JP2009148714A - Biological treatment method and apparatus of organic matter-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent pollution of a separation membrane when used for raw water for pure water production, by biologically treating organic matter-containing water. <P>SOLUTION: Anaerobic sludge containing methanogenic bacteria is held in a reactor 10. Organic matter-containing water mainly containing monomer organic matter (e.g., tetramethyl ammonium hydroxide) biodegraded by the methanogenic bacteria, is supplied to the reactor 10 from a raw water pipe 30 as treating water, to perform the anaerobic biological treatment by the methanogenic bacteria. Treated liquid obtained by the anaerobic biological treatment is separated into solid and liquid by a membrane separation apparatus 12 provided outside the reactor 10 to obtain separated water free from solid matter. The separated water is desalinated by a reverse osmosis membrane apparatus 14 to be raw material for pure water production. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biological treatment method and apparatus for anaerobically treating organic substance-containing water, and more particularly, to a biological treatment method and apparatus for biologically treating wastewater and using it as raw water for producing pure water.

  Aerobic microbial communities are thought to have a variety of organic matter resolution compared to anaerobic microbial communities. For this reason, the aerobic biological treatment using the aerobic microbial community is suitable for treating wastewater (for example, food wastewater) containing a complex polymer compound. In addition, since the rate of hydrolysis of high molecular organic substances is slow in anaerobic biological treatment, it is generally necessary to set the hydraulic residence time to 30 days or longer. In contrast, the standard hydraulic residence time for aerobic biological treatment is as short as about 0.5 days.

In recent years, water recovery has been progressing in which wastewater containing organic matter is biologically treated using facilities such as semiconductor manufacturing plants that use pure water to discharge the wastewater, and the treated water is used as a raw material for producing pure water. Conventionally, aerobic biological treatment is used in the biological treatment of organic-containing water that performs such water recovery. In the aerobic biological treatment, the treatment rate is often increased by increasing the amount of microorganisms retained in the biological treatment tank by immobilizing aerobic microorganisms on a carrier (for example, Patent Document 1). When using a support | carrier, the organic substance removal rate per biological treatment tank can be raised to about 1-2 kg-COD / m < ³ > / day, for example.

In the case of reusing the treatment liquid obtained by such biological treatment for pure water production, the treatment liquid is treated with a solid-liquid separation device to separate microorganisms, and then desalted with a reverse osmosis membrane separation device or the like. (For example, patent document 2).
JP-A-9-187785 JP 2007-175582 A

  As described above, when the waste water is reused as raw water for producing pure water, processing by a membrane separator is generally performed. However, separation membranes are prone to clogging depending on the operating conditions and the quality of the water to be treated. Especially when biological treatment liquid is membrane-separated, microorganisms and mucous substances generated by microorganisms tend to adhere to the membrane surface and cause clogging. There is. The mucilage produced by microorganisms is hardly decomposable mainly composed of high-molecular organic substances, and the amount of production increases almost in direct proportion to the amount of microorganisms retained in the biological treatment tank. Therefore, in the aerobic biological treatment using an aerobic microorganism having a high growth rate, a large amount of macromolecular organic matter is generated. In particular, when a biological treatment tank to which a carrier is added is used, the amount of high-molecular organic substances is increased because the amount of retained microorganisms is increased.

  On the other hand, since anaerobic microorganisms have a slower growth rate than aerobic microorganisms, the amount of macromolecular organic matter produced is relatively small. However, anaerobic biological treatment has a slow organic substance decomposition rate in the first place, so that the organic substance contained in the water to be treated (organic substance-containing water) cannot be completely decomposed, and its decomposition intermediate is easily contained in the treatment liquid. That is, when an aerobic biological treatment is performed, the reverse osmosis membrane may be contaminated by a microbial product. On the other hand, when anaerobic biological treatment is performed, there is a low risk of membrane contamination due to microbial products, but there is a high risk of membrane contamination due to organic substances remaining in the processing solution and decomposition intermediates.

  In addition, when the microbial cells contained in the treatment liquid are separated after biological treatment of the wastewater, the separation is insufficient by coagulation sedimentation or pressurized flotation, and the separated water contains microbial organisms and contaminates the reverse osmosis membrane. To do. In particular, when a carrier is added to the biological treatment tank, a screen or the like is required for solid-liquid separation of the carrier. However, a carrier with a large surface area to increase the activity has a small particle size and a screen. In order to avoid clogging, a solid-liquid separation device having a complicated structure and a wide sedimentation basin are required.

  On the other hand, if the biologically treated treatment liquid is subjected to solid-liquid separation with an immersion membrane provided in the biological treatment tank, microorganisms and the like can be well separated, and contamination of the subsequent reverse osmosis membrane can be prevented. However, there is a problem of clogging of the submerged membrane itself. In particular, when an aerobic treatment is performed, there is a problem that the permeated water amount is reduced due to clogging of the submerged membrane by a high molecular organic substance generated by microorganisms.

  Further, when the organic substance-containing water contains a nitrogen component, ammonia is oxidized in the aerobic biological treatment process to generate nitric acid, and the pH of the solution in the tank is lowered, so that an alkali for neutralization is required. Subsequently, when denitrification of nitric acid is performed under anaerobic conditions, an alkali is generated and the pH is raised, so that an acid needs to be added for neutralization. Thus, the acid or alkali added for neutralization in the biological treatment process becomes a salt load on the reverse osmosis membrane in the latter stage.

  As described above, when the organic substance-containing water is biologically treated and reused for producing pure water, the wastewater treatment process may adversely affect the treatment by the reverse osmosis membrane. The present invention has an object to provide a method and an apparatus capable of smoothly performing a treatment with a reverse osmosis membrane when reusing treated water as pure water production water in biological treatment of organic matter-containing water. .

  Anaerobic biological treatment of organic substances is divided into an acid production process from organic substances by acid-producing bacteria and a methane production process from acids by methanogenic bacteria. The present inventors have found that high-molecular organic substances that cause membrane contamination are metabolized mainly to acid-producing bacteria that are involved in the acid-generating process. Therefore, the present invention was completed by conceiving that the above-mentioned problem can be solved by causing methane generation without an acid generation step by the acid-producing bacteria group. Specifically, the present invention provides the following.

(1) Water containing organic matter is introduced into an anaerobic biological treatment tank, anaerobic biological treatment is performed by a group of methanogens in the anaerobic biological treatment tank, and the treatment liquid obtained by the anaerobic biological treatment is treated as an aerobic organism. A biological treatment method for water containing organic matter, wherein membrane separation is performed without treatment, and the separated water obtained by the membrane separation is treated with a reverse osmosis membrane.
(2) The biological treatment method for organic matter-containing water according to (1), wherein the organic matter-containing water comprises 70% or more of the monomeric organic matter relative to the total organic carbon.
(3) The biological treatment method for organic matter-containing water according to (1) or (2), wherein the anaerobic treatment is performed at a temperature of the liquid in the tank of 15 ° C. or higher and 40 ° C. or lower.
(4) The biological treatment method for organic matter-containing water according to (3), wherein the treatment liquid is subjected to the membrane separation and the reverse osmosis membrane treatment while being heated in the anaerobic treatment process.
(5) The monomer organic substance is any one or more selected from the group consisting of tetramethylammonium hydroxide, monoethanolamine, diethylene glycol monobutyl ether, isopropyl alcohol, dimethylacetamide, dimethylformamide, dimethylsulfoxide and acetic acid (1) To (4). The biological treatment method for organic substance-containing water according to any one of (4).
(6) An anaerobic biological treatment tank in which organic substance-containing water is introduced and methane is produced by the methanogenic bacteria group, and a treatment liquid connected to the anaerobic biological treatment tank and discharged from the anaerobic biological treatment tank is subjected to membrane separation. A biological treatment apparatus for organic matter-containing water, comprising: a membrane separation apparatus; and a reverse osmosis membrane apparatus for treating separated water of the membrane separation apparatus.
(7) The biological treatment apparatus for organic matter-containing water according to (6), wherein the organic matter-containing water has a ratio of monomer organic matter to total organic matter carbon of 70% or more.
(8) The anaerobic treatment tank is operated with the temperature of the liquid in the tank being 15 ° C or higher and 40 ° C or lower,
The treatment liquid is configured to be supplied to the membrane separation device and the reverse osmosis membrane device in a state of being heated in the anaerobic treatment tank, and the organic substance-containing water according to (6) or (7) Biological treatment equipment.
(9) The biological treatment of organic matter-containing water according to (8), further comprising a heat recovery heating device that recovers heat from the permeated water of the reverse osmosis membrane device and warms the anaerobic treatment tank with the recovered heat. apparatus.
(10) The biological treatment apparatus for organic matter-containing water according to any one of (6) to (9), wherein the membrane separation device includes a microfiltration membrane or an ultrafiltration membrane.
(11) The organic matter according to any one of (6) to (10), further comprising a cleaning device that supplies biogas generated in the anaerobic biological treatment tank to the membrane separation device to aerate and clean the membrane separation device. Biological treatment equipment for contained water.

  In this specification, “total organic carbon” is a general term for various organic carbon compounds contained in water, and includes not only non-volatile organic substances but also volatile organic substances that are not measured by a general TOC meter. “Monomer organic substance” is a generic term for organic substances of low molecular weight that can be directly absorbed by microorganisms among various organic substances contained in waste water. In contrast to “monomer organic matter”, organic matter that cannot pass through the cell wall of microorganisms and is decomposed by extracellular enzymes generally has a large molecular weight because the organic matter is polymerized. In this specification, “monomer organic matter” It is used as a term that refers to organic substances excluding molecular organic substances. Specific examples of monomeric organic substances include low molecular weight organic substances (eg, formic acid, acetic acid, methanol, methylamine, etc.), tetramethylammonium hydroxide, monoethanolamine, diethylene glycol monobutyl ether, isopropyl alcohol, which are used as substrates for methanogens. , Dimethylacetamide, dimethylformamide, and dimethylsulfoxide. In the present invention, organic substance-containing water having a high content ratio of a compound having a methyl group (tetramethylammonium, dimethylacetamide, dimethylformamide, dimethylsulfoxide) as a monomer organic substance is a suitable treatment target.

  In the present invention, the organic matter in the water to be treated is treated with an anaerobic organism by the methanogen group. It is preferable that the organic composition in the water to be treated is set so as to be mainly composed of monomeric organic substances. Monomer organic matter is biodegraded by the methanogen group, so the nature of the treated water is mainly composed of monomeric organic matter, so that the organic matter in the treated water can be successfully biodegraded to prevent residual organic matter in the treatment liquid. In addition, contamination of the subsequent separation membrane can be prevented. Further, in the present invention, in particular, depending on the acid-producing bacteria group, an organic substance-containing water having a high content of a compound having a methyl group (tetramethylammonium, dimethylacetamide, dimethylformamide, dimethylsulfoxide) as a monomer organic substance is treated. Suppressing the production of membrane contaminants prevents membrane contamination by polymeric organic matter.

  In the anaerobic treatment mainly composed of methanogens, the nitrification reaction does not occur substantially. For this reason, when a nitrogen compound is contained in to-be-processed water, a nitrogen component is not denitrified by a biological treatment process, but is brought into a reverse osmosis membrane apparatus. Therefore, the load of the reverse osmosis membrane device can be reduced when the water to be treated does not contain a nitrogen compound. On the other hand, when nitrogen compounds are contained in the water to be treated and the liquid supplied to the reverse osmosis membrane device contains nitrogen components, the nitrogen component concentrated in the reverse osmosis membrane suppresses the growth of microorganisms in the reverse osmosis membrane device. The inventors have found that this is possible. Therefore, under conditions where microorganisms are likely to grow in the reverse osmosis membrane device (for example, when about 10 to 30% of high molecular organic substances are contained in the water to be treated), the water to be treated may be positively incorporated with nitrogen compounds. Good.

  In order to satisfactorily biodegrade the organic matter in the water to be treated in the anaerobic biological treatment tank and prevent subsequent membrane contamination, the proportion of the monomer organic matter in the organic matter in the water to be treated is preferably high. When bacteria or high-molecular organic substances are contained in the water to be treated, biodegradation of acid-producing bacteria using these as substrates occurs, and soluble high-molecular organic substances that cause membrane contamination are generated. The metabolite of the acid-producing bacteria group is decomposed only about 30% when it is less than 15 ° C or exceeds 40 ° C, but about 90% is decomposed when it is 15 ° C or more and 40 ° C or less. Therefore, if the anaerobic biological treatment tank is set to 15 ° C. or higher and 40 ° C. or lower, film contamination can be prevented even if the content of organic substances other than the monomer organic substances is relatively high.

  The temperature condition is particularly preferably 30 ° C. or higher and 40 ° C. or lower. As described above, since the decomposition efficiency of the metabolite of the acid-producing bacteria group differs depending on the temperature condition, the property of the water to be treated may be changed depending on the temperature condition. Specifically, when the temperature condition is 15 ° C. or higher and lower than 30 ° C., the ratio of the monomer organic matter to the organic matter in the water to be treated is preferably 75% or more. Moreover, when temperature conditions are less than 15 degreeC or exceeds 40 degreeC, it is good to make the ratio of a monomer organic substance 90% or more.

  Further, if the pH is 6 or more and 9 or less, metabolites of the acid-producing bacteria group are decomposed well, but if the pH is outside this range, the decomposition rate is reduced to about 30%. Therefore, it is preferable to adjust the pH of the liquid in the anaerobic biological treatment tank to 6 or more and 9 or less, but when the amount of metabolites of the acid-producing bacteria group is small, that is, the ratio of the monomer organic substance is sufficiently high (substantially In some cases, the pH may not be adjusted.

  In addition to semiconductors, the present invention can be applied to manufacturing process wastewater of an electronic industry factory such as a liquid crystal display, so that it does not contain polymer components or miscellaneous compounds like food factory wastewater or wastewater treatment plant wastewater. It is possible to perform processing efficiently by anaerobic biological treatment. In addition to this, organic substances contained in water and wastewater whose concentration is relatively clear, such as chemical factory wastewater, can be applied to the target. Since these wastewaters have a clear composition, there is an advantage that the treatment capacity can be known by laboratory experiments.

  In the present invention, the organic matter in the water to be treated is mainly composed of monomeric organic matter, thereby suppressing the production of metabolites by the acid-producing bacteria group and decomposing the organic substance by the methanogenic bacteria group. In the present invention, a biological treatment liquid in which organic matter is sufficiently decomposed can be obtained without performing an aerobic biological treatment after an anaerobic biological treatment. Therefore, it is possible to suppress the production of high-molecular organic substances by the acid-producing bacteria group and the aerobic microorganism community, and to reduce the amount of remaining organic substances in the treatment liquid. For this reason, it is possible to prevent contamination of the separation membrane when performing membrane separation in the latter stage of the biological treatment process.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Hereinafter, the same members are denoted by the same reference numerals, and description thereof is omitted or simplified.

  FIG. 1 is a schematic view of a biological treatment apparatus (hereinafter simply referred to as “treatment apparatus”) 1 for organic substance-containing water used in the present invention. The treatment apparatus 1 includes an anaerobic biological treatment tank (hereinafter “reactor”) 10, a membrane separation device 12, and a reverse osmosis membrane device 14. A raw water pipe 30 is connected to the inlet of the reactor 10. The reactor 10 is connected to the membrane separation device 12 via a treatment liquid pipe 32, and the membrane separation device 12 is connected to the reverse osmosis membrane device 14 via a separation water pipe 34. A permeate pipe 36 is connected to the outlet of the reverse osmosis membrane device 14.

  A first heat exchanger 21 is provided in the middle of the raw water pipe 30, and a second heat exchanger 22 is provided in the middle of the permeated water pipe 36. The first heat exchanger 21 and the second heat exchanger 22 are connected by a fluid pipe 39, and a fluid used for heat exchange is circulated between the first heat exchanger 21 and the second heat exchanger 22. The first heat exchanger 21, the second heat exchanger 22, and the fluid pipe 39 constitute a heat recovery heating device.

  A sludge pipe 35 and a gas exhaust pipe 31 are connected to the reactor 10. Excess sludge in the reactor 10 is taken out from the waste mud pipe 35, and gas generated in the reactor 10 is taken out from the gas exhaust pipe 31. The gas exhaust pipe 31 is connected to the membrane separation device 12 and is configured to aeration-clean a separation membrane (not shown) provided in the membrane separation device 12 and functions as a cleaning device. Further, a return pipe 33 whose outlet end is connected to the reactor 10 is also connected to the membrane separation device 12. A brine tube 37 is connected to the reverse osmosis membrane device 14 on the concentration side.

  In the present invention, treated water is supplied from the raw water pipe 30 to the reactor 10. Desirably, to-be-treated water in which the monomer organic matter accounts for 70% or more of the whole organic matter is supplied to the reactor 10. Suitable operating conditions for the reactor 10 are, as described above, pH 6-9, temperature 15-40 ° C, especially 30-40 ° C. Under such conditions, membrane contamination by acid-producing fungal group metabolites can be prevented even when there are some high-molecular organic substances that do not serve as substrates of methanogenic bacterial groups.

  The methanogen group in the reactor 10 may be in either a granular state or a floating state. However, since the methanogen group is less prone to produce sticky matter than the acid-producing group, granule sludge is used. Hard to form. For this reason, the treatment liquid discharged from the reactor 10 is likely to contain sludge in the reactor 10.

  In the present invention, since the membrane separation device 12 is provided at the rear stage of the reactor 10, the microorganisms contained in the treatment liquid can be solid-liquid separated satisfactorily. The membrane separation device 12 is preferably provided separately from the reactor 10 as in this embodiment. The membrane may be an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane), and preferably has a pore size smaller than the diameter of a general methanogen, specifically, a pore size of about 100 nm or less. Preferably there is.

  The module type of the membrane separation device 12 is not particularly limited, but is preferably configured so that the sludge sent from the reactor 10 is less likely to block or stay inside the membrane separation device 12, such as a tubular type or a flat membrane. The format can be suitably used. Further, if the separation membrane for separating the liquid content and the solid content in the processing liquid is provided outside the reactor 10 as in the present embodiment, so-called outside tank type, the membrane surface flow rate can be easily controlled. It is preferable from the viewpoint of prevention of contamination.

  In the present embodiment, a gas exhaust pipe 31 is connected to the membrane separation device 12, and the treatment liquid is sent from the reactor 10 to the membrane separation device 12 together with the generated gas. The gas aeration-cleans the separation membrane while moving along the water channel to be treated in the membrane separation device 12. The processing liquid supplied to the membrane separation device 12 is separated into solid and liquid while passing through the inside of the device, and separated water from which the solid content has been removed is taken out from the permeation side. On the other hand, the concentrated sludge liquid in which the solid content is concentrated moves in the liquid flow path of the membrane separation device 12 together with the gas, and is returned to the reactor 10 from the return pipe 33.

  The methanogenic group has a slower growth rate than aerobic microorganisms. However, if such sludge is returned to maintain the sludge concentration in the reactor 10 at about 4,000 to 10,000 mg / L, aerobic microorganisms can be obtained. A decomposition rate comparable to that in the case of performing aerobic biological treatment with activated sludge can be obtained. Therefore, if the sludge concentration is within the above range, the hydraulic residence time of the reactor 10 can be set to about 0.5 to 2 days. The excess sludge is appropriately extracted from the reactor 10 through the sludge pipe 35, and the sludge concentration in the reactor 10 is adjusted.

  The separated water from which the solid content has been separated by the membrane separation device 12 is desalted by the reverse osmosis membrane device 14 provided at the subsequent stage of the membrane separation device 12 and used as raw water for pure water production. In this embodiment, the reactor 10 is operated at 30 to 40 ° C., and the temperature of the treatment liquid is also 30 to 40 ° C. Here, the treatment liquid discharged from the reactor 10 is sent to the membrane separation device 12 and the reverse osmosis membrane device 14 without being subjected to an aerobic treatment and without causing a temperature drop artificially. Since the liquid at around 30 ° C. is easily separated by reverse osmosis membrane, the flux of the reverse osmosis membrane device 14 can be increased by sending the treatment liquid from the reactor 10 to the reverse osmosis membrane device 14 in a warm state.

  The liquid removed from the reverse osmosis membrane device 14 is still warm. Therefore, in this embodiment, heat is recovered by exchanging the permeated water with the second heat exchanger 22 provided in the middle of the permeated water pipe 36 for extracting the permeated water. The heat exchange medium warmed by the heat exchange in the second heat exchanger 22 is sent to the first heat exchanger 21 via the fluid pipe 39. In the 1st heat exchanger 21, the raw | natural water sent from the raw | natural water pipe 30 is heated with the warmed heat exchange medium, and it sends to the reactor 10. FIG.

  The permeated water that has been treated by the reverse osmosis membrane device 14 and from which salts have been removed can be used as raw water for producing pure water. Specifically, devices constituting a pure water production apparatus such as a decarboxylation device, an ion exchange device, and an ultraviolet sterilization device are arranged after the reverse osmosis membrane device 14, and the reverse osmosis membrane device 14 is used by using these devices. Pure water can be produced by treating the permeated water taken out from the water. If the concentrated water is treated separately, water can be recovered in the same manner as the permeated water.

[Example 1]
As Example 1, an experiment using an experimental apparatus simulating the processing apparatus 1 shown in FIG. The reactor 10 of the experimental apparatus was operated with an effective volume of 1 m ³ and a hydraulic residence time of 0.5 days. In the reactor 10, granular sludge taken out from an anaerobic reactor for treating methanol was conditioned with a liquid to be treated, which will be described later, to hold floating sludge. The concentration of airborne sludge in the reactor 10 was 4,000 mg / L, and 40% of the existing amount (wet weight comparison) was a self-digesting residue of the methanogen group and 60% of the methanogen group.

  As the water to be treated, organic substance-containing water having a total organic carbon concentration of 750 mg / L, a nitrogen concentration of 218 mg / L, and a phosphorus concentration of 1.0 mg-P / L was used. The composition of the total organic matter was a tetramethylammonium hydroxide concentration of 250 mg / L, a monoethanolamine concentration of 250 mg / L, and an acetic acid concentration of 250 mg / L. The monomer organic content was substantially 100% of the total organic carbon. It was.

  The water to be treated was heated so that the temperature of the liquid in the tank in the reactor 10 was 35 ° C., and the pH of the liquid in the tank was adjusted to 7.5. 104 membrane-shaped UF membranes (pore diameter: 30 nm) having a diameter of 0.52 cm are arranged in the membrane separation device 12, and the biological treatment liquid discharged from the reactor 10 is caused to flow into the tube together with the gas. Was returned to the reactor 10. The amount of permeated water (flux) of the membrane separator 12 was 1.0 m / day.

  When the experiment for 30 days was continued under the above conditions, the flux of the membrane separation device 12 was able to maintain the above value, and the water flow resistance was 30 kPa at the maximum. The TOC concentration of the separated water obtained from the membrane separator 12 was in the range of 3 to 4 mg / L during the experiment period, and the TOC removal rate was 99.5%. Further, when this separated water was desalted at 750 kPa with a reverse osmosis membrane device 14 (spiral type having a wholly aromatic polyamide ultra-low pressure membrane as a reverse osmosis membrane), the amount of permeated water after 20 hours passed was 90% at the start of water flow was maintained.

[Example 2]
In Example 2, instead of the UF membrane used in Example 1, an MF membrane having a pore diameter of 400 nm was used. Other than that, the experiment was conducted under the same conditions as in Example 1. As a result, the TOC concentration of the separated water from the membrane separation apparatus equipped with the MF membrane was in the range of 3 to 4 mg / L. Further, the flux of the membrane separation device 12 is maintained at 1.0 m / day, and the flux when the separated water is treated by the reverse osmosis membrane device 14 in the same manner as in Example 1 is the original after 20 hours from the start of water flow. Of 90%. On the other hand, the maximum water resistance was 40 kPa, which was higher than Example 1. As the sludge in the reactor 10 had an average diameter of the methanogenic bacteria group of 800 nm, it was assumed that when the MF membrane was used, the methanogenic bacteria were clogged in the pores of the separation membrane, causing the membrane to be clogged. It was.

[Comparative Example 1]
In Comparative Example 1, the properties of the water to be treated were changed. Specifically, 500 mg-TOC / L of sewage sludge was added to the treated water used in Example 1, and the ratio of the monomer organic matter to the total organic carbon was 58%. Moreover, the sludge composition in the reactor 10 was also changed by using this treated water. Specifically, the floating sludge of the reactor 10 used in Comparative Example 1 has a sludge concentration of 8,000 mg / L, 20% of the existing amount (wet weight comparison) is a methane-producing fungus group, and an acid-producing fungus group is 20%. Met. The remaining 60% was bacteria derived from sewage sludge and autolysis residue.

  As described above, the experiment was performed under the same conditions as in Example 1 except that the properties of the water to be treated were changed and the microflora in the reactor 10 was changed. As a result, the flux of the membrane separation device 12 gradually decreased, and the water flow resistance exceeded 30 kPa 20 days after the start of the experiment. In Comparative Example 1, the TOC concentration of the separation water in the membrane separation device 12 was 18 to 43 mg / L.

[Example 3]
In Example 3, the amount of sewage sludge added to the water to be treated was 300 mg-TOC / L (a monomer organic substance ratio of about 71%). The sludge composition in the reactor 10 was also changed in accordance with the change in the treated water state. Specifically, the floating sludge of the reactor 10 used in Example 3 has a sludge concentration of 8,000 mg / L, 30% of the existing amount (compared with wet weight) is 30% of the methanogenic group, and the acid-producing group of bacteria. Met.

  The experiment was performed under the same conditions as in Comparative Example 1 except that the properties of the water to be treated and the microflora in the reactor 10 were changed. As a result, the flux of the membrane separation device 12 behaved in the same manner as in Example 1, the TOC concentration of separated water was 3 to 5 mg / L, and the flux of the reverse osmosis membrane device 14 treated with separated water was maintained at 88%.

  From the above experiment, it is shown that if 70% or more of the organic matter in the water to be treated is monomeric organic matter and anaerobic treatment is performed with sludge containing methanogens, clogging of the separation membrane at the later stage of biological treatment can be prevented. It was.

[Reference Example 1]
In Example 3, the temperature of the liquid in the tank of the reactor 10 was 10 ° C. As a result, the flux of the membrane separation device 12 decreased, and after 7 days, the water flow resistance exceeded 30 kPa. Separately from this, when the temperature of the liquid in the tank of the reactor 10 was set to 50 ° C., similarly, the flux of the membrane separation device 12 decreased, and the water flow resistance exceeded 30 kPa after 3 days.

[Reference Example 2]
In Example 3, the pH of the liquid in the tank of the reactor 10 was set to 5. As a result, the water flow resistance of the membrane separation device 12 increased rapidly, and the water flow resistance exceeded 30 kPa after 10 days. Separately from this, when the pH of the liquid in the tank of the reactor 10 was set to 10, similarly, the water flow resistance of the membrane separation device 12 rapidly increased, and the water flow resistance exceeded 30 kPa after 8 days.

[Comparative Example 2]
As Comparative Example 2, the reactor was an aerobic biological treatment tank by providing a diffuser for blowing air into the reactor. As a result of conducting the experiment under the same conditions as in Example 1 except that the reactor was changed to aerobic, the TOC concentration of the treatment liquid flowing out from the aerobic biological treatment tank was in the range of 3 to 4 mg / L as in Example 1. Met. However, the membrane separator 12 flux could maintain a predetermined flux only for 20 days. Further, the solution in the aerobic biological treatment tank contained soluble TOC at a concentration of 200 mg / L. On the other hand, the soluble TOC concentration of the liquid in the tank of the anaerobic reactor of Example 1 was about 10 mg / L. Thus, in Comparative Example 2, the soluble TOC concentration in the liquid in the tank is higher than that in Example 1, and the amount of the polymer organic matter constituting the soluble TOC is higher than that of the water to be treated introduced into the aerobic biological treatment tank. About 60 times.

  The conversion rate of sludge (bacteria) to organic matter in the water to be treated introduced into the biological treatment tank is 0.3 g / g for aerobic microorganisms and 0.04 g / g for anaerobic microorganisms. there were. Since high-molecular organic substances are produced by recent self-digestion, it was estimated that the higher the conversion rate, the more high-molecular organic substances were produced.

  Moreover, when the separation water membrane-separated with the membrane separation apparatus 12 in the comparative example 2 was processed with the reverse osmosis membrane similarly to Example 1, the amount of permeated water after 20 hours has fallen to 60% at the time of a water flow start. It was. By this comparative example 2 and Example 1, it was shown that it can replace with an aerobic biological process, and can suppress the production | generation of the high molecular organic substance which pollutes a separation membrane by performing the anaerobic biological process by a methanogen.

  Furthermore, in Comparative Example 2, the microbial community in the aerobic biological treatment tank contained nitrifying bacteria, and the nitrogen component in the raw water was oxidized to nitric acid. For this reason, the pH of the liquid in the aerobic biological treatment tank was lowered, and the water quality of the treatment liquid was deteriorated. Therefore, when the pH of the solution in the tank was below 5, the alkali was added to adjust the pH to 7. Moreover, after continuing aerobic conditions for a fixed time, it denitrified by stopping the air supply to a biological treatment tank and setting it as anaerobic conditions. In the case of denitrifying under anaerobic conditions, an inorganic acid was added to adjust the pH to 7. As a result of such batch-type denitrification treatment and pH adjustment, the salt concentration in the treatment liquid increased. For this reason, the osmotic pressure of the reverse osmosis membrane device at the latter stage of the membrane separation device is about 100 to 200 kPa higher than that of Example 1, and the desalination efficiency by the reverse osmosis membrane device is reduced. It was necessary to increase it by about%.

  From the above experiments, according to the present invention, the amount of macromolecular organic matter and undecomposed organic matter contained in the treatment liquid is reduced by performing anaerobic biological treatment with anaerobic sludge containing methanogenic bacteria as the main component of the water to be treated according to the present invention, It was shown that contamination of the separation membrane can be prevented.

  The present invention can be used for biologically treating organic substance-containing water and reusing it for the production of pure water.

The schematic diagram of the biological treatment apparatus used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biological treatment apparatus 10 Anaerobic biological treatment tank 12 Membrane separation apparatus 14 Reverse osmosis membrane apparatus 21 1st heat exchanger (heat recovery heating apparatus)
22 Second heat exchanger (heat recovery heating device)

Claims (11)

Introducing water containing organic matter into an anaerobic biological treatment tank,
Anaerobic biological treatment by the methanogen group in the anaerobic biological treatment tank,
Membrane separation without aerobic biological treatment treatment liquid obtained by the anaerobic biological treatment,
The biological treatment method of the organic substance containing water which processes the separated water obtained by the said membrane separation with a reverse osmosis membrane.   The method for biological treatment of organic matter-containing water according to claim 1, wherein the organic matter-containing water is composed of 70% or more of the monomer organic matter with respect to the total organic carbon.   The biological treatment method for organic matter-containing water according to claim 1 or 2, wherein the anaerobic treatment is performed by setting the temperature of the liquid in the tank to 15 ° C or higher and 40 ° C or lower.   The biological treatment method for organic matter-containing water according to claim 3, wherein the treatment liquid is subjected to the membrane separation and the reverse osmosis membrane treatment while being heated in the anaerobic treatment process.   The monomeric organic substance is at least one selected from the group consisting of tetramethylammonium hydroxide, monoethanolamine, diethylene glycol monobutyl ether, isopropyl alcohol, dimethylacetamide, dimethylformamide, dimethylsulfoxide, and acetic acid. The biological treatment method of the organic substance containing water in any one. An anaerobic biological treatment tank in which organic matter-containing water is introduced and methane is produced by the methanogen group,
A membrane separator connected to the anaerobic biological treatment tank and membrane-separating the treatment liquid discharged from the anaerobic biological treatment tank;
A biological treatment apparatus for water containing organic matter, comprising: a reverse osmosis membrane apparatus for treating separated water of the membrane separation apparatus.   The biological treatment apparatus for organic matter-containing water according to claim 6, wherein the organic matter-containing water has a ratio of monomer organic matter to total organic carbon of 70% or more. The anaerobic treatment tank is operated at a temperature of the liquid in the tank of 15 ° C. or more and 40 ° C. or less,
The biological treatment of organic substance-containing water according to claim 6 or 7, wherein the treatment liquid is configured to be supplied to the membrane separation device and the reverse osmosis membrane device while being heated in the anaerobic treatment tank. apparatus.   The biological treatment apparatus for organic matter-containing water according to claim 8, further comprising a heat recovery heating apparatus that recovers heat from the permeated water of the reverse osmosis membrane apparatus and warms the anaerobic treatment tank with the recovered heat.   The biological treatment apparatus for organic matter-containing water according to any one of claims 6 to 9, wherein the membrane separation device includes a microfiltration membrane or an ultrafiltration membrane.   The biological treatment of organic substance-containing water according to any one of claims 6 to 10, further comprising a cleaning device that supplies biogas generated in the anaerobic biological treatment tank to the membrane separation device to aerate and wash the membrane separation device. apparatus.

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