JPH105784A - Membrane activated sludge method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] By suppressing the time-dependent decrease in the amount of permeated water due to the attachment and deposition of a polymer substance or the like to a membrane module, it is possible to increase the throughput of an activated sludge apparatus and reduce the membrane cost.
Furthermore, the provision of a membrane separation activated sludge method with high treatment efficiency. SOLUTION: A mixed solution (activated sludge) containing a sludge-like substance generated in an aeration tank is filtered using a membrane module immersed in the aeration tank to obtain treated water as membrane permeated water. Of the alkaline water and acidic water produced in the diaphragm electrolyzer, the former is supplied to the secondary side of the membrane module to be subjected to membrane cleaning, and then permeated to the primary side of the membrane module to allow the mixed solution in the aeration tank. In the membrane separation activated sludge method, in which the latter flows into the membrane permeated water, and in the membrane separation activated sludge method, furthermore, between the oxygen-free tank and the aeration tank installed on the upstream side of the aeration tank. Circulating the mixed solution,
Decomposition reaction of organic substances and nitrogen compounds in raw wastewater, nitrification
A membrane separation activated sludge method for denitrification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wastewater containing organic substances and nitrogen compounds, such as domestic wastewater such as municipal sewage and settlement drainage, livestock human wastewater, marine processing wastewater, agricultural processing wastewater, and the like. The present invention relates to a membrane separation activated sludge method in which sludge-like reactants produced are subjected to solid-liquid separation by a membrane separation device.

[0002] More specifically, by suppressing the blockage of the pores of the membrane by sludge particles, it is possible to increase the throughput of the membrane separation activated sludge apparatus and extend the life of the membrane, and to reduce the organic matter contained in the raw wastewater. The present invention relates to a membrane separation activated sludge method capable of effectively performing a decomposition reaction of a substance and a nitrification and denitrification reaction of a nitrogen compound such as ammonia nitrogen, and having a high treatment efficiency.

[0003]

2. Description of the Related Art A membrane module immersed in an aeration tank to cope with the problem of deterioration of sedimentation and separation of activated sludge in the conventional standard activated sludge method and the advanced treatment of existing sewage treatment plants. A membrane separation activated sludge method using a constructed membrane separation apparatus has been proposed (Japanese Patent Publication No. 4-70958).

FIG. 3 shows the configuration of an activated sludge apparatus used in the membrane separation activated sludge method. In FIG. 3, reference numeral 12 denotes an aeration tank as a biological reaction tank, reference numeral 15 denotes a mixed solution (so-called activated sludge) of a liquid to be treated (raw effluent) and sludge-like reactants (hereinafter referred to as a mixed solution), and reference numeral 16 denotes a membrane module 17. 2 shows a membrane separation device including a suction device 18 such as a pump. This method uses a UF (ultrafiltration) membrane module, an MF
(Microfiltration) The mixed solution (activated sludge) is solid-liquid separated by immersing a membrane module 17 such as a membrane module, suctioning the secondary side of the membrane module 17 with a suction device 18 connected to a pipe, and reducing the pressure. The membrane permeated water is obtained as treated water, and is called an aeration tank immersion type membrane separation activated sludge method.

[0005] Fig. 4 is a block diagram of an activated sludge apparatus used in a membrane separation activated sludge method for biologically treating wastewater containing nitrogen compounds in addition to organic substances. 4, reference numeral 40 denotes an anoxic tank attached to the upstream side of the aeration tank 12, 41 denotes drainage, 42 denotes a liquid feed pump, 43 denotes a slow stirring device, and 44 denotes a lid. Indicates the same content.

In this method, as in the method of FIG. 3, the mixed solution 15 is separated into solid and liquid by the membrane module 17 to obtain membrane permeated water as treated water. The nitrification and denitrification of nitrogen compounds contained in the raw wastewater is performed by circulating the mixed solution 15 (or wastewater 41) between the two. ing.

According to the method shown in FIG. 3 or FIG.
Since a sedimentation / separation tank is not required, the quality of sedimentation / separation of activated sludge is no longer a problem, and a compact processing apparatus can be achieved, and a tertiary processing apparatus for advanced processing can be easily added. However, when the membrane separation method is applied as a solid-liquid separation method of the activated sludge method, organic polymer substances and solids (particles) in the activated sludge adhere to and accumulate on the membrane, and the amount of permeated water decreases with time. Thereby, the throughput of the activated sludge apparatus is reduced, and the life of the membrane is also shortened.

[0008] Therefore, in the membrane separation activated sludge method,
There is a strong demand for a technique capable of effectively increasing the amount of membrane permeated water over time to increase the amount of treatment and thereby reducing the membrane cost in wastewater treatment by extending the life of the membrane.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a membrane separation activated sludge method, which suppresses a time-dependent decrease in the amount of water permeated through a membrane due to adhesion and deposition of a polymer substance or the like on a membrane module.
An object of the present invention is to provide a membrane separation activated sludge method capable of increasing the throughput of an activated sludge apparatus and reducing the cost of a membrane, and having a high treatment efficiency.

[0010]

A first aspect of the present invention is a membrane separation activated sludge method used for treating raw wastewater containing organic substances, wherein the mixed sludge-like substance produced in an aeration tank is contained. The solution is filtered using a membrane module immersed in the aeration tank to obtain treated water that is a membrane permeate, while alkaline water and acidic water produced by a diaphragm type electrolyzer are separated from the alkaline water by the membrane. After being supplied to the module secondary side and subjected to membrane cleaning, it is permeated to the membrane module primary side and allowed to flow into the mixed solution in the aeration tank, and acidic water is allowed to flow into the membrane permeated water. This is a membrane separation activated sludge method.

A second invention is a membrane separation activated sludge method used for treating raw wastewater containing an organic substance and a nitrogen compound. The method comprises an oxygen-free tank installed upstream of an aeration tank and the aeration tank. By circulating the mixed solution containing the sludge-like reactant generated in the aeration tank during the above, while performing the decomposition reaction and nitrification and denitrification of organic substances and nitrogen compounds contained in the raw wastewater, While filtering the mixed solution using a membrane module immersed in the mixed solution in the aeration tank to obtain treated water that is a membrane permeated water, of the alkaline water and the acidic water produced by the diaphragm type electrolysis apparatus, After supplying the alkaline water to the secondary side of the membrane module and subjecting the membrane to membrane cleaning, the alkaline water is allowed to pass through the primary side of the membrane module and flow into the mixed solution in the aeration tank. /
Alternatively, there is provided a membrane separation activated sludge method characterized in that the activated sludge is caused to flow into drainage of the anoxic tank.

In the first invention and the second invention,
When the filtration of the mixed solution by the membrane module is stopped, the membrane is preferably washed with the alkaline water.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. An object of the present invention is to provide a membrane separation activated sludge method capable of suppressing a time-dependent decrease in the amount of permeated water in the membrane separation activated sludge method and further increasing the treatment efficiency of the membrane separation activated sludge method. As a result of various studies, the present invention has been achieved.

[0014] The cause of the time-dependent decrease in the amount of water permeated through the membrane in the membrane separation activated sludge method is that an organic polymer adheres and deposits on the surface of the membrane to form a sticky gel layer, and the sludge is formed on the gel layer. This is considered to be because particles accumulate to form a cake layer and cause so-called clogging. The present inventors have effectively and efficiently removed a sticky polymer gel layer adhering to and accumulating on a membrane in a membrane separation activated sludge method, and furthermore, a decomposition reaction of organic substances in an aeration tank and an oxygen-free tank. (Biological reaction), it has been found that the following constitution is effective as a method capable of effectively performing a nitrification / denitrification reaction of a nitrogen compound such as ammonia nitrogen.

[0015] To reduce the size of the treatment apparatus, an activated aeration tank immersion type membrane separation activated sludge method is used. : The membrane is washed with an alkaline solution. : As a membrane cleaning method using an alkali solution, pressurized alkaline water is intermittently supplied to the secondary side of the membrane module in a state where the membrane module is immersed in an aeration tank, and the membrane module is washed and used for membrane washing. The alkaline water permeates the primary side of the membrane module and flows into the mixed solution (activated sludge) in the aeration tank.

As the alkaline water, alkaline water produced by water membrane electrolysis is used, and by-produced acidic water is allowed to flow into the membrane permeated water. : Under the above conditions, an anoxic tank is attached before the aeration tank, and the mixed solution is circulated between the anoxic tank and the aeration tank to perform nitrification and denitrification of nitrogen compounds contained in the raw wastewater. Do.

With the above configuration, the following effects can be obtained. : It has become possible to effectively suppress the time-dependent decrease in the amount of permeated water due to the attachment and deposition of substances to the membrane module. : Since the membrane can be washed while the membrane module is immersed in the aeration tank, it is not necessary to remove the membrane module from the aeration tank each time and perform cleaning, etc.
The operation rate of the membrane separation activated sludge apparatus was improved, and the treatment efficiency was able to be increased.

[0018] The alkaline water used for membrane cleaning is allowed to permeate the primary side of the membrane module and flow into the mixed solution in the aeration tank, thereby decomposing organic substances in the aeration tank (biological reaction). Nitrification and denitrification reactions of ammonia nitrogen and the like can be performed effectively. : The acidic water by-produced during the electrolysis of the water in the membrane was allowed to flow into the permeated water, so that the pH of the treated water could easily be maintained within the reference value.

Hereinafter, a method of applying the present invention to a membrane separation activated sludge method to which the present invention is applied and alkaline water and acidic water produced by membrane electrolysis of water to a membrane separation activated sludge method will be described. [Membrane separation activated sludge method to which the first invention is applied:] FIG.
FIG. 1 shows an example of a specific configuration diagram of an activated sludge apparatus according to the membrane separation activated sludge method of the first invention.

Reference numerals 11 to 19 in FIG. 1 indicate the same contents as in FIG. The raw wastewater containing organic substances is supplied to an aeration tank 12 through a regulating tank 11, and the organic substances contained in the raw wastewater are actively activated by aeration from an air diffuser 14 sent from a blower 13. It is oxidatively decomposed by the aerobic bacteria to form a mixed solution 15 containing sludge-like reactants, that is, activated sludge.

A membrane module 17 is immersed in the mixed solution 15 in the aeration tank 12. The secondary side of the membrane module 17 is connected by piping to a suction device 18 such as a pump, and the suction side 18 suctions the secondary side of the membrane module 17 to reduce the pressure, so that the treated water is converted into membrane permeated water. can get. In addition, as the membrane module 17, a membrane module selected from a UF (ultrafiltration) membrane module and a MF (microfiltration) membrane module is preferably exemplified.

[Membrane Separation Activated Sludge Method to which the Second Invention is Applied] FIG. 2 shows an example of a specific configuration diagram of an activated sludge apparatus according to the membrane separation activated sludge method of the second invention. Reference numerals 11 to 19 and 40 to 44 in FIG. 2 indicate the same contents as in FIG. As described above, the membrane module 17 is preferably a UF (ultrafiltration) membrane module, an MF (microfiltration)
A membrane module selected from membrane modules is exemplified.

The method and structure of the oxygen-free tank 40 in FIG. 2 are not limited as long as they have the functions of circulating the mixed solution in the aeration tank, supplying the raw wastewater and stopping the supply of oxygen. The method of forming activated sludge from raw wastewater containing organic substances and obtaining treated water (membrane permeated water) in FIG. 2 is the same as the method of FIG. 1 described above, except for the following steps. That is,
The method of FIG. 2 further includes an anoxic tank 40 upstream of the aeration tank 12.
Is installed, and the raw wastewater is supplied from the adjustment tank 11 to the aeration tank 12 via the oxygen-free tank 40.

Further, in the method of FIG.
The mixed solution is circulated between the aeration tank 12 and the oxygen-free tank 40 by sending the mixed solution 15 from the aeration tank 12 to the oxygen-free tank 40 and overflowing the drainage 41 from the oxygen-free tank 40 to the aeration tank 12 by 42. The circulation causes nitrification of nitrogen compounds in raw wastewater.
Denitrification and dephosphorization are performed. The nitrification reaction in the aeration tank 12 is represented by the following equation.

NH ₄ ⁺ + 2O ₂ → NO ₃ ⁻ + H ₂ O + 2H ⁺ (1) The denitrification reaction in the oxygen-free tank 40 is represented by the following equation. 2NO ₃ ⁻ + 10H → N ₂ + 4H ₂ O + 2OH ⁻ (2) As shown in the above formula (1), the nitrification reaction is alkaline and the reaction easily proceeds, and the optimum pH is 8 to 9.

The denitrification reaction of the formula (2) is acidic and the reaction is easy to proceed, but the raw wastewater is often acidic, and the oxygen-free tank
In 40, pH adjustment is not necessarily required. In the present invention, the circulation system is not particularly limited. As described above, the example of the activated sludge apparatus to which the first invention and the second invention (hereinafter, collectively referred to as the present invention) are applied has been described. As shown in 2, diaphragm type electrolysis device
20 is attached.

Referring to FIG. 1 and FIG.
20 is an anode chamber 23 having an anode 22 by a diaphragm 21, and a cathode
A cathode compartment 25 having an anode 22 and a cathode 24.
Anode chamber 23 and cathode chamber 25
To supply acidic water and alkaline water, respectively. In addition, the membrane separation activated sludge device according to the present invention is further provided with an alkaline water storage tank 26, an acidic water storage tank 27, liquid feed pumps 28 and 29, switching valves 32 and 33,
During operation of the membrane separator 16, the treated water is neutralized by supplying the acidic water stored in the acidic water storage tank 27 to the treated water, and when the suction device 18 of the membrane separator 16 is stopped, the alkaline water storage tank 26 is stopped.
Is supplied to the secondary side of the membrane module 17.

That is, the membrane separation device 16 is usually operated by an intermittent suction method in many cases. In the present invention, the timing of stopping the suction of the mixed solution 15 is used, for example, for four times.
PH produced by membrane electrolysis of water about once every 15 minutes
The membrane module 17 can be washed by intermittently supplying alkaline water 30 having a pH of more than 7.0, preferably a pH of more than 8.0 and a pH of 10 or less to the secondary side of the membrane module 17.

In this case, when the operation of the suction device 18 is stopped and a pressure of about 0.2 to 1.0 atm (gauge pressure) is applied to the alkaline water on the secondary side of the membrane module 17 by the liquid sending pump 28, the alkaline water 30 After passing through the membrane, it is supplied to the mixed solution 15 in the primary side of the membrane module 17, that is, in the aeration tank 12.
Since the optimum pH of the mixed solution 15 in the aeration tank 12 is 8 to 9, the supply of the alkaline water 30 contributes to the optimization of the pH of the mixed solution 15.

However, if only the alkaline water 30 is supplied, the pH of the permeated water, that is, the treated water may exceed the upper limit of the water quality, pH = 8.7. For this reason, the acidic water 31 having a pH of less than 7.0, preferably 4.0 or more and less than 7.0, which is simultaneously produced (by-produced) in the diaphragm type electrolysis apparatus 20, is caused to flow into the membrane permeated water. In the second invention,
When the pH of the raw wastewater is alkaline, it is preferable to supply the acidic water 31 to the oxygen-free tank 40 to promote the above-described denitrification reaction (reaction formula (2)) in the oxygen-free tank 40.

According to the present invention, the acid water 31 and the alkaline water 30 are finally mixed and neutralized with the membrane permeated water, so that the standard value of the pH of the treated water can be easily satisfied.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Embodiment 1) The treatment of domestic wastewater was carried out using the above-mentioned membrane separation activated sludge apparatus according to the present invention shown in FIG.

The volume of the aeration tank 12 was 45 l, the throughput of the raw wastewater was 150 l / day, and the residence time of the raw wastewater in the aeration tank was 7.2 hours. The MF (microfiltration) membrane module used in the membrane separator 16 is a hollow fiber type having a pore size of 0.35 μm and an effective membrane area of 0.1 m ² . Air is supplied from the air diffuser 14 at a flow rate of 2 l / min by the blower 13, and while the mixed solution 15 in the aeration tank 12 is aerated, the secondary side of the membrane module 17 is depressurized to about 0.2 atm by the suction device 18. Then, the mixed solution 15 was sucked, and the wastewater treatment was continuously performed.

A part of the membrane permeated water was recirculated to the aeration tank 12 by the liquid sending pump 19. Further, the alkaline water 30 produced by the diaphragm electrolysis method of the water in the diaphragm type electrolysis device 20 and stored in the alkaline water storage tank 26 is once / ten minutes using the timing of stopping the suction of the suction device 18. The cleaning of the membrane module 17 was performed by intermittently supplying the membrane module 17 to the secondary side of the membrane module 17 at the frequency shown in FIG.

The supply of the alkaline water 30 to the secondary side of the membrane module 17 is performed by setting the pressure of the alkaline water at the outlet of the liquid feed pump 28 to 1.0 atm (gauge pressure) and allowing the alkaline water 30 to permeate the membrane. Primary side of membrane module 17, ie aeration tank
12 and the pH of the aeration tank 12 was adjusted to 8-9. Further, during operation of the suction device 18, by supplying the acidic water 31 by-produced by the diaphragm type electrolysis device 20 and stored in the acidic water storage tank 27 to the treated water as the membrane permeated water, the treated water is supplied. The pH was within the reference value.

As a result of continuous operation of the membrane separation activated sludge apparatus by the above-mentioned method, the amount of permeated water was 0.33 m ³ / m ² / day at the beginning of treatment of raw wastewater, and 0.33 m ³ / m after 24 hours. ² / day.
The average BOD of the raw wastewater during the continuous operation period was 195 mg / l, while the average BOD of the treated water was 1.7 mg / l. (Comparative Example 1) The diaphragm type electrolysis apparatus 20 was stopped, and alkaline water
The continuous operation of the membrane separation activated sludge apparatus was performed under the same conditions as in Example 1 except that the cleaning of the membrane module 17 by 30 was not performed.

[0037] As a result, membrane permeation water amount, the process starts early original wastewater 0.33m ³ / m ² / day, after 24h elapsed was at 0.12m ³ / m ² / day. The average BOD of raw wastewater during the continuous operation period was 191.
The average BOD of the treated water was 1.3 mg / l compared to mg / l. (Example 2) Domestic wastewater was treated using the membrane separation activated sludge apparatus according to the present invention shown in FIG. 2 described above.

The volume of the aeration tank 12 was 45 liters, the capacity of the anoxic tank 40 was 30 liters, the throughput of the raw wastewater was 150 l / day, and the residence time of the raw wastewater in the aeration tank was 7.2 hours. The MF (microfiltration) membrane module used in the membrane separator 16 has a pore size of 0.35 μm.
m, hollow fiber type with an effective membrane area of 0.1 m ² . Also,
The structure of the oxygen-free tank 40 is a square cylinder having a slow stirring device 43 for the mixed solution.

Air is supplied from the air diffuser 14 at a flow rate of 2 l / min by the blower 13, and while the mixed solution 15 in the aeration tank 12 is aerated, the secondary side of the membrane module 17 is moved to about 0.
The pressure was reduced to 2 atm, the mixed solution 15 was sucked, and the wastewater treatment was continuously performed. A part of the membrane permeated water was recirculated to the aeration tank 12 by the liquid sending pump 19. In addition, aeration tank 12 and anoxic tank
The mixed solution 15 (or effluent 41) is circulated at a circulation rate of 450 l / day between 40 and 40, and the decomposition reaction of organic substances and nitrogen compounds and nitrification and denitrification in the mixed solution 15 (or effluent 41) are performed. went.

Further, in the same manner as in Example 1, a membrane module made of alkaline water 30 manufactured by the diaphragm type electrolysis apparatus 20 is used.
Cleaning solution 17 and alkaline water 30 mixed solution in aeration tank 12
The pH of the aeration tank 12 was adjusted by flowing into the tank 15. Further, in the same manner as in Example 1, during the operation of the suction device 18, the pH of the treated water was kept within the reference value by using the acidic water 31 by-produced in the diaphragm type electrolysis device 20.

The result of the continuous operation of the membrane separation activated sludge unit by the above method, membrane permeation water amount, the process starts early original wastewater 0.33m ³ / m ² / day, after 24 h is 0.33 m ³ / there was at m ² / day.
Average BOD of raw wastewater during continuous operation: 205 mg / l,
Average TN (total nitrogen): 47 mg / l, average ammonium ion concentration: 45 mg (NH ₄ -N) / l, average BOD of treated water: 1.
4 mg / l, average TN (total nitrogen): 7.1 mg / l, average ammonium ion concentration: 0.1 mg (NH ₄ -N) / l.

(Comparative Example 2) The diaphragm type electrolysis apparatus 20 was stopped,
The continuous operation of the membrane separation activated sludge apparatus was performed under the same conditions as in Example 2 except that the membrane module 17 was not washed with the alkaline water 30. As a result, membrane permeation water amount, the process starts early original wastewater 0.33m ³ / m ² / day, after 24h elapses 0.11m ³ / m ² /
It was a day.

The average BOD of raw wastewater during the continuous operation period
: 198 mg / l, average TN (total nitrogen): 50 mg / l, average ammonium ion concentration: 47 mg (NH ₄ -N) / l, average BOD of treated water: 1.7 mg / l, average TN (Total nitrogen): 7.2mg /
l, average ammonium ion concentration: 0.1 mg (NH ₄ -N) / l. As described in detail above, according to the present invention,
In the treatment of wastewater by the membrane separation activated sludge method, the membrane module is washed with alkaline water produced by a diaphragm type electrolyzer, thereby suppressing the membrane blockage due to sludge particles caused by organic polymer substances. In addition, it is possible to increase the throughput of the membrane separation activated sludge apparatus by effectively suppressing the decrease in the amount of permeated water over time.

Further, as a result, the life of the membrane can be significantly extended, and the membrane cost in wastewater treatment can be significantly reduced. In addition, since the membrane can be effectively washed while the membrane is immersed in the aeration tank, there is no need to stop the membrane separation activated sludge apparatus for a long time, and the operation rate of the apparatus is improved, and the membrane separation activated sludge process is performed. It has become possible to increase the volume and processing efficiency.

Further, by supplying the alkaline water after the membrane module washing to the mixed solution (activated sludge) in the aeration tank, the decomposition reaction (biological reaction) of the organic substance in the raw wastewater in the aeration tank, ammonia nitrogen, etc. Nitrification and denitrification of nitrogen compounds in raw wastewater in aeration tanks and anoxic tanks can be performed effectively. Further, by making acidic water produced as a by-product in the diaphragm type electrolytic device flow into the membrane permeated water, it became easy to maintain the pH of the treated water at the reference value.

[0046]

According to the present invention, the following effects can be obtained. : It is possible to effectively suppress the time-dependent decrease in the amount of water permeated through the membrane due to the attachment / deposition of an organic polymer substance or the like to the membrane module, and increase the throughput of the membrane separation activated sludge equipment. As a result, it has become possible to significantly reduce the membrane cost in wastewater treatment.

[0047] Since the membrane can be washed while the membrane module is immersed in the aeration tank, the operation rate of the membrane separation activated sludge apparatus is improved, and the treatment amount and treatment efficiency of raw wastewater can be increased. It has become possible. : Decomposition reaction (organic reaction) of organic substances in the aeration tank by allowing the alkaline water used for membrane cleaning to permeate the primary side of the membrane module and flow into the mixed solution (activated sludge) in the aeration tank. Nitrification and denitrification of nitrogen compounds such as ammonia nitrogen in aeration tanks and anoxic tanks can be performed effectively.

[0048] Since the acidic water produced as a by-product during the electrolysis of the water into the membrane flows into the membrane permeated water, the pH of the treated water can be easily maintained within the reference value. That is, the present invention
Domestic sewage such as urban sewage and settlement drainage, livestock night drainage,
The treatment of wastewater containing organic substances such as marine processing wastewater and agricultural processing wastewater or additionally containing nitrogen compounds can be performed by a method which is far superior in both processing efficiency and economic efficiency to conventional processing techniques.

[Brief description of the drawings]

FIG. 1 is a specific configuration diagram showing an example of an activated sludge apparatus according to the membrane separation activated sludge method of the present invention.

FIG. 2 is a specific configuration diagram showing an example of an activated sludge apparatus according to the membrane separation activated sludge method of the present invention.

FIG. 3 is a specific configuration diagram showing an activated sludge apparatus used in a conventional membrane separation activated sludge method.

FIG. 4 is a specific configuration diagram showing an activated sludge apparatus used in a conventional membrane separation activated sludge method.

[Explanation of symbols]

 11 Regulating tank 12 Aeration tank (biological reaction tank) 13 Blower 14 Air diffuser 15 Mixed solution (activated sludge) 16 Membrane separator 17 Membrane module 18 Suction device 19, 28, 29, 42 Liquid feed pump 20 Diaphragm type electrolyzer 21 Diaphragm 22 Anode 23 Anode compartment 24 Cathode 25 Cathode compartment 26 Alkaline water storage tank 27 Acid water storage tank 30 Alkaline water 31 Acid water 32, 33 Switching valve 40 Oxygen-free tank 41 Drainage 43 Slow stirring device 44 Lid

Claims (3)

[Claims] 1. A membrane separation activated sludge method used for treating raw wastewater containing an organic substance, wherein a mixed solution containing a sludge-like substance generated in an aeration tank is immersed in the aeration tank. Filtration is performed using a membrane module to obtain treated water that is membrane permeated water, and, of alkaline water and acidic water produced by a diaphragm type electrolyzer, alkaline water is supplied to the membrane module secondary side to perform membrane cleaning. And then permeating the mixed solution in the aeration tank through the primary side of the membrane module, and allowing the acidic water to flow into the permeated water. 2. A membrane separation activated sludge method used for treating raw wastewater containing an organic substance and a nitrogen compound, wherein said activated sludge method comprises a step between an oxygen-free tank provided upstream of an aeration tank and said aeration tank. By circulating the mixed solution containing the sludge-like reactant generated in the aeration tank, the decomposition reaction and the nitrification and denitrification of the organic substances and nitrogen compounds contained in the raw wastewater are performed, and the While filtering the mixed solution using a membrane module immersed in the mixed solution to obtain treated water that is a membrane permeated water, alkaline water and alkaline water produced by a diaphragm type electrolysis apparatus are converted to alkaline water. After being supplied to the secondary side of the membrane module and subjected to membrane cleaning, it is allowed to pass through the primary side of the membrane module and flow into the mixed solution in the aeration tank, and the acidic water is allowed to pass through the membrane permeated water and / or the non-aqueous solution. Flow into the drain of the oxygen tank A membrane separation activated sludge method characterized by being introduced. 3. The membrane washing with the alkaline water is performed when the filtration of the mixed solution by the membrane module is stopped.
Or a membrane separation activated sludge method according to 2.