of electrons, it is preferable to increase the surface area so as to increase the adhesion of electricity producing bacteria. For example, a porous body having as large a porosity as possible, It is preferable to form micro-order irregularities.
The material of the positive electrode 221 is not particularly limited, and a known material can be employed. From the viewpoint of efficient recovery of electrical energy, a material having low electrical resistance is preferable, and from the viewpoint of cost, a material having high corrosion resistance is preferable. For example, carbon rods, carbon brushes, carbon felts, etc. It is preferable to use a carbon material or a metal material such as stainless steel or copper. The structure of the positive electrode 221 is not particularly limited as in the case of the negative electrode 211, and a known structure such as a sheet shape or a cylindrical shape can be employed.
The electron acceptor is not particularly limited, but it is preferable to use oxygen in the air as the electron acceptor by blowing air into the positive electrode chamber 22 from the viewpoint of running cost. Further, a mediator may be added to the negative electrode chamber 21 in order to promote the recovery of electrons from the electricity producing bacteria by the negative electrode 211. The mediator is not particularly limited, and a known one such as methylene blue can be used.

  Next, a water treatment process by the water treatment system 1000 and a sludge treatment (volume reduction) process by the sludge treatment apparatus 100 will be described. FIG. 2 is a flowchart showing a water treatment process by the water treatment system in the first embodiment, and FIG. 3 is a flowchart showing a sludge treatment process by the sludge treatment apparatus in the first embodiment. First, the aeration tank 1 is brought into an aerobic condition by the diffuser 2 with a predetermined amount of wastewater F1 flowing into the aeration tank 1, and the wastewater F1 is subjected to aerobic treatment (step ST01, aerobic treatment process). By this aerobic treatment, organic sludge is generated as the organic substances in the wastewater F1 are decomposed.

  Next, the wastewater F1 aerobically treated in step ST01 and the organic sludge generated by the aerobic treatment are transferred to the solid-liquid separation tank 4, and the wastewater F1 is treated as treated water F2 not containing sludge and sludge-containing treated water. Separate (step ST02, separation step). The treated water F2 is discharged out of the system as treated. A part of the sludge-containing treated water is sent to the sludge concentrating part 41 of the sludge treatment apparatus 100 via the extraction pipe 5, and the rest is returned to the aeration tank 1 via the return pipe 6.

Next, the sludge in the sludge-containing treated water is treated by the sludge treatment apparatus 100 (step ST03, sludge treatment step).
The sludge treatment in step ST03 is performed as follows. First, the sludge containing treated water sent to the sludge concentration part 41 is concentrated by aggregation or dehydration (step ST031, concentration process). The concentration of sludge in the treated water containing sludge after concentration (concentration of solids such as aerobic microorganisms) is not particularly limited, but as described in paragraph 0007, the higher the concentration of aerobic microorganisms, the higher the efficiency of anaerobic treatment. Therefore, 20000 mg / L or more is preferable and 30000 mg / L or more is more preferable from the viewpoint of anaerobic treatment efficiency. On the other hand, the higher the sludge concentration, the longer the sludge residence time in the anaerobic tank 10, and the required volume increases and the initial cost increases. In addition, high-concentration sludge increases the viscosity of the sludge-containing treated water, and the driving force of the circulation pump necessary for circulating the sludge-containing treated water between the anaerobic tank 10 and the microbial fuel cell 20 increases, and the forward piping The risk that 31 and the return pipe 32 are blocked increases. For this reason, 100000 mg / L or less is preferable from a viewpoint of cost and the stable circulation of sludge containing treated water, and 60000 mg / L or less is more preferable.

  Next, the sludge containing treated water concentrated through the anaerobic tank inlet pipe 42 is transferred and flows into the anaerobic tank 10 through the first inflow part 11 (step ST032, inflow process).

  Next, an anaerobic process is performed with respect to the sludge contained in the sludge containing treated water thrown in in the anaerobic tank 10 (step ST033, anaerobic process). In the anaerobic treatment, the organic sludge is first decomposed into low-molecular organic acids by acid-producing bacteria, and then the low-molecular organic acids are decomposed into methane and carbon dioxide by methanogenic bacteria. In addition, the rate at which acid-producing bacteria produce low-molecular organic acids is faster than the rate at which methanogenic bacteria degrade low-molecular organic acids, so the concentration and pH of low-molecular organic acids in sludge-containing treated water temporarily increase. To do.

  In parallel with the anaerobic treatment of step ST033, the microbial fuel cell 20 generates power while circulating the sludge-containing treated water being anaerobically treated between the anaerobic tank 10 and the microbial fuel cell 20 by the circulation means 30 ( Step ST034, power generation step). More specifically, the circulation pump 33 is driven at a predetermined timing after the inflow process, and the sludge-containing treated water being subjected to the anaerobic treatment is discharged from the second outflow portion 14 to the outward piping 31, Is allowed to flow from below the negative electrode chamber 21 of the microbial fuel cell 20. Since the sludge-containing treated water during the anaerobic treatment contains low-molecular organic acids generated from the sludge by acid-producing bacteria, the low-molecular organic acids flow into the negative electrode chamber 21 together with the sludge-containing treated water. The low-molecular organic acid that has flowed into the negative electrode chamber 21 is decomposed by the electricity-producing bacteria attached to the surface of the negative electrode 211 to generate electrons. The electrons are collected by the negative electrode 211, sent to the positive electrode 221 via an external circuit, and collected by the electron acceptor held in the positive electrode chamber 22. Thus, in the power generation step, power generation is performed by the decomposition of the low molecular organic acid sent to the negative electrode chamber 21 of the microbial fuel cell 20 by the circulation means 30.

  The sludge-containing treated water that has flowed into the negative electrode chamber 21 flows from the lower side to the upper side in parallel with the surface of the proton exchange membrane 23, and flows out to the return pipe 32 connected to the upper surface. The sludge-containing treated water that has flowed out to the return pipe 32 passes through the return pipe 32 and flows into the anaerobic tank 10 from the second inflow portion 13.

  Since the low-molecular organic acid is decomposed in the negative electrode chamber 21 as described above, the concentration of the low-molecular organic acid in the sludge-containing treated water flowing from the negative electrode chamber 21 to the anaerobic tank 10 through the return pipe 32 is the outgoing pipe 31. The concentration is lower than the concentration of the low-molecular organic acid in the sludge-containing treated water flowing from the anaerobic tank 10 to the negative electrode chamber 21, and the pH is also reduced. For this reason, by performing the anaerobic process of step ST033 and the power generation process of step ST034 in parallel, an increase in the pH of the sludge-containing treated water in the anaerobic tank 10 is suppressed, and the activity of methane-producing bacteria decreases due to the increase in pH. Is prevented.

  The sludge-containing treated water whose sludge has been sufficiently reduced by the anaerobic treatment step flows out of the anaerobic tank through the first outflow part 12, and is discharged out of the system through the anaerobic tank outlet pipe 51 (step ST035, Outflow process).

Since the sludge treatment apparatus 100 continuously treats sludge, the sludge is already reduced while the anaerobic treatment process and the power generation process are performed on the sludge-containing treated water flowing into the anaerobic tank 10. Since the discharge process for the sludge-containing treated water is also carried out, the flow rate of sludge-containing treated water flowing out from the first outflow part 12 (hereinafter referred to as discharge flow rate Q1 [m3 / day]) and the second outflow part 14 The balance between the flow rate of the sludge-containing treated water flowing out, that is, the flow rate of the sludge-containing treated water circulated by the circulation pump 33 (hereinafter, circulation flow rate Q2 [m3 / day]) is important. In the first embodiment, the number of contacts between the sludge-containing treated water and the negative electrode 211 is increased by increasing the circulation flow rate Q2 than the discharge flow rate Q1.
Moreover, since it is set as the structure which circulates sludge containing treated water between the anaerobic tank 10 and the negative electrode chamber 21 with the circulation means 30, the contact time of the low molecular organic acid in sludge containing treated water and the electroproduction bacteria adhering to the negative electrode 211 is set. Is adjustable by the circulation flow rate Q2, and does not depend on the size of the negative electrode chamber 21.

In the first embodiment, the sludge-containing treated water solids retention time (SRT: Sludge Retention Time) [day] in the anaerobic tank 10 is set to a predetermined value based on the discharge flow rate Q1. The volume V [m3] is set. SRT is a value represented by the following formula (1). Specifically, the product of the volume V of the anaerobic tank 10 and the solid concentration SC1 [g / m3] in the anaerobic tank 10 is treated with sludge. This is a value divided by the product of the water discharge Q2 [m3 / day] and the solid concentration SC2 “g / m3” of the sludge containing treated water flowing out.

SRT in the anaerobic tank 10 = (V × SC1) ÷ (Q1 × SC2) (1)

In addition, in order to maintain the quantity of the sludge containing treated water in the anaerobic tank 10 constant, it is preferable that the flow volume of the sludge containing treated water which flows into the anaerobic tank 10 and the discharge flow rate Q1 are the same.

  The SRT in the anaerobic tank 10 is not particularly limited, but is preferably 2 days or longer, more preferably 6 days or longer, and even more preferably 15 days or longer from the viewpoint of sufficient sludge decomposition. On the other hand, 40 days or less are preferable, 30 days or less are more preferable, and 20 days or less are more preferable from the viewpoint of preventing the anaerobic tank 10 from being enlarged and preventing an increase in initial cost due to efficient use of the anaerobic tank 10.

  The circulation flow rate Q2 is determined by the driving force of the circulation pump 33, and is not particularly limited as long as the low-molecular organic acid generated in the sludge and the anaerobic tank 10 is sufficiently decomposed. Whether or not the sludge has been sufficiently decomposed is determined, for example, by providing a sludge concentration measuring device (not shown) online on the anaerobic tank outlet pipe 51 to measure the concentration of sludge in the sludge-containing treated water flowing out of the anaerobic tank 10, What is necessary is just to judge by the density | concentration of the sludge having reached the target value. In addition, in order to prevent that the sludge containing treated water which has not reached the target value is discharged out of the system, the anaerobic tank outlet pipe 51 is branched halfway, and the sludge containing treated water is returned to the anaerobic tank 10 at one of the branches. Piping may be provided. A switching valve is provided at the branch, and the sludge-containing treated water is discharged out of the system only when the sludge concentration reaches the target value, and the sludge-containing treated water is returned to the anaerobic tank 10 when the target value is not reached. Add anaerobic treatment. In addition, as to whether or not the low molecular organic acid is sufficiently decomposed, whether or not the low molecular organic acid was sufficiently decomposed by providing a pH measuring device in the anaerobic tank 10 and measuring the pH in the anaerobic tank 10. It may be determined whether or not.

On the other hand, from the viewpoint of achieving both sufficient decomposition of low-molecular organic acids and sludge and suppression of increase in running cost of the circulation pump 33, appropriate circulation according to the ratio of sludge concentration before and after the sludge concentration in the sludge concentration unit 41, etc. It is also conceivable to set the flow rate Q2. Specifically, the sludge concentration of the sludge-containing treated water after being concentrated in the sludge concentration unit 41 is C [mg / L], the sludge concentration before being concentrated is X [mg / L], and flows into the anaerobic tank 10. The flow rate of the sludge containing treated water is set to Q0 [m3 / day], and the circulation flow rate Q2 is set to satisfy the following formula (2).

(C / X) ² × Q0 ≦ Q2 ≦ 5 × (C / X) ² × Q0 (2)

By setting the circulation flow rate Q2 so as to satisfy the above expression (2), it is possible to sufficiently decompose the low-molecular organic acid and sludge and to suppress an increase in running cost of the circulation pump 33.

The size of the negative electrode chamber 21 of the microbial fuel cell 20 is not particularly limited, and is preferably as close to the size of the negative electrode 211 as possible from the viewpoint of reducing dead space (a space where the sludge-containing treated water and the negative electrode do not contact). On the other hand, from the viewpoint of contact efficiency between the sludge-containing treated water and the negative electrode 211, the flow of the sludge-containing treated water in the negative electrode chamber 21 is preferably turbulent. For this reason, it is preferable to set the horizontal direction cross-sectional area D [m2] of the negative electrode chamber so as to satisfy the following formula (3).

5000 ≦ (Q / (D) ^0.5 × ρ) / (2 × 10 ⁻²² × C ² × exp (4850 / T)) ≦ 15000 Formula (3)

In equation (3), ρ [kg / m3] is the density of the sludge-containing treated water, and T [K] is the temperature of the sludge-containing treated water. C is the sludge concentration of the sludge-containing treated water after concentration in the same manner as the above formula (2). The middle side of Expression (3) indicates the Reynolds number of the flow of the sludge-containing treated water in the negative electrode chamber 21. That is, the expression (3) indicates that the circulation flow rate Q2 and the negative electrode chamber are set such that the flow of sludge containing treated water in the negative electrode chamber 21 becomes turbulent by setting the Reynolds number of the flow of sludge containing treated water in the negative electrode chamber 21 to 5000 or more. 21 indicates that a horizontal sectional area D of 21 is set. Due to the turbulent flow, the contact efficiency with the negative electrode 211 increases, and the contact time between the sludge-containing treated water and the electricity producing bacteria also increases. On the other hand, the Reynolds number is set to 15000 or less in order to provide an upper limit for the horizontal sectional area D of the negative electrode chamber 21 from the viewpoint of suppressing an increase in cost and an increase in dead space due to the enlargement of the negative electrode chamber 21.

  According to Embodiment 1, high concentration sludge can be efficiently treated. More specifically, since it was equipped with a circulation means for circulating the sludge-containing treated water during anaerobic treatment between the anaerobic tank and the microbial fuel cell, the negative electrode and sludge contained due to the increase in viscosity accompanying the increase in sludge concentration Efficient sludge treatment is possible by compensating the decrease in the contact efficiency of the treated water with an increase in the number of contacts by circulation. That is, the contact efficiency reduction per contact is compensated by contacting the sludge-containing treated water and the negative electrode a plurality of times by circulating the sludge-containing treated water. Furthermore, since the circulation flow rate of the sludge-containing treated water is larger than the discharge flow rate of the sludge-containing treated water to the outside of the system, a sufficient number of contacts is ensured.

  In addition, it is possible to prevent an increase in initial costs and an increase in maintenance costs in response to the increase in sludge concentration. More specifically, there is no need to increase the size of the negative electrode or increase the number of negative electrodes in order to cope with higher concentrations, and there is no increase in initial costs and maintenance costs associated with these. As described above, in the first embodiment, the sludge-containing treated water during the anaerobic treatment is circulated between the anaerobic tank and the microbial fuel cell to compensate for the decrease in the contact efficiency of the negative electrode and the sludge-containing treated water. It is.

  In addition, the negative electrode chamber can be used efficiently. More specifically, the negative electrode chamber can be reduced in size, and the size of the negative electrode chamber can be made closer to the size of the negative electrode, thereby reducing dead space (a space where the sludge-containing treated water and the negative electrode do not contact). It is possible to increase the proportion of the negative electrode in the negative electrode chamber, that is, the proportion of the electricity-producing bacteria. This is because by circulating the sludge-containing treated water, the contact time between the low-molecular organic acid in the sludge-containing treated water and the electricity-producing bacteria can be adjusted by the circulation flow rate and does not depend on the size of the negative electrode chamber. . Note that such efficient use of the negative electrode chamber also has an effect of suppressing the influence of a decrease in the contact efficiency between the sludge-containing treated water and the negative electrode due to an increase in the sludge viscosity.

Moreover, anaerobic processing can be performed efficiently. More specifically, the concentration of sludge in the sludge-containing treated water (concentration of solids such as aerobic microorganisms) is high in the concentration step before anaerobic treatment, and anaerobic microorganisms per unit mass However, since the amount of sludge to be treated per unit time is large, anaerobic treatment can be performed efficiently.

  In addition, electric energy can be efficiently obtained from the low molecular organic acid generated during the anaerobic treatment of sludge. More specifically, the electricity producing bacteria that decomposes low molecular organic acids and emits electrons are attached and held on the surface of the negative electrode, so the recovery of electrons by the negative electrode is highly efficient and the electric energy is efficient. Can be obtained.

In addition, it is possible to prevent the proton exchange membrane of the microbial fuel cell from being damaged and prevent the sludge-containing treated water from becoming stagnation in the negative electrode chamber and deteriorating the contact efficiency between the sludge-containing treated water and the negative electrode. More specifically, since the forward piping is connected to the lower surface of the negative electrode chamber and the return piping is connected to the upper surface, the flow of sludge-containing treated water in the negative electrode chamber is parallel to the surface of the proton exchange membrane. That is, since there is no flow perpendicular to the surface of the proton exchange membrane and no large force is applied to the proton exchange membrane, the proton exchange membrane is not easily damaged. Moreover, since the flow of the sludge-containing treated water becomes smooth, the sludge-containing treated water is brought into contact with the entire negative electrode without causing stagnation, and the contact efficiency is maintained.
If the proton exchange membrane has sufficient durability and there is little risk of stagnation in the sludge-containing treated water, for example, connecting the outgoing and return piping to the lower and upper sides of the negative electrode chamber A configuration in which a flow in a direction perpendicular to the surface of the proton exchange membrane is generated may be employed.

Embodiment 2. FIG.
A second embodiment of the present invention will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected about FIG. 1 or an equivalent part, and the description is abbreviate | omitted. FIG. 4 is an overall configuration diagram showing a sludge treatment apparatus and a water treatment system according to Embodiment 2 of the present invention. Equipment configuration, control system configuration, and flow system configuration of the sludge treatment apparatus and water treatment system according to Embodiment 2 Is shown. The basic configuration and operation of the water treatment system 2000 and the sludge treatment apparatus 200 are the same as those of the water treatment system 1000 and the sludge treatment apparatus 100 of the first embodiment, but the temperature of the sludge-containing treated water in the anaerobic tank 10 and A temperature / pH measurement unit 15 for measuring pH is provided in the anaerobic tank 10, and the temperature and pH in the anaerobic tank 10 are controlled and maintained at predetermined values based on the measurement result of the temperature / pH measurement unit 15. -The point provided with the pH adjustment part 16 differs from Embodiment 1. FIG.

  The temperature / pH adjusting unit 16 maintains the environment in the anaerobic tank 10 in an environment in which the methanogen is difficult to grow and activate when the low-molecular organic acid is hardly generated immediately after the start of the sludge treatment. It prevents that the low molecular organic acid in the sludge containing treated water of the anaerobic tank 10 reduces by fermentation (reaction which decomposes | disassembles a low molecular organic acid and produces | generates methane gas). The rate at which methanogens decompose low-molecular organic acids is very slow compared to the rate at which acid-producing bacteria produce low-molecular organic acids. Normally, low-molecular organic acids accumulate, but immediately after the start of sludge treatment. In the situation where almost no low-molecular organic acid is generated, etc., the low-molecular organic acid to be a substrate for the electricity-producing bacteria held in the negative electrode chamber 21 of the microbial fuel cell 20 is insufficient for the methanogen, There is a risk that the growth of electricity producing bacteria may be hindered. In this case, the density of the electricity-producing bacteria on the surface of the negative electrode 211 is reduced, and the low-molecular organic acid in the negative electrode chamber 21 is not sufficiently decomposed in the subsequent power generation process, resulting in a decrease in the activity of the methanogenic bacteria. There is a risk of causing sludge treatment efficiency reduction. In addition, it is necessary to maintain the inside of the anaerobic tank 10 also in the environment which does not prevent the low molecular organic acid by an acid producing bacteria.

  The temperature / pH adjusting unit 16 includes a submersible heater and a ribbon heater (not shown) for heating the sludge-containing treated water in the anaerobic tank 10 as temperature adjusting means, and a tank for storing acidic solution or alkaline solution as pH adjusting means. (Not shown) and a pump (not shown) for feeding an acidic solution or an alkaline solution into the anaerobic tank 10.

From the viewpoint of suppressing the growth and activation of methanogens in the anaerobic tank 10, the temperature of the sludge-containing treated water in the anaerobic tank 10 is preferably 30 ° C or lower, and more preferably 20 ° C or lower. Moreover, 10 degreeC or more is preferable and 15 degreeC or more is more preferable from a viewpoint of preventing that the production | generation of a low molecular organic acid is prevented by the activity fall of acid producing bacteria. The pH of the sludge-containing treated water in the anaerobic tank 10 is preferably 6.5 or less and more preferably 6.0 ° C. or less from the viewpoint of suppressing the growth and activation of methanogens in the anaerobic tank 10. Moreover, 4.5 or more are preferable and 5.2 or more are more preferable from a viewpoint which prevents the production | generation of a low molecular organic acid from being hindered by the activity fall of acid producing bacteria. In addition, since methane fermentation should not arise, if one of temperature or pH is set to said range and methane fermentation is prevented, the other range will not be specifically limited.

  According to the second embodiment, the same effect as in the first embodiment can be obtained.

  Moreover, the efficient process of a high concentration sludge can be implemented more reliably. More specifically, for the electricity producing bacteria used in the power generation process that is carried out in parallel with the anaerobic treatment process, the low molecule that is a substrate even when almost no low molecular organic acid is produced immediately after the start of sludge treatment, etc. In order to suppress the growth and activation of methanogens by the temperature and pH adjuster so that the organic acid is sufficiently supplied to the electricity producing bacteria, the electricity producing bacteria grow sufficiently and the surface of the negative electrode chamber of the microbial fuel cell It can prevent that the density of bacteria decreases. As a result, the low-molecular organic acid is sufficiently decomposed by the electricity-producing bacteria in the power generation process, preventing excessive accumulation of low-molecular organic acid in the sludge-containing treated water in the anaerobic tank, and high concentration in the anaerobic tank. Efficient treatment of sludge can be carried out more reliably.

  In the second embodiment, the temperature and the pH are adjusted to prevent the growth and activation of the methanogen. However, the degradation of the pH cannot be prevented only by the decomposition of the low molecular organic acid by the electricity producing bacteria. It is also conceivable to set the pH in the anaerobic tank 10 to a state suitable for activation of the methanogen using the temperature / pH adjusting unit 16.

Embodiment 3 FIG.
The third embodiment of the present invention will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected about FIG. 1 or an equivalent part, and the description is abbreviate | omitted. FIG. 5 is an overall configuration diagram showing a sludge treatment apparatus and a water treatment system according to Embodiment 3 of the present invention. Equipment configuration, control system configuration and flow system configuration of the sludge treatment apparatus and water treatment system according to Embodiment 3 Is shown. The water treatment system 3000 and the sludge treatment apparatus 300 have the same basic configuration and operation as the water treatment system 2000 and the sludge treatment apparatus 200 of the second embodiment, but detect sludge leakage that detects sludge in the positive electrode chamber 22. A portion 24, an electrolyte tank 7 that stores an electrolyte solution held in the positive electrode chamber 22, and an electrolyte solution circulation means 60 that circulates the electrolyte solution between the electrolyte solution tank 7 and the positive electrode chamber 22, The point from which the circulation means 30 was equipped with the negative electrode chamber electromagnetic valve 34, ie, the sludge containing liquid interruption | blocking means, differs from Embodiment 2.

  The sludge leakage detection unit 24 includes a sludge concentration meter (not shown), and periodically leaks sludge from the negative electrode chamber 21 to the positive electrode chamber 22 by sampling the electrolyte from the positive electrode chamber 22 to check for sludge. Is detected. The electrolyte solution after the check is returned to the positive electrode chamber 22. In the third embodiment, a sludge densitometer is used for checking the presence or absence of sludge, but a turbidity meter may be used.

The electrolytic solution circulating means 60 has one end connected to the electrolytic solution tank 7 and the other end connected to the positive electrode chamber 22, and one end of the electrolytic solution circulation pipe 61 that sends the electrolytic solution in the electrolytic solution tank 7 to the positive electrode chamber 22. Is connected to the positive electrode chamber 22, the other end is connected to the electrolytic solution tank 7, and an electrolytic solution return pipe 62 for returning the electrolytic solution in the positive electrode chamber 22 to the electrolytic solution tank 7 is provided. An electrolytic solution circulation pump 63 is provided on the electrolytic solution outward piping 61, and the positive electrode chamber electromagnetic valve 64, that is, electrolytic, is provided between the electrolytic solution tank 7 and the electrolytic solution circulation pump 63 on the electrolytic solution outward piping 61. Liquid blocking means is provided. The electrolytic solution circulation pump 63 circulates the electrolytic solution between the electrolytic solution tank 7 and the positive electrode chamber 22 to keep the amount and concentration of the electrolytic solution held in the positive electrode chamber 22 constant. The positive chamber solenoid valve 64 controls the flow of the electrolyte from the electrolyte tank 7 to the positive chamber 22.

  The electrolytic solution tank 7 is provided with an electrolytic solution inlet and outlet (not shown), and it is possible to easily add or replace the electrolytic solution.

  On the outgoing line 31, a negative electrode chamber electromagnetic valve 34 is provided between the second outflow portion 14 and the circulation pump 33. The negative electrode chamber electromagnetic valve 34 controls the flow of the sludge-containing treated water from the anaerobic tank 10 to the negative electrode chamber 21.

The sludge leakage detection unit 24 transmits a sludge leakage signal to a circulation control unit (not shown) when sludge leakage due to breakage of the proton exchange membrane 23 or the like is detected. The circulation control unit that has received the sludge leakage signal stops the circulation pump 33 and the electrolyte circulation pump 63, and then closes the negative electrode chamber electromagnetic valve 34 and the positive electrode chamber electromagnetic valve 64, thereby allowing the sludge-containing treated water and the electrolyte to flow. The anaerobic tank 10, the microbial fuel cell 20, and the electrolyte tank 7 are separated from each other. As a result, the sludge that flows from the anaerobic tank 10 to the negative electrode chamber 21 does not enter the positive electrode chamber 22 or the electrolyte tank 7 through the damaged portion of the proton exchange membrane 23, and the electrolyte in the positive electrode chamber 22 does not enter the anaerobic tank. 10 is not mixed.
In the third embodiment, the sludge leakage detection unit 24 is provided in the positive electrode chamber 22, but it may be provided online on the electrolyte return pipe 62.

  According to the third embodiment, the same effect as in the second embodiment can be obtained.

  In addition, the maintenance cost can be reduced and the maintenance period can be shortened to more stably carry out water treatment and sludge treatment. More specifically, a sludge leakage detection unit is provided in the positive electrode chamber, and when the leakage of sludge due to damage of the proton exchange membrane or the like is detected, the circulation pump and the electrolyte circulation pump are stopped, the negative electrode chamber electromagnetic valve and the positive electrode By separating the anaerobic tank, the microbial fuel cell, and the electrolyte tank by blocking the flow of the sludge-containing treated water and the electrolyte with the room solenoid valve, the sludge-containing treated water is mixed into the electrolyte tank and the electrolyte Prevents entry into an anaerobic tank. As a result, the maintenance target when the proton exchange membrane is damaged or the like is limited to the microbial fuel cell, the maintenance cost can be reduced and the maintenance period can be shortened, and the water treatment and the sludge treatment can be performed more stably. ing.

  Further, the amount and concentration of the electrolytic solution held in the positive electrode chamber can be easily stabilized. More specifically, an electrolytic solution tank for storing the electrolytic solution is provided, and an electrolytic solution circulating means for circulating the electrolytic solution between the electrolytic solution tank and the positive electrode chamber is provided. Therefore, the addition of the electrolytic solution to the positive electrode chamber, the positive electrode Since the electrolytic solution in the chamber can be replaced by the electrolytic solution circulation means, the amount and concentration of the electrolytic solution held in the positive electrode chamber can be easily stabilized.

Embodiment 4 FIG.
The fourth embodiment of the present invention will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected about FIG. 1 or an equivalent part, and the description is abbreviate | omitted. FIG. 6 is an overall configuration diagram showing a sludge treatment apparatus and a water treatment system according to Embodiment 4 of the present invention. Equipment configuration, control system configuration and flow system configuration of the sludge treatment apparatus and water treatment system according to Embodiment 4 Is shown. The basic configuration and operation of the water treatment system 4000 and the sludge treatment apparatus 400 are the same as those of the water treatment system 3000 and the sludge treatment apparatus 300 according to the third embodiment, but one anaerobic tank 10 and one electrolyte tank 7 respectively. On the other hand, the difference from Embodiment 3 is that two systems of microbial fuel cells are connected. Hereinafter, the two systems are referred to as A system and B system, and “A” or “B” is added to the end of the code to indicate which system is the system.

  Similar to the microbial fuel cell 20 of the third embodiment, the microbial fuel cell 20A includes a negative electrode chamber 21A in which the negative electrode 211A is inserted, a positive electrode chamber 22A in which the positive electrode 221A is inserted, a proton exchange membrane that separates the negative electrode chamber 21A and the positive electrode chamber 22A. 23A and a sludge leakage detection unit 24A for detecting sludge in the positive electrode chamber 22A. Similarly, the microbial fuel cell 20B includes a negative electrode chamber 21B in which the negative electrode 211B is inserted, a positive electrode chamber 22B in which the positive electrode 221B is inserted, a proton exchange membrane 23B, and a sludge leakage detection unit 24B.

The anaerobic tank 10 is configured to circulate the sludge-containing treated water with the negative electrode chamber 21A by the circulation means 30A, and circulates the sludge-containing treated water with the negative electrode chamber 21B by the circulation means 30B. It is configured.
The circulation means 30A is connected to the second outflow portion 14 in the same manner as the circulation means 30 of the third embodiment, and the forward piping 31A for sending the sludge-containing treated water from the anaerobic tank 10 to the negative electrode chamber 21A, and the second inflow portion. 13, and a return pipe 32 </ b> A that returns sludge-containing treated water from the negative electrode chamber 21 </ b> A to the anaerobic tank 10. A circulation pump 33A is provided on the outgoing line 31A, and a negative chamber electromagnetic valve 34A is provided between the second outflow portion 14 and the circulation pump 33A on the outgoing line 31A. Further, a forward branch point 35 is provided between the second outflow portion 14 and the negative electrode chamber electromagnetic valve 34A. Further, a return junction point 36 is provided on the return pipeline 32A.
One end of the circulation means 30B is connected to the forward branch point 35, the other end is connected to the negative electrode chamber 21B, and the other end is connected to the negative piping 21B, and one end is connected to the negative electrode chamber 21B. And the other end is connected to the return junction point 36, and a return pipe 32B for returning the sludge-containing treated water from the negative electrode chamber 21B to the anaerobic tank 10 is provided. A circulation pump 33B is provided on the outgoing line 31B, and a negative chamber electromagnetic valve 34B is provided between the outgoing branch point 35 and the circulation pump 33B on the outgoing line 31B.

The electrolytic solution tank 7 is configured to circulate the electrolytic solution between the positive electrode chamber 22A by the electrolytic solution circulating means 60A and also circulates the electrolytic solution between the positive electrode chamber 22B by the electrolytic solution circulating means 60B. It is configured as follows.
Similarly to the electrolytic solution circulating means 60 of the third embodiment, the electrolytic solution circulating means 60A has one end connected to the electrolytic solution tank 7 and the other end connected to the positive electrode chamber 22A, and from the electrolytic solution tank 7 to the positive electrode chamber 22A. Electrolyte outbound pipe 61A for sending the electrolyte, and one end connected to the positive electrode chamber 22A, the other end connected to the electrolyte tank 7, and an electrolyte return pipe 62A for returning the electrolyte from the positive electrode chamber 22A to the electrolyte tank 7 And. An electrolytic solution circulation pump 63A is provided on the electrolytic solution outward piping 61A, and a positive electrode chamber solenoid valve 64A is provided between the electrolytic solution tank 7 and the electrolytic solution circulation pump 63A on the electrolytic solution outward piping 61A. ing. Further, an electrolyte solution forward branch point 65 is provided between the electrolyte solution tank 7 and the positive electrode chamber electromagnetic valve 64A. In addition, an electrolyte return path junction 66 is provided on the electrolyte return pipe 62A.
The electrolytic solution circulation means 60B has one end connected to the electrolytic solution forward branch point 65, the other end connected to the positive electrode chamber 22B, and an electrolytic solution forward piping 61B that sends the electrolytic solution from the electrolytic solution tank 7 to the positive electrode chamber 22B; One end is connected to the positive electrode chamber 22B, the other end is connected to the electrolyte return path junction 66, and an electrolyte return pipe 62B that returns the electrolyte from the cathode chamber 22B to the electrolyte tank 7 is provided. An electrolytic solution circulation pump 63B is provided on the electrolytic solution forward piping 61B, and a positive electrode chamber electromagnetic valve 64B is provided between the electrolytic solution forward piping branch point 65 and the electrolytic solution circulation pump 63B on the electrolytic solution forward piping 61B. It has been.

Next, the operation will be described. The sludge treatment apparatus 400 normally performs decomposition of low-molecular organic acids by electricity-producing bacteria and circulation of sludge-containing treated water using one system of microbial fuel cells and circulation means, and one system is maintained for maintenance or the like. When the operation is stopped, the low-molecular organic acid is continuously decomposed and the sludge-containing treated water is circulated using the microbial fuel cell and the circulation means of the other system. Also, when the electrolyte is circulated using the electrolyte circulation means of one system at normal times and one of the systems is stopped for maintenance, etc., the electrolyte is circulated continuously using the electrolyte circulation means of the other system. Carry out liquid circulation. Hereinafter, a case where the sludge-containing treated water is decomposed and circulated and the electrolyte solution is circulated using the A system at the normal time will be described, but the same applies to the case where the B system is used at the normal time. In addition, since the sludge-containing treated water circulation and the electrolyte solution circulation are independent, the sludge-containing treated water circulation is carried out in the A system (B system), and the electrolytic solution circulation is carried out in the B system (A system). It is also possible to do.

  First, the circulation pump 33B and the electrolyte circulation pump 63B are stopped, the anode chamber solenoid valve 34A and the cathode chamber solenoid valve 64A are opened with the anode chamber solenoid valve 34B and the cathode chamber solenoid valve 64B closed, and the circulation pump 33A and the electrolysis pump 33A are electrolyzed. The liquid circulation pump 63A is driven. Thereby, while circulating the sludge containing treated water in the anaerobic tank 10 between the anaerobic tank 10 and the negative electrode chamber 21A, the low-molecular organic acid contained in the sludge containing treated water is retained in the negative electrode chamber 21A. Decompose into bacteria. Further, the amount and concentration of the electrolytic solution held in the positive electrode chamber 22A are kept constant while circulating the electrolytic solution between the electrolytic solution tank 7 and the positive electrode chamber 22A.

  When the sludge leakage detection unit 24A detects leakage of sludge due to damage to the proton exchange membrane 23A, etc., it becomes necessary to separate the anaerobic tank 10, the microbial fuel cell 20A, and the electrolyte tank 7, so that the circulation pump 33A and electrolysis The liquid circulation pump 63A is stopped, the negative electrode chamber electromagnetic valve 34A and the positive electrode chamber electromagnetic valve 64A are closed, and the flow of the sludge-containing treated water in the circulation means 30A and the flow of the electrolyte solution in the electrolyte circulation means 60A are interrupted. The system is switched by opening the solenoid valve 34B and the positive electrode chamber solenoid valve 64B and starting the circulation pump 33B and the electrolyte circulation pump 63B. Thereby, since the sludge containing treated water in the anaerobic tank 10 circulates between the anaerobic tank 10 and the negative electrode chamber 21B, the low molecular organic acid in the sludge containing treated water continues to be produced by the electricity producing bacteria in the negative electrode chamber 21B. Disassembled. Further, the electrolytic solution circulates between the electrolytic solution tank 7 and the positive electrode chamber 22B, and the amount and concentration of the electrolytic solution held in the positive electrode chamber 22B are kept constant.

  According to the fourth embodiment, the same effect as in the third embodiment can be obtained.

  Moreover, the treatment of high concentration sludge can be performed more stably. More specifically, since two microbial fuel cells and a circulation means are provided for one anaerobic tank, normally, in the negative electrode chamber of one of the microbial fuel cells, the electric production bacteria have low sludge content in the treated water. When decomposing molecular organic acid and shutting down one system for maintenance, etc., switch the system to circulate sludge-containing treated water, and continue to decompose low molecular organic acid in the negative electrode chamber of the microbial fuel cell of the other system. Let For this reason, since accumulation of organic acid can be prevented more reliably and the pH in the anaerobic tank can be maintained in a state suitable for the activity of the methanogen, high-concentration sludge can be treated more stably.

  In the fourth embodiment, the microbial fuel cell, the circulation means, and the electrolyte circulation means are two systems, but if the number is three or more, the entire system can be made more stable. In consideration of the initial cost, it is preferable to set the number to 2 or more and 3 or less.

Embodiment 5. FIG.
Embodiment 5 of the present invention will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected about FIG. 1 or an equivalent part, and the description is abbreviate | omitted. FIG. 7 is an overall configuration diagram showing a sludge treatment apparatus and a water treatment system according to Embodiment 5 of the present invention. Equipment configuration, control system configuration, and flow system configuration of the sludge treatment apparatus and water treatment system according to Embodiment 5 Is shown. The basic structure and operation of the water treatment system 5000 and the sludge treatment apparatus 500 are the same as those of the water treatment system 1000 and the sludge treatment apparatus 100 of the first embodiment, but a small anaerobic tank 101 having a smaller volume than the anaerobic tank 10. The second embodiment is different from the second embodiment in that the anaerobic tank 10 is replaced with a large-sized anaerobic tank 102 having a volume larger than that of the anaerobic tank 10 after the small-sized anaerobic tank 101.

  The small anaerobic tank 101 corresponds to the anaerobic tank 10 of the first embodiment, and the inside thereof is maintained under anaerobic conditions, and holds a high concentration of anaerobic microorganisms (not shown). Anaerobic microorganisms held in the small anaerobic tank 101 are acid-producing bacteria that decompose organic sludge contained in sludge-containing treated water to produce low-molecular organic acids, and low-molecular organic acids produced by acid-producing bacteria. Including methanogens that further decompose methane and produce carbon dioxide. The small anaerobic tank 101 has a first small anaerobic tank inlet 111 and a first small anaerobic tank outlet 121. The first small anaerobic tank inlet 111 corresponds to the first inlet 11 in Embodiment 1, and is connected to the anaerobic tank inlet pipe 42. The first small anaerobic tank outflow portion 121 corresponds to the first outflow portion 12 in the first embodiment, and is connected to the small anaerobic tank outlet pipe 511. The small anaerobic tank 101 has a second small anaerobic tank inflow portion 131 and a second small anaerobic tank outflow portion 141. The second small anaerobic tank inflow section 131 corresponds to the second inflow section 13 in the first embodiment, and is connected to the return pipe 32 of the circulation means 30. The second small anaerobic tank outflow portion 141 corresponds to the second outflow portion 14 in the first embodiment, and is connected to the forward piping 31 of the circulation means 30.

  The large anaerobic tank 102 has a large anaerobic tank inflow portion 112 and a large anaerobic tank outflow portion 122. The large anaerobic tank inflow section 112 is connected to the first small anaerobic tank outflow section 121 via the small anaerobic tank outlet pipe 511, and the sludge-containing treated water treated in the small anaerobic tank 101 enters the large anaerobic tank 102. It is configured to flow in. The large anaerobic tank outflow part 122 is connected to the large anaerobic tank outlet pipe 512, and the sludge-containing treated water treated in the large anaerobic tank 102 is discharged out of the system.

  The small anaerobic tank 101 and the large anaerobic tank 102 include a small anaerobic tank temperature / pH measuring unit 151, a small anaerobic tank temperature / pH adjusting unit 161, a large anaerobic tank temperature / pH measuring unit 152, and a large anaerobic tank temperature / pH, respectively. An adjustment unit 162 is provided. The small anaerobic tank temperature / pH measurement unit 151 corresponds to the temperature / pH measurement unit 15 of the second embodiment, and measures the temperature and pH of the sludge-containing treated water in the small anaerobic tank 101. The small anaerobic tank temperature / pH adjusting unit 161 corresponds to the temperature / pH adjusting unit 16 of the second embodiment, and the temperature and pH in the small anaerobic tank 101 are determined based on the measurement result of the small anaerobic tank temperature / pH measuring unit 151. Control and maintain a predetermined value. The large anaerobic tank temperature / pH measurement unit 152 measures the temperature and pH of the sludge-containing treated water in the large anaerobic tank 102. The large anaerobic tank temperature / pH adjusting unit 162 controls and maintains the temperature and pH in the large anaerobic tank 102 to predetermined values based on the measurement result of the large anaerobic tank temperature / pH measuring unit 152.

Next, a water treatment process by the water treatment system 5000 and a sludge treatment (volume reduction) process by the sludge treatment apparatus 500 will be described. First, the process until the sludge containing treated water concentrated in the sludge concentrating part 41 flows into the small anaerobic tank 101 is the same as that of the first embodiment. Next, anaerobic treatment is performed in the small anaerobic tank 101 while circulating sludge-containing treated water between the small anaerobic tank 101 and the negative electrode chamber 21 of the microbial fuel cell 20 as in the first embodiment.
The treatment in the negative electrode chamber 21 is the same as in the first embodiment, and the low-molecular organic acid in the sludge-containing treated water is decomposed by the electricity-producing bacteria. Embodiment 1 in which the flow rate of the sludge-containing treated water circulated between the small anaerobic tank 101 and the negative electrode chamber 21 is made larger than the flow rate of the sludge-containing treated water flowing out of the first small anaerobic tank outflow part 121. It is the same.

In the sludge treatment apparatus 500, the solids residence time necessary to sufficiently decompose the sludge in the sludge-containing treated water is ensured by the sum of the solids residence time in the small anaerobic tank 101 and the solids residence time in the large anaerobic tank 102. Therefore, in the fifth embodiment, the solid residence time in the small anaerobic tank 101 is shorter than the solid residence time in the anaerobic tank 10 of the first embodiment. For this reason, acid-producing bacteria grow in the small anaerobic tank 101, but slow-growing methanogens cannot grow sufficiently. As a result, most of the low-molecular organic acid produced by the acid-producing bacteria is sent to the negative electrode chamber 21, and the low-molecular organic acid serving as a substrate is sufficiently supplied to the electricity-producing bacteria in the negative electrode chamber 21. As a result, the bacterial density increases, and the low-molecular organic acid is efficiently decomposed in the negative electrode chamber.

  The sludge-containing treated water that has undergone the anaerobic treatment in the small anaerobic tank 101 is discharged from the first small anaerobic tank outflow portion 121 and flows into the large anaerobic tank 102 through the small anaerobic tank outlet pipe 511. The sludge-containing treated water flowing into the large anaerobic tank 102 has already been subjected to sludge volume reduction to some extent in the small anaerobic tank 101, and the organic matter load on the anaerobic microorganisms in the large anaerobic tank 102 is small. For this reason, the solids residence time in the large anaerobic tank 102 is made longer than the solids residence time in the anaerobic tank 10 of Embodiment 1 so that the methanogen grows sufficiently. As described above, since the organic matter load on the anaerobic microorganisms in the large anaerobic tank 102 is small, the low molecular organic acid does not accumulate and the pH does not decrease even if the solid residence time is increased.

  The solid residence time of the sludge-containing treated water in the small anaerobic tank 101 is preferably 5 days or less, more preferably 3 days or less from the viewpoint of sufficiently suppressing the growth of the methanogen. On the other hand, from the viewpoint of sufficiently growing acid-producing bacteria, one day or longer is preferable, and two days or longer is more preferable.

  The solid residence time of the sludge-containing treated water in the large anaerobic tank 102 is preferably 4 days or longer, more preferably 15 days or longer, and even more preferably 20 days or longer from the viewpoint of sufficiently growing the methanogen. On the other hand, 35 days or less is preferable and 30 days or less is more preferable from the viewpoint of preventing an increase in initial cost and an increase in the size of the large anaerobic tank 102 by efficiently using the large anaerobic tank 102.

  The total solid retention time of sludge-containing treated water in the small anaerobic tank 101 and the solid retention time of sludge-containing treated water in the large anaerobic tank 102 are 6 days or more from the viewpoint of sufficient decomposition of sludge in the sludge-containing treated water. Preferably, 20 days or more is more preferable. On the other hand, 40 days or less is preferable and 30 days or less is more preferable from the viewpoints of increasing the size of the small anaerobic tank 101 and the large anaerobic tank 102 and preventing an increase in initial cost.

The temperature of the sludge-containing treated water in the large anaerobic tank 102 is preferably 25 ° C. or higher, more preferably 35 ° C. or higher, from the viewpoint of sufficiently activating the methanogenic bacteria to increase the efficiency of methane fermentation. On the other hand, from the viewpoint of suppressing the heating cost, 65 ° C. or lower is preferable, and 55 ° C. or lower is more preferable.
The pH of the sludge-containing treated water in the large anaerobic tank 102 is preferably 6.5 or more, more preferably 6.8 or more, from the viewpoint of sufficiently activating the methane-producing bacteria and increasing the efficiency of methane fermentation. On the other hand, 8.0 or less is preferable and 7.4 or less is more preferable from the viewpoint of controlling the pH adjustment cost.

  According to the fifth embodiment, the same effect as in the first embodiment can be obtained.

  Moreover, the efficient process of a high concentration sludge can be implemented more reliably. More specifically, a small anaerobic tank and a large anaerobic tank with different solids residence times of sludge-containing treated water are provided, and the growth of methanogens is suppressed by shortening the solids residence time in the preceding small anaerobic tank. The sludge-containing treated water is circulated between the negative electrode chamber of the microbial fuel cell, and the sludge is decomposed by the acid-producing bacteria and the low-molecular organic acid is generated more efficiently and the low-molecular organic acid is decomposed by the electricity-producing bacteria. To do. In the latter large anaerobic tank, the solids residence time is lengthened to promote the growth of the methanogen. Here, the sludge-containing treated water that flows into the large anaerobic tank is a small anaerobic tank, and sludge volume reduction has already been performed to some extent, and the organic load on the anaerobic microorganisms is small. Organic acid does not accumulate and pH does not decrease. Therefore, in the large anaerobic tank 102, the activity of the methanogen is not suppressed, and the low molecular organic acid is decomposed by methane fermentation. Thus, since the volume reduction of the sludge by the small anaerobic tank of the front | former stage and the microbial fuel cell and the volume reduction by the large sized anaerobic tank of the back | latter stage are combined, the efficient process of a high concentration sludge can be implemented more reliably.

  Moreover, since methane fermentation by a methane producer is performed in a large anaerobic tank as described above, methane gas as an energy source can be recovered.

  It should be noted that within the scope of the present invention, the embodiments can be freely combined, or the embodiments can be appropriately modified or omitted.

DESCRIPTION OF SYMBOLS 1 Aeration tank, 4 Solid-liquid separation tank, 7 Electrolyte tank, 41 Sludge concentration part, 10 Anaerobic tank, 11 1st inflow part, 12 1st outflow part, 13 2nd inflow part, 14 2nd outflow Part, 15 temperature / pH measuring part, 16 temperature / pH adjusting part, 20, 20A, 20B microbial fuel cell, 21, 21A, 21B negative electrode chamber, 22, 22A, 22B positive electrode chamber, 211, 211A, 211B negative electrode, 221 221A, 221B Positive electrode, 23, 23A, 23B Proton exchange membrane, 24, 24A, 24B Sludge leakage detection unit, 30, 30A, 30B Circulation means, 31, 31A, 31B Outward piping, 32, 32A, 32B Return piping, 33, 33A, 33B Circulation pump, 34, 34A, 34B Anode chamber solenoid valve, 35 Forward branch point, 36 Return junction, 41 Sludge concentration section, 60, 60A, 6 0B Electrolyte forward circulation means, 61, 61A, 61B Electrolyte forward pipe, 62, 62A, 62B Electrolyte return pipe, 63, 63A, 63B Electrolyte circulation pump, 64, 64A, 64B Cathode chamber solenoid valve, 65 Electrolyte Outbound branch point, 66 electrolyte return path confluence, 101 small anaerobic tank, 102 large anaerobic tank, 111 first small anaerobic tank inflow section, 112 large anaerobic tank inflow section, 121 first small anaerobic tank outflow section, 122 large Anaerobic tank outflow section, 131 Second small anaerobic tank inflow section, 141 Second small anaerobic tank outflow section, 151 Small anaerobic tank temperature / pH measurement section, 152 Large anaerobic tank temperature / pH measurement section, 161 Small anaerobic tank temperature -PH adjuster, 162 Large anaerobic tank temperature-pH adjuster, 100, 200, 300, 400 Sludge treatment equipment, 1000, 2000, 3000, 4000, 500 0 Sludge treatment system, F1 wastewater, F2 treated water

Claims (24)

An anaerobic tank that retains anaerobic microorganisms that decompose organic sludge and anaerobically treats organic sludge contained in the sludge-containing liquid;
An electrode chamber in which a negative electrode for holding electrons producing bacteria that decomposes low-molecular organic acids generated in the anaerobic treatment and releases electrons and that collects electrons released to the electricity producing bacteria is inserted; and the negative electrode A microbial fuel cell having a positive electrode to which the recovered electrons are supplied;
A sludge treatment apparatus comprising: a circulating means for connecting the anaerobic tank and the electrode chamber and circulating the sludge-containing liquid between the anaerobic tank and the electrode chamber.   2. The anaerobic microorganism includes an acid-producing bacterium that decomposes the sludge to produce a low-molecular organic acid, and a methanogen that decomposes the low-molecular organic acid to produce methane. The sludge treatment apparatus described in 1. A temperature adjusting means for adjusting the temperature of the sludge-containing liquid in the anaerobic tank;
The sludge treatment apparatus according to claim 2, wherein the temperature adjusting means adjusts the temperature of the sludge-containing liquid in the anaerobic tank to a temperature at which the growth of the methanogen is suppressed. Further comprising pH adjusting means for adjusting the pH of the sludge-containing liquid in the anaerobic tank,
The sludge treatment apparatus according to claim 2 or 3, wherein the pH adjusting unit adjusts the pH of the sludge-containing liquid in the anaerobic tank to a pH at which the growth of the methanogen is suppressed. The electrode chamber includes a negative electrode chamber in which the sludge-containing liquid circulates between the negative electrode and the anaerobic tank, and a positive electrode chamber that is separated from the negative electrode chamber and in which the positive electrode is inserted and holds an electrolytic solution. And
The sludge treatment apparatus is
An electrolyte tank for storing the electrolyte held in the positive electrode chamber;
5. The apparatus according to claim 1, further comprising electrolyte solution circulation means for connecting the electrolyte solution tank and the cathode chamber and circulating the electrolyte solution between the electrolyte solution tank and the cathode chamber. The sludge treatment apparatus according to any one of the above. A sludge leakage detection unit for detecting sludge leakage from the negative electrode chamber to the positive electrode chamber;
Sludge-containing liquid blocking means for blocking the flow of the sludge-containing liquid in the circulation means based on the detection result of the sludge leakage detection section;
An electrolyte blocking means for blocking the flow of the electrolyte in the electrolyte circulation means based on the detection result of the sludge leakage detection section;
The sludge treatment apparatus according to claim 5, further comprising: A plurality of circulation means corresponding to the microbial fuel cells and the respective microbial fuel cells are provided,
The system for circulating the sludge-containing liquid is switched to another system when leakage of the sludge is detected in a microbial fuel cell of the system in which the sludge-containing liquid is circulating. Sludge treatment equipment.   A large-scale anaerobic tank having a volume larger than that of the anaerobic tank is further provided in a subsequent stage of the anaerobic tank and further anaerobically treating the sludge-containing liquid that holds the anaerobic microorganisms and is anaerobically treated by the anaerobic tank. The sludge treatment apparatus according to any one of claims 2 to 4, wherein the sludge treatment apparatus is provided. A large anaerobic tank temperature adjusting means for adjusting the temperature of the sludge-containing liquid in the large anaerobic tank;
The sludge treatment apparatus according to claim 8, wherein the large anaerobic tank temperature adjusting means adjusts the temperature of the sludge containing liquid in the large anaerobic tank to a temperature at which the methanogen is activated. A large anaerobic tank pH adjusting means for adjusting the pH of the sludge-containing liquid in the large anaerobic tank;
The sludge treatment apparatus according to claim 8 or 9, wherein the large anaerobic tank pH adjusting means adjusts the pH of the sludge-containing liquid in the large anaerobic tank to a pH that activates the methanogen.   The sludge treatment apparatus according to any one of claims 1 to 10, further comprising a sludge concentrating unit that concentrates the sludge-containing liquid that flows into the anaerobic tank. An aeration tank that holds activated sludge and aerobically treats water to be treated with the activated sludge;
A solid-liquid separation tank for separating a sludge-containing liquid containing organic sludge from the aerobically treated water to be treated;
The water treatment system provided with the sludge treatment apparatus of any one of Claim 1 to 11 which processes the sludge contained in the said sludge containing liquid. In an anaerobic tank holding anaerobic microorganisms that decompose organic sludge, an anaerobic treatment step that decomposes organic sludge contained in the sludge-containing liquid;
A power generation step of generating electricity by decomposing low-molecular organic acids generated during the anaerobic treatment step into electricity-producing bacteria in the electrode chamber of the microbial fuel cell,
A sludge treatment method, wherein the anaerobic treatment step and the power generation step are performed in parallel while circulating the sludge-containing liquid between the anaerobic tank and the electrode chamber.   The anaerobic treatment step includes a step of decomposing the organic sludge by acid-producing bacteria to produce a low molecular organic acid, and a step of decomposing the low molecular organic acid by a methanogen to produce methane. The sludge treatment method according to claim 13, further comprising a sludge treatment method.   The sludge treatment method according to claim 14, wherein, in the anaerobic treatment step, the temperature of the sludge-containing liquid in the anaerobic tank is adjusted to a temperature at which the growth of the methanogen is suppressed.   The sludge treatment method according to claim 14 or 15, wherein, in the anaerobic treatment step, the pH of the sludge-containing liquid in the anaerobic tank is adjusted to a pH at which the growth of the methanogen is suppressed. The electrode chamber holds the electricity producing bacteria, and a negative electrode chamber in which a negative electrode for collecting electrons emitted from the electricity producing bacteria is inserted and the sludge-containing liquid circulates between the anaerobic tank, and the negative electrode chamber A positive electrode chamber that is separated from the negative electrode and is supplied with the collected electrons in the negative electrode and holds an electrolyte solution;
The sludge treatment method according to any one of claims 13 to 16, wherein the electrolytic solution is circulated between an electrolytic solution tank storing the electrolytic solution held in the positive electrode chamber and the positive electrode chamber. . The sludge leakage is detected from the presence or absence of sludge in the positive electrode chamber, and when the sludge leakage is detected, the circulation of the sludge-containing liquid between the anaerobic tank and the negative electrode chamber is interrupted and the electrolysis is performed. The sludge treatment method according to claim 17, wherein circulation of the electrolytic solution between the liquid tank and the positive electrode chamber is interrupted. A plurality of the microbial fuel cells are provided,
The microbial fuel cell in which the sludge-containing liquid is circulated is switched to another microbial fuel cell when leakage of the sludge is detected in the microbial fuel cell in which the sludge-containing liquid is circulating. The sludge treatment method described in 1.   It is provided in the subsequent stage of the anaerobic tank, and the sludge containing liquid processed in the anaerobic treatment step and the power generation step is allowed to flow into a large anaerobic tank having a larger volume than the anaerobic tank, and further anaerobic treatment is performed. The sludge treatment method according to claim 14 to 16.   The sludge treatment method according to claim 20, wherein the temperature of the sludge-containing liquid in the large anaerobic tank is adjusted to a temperature at which the methanogen is activated.   The sludge treatment method according to claim 20 or 21, wherein the pH of the sludge-containing liquid in the large anaerobic tank is adjusted to a pH at which the methanogen is activated.   The sludge treatment method according to any one of claims 13 to 22, further comprising a concentration step of concentrating the sludge-containing liquid before the anaerobic treatment step. In the aeration tank holding the activated sludge, an aerobic process of treating the water to be treated with the activated sludge;
Separating the sludge-containing liquid containing organic sludge from the treated water subjected to the aerobic treatment;
A water treatment method comprising the step of treating the organic sludge by the sludge treatment method according to any one of claims 13 to 23.

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