JP2014061487A - Water treatment method and water treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method and a water treatment system capable of efficiently performing anaerobic biological treatment to the water to be treated.SOLUTION: Disclosed is a water treatment method comprising: a step in which, in a state where the water to be treated is introduced into a positive osmosis membrane device, the water to be treated is made present on the primary side of a first semi-permeable membrane device, and a hypertonic solution under the osmotic pressure higher than that of the water to be treated is present, the water from the water to be treated is permeated from the primary side of the semi-permeable membrane to the secondary side, thus the water to be treated is concentrated and concentrated water is obtained; and a step in which the concentrated water is introduced into an anaerobic tank and is subjected to anaerobic biological treatment.

Description

  The present invention relates to a water treatment method and a water treatment system using a forward osmosis membrane device.

  Conventionally, a method for generating biogas containing methane gas by anaerobic biological treatment of sewage, human waste, food waste and the like is known. For example, Patent Document 1 discloses a method in which a solid organic material obtained by solid-liquid separation of water to be treated is subjected to anaerobic biological treatment, and water to be treated whose solid content is separated by solid-liquid separation is treated with activated sludge. Is disclosed.

JP-A-9-122682

  In anaerobic biological treatment, it is desired to efficiently generate as much biogas as possible from organic substances contained in the water to be treated. In this regard, in the method disclosed in Patent Document 1, only a solid organic substance obtained by solid-liquid separation of the water to be treated is subjected to anaerobic biological treatment. There is a need to treat activated sludge separately from organic matter. Therefore, if the soluble organic matter in the water to be treated can also be subjected to anaerobic biological treatment, the amount of biogas recovered can be increased, and more efficient anaerobic biological treatment can be realized.

  This invention is made | formed in view of the said situation, The objective is to provide the water treatment method and water treatment system which can perform anaerobic biological treatment of the to-be-processed water efficiently.

  The water treatment method of the present invention that has been able to solve the above-mentioned problem is that the water to be treated is introduced into the forward osmosis membrane device and treated on the primary side of the first semipermeable membrane provided in the forward osmosis membrane device. By allowing water in the treated water to permeate from the primary side to the secondary side of the first semipermeable membrane in a state where a hypertonic solution having higher osmotic pressure than the treated water is present on the secondary side. The method is characterized in that it comprises a step of concentrating water to be treated to obtain concentrated water, and a step of introducing the concentrated water into an anaerobic tank to treat anaerobic organisms. According to the water treatment method of the present invention, concentrated water in which soluble organic substances are concentrated can be obtained by forward osmosis treatment of water to be treated, and this is subjected to anaerobic biological treatment. Increase the efficiency of anaerobic biological treatment. In addition, since organic matter in the water to be treated does not substantially permeate the first semipermeable membrane of the forward osmosis membrane device, the hypertonic solution present on the secondary side of the first semipermeable membrane does not require treatment for removing the organic matter. It becomes.

  It is preferable that the anaerobic treated water obtained by the anaerobic biological treatment is not returned to the primary side of the first semipermeable membrane of the forward osmosis membrane device. Since the anaerobic treated water obtained by the anaerobic biological treatment contains a large amount of dissolved organic matter generated by anaerobic decomposition of organic matter, the anaerobic treated water is used as the first semipermeable membrane of the forward osmosis membrane device. When returned to the primary side, the solute concentration of the water to be treated on the primary side of the first semipermeable membrane becomes high, and the permeation amount of water in the first semipermeable membrane may be reduced. Therefore, in order to ensure the amount of water permeated through the first semipermeable membrane of the forward osmosis membrane device, the anaerobic treated water is preferably not returned to the primary side of the first semipermeable membrane of the forward osmosis membrane device.

  Before the water to be treated is introduced into the forward osmosis membrane device, the solid content is preferably separated by solid-liquid separation means, and the solid content is preferably supplied to the anaerobic tank. By separating the solid content from the water to be treated in advance, the water in the water to be treated can easily permeate the first semipermeable membrane of the forward osmosis membrane device, and the amount of treatment is reduced. Can be planned.

  The water treatment method of the present invention further introduces a hypertonic solution into the reverse osmosis membrane device, and permeates the water in the hypertonic solution from the primary side to the secondary side of the second semipermeable membrane provided in the reverse osmosis membrane device. It is preferable to have the process of obtaining treated water by making it, and the process of returning the said hypertonic solution from a reverse osmosis membrane apparatus to a forward osmosis membrane apparatus. In this case, the hypertonic solution circulates between the forward osmosis membrane device and the reverse osmosis membrane device, and the hypertonic solution supplied to the forward osmosis membrane device is concentrated by the reverse osmosis membrane device to maintain the solute concentration as high as desired. Thus, the forward osmosis treatment can be stably performed.

  The present invention also provides a water treatment system suitably used in the water treatment method of the present invention. The water treatment system of the present invention includes a first semipermeable membrane, a primary side on which the treated water exists with the first semipermeable membrane interposed therebetween, and a secondary side on which a hypertonic solution having a higher osmotic pressure than the treated water exists. A forward osmosis membrane device in which water in the treated water is permeated from the primary side to the secondary side of the first semipermeable membrane to concentrate the treated water to obtain concentrated water; It has an anaerobic tank which carries out the anaerobic biological treatment of the concentrated water discharged | emitted from the primary side of the permeable membrane. In addition, in the water treatment system of this invention, it is preferable that the return flow path which returns the anaerobic treated water obtained by anaerobic biological treatment to the primary side of the 1st semipermeable membrane of a forward osmosis membrane apparatus is not provided. In addition, a solid-liquid separation unit that separates the solid content from the water to be treated is provided in the front stage of the forward osmosis membrane device, and the water to be treated from which the solid content is separated by the solid-liquid separation unit is the first half of the forward osmosis membrane device. It is preferable to supply to the primary side of a permeable membrane and to supply the said solid content to an anaerobic tank.

  The water treatment system of the present invention also includes a second semipermeable membrane, a primary side where a hypertonic solution is present across the second semipermeable membrane, and a secondary side where treated water having a lower osmotic pressure than the hypertonic solution is present. And a reverse osmosis membrane device for obtaining treated water by allowing water in the hypertonic solution to permeate from the primary side to the secondary side of the second semipermeable membrane; further provided on the secondary side of the first semipermeable membrane; A first flow path communicating with the outflow portion and the primary inflow portion of the second semipermeable membrane and transferring the hypertonic solution from the secondary side of the first semipermeable membrane to the primary side of the second semipermeable membrane; A hypertonic solution is communicated from the primary side of the second semipermeable membrane to the secondary side of the first semipermeable membrane in communication with the primary side outflow portion of the semipermeable membrane and the secondary side inflow portion of the first semipermeable membrane. Two flow paths are preferably provided.

  The forward osmosis membrane device may be provided in the water to be treated. By providing the forward osmosis membrane device in the water to be treated, water pressure is applied to the treated water on the primary side of the first semipermeable membrane corresponding to the depth of water in which the forward osmosis membrane device is installed, and the primary of the first semipermeable membrane. The penetration of water from the side to the secondary side is promoted, and it becomes easier to concentrate the water to be treated.

  According to the water treatment method and the water treatment system of the present invention, concentrated water in which soluble organic substances are concentrated is obtained by forward osmosis treatment of water to be treated, and anaerobic organisms are obtained by treating this with anaerobic organisms. Processing efficiency can be improved.

An example of the water treatment system of this invention is represented. The other example of the water treatment system of this invention is represented. The other example of the water treatment system of this invention is represented. The other example of the water treatment system of this invention is represented.

  The present invention relates to a water treatment method and a water treatment system using a forward osmosis membrane device, and more specifically, a water treatment method and water for treating anaerobic organisms by increasing the solute concentration of water to be treated using the forward osmosis membrane device. It relates to a processing system.

  The water treatment method of the present invention concentrates the water to be treated by introducing the water to be treated into the forward osmosis membrane device and permeating the water in the water to be treated into the semipermeable membrane provided in the forward osmosis membrane device. A forward osmosis treatment step for obtaining concentrated water, and an anaerobic treatment step for introducing the concentrated water into the anaerobic tank to treat the anaerobic organism. By adopting forward osmosis treatment instead of reverse osmosis treatment to concentrate the treated water, it is possible to avoid overloading the treated water against the osmotic pressure difference across the semipermeable membrane. In the osmosis treatment, the permissible range for the concentration and size of the solid content contained in the water to be treated is widened, so that it is not necessary to perform a pretreatment as advanced as the reverse osmosis treatment. Concentrated water obtained in the forward osmosis treatment process is a concentration of soluble organic matter in the water to be treated. Therefore, compared to the case where the water to be treated is treated directly with anaerobic organisms, anaerobic biological treatment is more efficient and anaerobic. The tank can be made compact.

  The treated water to be treated in the present invention is not particularly limited as long as it is a liquid (including slurry) containing an organic substance, and may contain an inorganic substance in addition to the organic substance. Examples of liquid substances containing organic substances include sewage, human waste, livestock manure, factory effluent generated from food factories, paper mills, etc., kitchen effluent, raw garbage, and liquid sludge generated by these treatments. These may use only 1 type and may mix and use 2 or more types.

  In the forward osmosis treatment step, the treated water is introduced into the forward osmosis membrane device, and the treated water is concentrated by the forward osmosis membrane device to obtain concentrated water having an increased solute concentration. The forward osmosis membrane device is provided with a semipermeable membrane for infiltrating water in the water to be treated. In the present invention, the semipermeable membrane provided in the forward osmosis membrane device is referred to as a “first semipermeable membrane”. Called.

  The first semipermeable membrane provided in the forward osmosis membrane device is not particularly limited as long as it is a membrane that transmits at least water molecules and does not transmit molecules or ions of a certain size or larger, and uses a known semipermeable membrane. Can do. As the first semipermeable membrane, a semipermeable membrane generally used for reverse osmosis treatment may be used, and the material constituting the membrane, the type of membrane, and the like are not particularly limited. Examples of the constituent material of the membrane include cellulose acetate, aromatic polyamide, polyvinyl alcohol, polysulfone, and the like, and examples of the membrane include a hollow fiber membrane, a spiral membrane, and a tubular membrane.

  The forward osmosis membrane device has a primary side and a secondary side across a first semipermeable membrane. In the present invention, the primary side and the secondary side sandwiching the semipermeable membrane are determined based on the permeation direction of the water that permeates the semipermeable membrane, and the water penetrates from the primary side to the secondary side as a whole. To do. It should be noted that water penetrates from the primary side to the secondary side of the semipermeable membrane as a whole even if a part of the water molecules penetrates from the secondary side to the primary side of the semipermeable membrane, Means that permeation from the primary side to the secondary side of the semipermeable membrane is dominant. The forward osmosis membrane device is divided into a primary side and a secondary side of the first semipermeable membrane across the first semipermeable membrane, and water to be treated exists on the primary side of the first semipermeable membrane. .

  In the forward osmosis membrane device, a hypertonic solution having a higher osmotic pressure than the water to be treated exists on the secondary side of the first semipermeable membrane. That is, in the forward osmosis membrane device, the osmotic pressure of the water to be treated existing on the primary side across the first semipermeable membrane is relatively low, and the osmotic pressure of the hypertonic solution existing on the secondary side is relatively high. . In the forward osmosis membrane device, the water in the water to be treated permeates from the primary side to the secondary side of the first semipermeable membrane using the osmotic pressure difference between the water to be treated and the hypertonic solution.

  The hypertonic solution is not particularly limited as long as it is an aqueous solution in which a solute is dissolved and exhibits an osmotic pressure higher than that of water to be treated. Under isothermal conditions, the hypertonic solution having a higher osmotic pressure than the treated water means that the hypertonic solution has a higher solute concentration (molar concentration) than the treated water. The hypertonic solution may be artificially prepared, or a solution having a high solute concentration existing outside may be used as the hypertonic solution. In the former case, a substance soluble in water may be used as the solute. For example, salts, saccharides, water-soluble polymers and the like can be used as the solute. In addition, an acid or an alkali may be used as a solute as long as it does not cause a problem with the semipermeable membrane or the device. In the latter case, brine such as seawater and salt lake water; urine and the like can be used as the hypertonic solution. Further, human waste treated water, landfill leachate treated water, some factory waste water treated water, and the like may contain salts at a relatively high concentration, and such treated water may be used as a hypertonic solution.

  The hypertonic solution may be prepared by reverse osmosis treatment. For example, the solute concentration of a solution having a high solute concentration present outside may be further increased by reverse osmosis treatment and used as a hypertonic solution. In the forward osmosis treatment process, the hypertonic solution is diluted by the permeation of water from the primary side to the secondary side of the first semipermeable membrane, but the hypertonic solution diluted with water is concentrated by the reverse osmosis treatment. The solute concentration may be increased and supplied again to the secondary side of the first semipermeable membrane of the forward osmosis membrane device.

  The osmotic pressures of the water to be treated and the hypertonic solution can be obtained based on the van't Hoff equation using the solute concentration (molar concentration) and temperature as parameters. Alternatively, after setting the water to be treated and the hypertonic solution to have the same liquid level across the semipermeable membrane, the permeation of the water to be treated and the hypertonic solution is observed by observing changes in the respective liquid levels. The magnitude of the pressure may be determined. In this case, if the liquid surface height of the hypertonic solution increases, it is determined that the hypertonic solution has a higher osmotic pressure than the water to be treated.

  In the forward osmosis treatment step, concentrated water is obtained from the treated water by allowing water in the treated water to permeate from the primary side to the secondary side of the first semipermeable membrane as described above. At this time, by treating the water to be treated with the forward osmosis membrane device, the organic matter in the water to be treated does not substantially permeate the first semipermeable membrane and exists on the secondary side of the first semipermeable membrane. The hypertonic solution does not require treatment for removing organic substances. On the other hand, for example, as in the method disclosed in Patent Document 1, in the case of subjecting the water to be treated to solid-liquid separation, the soluble organic matter in the water to be treated is contained as it is in the supernatant liquid that has been subjected to solid-liquid separation. A separate treatment of the soluble organic matter contained in the supernatant water is required.

  In the present invention, by adopting forward osmosis treatment instead of reverse osmosis treatment to remove and concentrate water from the water to be treated, it counters the osmotic pressure difference between the semipermeable membranes as in reverse osmosis treatment. It is not necessary to apply excessive pressure to the water to be treated. Further, in the treatment with a reverse osmosis membrane device, in general, in order to prevent clogging of the device, advanced pretreatment using a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), activated carbon or the like is required. However, in the treatment with the forward osmosis membrane device, the tolerance for the concentration and size of the solid content contained in the water to be treated is widened, so the device is less likely to be clogged even if the pretreatment is not as advanced as the reverse osmosis treatment. . That is, in the forward osmosis membrane device, forward osmosis treatment can be performed even when water to be treated having a slightly higher solid content concentration or water to be treated containing solid contents of various particle sizes is used. Therefore, it becomes possible to efficiently concentrate the water to be treated, and it is not necessary to provide ancillary equipment (for example, pretreatment equipment) for preventing clogging of the apparatus.

  The concentrated water obtained in the forward osmosis treatment step, that is, the concentrated water flowing out from the primary side of the first semipermeable membrane of the forward osmosis membrane device, is introduced into an anaerobic tank and subjected to an anaerobic biological treatment. Anaerobic treated water is obtained by treating the concentrated water with an anaerobic organism. In the anaerobic treatment step, the concentrated water is placed in an anaerobic state, so that organic matter in the concentrated water is anaerobically digested (specifically, acid fermentation, methane fermentation, etc.) by the action of microorganisms. Concentrated water is made by concentrating dissolved organic substances in the water to be treated in the forward osmosis treatment process. Improvement of gas generation efficiency etc.) and anaerobic tank can be made compact.

  An anaerobic tank will not be specifically limited if concentrated water can be put in an anaerobic state, A well-known anaerobic tank can be used. The anaerobic tank may be provided with a stirring means for stirring the concentrated water. Examples of the agitation means include a mechanical agitation device and an air diffuser for gas agitation of concentrated water (anaerobic treated water).

  The anaerobic biological treatment (anaerobic digestion) may be performed according to a known method. The temperature of the anaerobic biological treatment is not particularly limited as long as the organic matter in the concentrated water is anaerobically decomposed, but in general, the organic matter is efficiently decomposed at a medium temperature range of about 35 ° C or a high temperature range of about 55 ° C. It can be performed.

  In the anaerobic treatment process, biogas can be generated by methane fermentation. The generated biogas can be used as an energy source. For example, energy may be recovered by supplying it to a gas turbine and burning it, or methane contained in the biogas may be used as fuel for the fuel cell. Good. Of course, you may just burn and use heat. Further, biogas may be used to gas-stir concentrated water (anaerobic treated water) in an anaerobic tank.

  If the solid content of the treated water is high or if the treated water contains coarse contaminants, separate the solid from the treated water before introducing the treated water into the forward osmosis membrane device. Thus, it is preferable to supply the solid content to the anaerobic tank without going through the forward osmosis membrane device. By separating the solid content from the water to be treated in advance, the water in the water to be treated can easily permeate the first semipermeable membrane of the forward osmosis membrane device, and the amount of treatment is reduced. Can be planned. In addition, by supplying the solid content to the anaerobic tank, the solid content is anaerobically decomposed, and an increase in the amount of biogas generated from the anaerobic tank is expected. In order to separate the solid content from the water to be treated, solid-liquid separation means may be provided in the front stage of the forward osmosis membrane device. Examples of the solid-liquid separation means include a precipitation tank and a screen.

  The anaerobic treated water obtained by the anaerobic biological treatment contains a large amount of soluble organic substances produced by anaerobic decomposition of organic substances. Therefore, it is preferable that the anaerobic treated water is appropriately treated according to the water quality.

  The anaerobic treated water is preferably separated from solids such as sludge by solid-liquid separation treatment (for example, membrane separation treatment or mechanical dehydration). Anaerobic treated water whose solid content concentration has been reduced by solid-liquid separation treatment is subjected to anaerobic treatment by, for example, biological treatment (aerobic biological treatment) or chemical treatment (flocculation treatment, oxidation treatment, stripping, etc.). Soluble organics in water can be removed.

  In addition, it is preferable that anaerobic treated water (including anaerobic treated water whose solid content concentration is reduced by solid-liquid separation treatment) is not returned to the primary side of the first semipermeable membrane of the forward osmosis membrane device. Since anaerobic treated water contains a lot of dissolved organic matter generated by anaerobic decomposition of organic matter, when the anaerobic treated water is returned to the primary side of the first semipermeable membrane of the forward osmosis membrane device, This is because the solute concentration of the water to be treated on the primary side of the first semipermeable membrane becomes high, and the amount of water permeated through the first semipermeable membrane may be reduced.

  Next, configuration examples of the water treatment method and the water treatment system of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments shown in the drawings.

  FIG. 1 shows a first embodiment of the water treatment system of the present invention. The water treatment system shown in FIG. 1 includes a forward osmosis membrane device 1 having a first semipermeable membrane and an anaerobic tank 11. The water to be treated 21 is introduced into the forward osmosis membrane device 1 and concentrated to obtain concentrated water 25. The concentrated water 25 is introduced into the anaerobic tank 11 and subjected to anaerobic biological treatment, and an anaerobic treated water 27 is obtained.

  The forward osmosis membrane device 1 has a primary side and a secondary side across a first semipermeable membrane. The treated water 21 is introduced to the primary side of the first semipermeable membrane, and the hypertonic solution 22 having a higher osmotic pressure than the treated water 21 is introduced to the secondary side of the first semipermeable membrane. As a result, in the forward osmosis membrane device 1, the treated water 21 exists on the primary side of the first semipermeable membrane, and the hypertonic solution 22 having a higher osmotic pressure than the treated water 21 exists on the secondary side. . In the forward osmosis membrane device 1, in this state, the water to be treated 21 is permeated from the primary side to the secondary side of the first semipermeable membrane, whereby the water to be treated 21 is concentrated and the concentrated water 25 is obtained. .

  In the water treatment system shown in FIG. 1, seawater is used for the hypertonic solution 22 introduced into the secondary side of the first semipermeable membrane. Seawater is pumped up from the sea and supplied to the forward osmosis membrane device 1, and the hypertonic solution 23 discharged from the forward osmosis membrane device 1 is returned to the sea. Thus, by using seawater as the hypertonic solution 22, forward osmosis treatment can be performed at low cost.

  The concentrated water 25 concentrated in the forward osmosis membrane device 1 is introduced into the anaerobic tank 11 and subjected to anaerobic biological treatment. At this time, since the amount of water of the concentrated water 25 is smaller than that of the water 21 to be treated, the volume of the anaerobic tank 11 can be made compact. In addition, since the concentrated water 25 is obtained by concentrating soluble organic substances more than the water 21 to be treated, the amount of biogas generated per volume can be improved.

  FIG. 2 shows a second embodiment of the water treatment system of the present invention. The water treatment system of the second embodiment does not use seawater as the hypertonic solution, but circulates and uses the hypertonic solution while treating it with the reverse osmosis membrane device, and the water to be treated before the forward osmosis membrane device. It differs from the water treatment system of the first embodiment in that solid-liquid separation means (precipitation tank) for separating solids is provided and that anaerobic treated water is solid-liquid separated by membrane separation treatment. In the following description, the description of the same part as the description of the first embodiment is omitted.

  The water treatment system shown in FIG. 2 further includes a reverse osmosis membrane device 5 having a second semipermeable membrane. As the reverse osmosis membrane device 5, a known device used for reverse osmosis treatment may be used, and the material and the form of the membrane constituting the second semipermeable membrane of the reverse osmosis membrane device 5 are not particularly limited.

  The reverse osmosis membrane device 5 has a primary side and a secondary side across the second semipermeable membrane. And the 1st flow path 6 is provided in communication with the secondary side outflow part of the 1st semipermeable membrane of the forward osmosis membrane apparatus 1, and the primary inflow part of the 2nd semipermeable membrane of the reverse osmosis membrane apparatus 5, A second flow path 7 is provided in communication with the primary side outflow portion of the second semipermeable membrane of the reverse osmosis membrane device 5 and the secondary side inflow portion of the first semipermeable membrane of the forward osmosis membrane device 1. The secondary inflow portion and the secondary outflow portion of the first semipermeable membrane, and the primary inflow portion and the primary outflow portion of the second semipermeable membrane are respectively the portion into which the hypertonic solutions 22 and 23 flow in or the outflow portion. To be determined

  The hypertonic solution 23 flowing out from the secondary side of the first semipermeable membrane of the forward osmosis membrane device 1 passes through the first flow path 6 and is transferred to the primary side of the second semipermeable membrane of the reverse osmosis membrane device 5. . In the reverse osmosis membrane device 5, the hypertonic solution 23 exists on the primary side of the second semipermeable membrane, while the treated water having a lower osmotic pressure than the hypertonic solution 23 is present on the secondary side of the second semipermeable membrane. 24 exists. In the reverse osmosis membrane device 5, in this state, the hypertonic solution 23 existing on the primary side of the second semipermeable membrane is pressurized, so that the water in the hypertonic solution 23 is changed from the primary side to the secondary side of the second semipermeable membrane. The treated water 24 is obtained by infiltration. As a result, water is removed from the hypertonic solution 23 by the reverse osmosis membrane device 5 and the solute concentration is increased. The hypertonic solution 22 whose solute concentration has been increased and has flowed out from the primary side of the second semipermeable membrane of the reverse osmosis membrane device 5 passes through the second flow path 7 and becomes the second semipermeable membrane of the forward osmosis membrane device 1. It is transferred to the next side. That is, the hypertonic solution 23 flowing out from the forward osmosis membrane device 1 is introduced into the reverse osmosis membrane device 5 to increase the solute concentration, and the hypertonic solution 22 having the increased solute concentration is transferred from the reverse osmosis membrane device 5 to the forward osmosis membrane device. 1 will be returned.

  When the water treatment system shown in FIG. 2 is used, the water treatment method of the present invention introduces water to be treated into the forward osmosis membrane device, and places it on the primary side of the first semipermeable membrane provided in the forward osmosis membrane device. Water to be treated is allowed to permeate from the primary side to the secondary side of the first semipermeable membrane in a state where the water to be treated is present and a hypertonic solution having a higher osmotic pressure than the water to be treated is present on the secondary side. The process of concentrating water to be treated to obtain concentrated water, and introducing a hypertonic solution into the reverse osmosis membrane device from the primary side to the secondary side of the second semipermeable membrane provided in the reverse osmosis membrane device There are a step of obtaining treated water by permeating water in the hypertonic solution and a step of returning the hypertonic solution from the reverse osmosis membrane device to the forward osmosis membrane device.

  In the water treatment system shown in FIG. 2, the hypertonic solution 22 and 23 supplied to the forward osmosis membrane device 1 by circulating the hypertonic solutions 22 and 23 between the forward osmosis membrane device 1 and the reverse osmosis membrane device 5 in this way. Thus, the forward osmosis treatment can be stably carried out while maintaining the solute concentration of the solution as high as desired. That is, the hypertonic solution 23 that flows out from the forward osmosis membrane device 1 is diluted with water and has a lower solute concentration than the hypertonic solution 22 that flows into the forward osmosis membrane device 1. Is supplied again, a sufficient osmotic pressure difference is not ensured between the primary side and the secondary side of the first semipermeable membrane of the forward osmosis membrane device 1, and the amount of water permeating through the first semipermeable membrane is reduced. Therefore, by treating the hypertonic solution 23 flowing out from the forward osmosis membrane device 1 with the reverse osmosis membrane device 5 and returning it to the forward osmosis membrane device 1, the hypertonic solution 22 having an increased solute concentration can be obtained. 1 so that the forward osmosis treatment can be performed stably.

  Further, since the hypertonic solutions 22 and 23 basically circulate through a closed system between the forward osmosis membrane device 1 and the reverse osmosis membrane device 5, contamination of impurities and the like is prevented, and a microfiltration membrane (MF membrane) ), Ultrafiltration membrane (UF membrane), pretreatment with activated carbon or the like, and reverse osmosis treatment can be performed relatively easily.

  The second flow path 7 is preferably provided with a solute concentration adjusting means for the hypertonic solution 22 introduced into the forward osmosis membrane device 1. In FIG. 2, an adjustment tank 9 is provided in the second flow path 7, a solute or dilution water supply device 10 is provided in the adjustment tank 9, and the solute or dilution water is supplied from the supply device 10, thereby allowing the hypertonic solution 22. It is comprised so that the solute density | concentration of can be adjusted. In order to adjust the permeation amount of the first semipermeable membrane of water in the treated water 21 in the forward osmosis membrane device 1, adjusting the solute concentration of the hypertonic solution 22 is a main operating factor. Accordingly, when the hypertonic solution 22 flowing out from the reverse osmosis membrane device 5 does not have a desired solute concentration, the solute concentration of the hypertonic solution 22 is adjusted by the solute concentration adjusting means provided in the second flow path 7. It is preferable to do.

  To the hypertonic solutions 22 and 23, an agent for cleaning the first semipermeable membrane of the forward osmosis membrane device 1 or the second semipermeable membrane of the reverse osmosis membrane device 5 and an agent for preventing fouling are added. Also good. Such agents include acids, alkalis, bactericides, oxidants and the like.

  In the water treatment system shown in FIG. 2, a precipitation tank 4 is provided in the front stage of the forward osmosis membrane device 1 as a solid-liquid separation means for separating the solid content from the treated water 21. In the water 21 to be treated, the solid content 26 is precipitated and separated in the settling tank 4, and the treated water 21 ′ flowing out of the settling tank 4 and having a reduced solid content concentration is used as the primary semipermeable membrane of the forward osmosis membrane device 1. Supply to the side. The forward osmosis membrane device 1 can be reduced in size by reducing the solid content concentration of the water 21 to be treated using the sedimentation tank 4 and supplying it to the forward osmosis membrane device 1. The solid content 26 precipitated and separated in the settling tank 4 is supplied to the anaerobic tank 11 and anaerobic biological treatment is performed together with the concentrated water 25.

  In the water treatment system shown in FIG. 2, the anaerobic treated water 27 flowing out from the anaerobic tank 11 is solid-liquid separated by the membrane filter medium 15 to obtain an anaerobic treated water 27 ′ subjected to solid-liquid separation. The membrane filter medium 15 is provided in the water tank 14, and the anaerobic treated water 27 flowing out from the anaerobic tank 11 is introduced into the water tank 14, so that the membrane filter medium 15 is immersed in the anaerobic treated water 27. With the membrane filter medium 15, the solid content contained in the anaerobic treated water 27 flowing out from the anaerobic tank 11 can be highly solid-liquid separated to obtain an anaerobic treated water 27 ′ having a very low solid content concentration.

  Sludge 29 is periodically extracted from the water tank 14, and at least a part of the sludge 29 is returned to the anaerobic tank 11. By treating the anaerobic treated water 27 in this way, the microorganism concentration (sludge concentration) of the concentrated water 25 in the anaerobic tank 11 can be kept high, and the anaerobic tank 11 can be downsized.

  The water tank 14 is preferably provided with an air diffuser 16 below the membrane filter medium 15, and by providing the air diffuser 16 in this manner, the surface (membrane) of the membrane filter medium 15 by the bubbles supplied from the air diffuser 16. Surface) can be washed by a cross flow method, and a stable solid-liquid separation process using the membrane filter medium 15 can be realized. As the gas supplied from the air diffuser 16, it is preferable to recover and use biogas generated from the anaerobic tank 11 or the water tank 14.

  As the membrane filter medium 15, a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane) may be used. There are no particular restrictions on the material or type of the membrane filter medium 15, and examples of the membrane material include organic membranes such as cellulose acetate, polysulfone, polyethylene, chlorinated polyethylene, polypropylene, and polyacrylonitrile; alumina, zirconia, and the like. Examples of the type of membrane include a hollow fiber membrane, a tubular membrane, a flat membrane, and a monolith membrane.

  The anaerobic treated water 27 and 27 ′ has a high concentration of dissolved organic matter due to the anaerobic decomposition of the concentrated water 25, and therefore, when this is returned to the forward osmosis membrane device 1, the first semipermeable membrane There is a possibility that the solute concentration of the water to be treated on the primary side becomes higher, and the amount of water permeated through the first semipermeable membrane is reduced. Therefore, it is preferable that the anaerobic treated water 27, 27 ′ is not returned to the primary side of the first semipermeable membrane of the forward osmosis membrane device 1, and the water treatment system shown in FIG. Absent.

  FIG. 3 shows a third embodiment of the water treatment system of the present invention. The water treatment system of the third embodiment is the second in that the adjustment tank 8 is provided in the first flow path 6 and the anaerobic treated water 27 is introduced into the dehydrator 13 for solid-liquid separation. Different from the water treatment system of the embodiment. In the following description, the description of the same part as the description of the second embodiment is omitted.

  In the water treatment system shown in FIG. 3, the adjustment tank 8 is provided in the first flow path 6 of the circulation line of the hypertonic solutions 22 and 23, and the adjustment tank 9 is provided in the second flow path 7. The adjustment tank 8 can receive and store the hypertonic solution 23 flowing out from the forward osmosis membrane device 1, and can supply the hypertonic solution 23 to the reverse osmosis membrane device 5 through the first flow path 6. The adjustment tank 9 can receive and store the hypertonic solution 22 that has flowed out of the reverse osmosis membrane device 5, and can supply the hypertonic solution 22 to the forward osmosis membrane device 1 through the second flow path 7. By providing the adjustment tanks 8 and 9 in this way, the processing of the forward osmosis membrane device 1 and the reverse osmosis membrane device 5 can be performed independently.

  For example, in the water treatment system shown in FIG. 2, the amount of the hypertonic solution 23 introduced into the reverse osmosis membrane device 5 is the treatment capacity of the forward osmosis membrane device 1, that is, the hypertonic solution introduced into the forward osmosis membrane device 1. It depends on the amount of 22 and the amount of water permeated through the first semipermeable membrane. However, in the water treatment system shown in FIG. 3, fluctuations in the treatment capacity of the forward osmosis membrane device 1 can be mitigated by the adjustment tank 8, and the amount of the hypertonic solution 23 introduced into the reverse osmosis membrane device 5 can be reduced by forward osmosis. It can be set independently from the processing capability of the membrane device 1. Similarly, fluctuations in the processing capacity of the reverse osmosis membrane device 5 can be mitigated by the adjustment tank 9, and the amount of the hypertonic solution 22 introduced into the forward osmosis membrane device 1 is independent of the processing capacity of the reverse osmosis membrane device 5. Can be set.

  In the water treatment system shown in FIG. 3, the anaerobic treated water 27 is also introduced into the dehydrator 13 to separate the liquid into the anaerobic treated water 27 ′ having a reduced solid content concentration and the dehydrated sludge 28. . The anaerobic treated water 27 ′ that has been subjected to the solid-liquid separation is discharged as it is depending on the water quality or is further processed.

  FIG. 4 shows a fourth embodiment of the water treatment system of the present invention. In the water treatment system of the fourth embodiment, the forward osmosis membrane device 1 is provided in the water 21 to be treated, the screen 12 is provided as a solid-liquid separation means in the previous stage of the forward osmosis membrane device 1, It differs from the water treatment system of the third embodiment in that the membrane filter medium 15 is immersed in the anaerobic tank 11 and the anaerobic treated water 27 is removed by nitrogen by anaerobic ammonia oxidation treatment. In the following description, the description of the part overlapping with the description of the third embodiment is omitted.

  In the water treatment system shown in FIG. 4, the forward osmosis membrane device 1 is provided in the water tank 2, and the forward osmosis membrane device 1 is immersed in the water to be treated 21 in the water tank 2. By supplying the treated water 21 to the water tank 2, the treated water 21 is introduced to the primary side of the first semipermeable membrane of the forward osmosis membrane device 1. By providing the forward osmosis membrane device 1 in the treated water 21, water pressure is applied to the treated water 21 on the primary side of the first semipermeable membrane corresponding to the depth of water in which the forward osmosis membrane device 1 is installed. The permeation of water from the primary side to the secondary side of the semipermeable membrane is promoted, and the water 21 to be treated is easily concentrated.

  When the forward osmosis membrane device 1 is provided in the water 21 to be treated, it is preferable to provide the air diffuser 3 in the water tank 2 below the forward osmosis membrane device 1. By providing the air diffuser 3 as described above, the membrane surface of the first semipermeable membrane of the forward osmosis membrane device 1 can be washed by the cross-flow method with the bubbles supplied from the air diffuser 3. It prevents clogging of the permeable membrane and facilitates the forward osmosis treatment stably. As the gas supplied from the air diffuser 3, biogas generated from the anaerobic tank 11 or the like may be recovered and used, or air may be used.

  In the water treatment system shown in FIG. 4, a screen 12 that separates impurities from the water to be treated 21 is provided in the front stage of the forward osmosis membrane device 1 in the water tank 2. The screen 12 removes coarse impurities (solid content 26) from the water 21 to be treated. As a result, damage to the forward osmosis membrane device 1 and other facilities and equipment can be prevented, and water treatment can be suitably performed. The contaminants (solid content 26) removed by the screen 12 are supplied to the anaerobic tank 11 and are subjected to anaerobic biological treatment together with the concentrated water 25. For example, when the solid content removed by the screen 12 is pruned branches, plants, etc., the degradation efficiency of the anaerobic biological treatment is performed by crushing before supplying the foreign matter (solid content 26) to the anaerobic tank 11. You may make it raise.

  In the water treatment system shown in FIG. 4, the membrane filter medium 15 is provided in the anaerobic tank 11, and the membrane filter medium 15 is immersed in the anaerobic treated water 27 (concentrated water 25) of the anaerobic tank 11. The membrane filter medium 15 may be provided in the anaerobic tank 11 in this way. As in the water treatment system shown in FIG. 2, it is preferable to provide an air diffuser 16 for cross-flow cleaning the surface (membrane surface) of the membrane filter medium 15 below the membrane filter medium 15.

  Sludge 29 is periodically extracted from the anaerobic tank 11, and the sludge 29 is introduced into the dehydrator 19 in the water treatment system shown in FIG. 4. The dehydrated sludge 32 and the dehydrated separated water 33 are discharged from the dehydrator 19, and the dehydrated separated water 33 is returned to the anaerobic tank 11.

  From the membrane filter medium 15 in the anaerobic tank 11, anaerobic treated water 27 having a very low solid content is obtained as membrane filtrate. In the anaerobic treated water 27, ammonia generated by anaerobic digestion of organic substances may be dissolved at a high concentration. In the water treatment system shown in FIG. 4, ammonia is removed from the anaerobic treated water 27. Therefore, the anaerobic treated water 27 is subjected to an anaerobic ammonia oxidation treatment. Specifically, a part of the anaerobic treated water 27 is introduced into the aerobic tank 17 to oxidize ammonia to nitrous acid in the presence of nitrifying bacteria, and then the effluent 30 from the aerobic tank 17 The other part of the anaerobic treated water 27 is introduced into an anaerobic tank (anoxic tank) 18 to generate nitrogen gas from nitrous acid and ammonia in the presence of autotrophic denitrifying bacteria. By performing the anaerobic ammonia oxidation treatment on the anaerobic treated water 27, the ammonia in the anaerobic treated water 27 can be efficiently removed. In addition, all the anaerobic treated water 27 is introduced into the aerobic tank 17 to perform a partial nitritation treatment that oxidizes a part of ammonia to nitrous acid, and then the effluent 30 from the aerobic tank 17 is anaerobic. Nitrogen gas may be generated from the nitrous acid generated in the aerobic tank 17 and unreacted ammonia by being introduced into the tank 18. The anaerobic ammonia oxidation treated water 31 is discharged according to the water quality or is subjected to further treatment.

  INDUSTRIAL APPLICABILITY The present invention can be used for treatment of sewage, human waste, livestock manure, factory effluent generated from food factories, paper mills, etc., kitchen effluent, raw garbage, and liquid sludge generated by these treatments.

1: Forward osmosis membrane device 4: Precipitation tank 5: Reverse osmosis membrane device 6: First flow path 7: Second flow path 11: Anaerobic tank 12: Screen 21: Water to be treated 22, 23: Hypertonic solution 24: Treated water 25: Concentrated water 27, 27 ': Anaerobic treated water

Claims (9)

The treated water is introduced into the forward osmosis membrane device, the treated water is present on the primary side of the first semipermeable membrane provided in the forward osmosis membrane device, and the osmotic pressure is higher on the secondary side than the treated water. A step of concentrating the water to be treated to obtain concentrated water by allowing the water in the water to be treated to permeate from the primary side to the secondary side of the first semipermeable membrane in the presence of the hypertonic solution;
And a step of treating the anaerobic organism by introducing the concentrated water into an anaerobic tank.   The water treatment method according to claim 1, wherein the anaerobic treated water obtained by the anaerobic biological treatment is not returned to the primary side of the first semipermeable membrane of the forward osmosis membrane device. Before the treated water is introduced into the forward osmosis membrane device, the solid content is separated by solid-liquid separation means,
The water treatment method according to claim 1 or 2, wherein the solid content is supplied to the anaerobic tank. Further, treated water is obtained by introducing the hypertonic solution into the reverse osmosis membrane device and permeating the water in the hypertonic solution from the primary side to the secondary side of the second semipermeable membrane provided in the reverse osmosis membrane device. Process,
The water treatment method according to any one of claims 1 to 3, further comprising a step of returning the hypertonic solution from the reverse osmosis membrane device to the forward osmosis membrane device. A first semipermeable membrane, a primary side on which the treated water is present with the first semipermeable membrane interposed therebetween, and a secondary side on which a hypertonic solution having a higher osmotic pressure than the treated water is present; Forward osmosis membrane device in which the water to be treated is concentrated to obtain concentrated water by infiltrating the water from the primary side to the secondary side of the first semipermeable membrane,
A water treatment system comprising: an anaerobic tank for treating an anaerobic organism with concentrated water discharged from the primary side of the first semipermeable membrane.   The water treatment system according to claim 5, wherein a return flow path for returning the anaerobic treated water obtained by the anaerobic biological treatment to the primary side of the first semipermeable membrane of the forward osmosis membrane device is not provided. In front of the forward osmosis membrane device, solid-liquid separation means for separating solids from the water to be treated is provided,
The to-be-processed water by which solid content was isolate | separated by the said solid-liquid separation means is supplied to the primary side of the 1st semipermeable membrane of the said forward osmosis membrane apparatus, The said solid content is supplied to the said anaerobic tank. Water treatment system as described in. Water in the hypertonic solution comprising a second semipermeable membrane, a primary side on which the hypertonic solution exists and a secondary side on which treated water having a lower osmotic pressure than the hypertonic solution exists, with the second semipermeable membrane interposed therebetween Is further provided with a reverse osmosis membrane device for obtaining treated water by permeating from the primary side to the secondary side of the second semipermeable membrane,
The hypertonic solution is transferred from the secondary side of the first semipermeable membrane to the primary side of the second semipermeable membrane in communication with the secondary side outflow portion of the first semipermeable membrane and the primary side inflow portion of the second semipermeable membrane. A first flow path,
A hypertonic solution is transferred from the primary side of the second semipermeable membrane to the secondary side of the first semipermeable membrane in communication with the primary side outflow portion of the second semipermeable membrane and the secondary inflow portion of the first semipermeable membrane. The water treatment system as described in any one of Claims 5-7 with which the 2nd flow path to perform is provided.   The water treatment system according to any one of claims 5 to 8, wherein the forward osmosis membrane device is provided in water to be treated.

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