JP2018015684A - Wastewater treatment apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wastewater treatment apparatus and method capable of efficiently recovering energy from wastewater while suppressing fouling of a membrane.SOLUTION: A wastewater treatment apparatus comprises: a solid-liquid separation tank 1 for solid-liquid separating precipitating organic matter in wastewater to obtain separated sludge and a separated liquid; a forward osmotic membrane device 3 having a semipermeable membrane and bringing the separated liquid into contact with a driving liquid having a higher osmotic pressure than the separated liquid through the semipermeable membrane to obtain concentrated water and treated water; a disinfectant supply device 4 for supplying a disinfectant to the separated liquid before flowing into the forward osmosis membrane device 3; a concentrated water storage tank 5 for storing the concentrated water; and an anaerobic treatment tank 6 for decomposing the concentrated water and separated sludge to convert them into methane gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wastewater treatment device and a wastewater treatment method, and more particularly, to a wastewater treatment device and a wastewater treatment method capable of recovering energy from organic wastewater such as sewage or industrial wastewater.

  In the technical field of water treatment, there is known a water treatment apparatus that desalinates seawater and purifies sewage or industrial wastewater using a forward osmosis membrane (FO membrane: Forward Osmosis Membrane). FO membranes are a type of osmosis process that uses the phenomenon of flowing water from a thick solution side to a thin solution side with a semi-permeable membrane interposed between them to desalinate salt water and to contain water containing pathogens and harmful substances. Purification is performed.

  Non-Patent Document 1 discloses a method in which the outflow wastewater from the first sedimentation basin is treated with an FO membrane device using seawater as the driving liquid, and the concentrated wastewater is mixed with the sludge from the first sedimentation basin and introduced into the anaerobic digester. It is disclosed. Specifically, FIG. As shown in 1b, it is composed of an initial sedimentation basin, an FO membrane device, and an anaerobic digester, and the effluent water from the initial sedimentation basin is taken into the FO membrane device to obtain concentrated drainage by seawater of the driving liquid. At the same time, the concentrated drainage and the sedimentation sludge from the first sedimentation basin are mixed and anaerobic treatment is performed in an anaerobic digester.

  Patent Document 1 includes a flocculant injection device and a solids separation device, and a FO membrane as a semipermeable membrane device as a pretreatment coagulation sediment, and according to the amount of fouling components contained in seawater, It is disclosed to desalinate by controlling the pretreatment so as to reduce fouling of the semipermeable membrane.

  Patent Document 2 discloses an example in which sewage, human waste, and factory wastewater are treated water, and the concentrated water is directly obtained from the treated water using a forward osmosis membrane device. A configuration for aeration processing is disclosed.

JP 2012-223723 A JP 2014-61486 A

Processing municipal wastewaters by forward osmosis using CTA membrane J. Mem. Sci. 468 pp.269-275, 2014

  However, the technique of Non-Patent Document 1 has a problem in that components that do not settle in the first sedimentation basin adhere to the membrane surface, and fouling of the membrane frequently occurs. The deposits on the membrane surface can be removed by washing, but the components that can be recovered as energy from the concentrated water are also removed by frequently performing the removing operation.

  Although the technique described in Patent Document 1 can suppress fouling of the membrane, since it is a technique aimed at seawater desalination, there is a description and suggestion about recovering energy from treated water. Not.

  In the technique described in Patent Document 2, since the water to be treated is directly introduced into the FO membrane to concentrate the water to be treated, the organic solids and the soluble organic matter contained in the water to be treated cause FO early. Biofouling occurs on the membrane surface. Further, the invention described in Patent Document 2 neither describes nor suggests recovering energy from the water to be treated.

  The present invention has been made in view of the above problems, and an object thereof is to provide a wastewater treatment apparatus and a wastewater treatment method capable of efficiently recovering energy from wastewater while suppressing fouling of the membrane. To do.

  In order to achieve the above-mentioned object, the present inventors diligently studied, and in advance adjusted the properties of the inflow water flowing into the membrane separation device into a form in which membrane fouling hardly occurs, and the sludge obtained in each step And it was found that energy can be recovered efficiently by extracting the treated water and performing methane fermentation.

  The present invention completed on the basis of the above knowledge is, in one aspect, a solid-liquid separation tank for separating solid-liquid precipitates in waste water to obtain separated sludge and a separated liquid, a semipermeable membrane, and a semipermeable membrane A osmotic membrane device for obtaining concentrated water and treated water by bringing the separated liquid into contact with a driving liquid having a higher osmotic pressure than the separated liquid, and a bactericide in the separated liquid before flowing into the forward osmotic membrane apparatus. There is provided a wastewater treatment apparatus including a disinfectant supply apparatus to be supplied, a concentrated water storage tank for storing concentrated water, and an anaerobic treatment tank for decomposing the concentrated water and separated sludge and converting them into methane gas.

  In one embodiment, the wastewater treatment apparatus according to the present invention further includes an organic substance supply line capable of supplying organic substances contained in the drainage or separated sludge to the concentrated water storage tank.

  In another aspect, the present invention includes a first solid-liquid separation device that separates solid-liquid precipitates in wastewater to obtain separated sludge and a separated liquid, and a semipermeable membrane, with the semipermeable membrane interposed therebetween. A normal osmosis membrane device that obtains concentrated water and treated water by bringing the separation liquid into contact with a driving liquid having a higher osmotic pressure than the separation liquid, and a coagulant added to the separation liquid before flowing into the forward osmosis membrane apparatus to solidify it. There is provided a wastewater treatment apparatus comprising a second solid-liquid separation apparatus for liquid separation, and an anaerobic treatment tank for decomposing concentrated water and separated sludge to convert them into methane gas.

  In another embodiment of the wastewater treatment apparatus according to the present invention, the anaerobic treatment tank includes an anaerobic digestion tank for methane fermentation of separated sludge and an anaerobic wastewater treatment tank for methane fermentation of concentrated water.

  In yet another embodiment of the wastewater treatment apparatus according to the present invention, the driving liquid is seawater containing any of iron, cobalt, nickel, zinc, tungsten, manganese, molybdenum, selenium, and boron, and a seawater desalination treatment facility. Includes either concentrated water or high-salt drainage discharged from leachate treatment facilities.

  In another aspect of the present invention, solid organic liquid in the waste water is separated into solid and liquid to obtain a separated sludge and a separated liquid, and the separated liquid is supplied to a forward osmosis membrane apparatus including a semipermeable membrane. By contacting the separation liquid with a driving liquid having a higher osmotic pressure than the separation liquid through the permeable membrane, concentrated water and treated water are obtained, and a bactericide is added to the separation liquid before flowing into the forward osmosis membrane apparatus. There is provided a wastewater treatment method including supplying, storing concentrated water, and decomposing and converting the concentrated water and separated sludge into methane gas.

  In another aspect of the present invention, solid organic liquid in the waste water is separated into solid and liquid to obtain a separated sludge and a separated liquid, and the separated liquid is supplied to a forward osmosis membrane apparatus including a semipermeable membrane. Concentrated water and treated water are obtained by contacting the separation liquid with a driving liquid having a higher osmotic pressure than the separation liquid through the permeable membrane, and a flocculant is added to the separation liquid before flowing into the forward osmosis membrane device. Thus, there is provided a waste water treatment method including solid-liquid separation and decomposition of concentrated water and separated sludge to convert them into methane gas.

  In one embodiment, the wastewater treatment method according to the present invention is a seawater containing one of iron, cobalt, nickel, zinc, tungsten, manganese, molybdenum, selenium, and boron, concentrated water of a seawater desalination facility, Or high salt concentration wastewater discharged from leachate treatment facilities.

  According to the present invention, it is possible to provide a wastewater treatment apparatus and a wastewater treatment method capable of efficiently recovering energy from wastewater while suppressing fouling of the membrane.

It is the schematic which shows an example of the waste water treatment equipment which concerns on the 1st Embodiment of this invention. It is the schematic which shows an example of the waste water treatment equipment which concerns on the 2nd Embodiment of this invention. It is the schematic which shows an example of the waste water treatment equipment which concerns on the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention specifies the structure, arrangement, etc. of components as follows. Not what you want.

(First embodiment)
As shown in FIG. 1, the waste water treatment apparatus according to the first embodiment of the present invention is a solid-liquid separation tank 1 (first) that separates solid-liquid precipitates in waste water to obtain separated sludge and separated liquid. 1 and a semi-permeable membrane, and through the semi-permeable membrane, the separated liquid is brought into contact with a driving liquid having a higher osmotic pressure than the separated liquid to obtain concentrated water and treated water. The apparatus 3, the bactericide supply apparatus 4 for supplying the bactericide to the separation liquid before flowing into the forward osmosis membrane apparatus 3, the concentrated water storage tank 5 for storing the concentrated water, the concentrated water and the separated sludge are decomposed. And an anaerobic treatment tank 6 for converting to methane gas.

  The type of wastewater to be supplied is not particularly limited, but organic wastewater containing at least contaminants such as soluble organic matter and turbidity is preferably used. Specifically, sewage, primary treated water of sewage, secondary treated water of sewage, human waste, livestock wastewater, various production wastewater, and the like can be used as wastewater according to the present embodiment.

  The water quality of the wastewater is not limited to the following, but for example, the biochemical oxygen demand (BOD) is 10 to 1000 mg / L, the chemical oxygen demand (CODcr) is 20 to 3000 mg / L, suspended matter ( SS) can supply organic wastewater having a concentration of about 20 to 3000 mg / L.

  As the solid-liquid separation tank 1, for example, an initial sedimentation tank is preferably used. In addition, the specific means of solid-liquid separation is not specifically limited, Arbitrary means of gravity sedimentation separation, centrifugation, levitation separation, aggregation separation, and membrane separation can be utilized. The separation liquid obtained in the solid-liquid separation tank 1 is sent to a forward osmosis membrane device (FO membrane device). The separated sludge separated in the solid-liquid separation tank 1 is sent to the anaerobic treatment tank 6 through the pipe SL2.

  The forward osmosis membrane device 3 includes a semipermeable membrane (FO membrane), and the separated liquid separated from the solid-liquid separation tank 1 is supplied to the primary side of the semipermeable membrane. A driving liquid (draw solution) having a higher osmotic pressure than the separation liquid is supplied to the secondary side of the semipermeable membrane. By using the forward osmosis membrane device 3, it is not necessary to use a large pump for pressurization in the device as compared with a reverse osmosis membrane (RO) device or the like, so that power can be reduced.

  The separated liquid flowing into the forward osmosis membrane device 3 comes into contact with the driving liquid through the semipermeable membrane, whereby concentrated water and treated water are obtained. The treated water can be discharged to the outside of the forward osmosis membrane device 3. The concentrated water is sent to the concentrated water storage tank 5 through the pipe CL. The driving liquid supplied into the forward osmosis membrane device 3 is preferably seawater, concentrated water (brine) of a seawater desalination treatment facility, high salt concentration drainage discharged from a leachate treatment facility, or the like.

  The presence of trace amounts of substances such as iron, cobalt, nickel, zinc, tungsten, manganese, molybdenum, selenium, and boron is important for the activity of microorganisms that manage the anaerobic digestion process performed in the anaerobic treatment tank 6 of FIG. However, components in the driving fluid such as seawater containing these trace amounts of substances, concentrated water (brine) of seawater desalination facilities, and high-salt concentration wastewater discharged from leachate treatment facilities are used for the primary side of the semipermeable membrane. By flowing in, it becomes a nutrient source for performing the anaerobic digestion treatment, and the anaerobic digestion reaction can be performed more stably.

Specifically, in order to more efficiently energize concentrated water (methane gasification) in the anaerobic treatment tank 6, the solute leakage rate of the FO film defined below is 0.0001 to 0.1. It is preferable to set the type and operating conditions of the FO film.
Solute Leak Rate = (Concentrated Salinity Concentration ÷ Concentration Rate-Salinity Concentration in Raw Wastewater) ÷ Drive Liquid Salinity Concentration Rate = Raw Wastewater Flow Rate / Concentrated Water Flow Rate

  The FO film is not particularly limited, and various semi-permeable films can be used, but it is preferable to use a film in which the salt of the driving liquid partially flows from the secondary side to the primary side. For example, various materials such as cellulose acetate, polyamide, polysulfone, polyvinylidene fluoride, polyethylene, and vinyl chloride can be used. The shape of the FO film is not particularly limited, and a film having an arbitrary shape such as a flat film, a spiral film, or a hollow paper film can be used.

  As the disinfectant supplied from the disinfectant supply device 4 to the separation liquid flowing into the forward osmosis membrane device 3, a slime control agent is preferably used. Examples of slime control agents include chlorinated slime control agents such as sodium hypochlorite, oxidizing slime control agents such as hydrogen peroxide, 5-chloro-methyl-isothiazolin-3-one (MIT), and halocyanoacetamide compounds. Organic slime control agents can be used.

  Chlorine slime control agents such as sodium hypochlorite may deteriorate the FO film material due to its strong oxidizing power of residual chlorine, but react with this in wastewater containing ammonia to produce chloramine. To do. Since this chloramine has a milder oxidizing power than the advantageous residual chlorine, fouling can be prevented while suppressing oxidative deterioration of the film material.

  If the amount of the oxidizing agent added is too large, it may adversely affect the methane fermentation treatment of the concentrated water in the subsequent anaerobic treatment tank 6, and if it is too small, the effect of suppressing fouling of the FO membrane cannot be obtained advantageously. It is preferable to add the bactericide so that the concentration of the bactericide in the separation liquid supplied to the forward osmosis membrane device 3 is, for example, 0.1 to 100 mg / L, and more preferably 0.5 to 50 mg / L. Degree.

  In addition, it is preferable to control the addition amount (concentration) of a disinfectant according to the component fluctuation | variation etc. of the liquid supplied to the forward osmosis membrane apparatus 3. FIG. For example, a differential pressure gauge (not shown) for measuring the transmembrane pressure difference of the forward osmosis membrane is disposed in the forward osmosis membrane device 3, and the membrane pressure calculated from the value of the transmembrane differential pressure or the detection result of the differential pressure gauge. Addition of bactericidal agent using a control device (not shown) that sends a signal that increases the addition amount of the bactericidal agent to the bactericidal agent supply device 4 when the value of the permeation flow rate becomes a predetermined value or less. The amount can be controlled continuously or intermittently. This makes it possible to suppress membrane fouling for a long period of time even when the water quality of the wastewater fluctuates. Further, the control is performed such that the inlet pressure and the concentrated water pressure of the forward osmosis membrane module are measured and a signal for increasing the amount of the sterilizing agent added is sent to the sterilizing agent supply device 4 according to the differential pressure (pressure loss). A mechanism may be used.

  The disinfectant supplied from the disinfectant supply device 4 retains the disinfecting effect from the inside of the forward osmosis membrane device 3 to the outlet from which the concentrated water is discharged, and the disinfecting effect after being discharged from the forward osmosis membrane device 3. It is most preferable not to be retained in order to efficiently recover energy from the concentrated water. On the other hand, from the viewpoint of suppressing fouling of the forward osmosis membrane, it is preferable to add a sufficient bactericidal agent to the liquid (separated liquid) supplied to the forward osmosis membrane device 3, and thus the forward osmosis membrane device 3 The fungicide component remains in the concentrated water obtained from

  In the wastewater treatment apparatus according to the present embodiment, the concentrated water obtained by the forward osmosis membrane device 3 can be stored for a certain period in the concentrated water storage tank 5 to such an extent that the effect of the bactericide is deactivated. For example, the concentrated water stored in the concentrated water storage tank 5 is allowed to stand in the atmosphere, or an air diffuser (not shown) is provided in the concentrated water storage tank 5 to diffuse and stir the concentrated water. By this, it is possible to decompose the bactericidal agent and lose its bactericidal effect. Depending on the concentration of the bactericide in the concentrated water, for example, the concentrated water is preferably stored in the atmosphere for 0.2 hours or more, more preferably 1.0 hours or more.

  It is preferable that the concentrated water storage tank 5 is connected to organic matter supply lines OL1 and OL2 capable of supplying organic substances contained in the separated sludge separated in the drainage (inflow raw water) or the solid-liquid separation tank 1. As shown in FIG. 1, the organic substance supply line OL2 is connected to a supply line SL2 that supplies separated sludge separated in the solid-liquid separation tank 1, and a part of the separated sludge is extracted from the supply line SL2 to obtain concentrated water. It is possible to supply to the storage tank 5. The organic substance supply line OL <b> 1 can extract a part of the waste water that is the inflow raw water and supply it to the concentrated water storage tank 5. By mixing the organic matter contained in the waste water and the concentrated sludge with the concentrated water, the disinfectant in the concentrated water can be decomposed earlier.

  For example, when mixing at least one of separated sludge and waste water with concentrated water, about 0.1 to 10 times the effective sterilization amount contained in the concentrated water is optimal. The effective sterilization amount is defined by the amount (weight) of the organic substance contained in the liquid as the amount (weight) of the bactericide. For example, if the residual chlorine is 0.5 mg / L, an organic substance amount of 0.05 to 5 mg / L is required. Thus, by mixing organic substances contained in drainage and concentrated sludge, the storage time can be shortened, for example, 0.05 hours or more, more typically 0.5 hours or more. Thus, the volume of the concentrated water storage tank 5 can be reduced.

  The anaerobic treatment tank 6 is not particularly limited as long as it is an apparatus installed for the purpose of decomposing concentrated water and separated sludge and converting them into methane gas. As the anaerobic treatment tank 6, for example, a biological treatment apparatus that performs anaerobic biological treatment of separated sludge and concentrated water and decomposes them into fuel gas such as methane gas or carbon dioxide gas can be used.

  In the subsequent stage of the anaerobic treatment tank 6, there are a dryer or a carbonization device for drying or carbonizing the digested sludge obtained by subjecting the concentrated water and the separated sludge to methane fermentation in the anaerobic digestion tank to methane fermentation into fuel sludge. Further, it may be arranged.

  When installing an anaerobic treatment tank as the anaerobic treatment tank 6, the optimum pH is set to 6.5 to 7.5, and the medium temperature methane fermentation treatment or 30 to 35 ° C. with 30 to 35 ° C. as the optimum temperature. It is possible to perform a high-temperature methane fermentation treatment at an optimum temperature. In order to maintain anaerobic bacteria, temperature control and pH control are extremely important. The effluent and the treated sludge obtained by anaerobic digestion in the anaerobic treatment tank 6 are solid-liquid separated in the solid-liquid separation tank 7, and the supernatant can be discharged as treated water.

  The waste water treatment method according to the first embodiment can be carried out using the waste water treatment apparatus shown in FIG. First, in the solid-liquid separation tank 1, the sedimentary organic matter in the wastewater which is raw water is subjected to solid-liquid separation to obtain separated sludge and separated liquid. Next, the separation liquid obtained in the solid-liquid separation tank 1 is supplied to a forward osmosis membrane device 3 having a semipermeable membrane, and the separation liquid is driven through a semipermeable membrane with a driving liquid having a higher osmotic pressure than the separation liquid. By contacting, concentrated water and treated water are obtained. At that time, a bactericide is supplied to the separation liquid before flowing into the forward osmosis membrane device 3. Concentrated water obtained by the forward osmosis membrane device 3 is stored in the concentrated water storage tank 5 for a certain period of time, and the disinfectant remaining during concentration is decomposed. Thereafter, the concentrated water stored in the concentrated water storage tank 5 is supplied to the anaerobic treatment tank 6 together with the separated sludge separated in the solid-liquid separation tank 1, and the concentrated water and the separated sludge are decomposed in the anaerobic treatment tank 6. And convert it to methane gas.

  According to the waste water treatment device and the waste water treatment method according to the first embodiment, since the bactericide is supplied to the separation liquid before flowing into the forward osmosis membrane device 3, the half installed in the forward osmosis membrane device 3. Fouling of the permeable membrane can be suppressed for a long time. On the other hand, the concentrated water of the forward osmosis membrane device 3 is added with a bactericide that reduces biological activity. Therefore, if the concentrated water is subjected to methane fermentation directly in the anaerobic treatment tank 6, the methane fermentation bacteria are damaged. In response, the amount of methane gas recovered may decrease.

  According to the wastewater treatment method and apparatus according to the first embodiment, the concentrated water to which the sterilizing agent is added is stored in the concentrated water storage tank 5 for a certain period of time. After decomposition, concentrated water can be supplied to the anaerobic treatment tank 6. Thereby, the extinction of the anaerobic bacteria used in the anaerobic treatment tank 6 can be suppressed, and the generation efficiency of methane gas recovered as energy can be improved. Alternatively, a part of the separated sludge or waste water separated into solid and liquid is supplied to the concentrated water storage tank 5 through the organic substance supply lines OL1 and OL2 and mixed with the concentrated water, thereby decomposing the disinfectant in the concentrated water. Can be expedited.

(Second Embodiment)
As shown in FIG. 2, the waste water treatment apparatus according to the second embodiment is that the second solid-liquid separation device 2 is disposed upstream of the bactericide supply device 4. Different from the device. As the second solid-liquid separation device, any one of a coagulation sedimentation device, a coagulation sand filtration device, a coagulation membrane filtration device, a coagulation sedimentation device and a sand filtration or a membrane filtration device can be adopted.

  That is, the wastewater treatment apparatus according to the second embodiment includes a first solid-liquid separation apparatus (solid-liquid separation tank) 1 that separates solid-liquid precipitates in wastewater to obtain separated sludge and a separated liquid. A forward osmosis membrane device 3 that includes a semipermeable membrane and obtains concentrated water and treated water by contacting the separation liquid with a driving liquid having a higher osmotic pressure than the separation liquid through the semipermeable membrane; 2 is provided with a second solid-liquid separation device 2 that adds a flocculant to the separation liquid before flowing into the solid liquid and separates the concentrated water and the separated sludge and converts them into methane gas. . In the wastewater treatment apparatus shown in FIG. 2, the disinfectant supply apparatus 4 may or may not be arranged. The configuration other than the second solid-liquid separation device 2 is substantially the same as the configuration shown in FIG.

  In the separation liquid of the solid-liquid separation tank 1, fine organic solids and soluble organic substances that cannot be removed in the solid-liquid separation tank 1 remain, so that the second solid-liquid separation apparatus 2 aggregates into the separation liquid. Add an agent to coagulate and precipitate organic matter. Thereby, since the organic substance density | concentration in the separation liquid which flows into the forward osmosis membrane apparatus 3 can be reduced, the proliferation of the microorganisms which use an organic substance as a substrate in the forward osmosis membrane apparatus 3 is suppressed, and the fouling of a membrane is suppressed for a long period of time. Can do.

  The second solid-liquid separation device 2 includes a first reaction tank 21 for adding a flocculant to the separated liquid from the solid-liquid separation tank 1, and a flocculant aid for the separated liquid flowing out from the first reaction tank 21. The second reaction tank 22 and the coagulation sedimentation tank 23 for solid-liquid separation of the separation liquid flowing out from the second reaction tank 22 can be provided. In the example of FIG. 2, the example provided with the two reaction tanks 21 and 22 is shown, but the number of the reaction tanks 21 and 22 is not particularly limited, and for example, a single reaction tank may be used.

  A coagulant can be used for the flocculant used in the present embodiment. As the coagulant, it is preferable to use a commonly used organic coagulant. The organic coagulant has an organic substance as a main component as compared with a conventional inorganic flocculant and can be decomposed by anaerobic digestion. Examples of organic coagulants include condensed polyamines, dicyandiamide / formalin condensates, polyethyleneimine, polyvinylimidarin, polyvinylpyridine, diallylamine salts / sulfur dioxide copolymers, polydimethyldiallylammonium salts, polydimethyldiallylammonium salts / dioxides. Examples thereof include a sulfur copolymer, a polydimethyldiallylammonium salt / acrylamide copolymer, a polydimethyldiallylammonium salt / diallylamine hydrochloride derivative copolymer, and an allylamine salt polymer.

  Specific examples of the condensed polyamine include a condensate of alkylene dichloride and alkylene polyamine, a condensate of aniline and formalin, a condensate of alkylene diamine and epichlorohydrin, a condensate of ammonia and epichlorohydrin, and the like. Examples of the alkylene diamine condensed with epichlorohydrin include dimethylamine, diethylamine, methylpropylamine, methylbutylamine, and dibutylamine. The coagulant is a polymer having a relatively small molecular weight, and can make colloidal particles in the water to be treated and SS have small flocs. The amount of these coagulants injected depends on the quality of the raw water, but is in the range of 1 to 1000 mg / L.

  An inorganic flocculant may be used alone instead of the organic coagulant. An organic coagulant and an inorganic coagulant can be used in combination in order to further strengthen the floc and improve the solid-liquid separation. Generally, as the inorganic flocculant, iron-based or aluminum-based inorganic flocculants that are already used can be used. Specific examples include sulfate bands, polyaluminum chloride (PAC), aluminum chloride, polyferric sulfate (polyiron), ferric chloride, and mixtures thereof. The injection amount of these inorganic flocculants is in the range of 1 to 1000 mg / L depending on the quality of raw water.

  As the coagulation aid, the polymer coagulant is usually nonionic such as poly (meth) acrylamide, its hydrolyzate, poly (meth) acrylic acid, (meth) acrylamide and alkylamino (meth) acrylamide copolymer, etc. Anionic, cationic or amphoteric polymer flocculants can be used. The addition amount of the polymer flocculant is usually about 0.5 to 5 mg / L with respect to the amount of drainage. As a solid-liquid separation method of the coagulation sedimentation tank 23, any solid-liquid separation method such as precipitation, pressurized flotation, and membrane can be used. Aggregated sludge obtained in the aggregation sedimentation tank 23 is sent to the anaerobic treatment tank 6 through the supply line SL3.

  Compared with the solid content that naturally settles in the solid-liquid separation tank 1 such as the first sedimentation basin, the microorganisms contained in the SS suspended in the separation liquid have a high biological activity. This high activity effectively raises the oxidation-reduction potential of the solution to bring the solution into a reducing atmosphere, so that when supplied to the forward osmosis membrane device 3, fouling may occur early.

  According to the waste water treatment apparatus according to the second embodiment, by arranging the second solid-liquid separation apparatus 2, the organic matter in the separated liquid separated in the solid-liquid separation tank 1 is further coagulated and precipitated, The amount of microorganisms supplied to the forward osmosis membrane device 3 can be reduced. By further using the sterilizing agent supply device 4, fouling of the semipermeable membrane in the forward osmosis membrane device 3 can be further suppressed for a long period of time. When membrane filtration is used for the second solid-liquid separation device 2, an oxidizing agent is added to the first stage of the second solid-liquid separation device 2 or the second solid-liquid separation device 2 to perform membrane fouling. It is good to suppress.

  Furthermore, by supplying a part of the coagulated sludge obtained in the coagulation sedimentation tank 23 through the organic substance supply line OL3 connecting between the supply line SL3 and the concentrated water storage tank 5, the disinfectant supply device 4 When disinfectant is supplied, the disinfectant remaining in the concentrated water can be quickly decomposed, so that the disinfectant can stably recover energy without killing the anaerobic bacteria in the anaerobic treatment tank 6. It can be carried out. Furthermore, energy separation can be efficiently recovered from organic matter in the wastewater by subjecting the separated sludge and the coagulated sludge derived from the wastewater to methane fermentation in the anaerobic treatment tank 6.

  Note that the wastewater treatment method according to the second embodiment can be carried out using the wastewater treatment apparatus shown in FIG. First, in the solid-liquid separation tank 1, the sedimentary organic matter in the wastewater which is raw water is subjected to solid-liquid separation to obtain separated sludge and separated liquid. Next, the separation liquid obtained in the solid-liquid separation tank 1 is subjected to solid-liquid separation in the second solid-liquid separation apparatus 2 by adding a flocculant. Further, a bactericide is supplied to the separated liquid after the solid-liquid separation by adding a flocculant, if necessary, and supplied to the forward osmosis membrane device 3 having a semipermeable membrane. The forward osmosis membrane device 3 obtains concentrated water and treated water by bringing the separation liquid into contact with the driving liquid having a higher osmotic pressure than the separation liquid through the semipermeable membrane. Since the subsequent treatment process can be made substantially the same as the waste water treatment method according to the first embodiment, the description is omitted.

(Third embodiment)
As shown in FIG. 3, the wastewater treatment apparatus according to the third embodiment is that the anaerobic treatment tank 6 includes an anaerobic digestion tank 61 and an anaerobic wastewater treatment tank 62. Different from processing equipment. Since others are substantially the same as the waste water treatment apparatus shown in FIG. 2, description is abbreviate | omitted.

  Since the excess sludge and coagulated sludge obtained in the solid-liquid separation tank 1 or the second solid-liquid separation apparatus 2 and the concentrated water obtained in the forward osmosis membrane apparatus 3 have different water concentrations and organic substance concentrations, an anaerobic treatment tank The optimum residence time in the reaction vessel in 6 is different. Therefore, as shown in FIG. 3, excess sludge and coagulated sludge generated in the solid-liquid separation tank 1 and the second solid-liquid separation apparatus 2 are treated in the anaerobic digestion tank 61 (anaerobic treatment in FIGS. 1 and 2). Corresponding to the tank 6), it is preferable from the viewpoint of efficiency that the concentrated water is individually treated so as to be treated in the anaerobic waste water treatment tank 62.

  Anaerobic digestion can be performed on excess sludge and agglomerated sludge. In an anaerobic digester, it is heated to maintain about 55 ° C or about 25 ° C. In the anaerobic digester, sludge is decomposed into gas such as methane gas, carbon dioxide, hydrogen sulfide, water-soluble nitrogen, phosphorus, etc. by the action of acid-fermenting bacteria and methane-fermenting bacteria. By recovering the generated methane gas, energy can be used. Since the excess sludge obtained from the solid-liquid separation tank 1 is easily decomposable and easily fermented with methane, the amount of methane gas generated can be increased. The sludge residence time is about 10 to 40 days, and any time can be taken according to the sludge decomposition performance.

  A biological treatment apparatus can be used for the anaerobic waste water treatment tank 62 for concentrated water. Biological treatment devices include devices that employ high-load anaerobic treatment methods such as anaerobic fixed bed method, anaerobic fluidized bed method, and upward flow sludge bed method (UASB method, EGSB method). It may be. The anaerobic waste water treatment tank 62 may be a one-phase system that performs acid fermentation and methane fermentation in one tank, or may be a two-phase system that performs acid fermentation and methane fermentation in separate reaction tanks. In order to maintain anaerobic bacteria, temperature control and pH control are extremely important. For example, the temperature and pH of the anaerobic wastewater treatment tank 62, raw water (concentrated water and concentrated sludge) of methane fermentation, treated water, etc. are detected, and the values are fed back or fed forward for operation while performing each control. It is preferable. The residence time of the inflow water flowing into the anaerobic treatment wastewater treatment tank 62 varies depending on the organic matter concentration, but when the organic matter concentration is high, it is preferable to treat the circulating water after circulating the treated water or the like to reduce the concentration, Generally, the processing time is about 0.1 to 10 hours.

  The processed product obtained in the anaerobic digestion tank 61 is subjected to solid-liquid separation in the solid-liquid separation tank 8, and the treated water is discharged to the outside. The processed product obtained in the anaerobic waste water treatment tank 62 is separated into a solid and a liquid in the solid / liquid separation tank 7, and the treated water is discharged to the outside.

  According to the waste water treatment apparatus according to the third embodiment, anaerobic digestion can be performed on sludge and concentrated water using separate apparatuses, and thus the methane fermentation process can be performed more efficiently with the optimum residence time. be able to.

  Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

Example 1
A verification test was conducted with the wastewater treatment apparatus shown in FIG. Sewage was used as drainage. The properties of sewage were BOD 150 mg / L, soluble BOD 80 mg / L, and SS 100 mg / L. First, sewage was first introduced into a settling basin and separated into a solid and a supernatant liable to settle. The supernatant liquid is introduced into a reaction tank (not shown), and after adding 1 mg / L of slime control agent (Evas Perth MB605 (manufactured by Watering)), it is introduced into the FO membrane device and seawater with a salt concentration of 3.5% Concentrated 10 times through the FO membrane. As the FO membrane, a cellulose acetate membrane was used. The concentrated water obtained from the FO membrane device was first mixed with excess sludge in the settling basin and stored in a storage tank for 0.5 hour. The concentrated water after storage was introduced into an anaerobic wastewater treatment device.

  In the anaerobic wastewater treatment equipment, the pH of the anaerobic digestion tank (anaerobic treatment tank) is set to 7, the temperature of the digestion tank is heated to 35 ° C., and the treatment is performed for 30 days (HRT). The water decomposition rate was 50%, and 10.5 L / day of methane gas could be recovered. Further, in Example 1, the FO film was washed at a frequency of about once every 1.5 weeks, and no fouling of the film was observed, and the operation was stable.

(Example 2)
A verification test was conducted with the wastewater treatment apparatus shown in FIG. Sewage was used as drainage in the same manner as in Example 1. The properties of sewage were BOD 150 mg / L, soluble BOD 80 mg / L, and SS 100 mg / L. First, sewage was first introduced into a settling basin and separated into a solid and a supernatant liable to settle. The supernatant was introduced into the reaction vessel, 50 mg / L of an organic coagulant (Ebagulose L-90) was added, and Ebagulose A-151 (manufactured by Watering) was added as a coagulant aid so as to be 2 mg / L. In the coagulation sedimentation tank, it was separated into treated water and coagulated sludge. The BOD of the coagulation sedimentation tank treated water was 10 mg / L. The supernatant liquid is introduced into a reaction tank (not shown), and after adding 1 mg / L of slime control agent (Evas Perth MB605 (manufactured by Watering)), it is introduced into the FO membrane device and seawater with a salt concentration of 3.5% Concentrated 10 times through the FO membrane. As the FO membrane, a cellulose acetate membrane was used. The concentrated water obtained from the FO membrane device was first mixed with excess sludge from the settling tank and coagulated sludge from the coagulating sedimentation tank, and stored in a storage tank for 0.1 hour. The concentrated water after storage was introduced into an anaerobic wastewater treatment device.

  In the anaerobic wastewater treatment equipment, the pH of the anaerobic digester (anaerobic tank) is set to 7, the temperature of the digester is heated to 35 ° C, and it is treated for 30 days (HRT). The water decomposition rate was 50%, and 12 L / day of methane gas could be recovered. In Example 2, the cleaning frequency of the FO film was sufficient once every two weeks.

(Example 3)
A verification test was conducted with the wastewater treatment apparatus shown in FIG. Sewage was used as waste water in the same manner as in Example 1 and Example 2. The properties of sewage were BOD 150 mg / L, soluble BOD 80 mg / L, and SS 100 mg / L. First, sewage was first introduced into a settling basin and separated into a solid and a supernatant liable to settle. After the supernatant was introduced into the reaction vessel and 100 mg / L of polyaluminum chloride was added, Ebagulose A-151 (manufactured by Watering) was added as an agglomeration aid to 2 mg / L. In the coagulation sedimentation tank, it was separated into treated water and coagulated sludge. The BOD of the coagulation sedimentation tank treated water was 10 mg / L. The supernatant liquid is introduced into a reaction tank (not shown), and after adding 1 mg / L of slime control agent (Evas Perth MB605 (manufactured by Watering)), it is introduced into the FO membrane device and 10 times through seawater and FO membrane. Concentrated. Cellulose acetate was used for the FO membrane. The concentrated water obtained from the FO membrane apparatus was first mixed with a part of the excess sludge from the settling tank and a part of the coagulated sludge from the coagulation sedimentation tank, and stored in the storage tank for 0.1 hour. Concentrated water after storage, surplus sludge and agglomerated sludge were separately introduced into an anaerobic wastewater treatment apparatus.

  In the anaerobic waste water treatment apparatus, the concentrated water was an upward flow sludge bed type EGSB methane fermentation apparatus, and the residence time of the liquid was 10 hours. Excess sludge and coagulated sludge have an anaerobic digestion tank (anaerobic treatment tank) with a pH of 7, the digestion tank temperature is heated to 35 ° C, and the decomposition rate of concentrated water treated in 30 days of treatment (HRT) Was 90%, and 5 L / day of methane gas could be recovered. The sludge decomposition rate was 50%, and 7 L / day of methane gas could be recovered. In Example 3, the cleaning frequency of the FO film was sufficient once every 1.5 weeks.

(Comparative example)
In the wastewater treatment apparatus shown in FIG. 1, a verification test was performed under the same conditions as in Example 1 except that the bactericide was not supplied to the separated liquid by the bactericide supply apparatus 4. The degradation rate of sludge and concentrated water was 50%, and 10.0 L / day of methane gas could be recovered. However, compared with Example 1, the BOD load on the FO membrane was high, and the number of washings was 2 days. It became apparent once more.

1 ... 1st solid-liquid separation apparatus (solid-liquid separation tank)
DESCRIPTION OF SYMBOLS 2 ... 2nd solid-liquid separation apparatus 3 ... Forward osmosis membrane apparatus 4 ... Bactericidal agent supply apparatus 5 ... Concentrated water storage tank 6 ... Anaerobic treatment tank 7 ... Solid-liquid separation tank 8 ... Solid-liquid separation tank 21 ... 1st Reaction tank 22 ... Second reaction tank 23 ... Coagulation sedimentation tank 61 ... Anaerobic digestion tank 62 ... Anaerobic wastewater treatment tank

Claims (8)

A solid-liquid separation tank for solid-liquid separation of sedimentary organic matter in the waste water to obtain separated sludge and separated liquid;
A forward osmosis membrane device comprising a semipermeable membrane and obtaining concentrated water and treated water by contacting the separation liquid with a driving liquid having a higher osmotic pressure than the separation liquid through the semipermeable membrane;
A sterilizing agent supply device for supplying a sterilizing agent to the separation liquid before flowing into the forward osmosis membrane device;
A concentrated water storage tank for storing the concentrated water;
A wastewater treatment apparatus comprising: an anaerobic treatment tank that decomposes the concentrated water and the separated sludge to convert them into methane gas.   The wastewater treatment apparatus according to claim 1, further comprising an organic substance supply line capable of supplying organic substances contained in the wastewater or the separated sludge to the concentrated water storage tank. A first solid-liquid separation device for solid-liquid separation of the sedimentary organic matter in the waste water to obtain a separated sludge and a separated liquid;
A forward osmosis membrane device comprising a semipermeable membrane and obtaining concentrated water and treated water by contacting the separation liquid with a driving liquid having a higher osmotic pressure than the separation liquid through the semipermeable membrane;
A second solid-liquid separation device for adding a flocculant to the separation liquid before flowing into the forward osmosis membrane device to perform solid-liquid separation;
A wastewater treatment apparatus comprising: an anaerobic treatment tank that decomposes the concentrated water and the separated sludge to convert them into methane gas. The anaerobic treatment tank is
An anaerobic digester for methane fermentation of the separated sludge;
The waste water treatment apparatus of any one of Claims 1-3 provided with the anaerobic waste water treatment tank which methane-ferments the said concentrated water.   The driving liquid is high salt concentration discharged from seawater containing any of iron, cobalt, nickel, zinc, tungsten, manganese, molybdenum, selenium, boron, concentrated water of seawater desalination treatment facility, or leachate treatment facility The wastewater treatment apparatus according to any one of claims 1 to 4, comprising any one of wastewater. Solid-liquid separation of the sedimentary organic matter in the waste water, obtaining separated sludge and separated liquid,
The separation liquid is supplied to a forward osmosis membrane device having a semipermeable membrane, and the concentrated liquid and the treated water are brought into contact with the driving liquid having a higher osmotic pressure than the separation liquid through the semipermeable membrane. And getting
Supplying a bactericide to the separation liquid before flowing into the forward osmosis membrane device;
Storing the concentrated water;
A wastewater treatment method comprising: decomposing the concentrated water and the separated sludge and converting them into methane gas. Solid-liquid separation of the sedimentary organic matter in the waste water, obtaining separated sludge and separated liquid,
Concentrated water and treated water are supplied by supplying the separation liquid to a forward osmosis membrane device including a semipermeable membrane, and bringing the separation liquid into contact with a driving liquid having a higher osmotic pressure than the separation liquid through the semipermeable membrane. And getting
Adding a flocculant to the separation liquid before flowing into the forward osmosis membrane device to perform solid-liquid separation;
A wastewater treatment method comprising: decomposing the concentrated water and the separated sludge and converting them into methane gas.   The driving liquid is high salt concentration discharged from seawater containing any of iron, cobalt, nickel, zinc, tungsten, manganese, molybdenum, selenium, boron, concentrated water of seawater desalination treatment facility, or leachate treatment facility The wastewater treatment method according to claim 6 or 7, comprising wastewater.

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