JP5194783B2 - Biological treatment method and apparatus for water containing organic matter - Google Patents

Description

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

In recent years, water recovery has been progressing in which wastewater containing organic matter is biologically treated in facilities such as semiconductor manufacturing plants that use pure water to discharge the wastewater, and the treated liquid is used as a raw material for the production of pure water. In the biological treatment process in which such water recovery is performed when the organic component-containing water contains a nitrogen component, conventionally, nitrogen compounds are oxidized under aerobic conditions to produce nitric acid or nitrous acid, and denitrification is performed under anoxic conditions. Is going. The treatment liquid from which nitrogen has been removed by such biological denitrification is subjected to solid-liquid separation, and further desalted by a reverse osmosis membrane (RO membrane) device to be used as a raw material for producing pure water (for example, Patent Document 1).
JP 2007-175582 A

  In biological treatment to remove nitrogen components, organic nitrogen is mineralized by microorganisms to produce ammonia, and this ammonia is oxidized to nitrous acid or nitric acid by aerobic nitrifying bacteria. In this process, since the oxidation proceeds, the pH of the solution in the tank is lowered, so that an alkali for neutralization is required. Next, nitric acid or nitrous acid is reduced to nitrogen gas by anaerobic denitrifying bacteria, and in the process, alkali is generated and the pH is raised. For this reason, in a denitrification process, addition of an acid is needed for neutralization. In this way, when removing the nitrogen component, the acid or alkali added for neutralization becomes a load on the subsequent RO membrane.

Thus, the reaction proceeded to nitrous acid or nitric acid generation, the case of denitrifying this, nitrous acid and nitric acid is a strong acid, and strong alkali OH ^- because is generated, neutralizing the strong acid and strong alkali It is necessary to let On the other hand, in the step of oxidizing the nitrogen compound, if the biological reaction is stopped at the time when ammonia is generated, it is sufficient to neutralize weakly alkaline ammonia, and there is no need to neutralize strong acid or strong alkali. In order to stop the biological denitrification of nitrogen compounds at the stage of ammonia production, nitrifying bacteria having a slow growth rate may be prevented from growing in the biological reaction tank. Specifically, if the sludge residence time in the biological reaction tank is shortened, the nitrifying bacteria will flow out (wash out) from the biological reaction tank and are not retained in the tank, so the reaction can be stopped by ammonia production.

  However, in order to wash out nitrifying bacteria, the sludge residence time in the biological reaction tank needs to be 4 days or less. When the sludge residence time is lowered to about 4 days or less, organic substances contained in the water to be treated are not sufficiently decomposed. For this reason, the biologically treated treatment liquid contains a large amount of residual organic matter, and microorganisms are likely to grow using the residual organic matter as a substrate in the RO membrane device. Proliferated microorganisms cause the RO membrane to be clogged and reduce the desalting performance of the RO membrane.

  In other words, biological treatment of organic substance-containing water under aerobic conditions and nitrification advances, increasing the load on the RO membrane device due to the addition of a neutralizing agent, while remaining if sludge residence time is shortened to suppress the progress of nitrification. Contamination of RO membrane with organic matter is caused. In the present invention, when organic matter-containing water is biologically treated for such a problem and the treated liquid is reused as pure water production water, contamination of the RO membrane is prevented while avoiding an increase in load on the RO membrane. For the purpose.

  In order to solve the above-mentioned problems, the present invention removes organic substances in water to be treated without proceeding nitrification reaction by biologically treating organic substance-containing water under anaerobic conditions, and remaining ammonium salt in the treatment liquid after biological treatment. Is concentrated with a RO membrane device and processed separately. Specifically, the present invention provides the following.

(1) An anaerobic biological treatment tank in which organic substance-containing water is introduced and methane is produced by a methanogen 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. The biological treatment apparatus of organic substance containing water provided with a membrane separator, the reverse osmosis membrane apparatus which processes the separation water of the said membrane separator, and the concentrated water treatment apparatus which processes the concentrated water of the said reverse osmosis membrane apparatus.
(2) The biological treatment apparatus for organic matter-containing water according to (1), wherein the concentrated water treatment apparatus includes a biological treatment tank different from the anaerobic biological treatment tank.
(3) The biological treatment apparatus for organic substance-containing water according to (1) or (2), wherein the concentrated water treatment apparatus includes an evaporator that introduces the concentrated water, evaporates, and extracts distilled water.
(4) The organic substance according to any one of (1) to (3), wherein the concentrated water treatment apparatus includes a reaction column that adds a chemical that insolubilizes impurities in the concentrated water to the concentrated water to separate solids. Biological treatment equipment for contained water.
(5) Organic matter-containing water is introduced into the anaerobic biological treatment tank containing the methanogenic bacteria group, and the anaerobic biological treatment is performed, and the treatment liquid obtained by the anaerobic biological treatment is subjected to membrane separation without the aerobic 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, and processes the concentrated water obtained by the said reverse osmosis membrane process.
(6) The biological treatment method for organic matter-containing water according to (5), wherein the organic matter-containing water contains a nitrogen compound.
(7) The concentrated water according to (5) or (6), wherein the concentrated water is biologically treated separately from the anaerobic biological treatment, is distilled using an evaporator, and / or is made insoluble by chemicals. Biological treatment method of water containing organic matter.

  The nature of the organic substance-containing water that is the treated water is not particularly limited, and includes various organic substances including non-volatile organic substances and volatile organic substances as organic carbon, including not only organic carbon compounds but also nitrogen compounds. Good. The organic carbon compound preferably has a high proportion of low-molecular organic substances (hereinafter referred to as “monomer organic substances”) that can be directly absorbed by microorganisms (for example, 70% or more based on the total organic carbon). Since the monomer organic matter is decomposed by the methanogenic bacteria group, the acid producing bacteria group is unlikely to grow in the anaerobic biological treatment process if the monomer organic substance is mainly organic substance-containing water. According to the knowledge of the present inventors, if the growth of the acid-producing bacteria group is suppressed, the production of macromolecular metabolites produced by these microorganisms can be suppressed, and RO membrane contamination by the metabolites can be prevented. 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.

  To-be-treated water removes organic substances by anaerobic biological treatment mainly composed of methanogens in an anaerobic biological treatment tank. When the anaerobic biological treatment is performed under such a condition that the temperature of the liquid in the tank is 15 ° C. or higher and 40 ° C. or lower, about 90% of the microorganism is decomposed even if the microorganism produces a high molecular organic substance. Further, it is preferable to adjust the pH of the liquid in the tank to 6 or more and 9 or less because about 90% of the high-molecular organic matter produced by the microorganism is decomposed.

  The liquid in the anaerobic biological treatment tank may contain an ammonium salt contained in the for-treatment water and / or an ammonium salt generated by decomposing an organic nitrogen compound contained in the for-treatment water. Such an ammonium salt reacts with carbon dioxide generated by the decomposition of organic matter in an anaerobic biological treatment tank to produce ammonium bicarbonate. Therefore, even when a nitrogen compound is contained in the water to be treated, the pH of the liquid in the anaerobic biological treatment tank can be maintained near neutral without adding a neutralizing chemical.

  Since the microorganisms are contained in the treatment liquid flowing out from the anaerobic biological treatment tank, after solid-liquid separation, the water from which the solid content has been removed (separated water) is desalted by the RO membrane device, and the raw material for producing pure water And For the solid-liquid separation, a membrane separation device including a filtration membrane may be used. As the separation membrane, an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane) may be used, and it is preferable to use a membrane having a pore diameter (for example, 100 nm or less) smaller than the diameter of a general methanogen group.

  In addition, the treatment liquid from the anaerobic biological treatment tank includes ammonium bicarbonate generated in the anaerobic biological treatment tank, organic matter that has not been biologically treated, and the like. Although some of these residual substances are removed by the membrane separator, other parts are not removed by the membrane separator but brought into the RO membrane device and concentrated. Therefore, the concentrated water (brine) discharged from the RO membrane device contains ammonium bicarbonate or the like approximately 10 times concentrated. Therefore, the brine is treated by biological, chemical, and / or physical methods separately from the water to be treated.

  The treatment method of the brine may be selected according to the property thereof. For example, the biological treatment includes a treatment for biodenitrification aerobically or anaerobically. For biodenitrification, either heterotrophic or autotrophic denitrifying microorganisms may be used.

  Examples of the chemical treatment include a method of changing the pH to insolubilize impurities contained in the brine, and a method of adding chemicals that form compounds with the impurities in the brine. Examples of chemicals used in the chemical treatment include acids or alkalis that change pH, flocculants, and seed crystals that precipitate impurities in brine. More specifically, sulfuric acid that reacts with an ammonium salt to produce ammonium sulfate, various acids that coagulate proteins, and the like can be mentioned.

  The physical treatment includes distillation, and ammonia may be volatilized by aeration. Distillation is preferably performed under acidic conditions in order to prevent ammonia from being volatilized as a gas, and may be heated under reduced pressure. On the other hand, when ammonia is volatilized by aeration, a large amount of air may be aerated as an alkaline condition.

  The brine may be processed by combining the above processing methods. For example, after adding an acid to a brine to insolubilize ammonia (amine), the water is recovered by distillation using an evaporator. This method has an advantage that the amount of waste containing ammonia can be reduced and water can be recovered.

  In the present invention, the organic matter-containing water is biologically treated under anaerobic conditions, thereby suppressing the nitrification reaction, suppressing the increase in salt concentration due to the addition of chemicals for pH adjustment, and suppressing the formation of high molecular organic substances. Can prevent contamination. Moreover, the water recovery rate can be raised by concentrating the substance which was not removed by the anaerobic process with a reverse osmosis membrane apparatus, and processing separately.

  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 diagram of a biological treatment apparatus (hereinafter simply referred to as “treatment apparatus”) 1 for organic substance-containing water according to a first embodiment of the present invention. The treatment apparatus 1 includes an anaerobic biological treatment tank (hereinafter referred to as “reactor”) 10, a membrane separation apparatus 12, a reverse osmosis membrane apparatus 14, and an Anammox tank 41 as a concentrated water treatment apparatus. 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. The brine pipe 37 is connected to the Anammox tank 41.

  In the present invention, organic substance-containing water containing a nitrogen compound is supplied to the reactor 10 as raw water through the raw water pipe 30. 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 bacteria group metabolites can be prevented even when treating organic-containing water containing high-molecular organic substances that do not serve as a substrate for the methanogen group.

  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 and solid content in the processing liquid is provided outside the reactor 10 as in this embodiment, so-called outside-tank type makes it easy to control the membrane surface flow rate. It is preferable from the viewpoint of preventing surface 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. In the present invention, 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. Concentrated water enriched with salts discharged from the reverse osmosis membrane device 14 is discharged from the brine pipe 37.

  The processing apparatus 1 of 1st Embodiment has the biological treatment tank holding an autotrophic denitrification microorganisms (Anammox microorganism) as a concentrated water processing apparatus. In the Anammox tank 41, a part of the ammonia in the concentrated water supplied from the brine pipe 37 is oxidized to nitrous acid under microaerobic conditions, and nitrogen gas is released from ammonia and nitrous acid by the biological reaction of Anammox microorganisms under anaerobic conditions. Is produced and nitrogen is removed.

  The effluent from the Anammox tank 41 can be taken out from the pipe 42, further processed as necessary, and reused as raw water for pure water production. Alternatively, if necessary, the effluent may be solid-liquid separated by a solid-liquid separator (not shown), the solid content may be returned as return sludge, and the liquid content discharged or recovered.

  The concentrated water discharged from the reverse osmosis membrane device 14 may be treated by a method other than biological treatment. FIG. 2 is a schematic diagram of the processing apparatus 2 according to the second embodiment of the present invention. The treatment apparatus 2 is different from the treatment apparatus 1 in that it has a reaction column 43 instead of the Anammox tank 41 as a concentrated water treatment apparatus. A chemical injection device (not shown) is connected in the middle of the brine pipe 37 for supplying concentrated water to the reaction column 43, and a chemical that reacts with ammonia in the concentrated water to produce a solid is added. For example, phosphoric acid and a magnesium salt are added as chemicals to the concentrated water, and ammonium magnesium phosphate is generated in the reaction column 43 to produce struvite crystals. The struvite crystals are taken out from the reaction column 43 and can be used as fertilizer or the like, and the deammonia water separated from the crystals and from which ammonia has been removed can be recovered and used as raw water for producing pure water.

  FIG. 3 is a schematic diagram of the processing apparatus 3 according to the third embodiment of the present invention. The treatment device 3 includes an evaporator 45 as a concentrated water treatment device. In the processing apparatus 3, the concentrated water is introduced into the evaporator 45 and distilled under reduced pressure, and the distilled water is taken out from the distilled water pipe 46 and used as raw water for producing pure water. Although not shown in the figure, prior to the distillation treatment, it may be configured to add sulfuric acid to the concentrated water, and the pH of the concentrated water may be about 4 to 6, and ammonia may be recovered using ammonium sulfate.

  FIG. 4 shows another method for treating concentrated water by combining two or more of biological treatment, chemical treatment, and physical treatment. In the treatment apparatus 4 of FIG. 4, the concentrated water treatment apparatus is configured by combining a biological treatment tank (Anammox tank 41) and an evaporator 45. In this processing apparatus 4, the amount of acid added to adjust the pH of the water to be treated supplied to the evaporator 45 can be reduced by first biologically treating the concentrated 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 methanogenic bacteria group and 60% of the methanogenic bacteria group.

  As the water to be treated, organic substance-containing water having a total organic carbon (TOC) concentration of 500 mg / L, a nitrogen concentration of 152 mg / L, and an inorganic salt concentration of 1,180 mg / L was used. Most of the carbon and nitrogen were derived from tetramethylammonium hydroxyl, and the concentrations were 480 mg / L as TOC and 140 mg / L as N.

  The water to be treated was heated so that the temperature of the liquid in the tank in the reactor 10 was 35 ° C. 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. Separation water obtained from the membrane separator 12 was concentrated at a rate of 0.75 MPa by a reverse osmosis membrane device 14 (spiral type equipped with a wholly aromatic polyamide ultra-low pressure membrane as a reverse osmosis membrane).

  Thirty days after the experiment was started under the above conditions, tetramethylammonium hydroxide was decomposed, the TOC concentration of the separated water from the membrane separator 12 was 5 mg / L, and trimethylamine and ammonia were produced. Most of the TOC of the separated water was trimethylamine, the concentration of which was 4 mg / L, and the remaining 1 mg / L was a macromolecular organic matter produced by microorganisms. Moreover, the ammonia concentration of the separated water was in the range of 135 to 140 mg-N / L. This ammonia reacted with carbon dioxide (concentration of about 120 mg-C / L) generated by methane fermentation in the reactor 10 to produce ammonium bicarbonate. For this reason, the pH of the liquid in the tank of the reactor 10 could be maintained at pH 7.0 to 7.5 without adding a neutralizing agent.

  The reverse osmosis membrane device 14 obtained by desalting the separated water could be operated for 60 days from the start of the experiment at 0.75 MPa and a flux of 0.95 m / day. The concentrated water obtained from the reverse osmosis membrane device 14 has a pH of approximately 8.5, a trimethylamine concentration of 40 mg-C / L, an ammonium bicarbonate concentration of 1,400 mg-N / L, and a polymer organic matter concentration of 10 mg-C / L. The recovery rate was almost 100% for salts (ammonium salts) and organic substances.

The concentrated water was biologically treated in the Anammox tank 41 under microaerobic / anoxic conditions. The load on the Anammox tank 41 was 3 kg-N / m ³ / day. By the treatment in the Anammox tank 41, 99% of trimethylamine and ammonia in the concentrated water are biodegraded, and the BOD concentration of the treatment liquid flowing out from the Anammox tank 41 is 10 mg / L or less, the SS concentration is 10 mg / L or less, and the nitrogen concentration is It was 10 mg-N / L.

[Example 2]
In Example 2, an experiment was performed under the same conditions as in Example 1 except that an experimental apparatus simulating the processing apparatus 2 of FIG. 2 was used. In Example 2, an aqueous solution of 2% magnesium chloride as a magnesium salt was added in the middle of the brine tube 37 at an addition amount of 800 mg / L, and a potassium phosphate solution was added. Further, sodium hydroxide was added to adjust the pH to 11, and ammonium bicarbonate was dissociated to release ammonium ions. The reaction column 43 has a capacity of 20 L, and when concentrated water added with the above chemicals is passed through under the condition of 200 L / day, ammonium ions react with phosphorus and magnesium to produce struvite crystals with a diameter of about 2 to 3 mm. It was. The treated water taken out from the reaction column 43 via the pipe 45 had a TOC concentration of 50 mg / L and a nitrogen concentration of 140 mg / L, and 90% of the ammonia contained in the concentrated water could be removed. Further, when the struvite crystal was taken out from the reaction column 43 and analyzed, its main components were ammonia, phosphorus and magnesium, which contained almost no heavy metals and could be used as a fertilizer.

[Example 3]
In Example 3, an experiment was performed under the same conditions as in Example 1 except that an experimental apparatus simulating the processing apparatus 3 of FIG. 3 was used. In Example 3, sulfuric acid was added in the middle of the brine pipe 37 from a chemical injection device (not shown), and the alkalinity of the concentrated water supplied to the evaporator 45 was set to 0 (pH 4.8). The evaporator 45 was distilled by reducing the pressure and heating the concentrated water to 40 ° C., and the distilled water was taken out from the distilled water pipe 46. The TOC concentration of distilled water was 0.01 mg-C / L, and the nitrogen concentration was 0.2 mg-N / L. Further, when the slurry of ammonium sulfate remaining in the evaporator 45 was recovered, 98% of the ammonium in the concentrated water could be recovered as the ammonium sulfate slurry.

[Example 4]
In Example 4, the processing apparatus obtained by the biological treatment in the Anammox tank 41 of Example 1 was further distilled by the evaporator 45 using the experimental apparatus simulating the processing apparatus 4 of FIG. In Example 4, since the ammonia concentration of the liquid supplied to the evaporator 45 was 70 mg-N / L, which was lower than that in Example 3, the amount of acid added to lower the pH was the same as in Example 3. 1/20. Moreover, the water quality of the distilled water taken out from the evaporator 45 was a TOC concentration of 0 mg-C / L and a nitrogen concentration of 0 mg-N / L.

[Comparative Example 1]
As Comparative Example 1, the reactor was an aerobic biological treatment tank by providing a diffuser for blowing air into the reactor. The experiment was conducted under the same conditions as in Example 1 except that the reactor was changed to aerobic. However, since the pH of the aerobic biological treatment tank was not adjusted, a nitrification reaction was observed one week after the start of the experiment. The pH of the internal solution decreased to about 5.0 to 5.5. As a result, the TOC concentration of the treatment liquid flowing out from the aerobic biological treatment tank is about 100 to 120 mg / L, and the flux of the reverse osmosis membrane device for desalting the separated water obtained from the membrane separation device is that of Example 1. It became half.

[Comparative Example 2]
In Comparative Example 1, sodium hydroxide was added to the aerobic biological treatment tank so that the pH of the liquid in the tank was in the range of 6.5 to 7.5. As a result, the TOC concentration of the treatment liquid flowing out from the aerobic biological treatment tank could be reduced to 10 mg / L. However, the treatment liquid contained nitric acid at a concentration of about 130 to 140 mg / L, and the salt concentration was increased by sodium hydroxide added for pH adjustment. For this reason, the flux of the reverse osmosis membrane device for desalting the separated water obtained from the membrane separation device remained at 60% of Example 1.

[Comparative Example 3]
In Comparative Example 2, a denitrification tank was provided at the subsequent stage of the aerobic biological treatment tank to obtain the treatment apparatus 5 having the configuration shown in FIG. The treatment apparatus 5 has an aerobic biological treatment tank (aerobic reactor 10 ') instead of the anaerobic biological treatment apparatus (reactor 10) used in the examples, and denitrifying bacteria are placed in the subsequent stage of the aerobic reactor 10'. A holding denitrification tank 13 and a re-aeration tank 11 are provided. Methanol was added to the treatment liquid flowing out from the aerobic reactor 10 ′, and sulfuric acid was added to the denitrification tank 13 to maintain the pH at 6.5 to 7.5 for denitrification treatment. The effluent from the denitrification tank 13 was sent to the re-aeration tank 11 via the pipe 32B, re-aerated in the re-aeration tank 11, and then sent to the membrane separation device 12 via the pipe 32C. As a result, for two weeks after the start of the experiment, the flux of the reverse osmosis membrane device 14 for desalting the separated water obtained from the membrane separation device 12 was 80% of that in Example 1. However, one month after the start of the experiment, the flux of the reverse osmosis membrane device 14 decreased to 50% of Example 1.

  Therefore, when the reverse osmosis membrane was removed and observed with a microscope, a large amount of biofilm was adhered to the surface. Since almost no biofilm adhered to the reverse osmosis membrane of the reverse osmosis membrane device used in Example 1, it was presumed that in Comparative Example 3, the flux decreased due to the biofilm adhesion. In the examples, there are two possible reasons why the biofilm did not adhere to the reverse osmosis membrane. In the reverse osmosis membrane device, the salt was concentrated and the pH of the brine rose to 8.5, so that ammonia was dissociated from ammonium bicarbonate, and the growth of microorganisms was suppressed due to the toxicity of ammonia. Another reason is that the methanogen group has a slower growth rate than aerobic microorganisms and it is difficult to form a biofilm.

  From the above, it was shown that organic matter-containing water can be anaerobically treated with methanogens to biodegrade the organic matter without adding a pH adjuster and suppress the amount of macromolecular organic matter that contaminates the separation membrane. .

  Also, biofilms in reverse osmosis membrane devices are produced by producing ammonium bicarbonate from ammonia and carbon dioxide in an anaerobic treatment process by a group of methanogens and concentrating them in a reverse osmosis membrane device without aerobic treatment. It was shown that the formation of can be suppressed. That is, it was shown that contamination of the reverse osmosis membrane can be prevented when a substance that could not be removed in the anaerobic treatment step is concentrated by the reverse osmosis membrane device.

  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 which concerns on 1st Embodiment of this invention. The schematic diagram of the biological treatment apparatus which concerns on 2nd Embodiment of this invention. The schematic diagram of the biological treatment apparatus which concerns on 3rd Embodiment of this invention. The schematic diagram of the biological treatment apparatus which concerns on 4th Embodiment of this invention. The schematic diagram of the experimental apparatus used by the comparative example.

Explanation of symbols

1 Biological treatment device 10 Anaerobic biological treatment tank (reactor)
DESCRIPTION OF SYMBOLS 12 Membrane separator 14 Reverse osmosis membrane device 21 1st heat exchanger 22 2nd heat exchanger 41 Anammox tank (concentrated water processing apparatus)
43 Reaction column 45 Evaporator

Claims (7)

A biological treatment apparatus comprising: a biological treatment tank; and a reverse osmosis membrane device provided at a subsequent stage of the biological treatment tank, and used as raw water for producing pure water,
An anaerobic biological treatment tank in which organic matter-containing water having a ratio of monomeric organic matter to total organic matter carbon of 70% or more is introduced and methane is produced by a methanogen group;
A membrane separation device that is connected to the anaerobic biological treatment tank and membrane-separates the treatment liquid discharged from the anaerobic biological treatment tank;
A reverse osmosis membrane device for treating the separated water of the membrane separation device;
A biological treatment apparatus for organic matter-containing water, comprising: a concentrated water treatment apparatus for treating the concentrated water of the reverse osmosis membrane apparatus.   The biological treatment apparatus for organic matter-containing water according to claim 1, wherein the concentrated water treatment apparatus includes a biological treatment tank different from the anaerobic biological treatment tank.   The biological treatment apparatus for organic matter-containing water according to claim 1 or 2, wherein the concentrated water treatment apparatus includes an evaporator that introduces the concentrated water and evaporates it to take out distilled water.   The biological treatment of organic substance-containing water according to any one of claims 1 to 3, wherein the concentrated water treatment apparatus includes a reaction column that separates solids by adding a chemical that insolubilizes impurities in the concentrated water to the concentrated water. apparatus. A biological treatment method of organic matter-containing water that is biologically treated with organic matter-containing water, desalted with a reverse osmosis membrane and used as raw water for producing pure water,
An anaerobic biological treatment tank containing the methanogenic bacteria group is introduced with organic matter-containing water in which the ratio of the monomeric organic matter to the total organic carbon is 70% or more, and the anaerobic biological treatment is performed.
Membrane separation without aerobic biological treatment treatment liquid obtained by the anaerobic biological treatment,
Treating the separated water obtained by the membrane separation with a reverse osmosis membrane,
The biological treatment method of the organic substance containing water which processes the concentrated water obtained by the said reverse osmosis membrane process.   The biological treatment method for organic matter-containing water according to claim 5, wherein the organic matter-containing water contains a nitrogen compound.   The organism of organic substance-containing water according to claim 5 or 6, wherein the concentrated water is biologically treated separately from the anaerobic biological treatment, distilled using an evaporator, and / or treated by insolubilizing impurities with a chemical. Processing method.

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