JP2014144389A - Method for treating organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating organic waste water where: a membrane separation unit including a sheet-like membrane in a treatment tank storing a microorganism-containing liquid injected with the organic waste water is immersed; a membrane filtration step to obtain filtered water by performing a membrane filtration treatment with the sheet-like membrane is included; and serious membrane contamination can be suppressed even in a high flux.SOLUTION: A method for treating organic waste water comprises: a first membrane cleaning step to hold a predetermined time in a state of stopping the injection of a first chemical solution and a sheet-like membrane treatment after the first chemical solution containing one or more medicines selected from the group consisting of an acid, an alkali and an oxidizer is injected to the filtered water flow passage side of a sheet-like membrane; and a second membrane cleaning step to hold a predetermined time longer than a time in the first membrane cleaning step in a state of stopping the injection of a second chemical solution and a sheet-like membrane treatment after the second chemical solution containing the same kind of the medicines as the first chemical solution in a higher concentration is injected to the filtered water flow passage side of the sheet-like membrane. The second membrane cleaning step is performed after a membrane filtration step and the first membrane cleaning step are alternately performed a plurality of times.

Description

  The present invention relates to a method for treating organic wastewater using a membrane separator, and more specifically, by including two types of membrane washing steps, stable operation can be realized even when the membrane filtration flux is set high, and the whole The present invention relates to a method for treating organic wastewater that contributes to energy saving and low cost by reducing the amount of chemicals used, and that can achieve a longer membrane life.

  Organic wastewater is obtained by injecting organic wastewater into a treatment tank containing activated sludge, and separating the activated sludge into solid and liquid using a membrane separation device installed so as to be immersed in the activated sludge in the treatment tank. Wastewater treatment methods are known.

  The membrane separation device is provided with a separation membrane such as a sheet-like membrane (flat membrane) or a hollow fiber membrane, and microorganisms are applied to the membrane surface by the scrubbing effect of air supplied from an air diffuser provided at a vertically lower portion. While suppressing the progress of membrane contamination such as adhesion, the activated sludge can be removed by applying a pressure difference (hereinafter referred to as membrane filtration pressure) between the primary and secondary sides of the separation membrane by suction or water head difference. Solid-liquid separation is performed, and the resulting clean separation membrane filtrate is taken out of the treatment tank. However, normally, membrane contamination progresses, such as the accumulation of untreated microorganisms and microbial metabolites in the membrane pores. As a result, the membrane filtration pressure gradually increases, and membrane filtration per unit membrane area. The flow rate (hereinafter referred to as flux) decreases.

  In such a case, as a method of recovering membrane filtration performance, a chemical solution such as sodium hypochlorite or acid is injected from the filtrate side of the sheet membrane, and this chemical solution is kept constant in the filtrate channel. In-line cleaning in which a chemical solution and a membrane pore-occluding substance are brought into contact with each other by holding for a period of time, or out-of-system cleaning in which a membrane separation apparatus is taken out of a processing tank to perform physical cleaning or chemical cleaning is generally known. Further, for example, as in Patent Document 1, a chemical solution such as an oxidizing agent such as sodium hypochlorite or an acid is injected from the filtrate side of the sheet-like membrane to permeate the membrane, and this chemical solution is passed through the filtrate water flow path. For 1 to 2 hours, and then injecting approximately the same amount of washing water as the chemical solution from the filtered water side to permeate the separation membrane, the chemical solution accumulates more in the membrane pores and membrane surface. The cleaning effect is increased.

Japanese Patent Laid-Open No. 10-66844

  However, in the method of Patent Document 1, in the state where the membrane filtration performance is remarkably lowered, the pore clogging substances of some separation membranes exist as a strong lump, and furthermore, a strong sludge cake is formed on the membrane surface. It may be done. Usually, the separation membrane portion where the progress of membrane contamination as described above is remarkable and the separation membrane portion where the membrane contamination does not progress so much are unevenly distributed, and the problem becomes apparent as a decrease in membrane filtration performance as a whole. In such a state, even if the in-line cleaning or the out-of-system cleaning is performed, the chemical solution permeates well at the portion where the resistance of the separation membrane is low, that is, the separation membrane portion where the membrane contamination is not advanced so much, and a high cleaning effect is obtained. However, there is a problem that the membrane filtration performance is not recovered at a portion where the resistance of the separation membrane is large, that is, at the separation membrane portion where the membrane contamination is remarkably progressing, and the membrane pores are not sufficiently contacted with the sludge cake. Further, the above-mentioned strong pore-occluding substance lump or sludge cake has a problem that the chemical filtration is difficult to permeate to the central portion and the membrane filtration performance may not be sufficiently recovered. Such a problem tends to become more serious as the flux becomes higher, and it has been difficult to realize energy saving and low cost by increasing the design flux.

  Therefore, this invention makes it a subject to provide the processing method of the organic waste water which can suppress that a film | membrane contamination becomes serious even if it is high flux.

  In order to solve the above problems, the present invention has the following configurations (1) to (7).

  (1) A membrane separation device including a sheet-like membrane is immersed in a treatment tank storing a microorganism-containing liquid into which organic waste water has been injected, and filtered water is obtained by performing membrane filtration with the sheet-like membrane. An organic wastewater treatment method including a membrane filtration step, wherein a first chemical solution containing one or more chemicals selected from the group consisting of an acid, an alkali, and an oxidizing agent is injected into the filtered water flow path side of the sheet-like membrane. Then, in the state where the injection of the first chemical solution and the membrane filtration process are stopped, the same type as the first chemical solution is provided on the filtered water flow path side of the sheet-like membrane for a predetermined time. After injecting the second chemical solution containing a higher concentration of the chemical than the first chemical solution, the injection of the second chemical solution and the membrane filtration process are stopped, which is longer than the first membrane cleaning step. A second membrane cleaning step for holding for a time, and the membrane filtration step After a plurality of times and a serial first membrane cleaning step alternately, the method of treating organic waste water of the sheet-like film which comprises carrying out the second membrane cleaning process.

  (2) The organic wastewater for sheet-like membrane according to (1), wherein the injection rate of the first chemical solution and the injection rate of the second chemical solution are smaller than the membrane filtration rate in the membrane filtration step. Processing method.

  (3) The organic concentration of the sheet-like film according to (1) or (2), wherein the drug concentration in the second drug solution is 4 to 40 times the drug concentration in the first drug solution Of waste water.

  (4) The holding time in the second film cleaning step is not less than 4 times and not more than 40 times the holding time in the first film cleaning step. The processing method of the organic waste water of the sheet-like film | membrane as described.

  (5) The sheet-like membrane organic wastewater according to any one of (1) to (4), wherein an average pore diameter on the membrane surface of the sheet-like membrane is 0.01 μm to 0.2 μm Processing method.

  (6) The sheet-like membrane has a multilayer structure, and the average pore size on the membrane surface on the organic waste water side is smaller than the average pore size on the membrane surface on the filtrate channel side (1) to ( The processing method of the organic waste water of the sheet-like film | membrane in any one of 5).

  (7) The method for treating organic wastewater of a sheet-like membrane according to any one of (1) to (6), wherein the filtered water is subjected to a semipermeable membrane treatment.

  In the present invention, by repeating the membrane filtration step and the first membrane washing step, the chemical solution is washed before the deterioration of the membrane filtration performance becomes significant. Therefore, the first chemical solution is effective over the entire separation membrane. It is possible to spread and remove membrane pollutants, thereby suppressing the seriousness of membrane contamination. As a result, the life of the membrane can be extended and the flux can be set high, which can contribute to a reduction in operating cost and power consumption. Moreover, since the density | concentration of a 1st chemical | medical solution is small compared with a 2nd chemical | medical solution and the implementation frequency of a 2nd film | membrane washing | cleaning process can be reduced significantly, the amount of chemical | medical solution usage can also be reduced as a whole.

  Further, when the membrane filtrate is subjected to a semipermeable membrane treatment, when the membrane contamination is serious, the quality of the membrane filtrate water tends to deteriorate, and the performance of the subsequent semipermeable membrane treatment tends to deteriorate. In the present invention, since serious membrane contamination can be suppressed, the performance of the subsequent semipermeable membrane treatment can be maintained high.

It is the schematic which shows an example of the waste water treatment apparatus for enforcing the processing method of the organic waste water of this invention. It is a schematic perspective view which shows two adjacent membrane elements in a membrane separator.

  Hereinafter, the present invention will be described in more detail.

  FIG. 1 is a schematic view showing an example of a wastewater treatment apparatus for carrying out the organic wastewater treatment method of the present invention.

  In FIG. 1, the organic waste water 1 is inject | poured into the activated sludge 2 currently stored by the processing tank 3a. The activated sludge 2 is transferred to the next treatment tank 3, and a membrane separation device 4 is immersed in the treatment tank 3. The activated sludge 2 in the treatment tank 3 is returned and circulated by the pump 32 to the treatment tank 3a through the sludge circulation line 31. Here, it is good also considering the processing tank 3 and the processing tank 3a as one processing tank. In this case, the sludge return line 31 and the pump 32 can be omitted. Further, the membrane separation device 4 is provided with a membrane 5, and an air diffuser 6 is installed in a vertically lower part thereof. Gas is supplied from the blower 7 to the air diffuser 6, and bubbles are generated from the air diffuser 6. The gas-liquid mixed flow generated by the generation of bubbles cleans the surface of the membrane 5 and suppresses microorganisms and trace substances in the activated sludge 2 from adhering to the surface of the membrane 5. Moreover, the suction filtration of the membrane filtration side by the pump 8 causes a pressure difference between the primary side (active sludge 2 side) of the membrane 5 and the secondary side (membrane sludge water side), and the activated sludge 2 is subjected to membrane filtration. By doing so, membrane filtration water 9 is obtained. This is called a membrane filtration step. In the membrane filtration step, continuous filtration in which membrane filtration is always continued may be used, but intermittent filtration in which membrane filtration is stopped every predetermined time may be used.

  Here, in the first membrane cleaning step, membrane filtration is stopped, and the first chemical solution 10 is injected from the filtered water side of the membrane 5 using the pump 11 or the like. Thereafter, the injection of the first chemical 10 is stopped and held for a predetermined time. In the present invention, the first membrane cleaning step and the membrane filtration step are repeated a plurality of times. The first membrane cleaning step is preferably carried out periodically every predetermined period from twice a week to once a month regardless of the state of filtration performance deterioration of the membrane 5. Thereby, it can suppress that film | membrane contamination becomes serious. Further, in the first membrane cleaning step, when the membrane filtration pressure becomes a predetermined value or more (for example, 2 to 5 kPa or more from the operation start initial value), or the membrane filtration flow rate becomes a predetermined value or less (for example, the operation start initial value). It is also preferable to carry out when it is 2-5% or more lower. By performing the first film cleaning step before the film contamination becomes serious in this way, it is possible to suppress the film contamination from becoming serious even during high flux operation, thereby realizing energy saving and low cost.

  In the second membrane cleaning step, the membrane filtration is stopped, and the second chemical solution containing the same type of drug as the first chemical solution at a higher concentration than the first chemical solution is provided on the filtered water flow path side of the sheet-like membrane. After the injection, the second chemical solution injection and the membrane filtration treatment are stopped, and the holding is performed for a longer time than the first membrane cleaning step. In the present invention, after the first membrane cleaning step and the membrane filtration step are repeated a plurality of times, the second membrane cleaning step is performed. In the second membrane cleaning step, when the membrane filtration performance recovery of the first membrane cleaning step is reduced (for example, the membrane filtration pressure immediately after the first membrane cleaning step is 2-5 kPa from the initial operation start value). Or when the membrane filtration pressure becomes equal to or higher than a predetermined value, or when the membrane filtration flow rate becomes equal to or lower than a predetermined value, the first membrane cleaning step When the execution interval becomes smaller (for example, when it becomes less than half of the first first membrane cleaning step), or the membrane filtration pressure is equal to or higher than a predetermined value (for example, 10 to 20 kPa or more higher than the initial operation start value). It is preferable to carry out the process when the flow rate of the membrane becomes equal to or less than a predetermined value (for example, 10 to 20% or more lower than the initial operation start value). Thereby, membrane contaminants that could not be removed even in the first membrane cleaning step can be removed, and membrane filtration performance can be recovered.

Here, “the same type of drug as the first drug solution” included in the second drug solution means that the drug having the largest molar concentration among the one or more drugs included in the first drug solution is the second drug solution. It also includes that. At this time, it is assumed that the drugs of the same kind are ionized and bonded with hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) due to the pH of the chemical solution and the influence of other components contained in the chemical solution.

  The membrane filtrate 9 is preferably subjected to a semipermeable membrane treatment. In FIG. 1, the membrane filtrate 9 is supplied to the semipermeable membrane device 40 via the high-pressure pump 41 and processed by the semipermeable membrane incorporated in the semipermeable membrane device 40, so that the salt concentration is higher than the membrane filtrate 9. Is separated into a semipermeable membrane permeated water 42 having a small salt concentration and a semipermeable membrane concentrated water 43 having a salt concentration larger than that of the membrane filtrate 9. The semipermeable membrane permeated water 42 obtained by this treatment can be used for industrial water, agricultural water, irrigation water, groundwater replenishment water, indirect drinking water, landscape water, and the like.

  Here, the organic waste water 1 is not particularly limited as long as it is a waste water containing organic matter, and examples thereof include sewage, rural settlement waste water, and organic industrial waste water. The organic waste water may be diluted with water.

  As long as the microorganism-containing liquid is a liquid containing microorganisms as exemplified by the activated sludge 2, the type and concentration of microorganisms are not particularly limited. It is preferably a microorganism or microbial community structure that can efficiently treat organic substances contained in organic wastewater, and can usually be acclimatized by injecting organic wastewater.

  The shape and material of the treatment tank 3 are not particularly limited as long as the treatment tank 3 can store a microorganism-containing liquid such as the activated sludge 2. In general, rectangular concrete or steel plate is often used.

  The membrane separation device 4 is arranged in parallel so that the sheet-like membrane shown by the membrane 5 in FIG. 1 is parallel to the membrane surface in the vertical direction, and the membrane surfaces are parallel to each other with a predetermined interval. Has been. For example, as shown in FIG. 2, a sheet-like separation membrane 5 is disposed on both the front and back surfaces of a frame 401 formed of resin, metal, or the like, and communicates with the internal space surrounded by the separation membrane 5 and the frame 401. There is a structure in which a plurality of membrane elements 400 having a structure in which a water outlet 402 is provided on an upper portion of a frame 401 are arranged so that adjacent membranes 5 are spaced apart from each other. An air diffuser 6 is disposed in a vertically lower part of the sheet-like film. The air diffuser 6 may have any structure that diffuses gas supplied by a gas supply device such as the blower 7 as bubbles. For example, a pipe provided with a hole or a fine bubble diffuser pipe provided with a fine slit in a rubber sheet can be applied.

  In the present invention, the membrane 5 is a sheet-like separation membrane. Unlike hollow fiber membranes, where the primary side area is larger than the secondary side, the sheet-like membrane has the same area on the primary side and secondary side of the membrane. The first chemical solution and the second chemical solution injected from the roadside efficiently diffuse and penetrate into the membrane pores and the membrane surface even in a short time, and the cleaning effect of the dirt component adhering to the membrane can be enhanced. In particular, the smaller the filtration resistance of the sheet membrane, the higher the permeation rate of the chemical solution and the higher the cleaning effect, so the sheet membrane has a multilayer structure, and the average pore diameter on the membrane surface on the organic waste water side is It is preferably smaller than the average pore diameter on the membrane surface.

  Moreover, it is preferable that the average pore diameter in the film | membrane surface of a sheet-like film | membrane is 0.01 micrometer or more and 0.2 micrometers or less. When the average pore diameter is 0.01 μm or more, an increase in membrane filtration resistance is suppressed and not only the filtration efficiency in the membrane filtration step is improved, but also the chemical solution penetration in the washing step is increased, and the washing effect is improved. In addition, the microorganism-containing liquid which is the liquid to be filtered contains microorganisms, but if the average pore diameter is 0.2 μm or less, the microorganisms basically do not enter the inside of the membrane pores and do not enter the membrane surface. stay. That is, the contaminants inside the membrane pores are microbial metabolites, minute untreated substances, and the like, and the amount of contaminants is small, so that the amount of chemicals required for cleaning can be small. That is, the cleaning effect in the first cleaning process performed with a small chemical solution concentration and high frequency is increased. Moreover, when the membrane filtration process is started after the completion of the first and second membrane cleaning processes, the quality of the membrane filtrate water tends to deteriorate for a certain time immediately after the completion of the membrane cleaning process. The larger the average pore diameter, the greater the degree of water quality deterioration and the longer it takes to recover.When membrane filtration water is subjected to semipermeable membrane treatment, semipermeable membrane treatment cannot be performed until the water quality is restored. The amount of permeable membrane treatment is small and the operating rate is lowered. In particular, when the average pore diameter exceeds 0.2 μm, since the presence or absence of microorganisms into the membrane pores is important, the influence becomes large. Therefore, by using a sheet-like membrane having an average pore diameter of 0.2 μm or less, the water quality recovery time after completion of the membrane cleaning step is shortened, and the semipermeable membrane treatment operation rate can be maintained high.

  Examples of the material for the sheet-like film include polyethylene, polypropylene, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone (PES), polyether-etherketone (PEEK), and polyphenylene sulfide. Examples thereof include organic substances such as sulfone (PPSS), polyphenylene sulfone (PPSO), polyvinyl alcohol, cellulose acetate, polyacrylonitrile, polyamide, and polyimide, and inorganic substances such as ceramic and metal. In particular, a polyvinylidene fluoride (PVDF) film having excellent chemical resistance is preferable.

  Here, in the present invention, the average pore diameter of the membrane surface is the average value of the pore diameter in the surface portion of the separation membrane, and the surface of the separation membrane is observed by observation with a scanning electron microscope. The pore diameter observed on the surface is measured, and the average value is defined as the average pore diameter.

  The 1st chemical | medical solution 10 and the 2nd chemical | medical solution 20 contain 1 or more types of chemical | medical agents chosen from the group which consists of an acid, an alkali, and an oxidizing agent. As the acid, citric acid, oxalic acid, sulfuric acid, caustic soda as the alkali, and sodium hypochlorite, chloramine as the oxidizing agent are preferably used. Since the microorganism-containing liquid contains a large amount of organic substances, sodium hypochlorite is particularly suitable from the viewpoint of cost and cleaning effect.

  In FIG. 1, the first chemical solution and the second chemical solution are injected into the filtrate flow path side by the pump 11 and the pump 22, respectively. However, at this time, the first chemical solution and the second chemical solution may be injected using a gravity difference regardless of the pump.

  Moreover, it is preferable that the injection | pouring rate of a 1st chemical | medical solution and the injection | pouring rate of a 2nd chemical | medical solution are smaller than the membrane filtration rate in a membrane filtration process. Thereby, not only can the chemical solution contact the membrane contaminant efficiently and the chemical solution can be effectively utilized, but also the amount of the chemical solution that flows out into the microorganism-containing liquid can be suppressed, and damage, inactivation, death, etc. of the microorganism due to the chemical solution can be suppressed.

  Moreover, it is also preferable that the chemical | medical agent density | concentration in a 2nd chemical | medical solution is 4 to 40 times the chemical | medical agent concentration in a 1st chemical | medical solution. If the concentration is smaller than four times, the concentration of the first chemical solution is too high, so that the amount of the chemical solution flowing out to the microorganism-containing solution through the membrane increases, leading to damage, inactivation, or death of the microorganism, and the subsequent microorganism-containing solution. The membrane filterability may be deteriorated, or the amount of the chemical solution used as a whole may be increased, and the effect of reducing the chemical amount may not be obtained. Alternatively, since the concentration of the second chemical solution is too low, the film contaminants remaining even in the first film cleaning process cannot often be removed in the second film cleaning process. On the other hand, if it is larger than 40 times, the concentration of the first chemical solution is too low, so that the film cleaning effect in the first film cleaning process is small, and stable operation with high flux may not be possible. Or, since the second chemical concentration is too high, the first chemical concentration is too high, so the amount of chemical flowing out to the microorganism-containing liquid through the membrane increases, leading to damage, inactivation, and death of the microorganism, This causes a decrease in the membrane filterability of the microorganism-containing liquid. For example, when sodium hypochlorite is used as the first and second chemical solutions, if the second chemical concentration is 4000 mg / L, the first chemical concentration is preferably set to 100 to 1000 mg / L.

  Furthermore, it is preferable that the holding time in the second film cleaning step is not less than 4 times and not more than 40 times the holding time in the first film cleaning step. If it is less than four times, the time for the chemical solution and the membrane contaminants to contact with each other in the second membrane cleaning step becomes insufficient, and the membrane contaminants remaining in the first membrane cleaning step are also removed in the second membrane cleaning step. There are many cases where this is not possible. Alternatively, since the time for the chemical solution and the membrane contaminant to contact in the first membrane cleaning step is too long, the time for stopping the membrane filtration increases, which is inefficient. On the other hand, if it is larger than 40 times, the time for the chemical solution and the film contaminant to contact in the first film cleaning process is too short, so the film cleaning effect in the first film cleaning process is small and stable at high flux. It may become impossible to drive. For example, when the holding time in the second cleaning step is 4 hours, the holding time in the first cleaning step is preferably set to 6 minutes to 1 hour.

  In the semipermeable membrane treatment, the membrane separation usually has a function of containing the semipermeable membrane, structurally separating the raw water (solid content removal water) and the permeated water (product water), and collecting the permeated water. Elements are used. The form of the membrane separation element is not particularly limited. However, in the case of a hollow fiber membrane, a structure in which a plurality of hollow fibers are bundled and an end is bonded to a permeate collecting part. Examples include a spiral structure in which an envelope is formed, an end is bonded to a central pipe serving as a water collecting pipe, and a flat membrane is wound around and fixed. Furthermore, permeated water and concentrated water can be obtained by accommodating one or more membrane separation elements in a pressure-resistant container and pressurizing from the raw water (solid content removal water) side. At that time, the connection configuration of multiple pressure-resistant containers (such as a configuration in which permeated water or concentrated water is connected to a different pressure-resistant container), recovery rate of permeated water, concentration rate of concentrated water, processing time, processing temperature, etc. Conditions and the like are variously changed depending on the scale of the apparatus, production capacity, required water quality, and the like. Examples of the material of the semipermeable membrane include polymer materials such as cellulose acetate polymer, polyamide, polyester, polyimide, and vinyl polymer. In addition, the membrane structure has a dense layer on at least one side of the membrane, and an asymmetric membrane having fine pores with gradually increasing pore diameters from the dense layer to the inside of the membrane or the other side, and a dense membrane on the asymmetric membrane. And a composite membrane having a very thin separation functional layer formed of the above material.

DESCRIPTION OF SYMBOLS 1 Organic waste water 2 Activated sludge 3, 3a Treatment tank 4 Membrane separation device 5 Membrane 6 Air diffuser 7 Blower 8, 11, 21, 32 Pump 9 Membrane filtrate 10 First chemical solution 20 Second chemical solution 31 Sludge circulation line 40 Semipermeable membrane device 41 High pressure pump 42 Semipermeable membrane permeated water 43 Semipermeable membrane concentrated water 400 Membrane element 401 Frame 402 Treated water outlet

Claims (7)

A membrane filtration step in which a membrane separation device including a sheet-like membrane is immersed in a treatment tank storing a microorganism-containing liquid into which organic waste water is injected, and membrane filtration is performed with the sheet-like membrane to obtain filtered water A method for treating organic wastewater containing
After injecting the first chemical liquid containing one or more kinds of drugs selected from the group consisting of acids, alkalis, and oxidants into the filtered water flow path side of the sheet-like membrane, the injection of the first chemical liquid and the membrane filtration treatment are performed. A first film cleaning step of holding for a predetermined time in a stopped state;
After injecting a second chemical solution containing the same type of drug as the first chemical solution at a higher concentration than the first chemical solution into the filtered water flow path side of the sheet-like membrane, the injection of the second chemical solution and the membrane Including a second membrane cleaning step of holding the filtration process for a longer time than the first membrane cleaning step,
An organic wastewater treatment method for a sheet-like membrane, wherein the membrane filtration step and the first membrane washing step are alternately carried out a plurality of times, and then the second membrane washing step is carried out. The method for treating organic wastewater of a sheet-like membrane according to claim 1, wherein the injection rate of the first chemical solution and the injection rate of the second chemical solution are smaller than the membrane filtration rate in the membrane filtration step. . 3. The method for treating organic wastewater of a sheet-like film according to claim 1, wherein the drug concentration in the second chemical solution is 4 to 40 times the drug concentration in the first chemical solution. . The sheet-like film according to any one of claims 1 to 3, wherein the holding time in the second film cleaning step is 4 to 40 times the holding time in the first film cleaning step. Treatment method of organic wastewater. The method for treating organic wastewater of a sheet-like membrane according to any one of claims 1 to 4, wherein an average pore diameter on the membrane surface of the sheet-like membrane is 0.01 µm or more and 0.2 µm or less. The sheet-like membrane has a multilayer structure, and the average pore size on the membrane surface on the organic waste water side is smaller than the average pore size on the membrane surface on the filtrate channel side. The processing method of the organic waste water of the sheet-like film | membrane as described in 2. The method for treating organic wastewater of a sheet-like membrane according to any one of claims 1 to 6, wherein the filtrate is subjected to a semipermeable membrane treatment.

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