JPH1119695A - Membrane utilizing waste water treatment and water purifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the membrane utilizing waste water treating method by which the settled sludge drawn off from a settling basin and the backwashing water discharged from a filter basin are concentrated to a stabilized sludge concn. throughout the year without needing a large site area and to furnish a water purifier using the method. SOLUTION: The raw water taken in from rivers, etc., is flocculated, settled, filtered and purified. Namely, the sludge settled on the bottom of a settling basin during the treatment and the waste backwashing water discharged from a filter basin are mixed, the mixture is supplied to a membrane treating device 7 and separated into membrane-filtered water and sludge, and the filtered water is utilized as service water. The sludge is concentrated to 5-10% solid content and discharged from the membrane treating device. The concd. sludge has a stabilized solid content. In this case, >=2 kinds of the org. membranes having a different packing rate from one another are used as the membrane module used in the treating device, and an internal pressure-type crossflow system is introduced in the membrane treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane-based wastewater treatment method for wastewater generated in the treatment of raw water such as rivers, and a water treatment apparatus using the treatment method. Regarding the treatment of settled sludge withdrawn and backwash wastewater discharged from filtration ponds, it relates to a membrane-based wastewater treatment method using a membrane module, and using this treatment method, stable sludge treatment and effective use of backwash wastewater. The present invention relates to a water purification treatment apparatus in which the water recovery rate is improved by aiming at water purification.

[0002]

2. Description of the Related Art Conventionally, in a water purification plant which performs coagulation sedimentation / filtration treatment, water purification treatment is performed according to a treatment flow as shown in FIG. First, referring to the same figure, the water purification process will be described. After receiving the raw water at the landing well 21, it is led to a chemical mixing pond 22 to which a coagulant is added and mixed.
The suspended components in the raw water are aggregated in the floc formation pond 23. The water to be subjected to the coagulation treatment is supplied to the sedimentation basin 24 and solid-liquid separated into sedimentation sludge and supernatant water. The supernatant water obtained in the sedimentation basin 24 is further chlorinated through the filtration basin 25 and supplied as tap water.

Next, the sludge treatment will be described. The settled sludge pulled out from the bottom of the sedimentation basin 24 is discharged from the sludge basin 26.
After being sent to the condensing tank 27, it is concentrated by gravity sedimentation and supplied to a dehydrator 28. In addition, filtration pond 2
The backwash wastewater discharged by the backwash operation periodically performed in 5 is sent to a drainage pond 29 and separated into settled sludge and supernatant water. The settled sludge is supplied to the sludge pond 26, and the supernatant water is returned to the landing well 21 together with the supernatant water obtained in the sludge pond 26 and the concentration tank 27.

[0004]

In the conventional water purification treatment shown in FIG. 6, the concentration of the concentrated sludge in the thickening tank 37 for thickening the sludge is susceptible to seasonal fluctuations. In the case of the above, it is about 2%. For this reason, the volume and the solid concentration of the concentrated sludge mixture supplied from the concentration tank 37 to the dehydrator 38 fluctuate significantly. Therefore, the processing capacity of the dehydrator 38 needs to be able to process a large-capacity, low-concentration mixed sludge mixed solution in winter, and the equipment becomes large in size, which is not economical.

[0005] From the viewpoint of improving the water recovery rate, the supernatant water in the sludge pond 36, the drain pond 39, and the concentration tank 37 is returned to the landing well 31 as needed. However, there is a concern that the quality of the supernatant water may deteriorate with the deterioration of the raw water quality, and it is necessary to increase the amount of the coagulant added to the chemical mixing pond 32 in order to prevent the deterioration of the supernatant water quality. is there. As a result, the amount of settled sludge in the settling basin 34 increases, and the load of the dehydration step also increases. In particular, in raw water where chlorine-resistant pathogenic microorganisms such as Cryptosporidium exist, Cryptosporidium may also be present in the supernatant water returned to the landing well and may gradually accumulate in the system. Is not preferred.

[0006] Therefore, it is necessary to reduce the turbidity of the water returned to the landing well 31 as much as possible to prevent chlorine-resistant pathogenic microorganisms such as cryptosporidium from circulating in the system. An important operation guideline for removing chlorine-resistant pathogenic microorganisms such as Cryptosporidium in the main flow of coagulation sedimentation-sand filtration is that the turbidity of coagulation sedimentation treatment water is as low as 0.1 degrees or less. And to take measures to prevent the growth of chlorine-resistant pathogenic microorganisms.

However, in practice, measures are taken to cope with this by increasing the amount of coagulant added and increasing the frequency of pulling out the settling sludge in the sedimentation basin.
This leads to an increase in the amount of sludge to be treated. Even when such an operation is performed, when the extracted sludge is concentrated in a conventional gravity type concentration tank 37 and the supernatant water is returned to the landing well 31 or the like, the supernatant water is not necessarily used. Since it is not always in a clear state, there is a problem that turbid components including chlorine-resistant pathogenic microorganisms circulate in the water purification system.

Next, a method for condensing the settled sludge in the water purification plant is disclosed in Japanese Patent Application Laid-Open No. 8-257600. According to this prior document, water sludge settled at the bottom of a chemical sedimentation tank is injected into an internal pressure type membrane module to perform membrane filtration, and the membrane concentrated sludge concentrated from the membrane module is intermittently supplied to a thickener by physical washing. And a method of concentrating to a concentration that allows dehydration. However, in this prior document, since a ceramic inorganic membrane is used as the membrane module, the membrane may be damaged when the membrane module is replaced. Moreover, since the physical washing interval is set to 2 hours or more in the dead-end type filtration operation, sediment sludge adheres to the membrane surface and causes clogging in a relatively short period of time. , It is necessary to perform chemical cleaning, and there is a problem that the cost and labor for the chemical cleaning operation are increased, leading to an increase in cost. Further, the ceramic membrane is expensive, and has a drawback that the equipment cost rises. Furthermore, since the membrane-concentrated sludge is supplied to the thickener to gravity-concentrate and take out the final sludge after solid-liquid separation, it is difficult to constantly send a stable sludge concentration throughout the year to the dehydrator as described above. There is a problem.

The present invention has been completed as a result of intensive studies to overcome the problems of the prior art as described above.
A membrane-based wastewater treatment method and a wastewater treatment method capable of concentrating sediment sludge drawn out from a sedimentation tank and backwash wastewater discharged from a filtration pond to a stable sludge concentration throughout the year without requiring a large site area. The purpose is to provide a water purification device that utilizes the water purification device. Furthermore, in addition to the above objects, the water recovery rate is improved, and the chlorine-resistant pathogenic microorganisms and the like do not circulate in the water purification system, so that an economical membrane-based wastewater treatment method and a water purification device using the treatment method are provided. It is intended to provide.

[0010]

Means for Solving the Problems In order to solve the above problems, the invention of claim 1 is a method for purifying raw water taken from a river or the like by coagulating sedimentation / filtration, and purifying the sedimentation pond in the process. The settled sludge settled at the bottom and the backwash wastewater discharged from the filtration pond are mixed and supplied to the membrane treatment device, separated into membrane filtrate and sludge by the membrane treatment device, and the membrane filtrate is supplied to the tap water. It is used as water, and the solid concentration of the sludge is 5-10
%. In this configuration, sediment sludge generated in the water purification treatment by coagulation sedimentation / filtration treatment and backwash wastewater are treated with a membrane treatment device, and the membrane filtration water is used as tap water after chlorine disinfection and discharged from the membrane treatment device. The concentrated sludge to be produced has a stable solid substance concentration and is dehydrated by a dehydrator.

According to a second aspect of the present invention, in the membrane-based wastewater treatment method according to the first aspect, two or more types of organic membranes having different membrane filling rates are used as membrane modules used in the membrane treatment apparatus. This is a membrane-based wastewater treatment method characterized by the following characteristics. In this configuration, clogging of the membrane is prevented from occurring in a short period of time by setting the membrane filling rate of the membrane module in the membrane processing apparatus to two or more types.

According to a third aspect of the present invention, in the membrane-based wastewater treatment method according to the first aspect, two or more types of organic membranes having different membrane inner diameters are used as membrane modules used in the membrane treatment apparatus. This is a feature of the membrane wastewater treatment method. In this configuration, clogging of the membrane is prevented from occurring in a short period of time by setting the membrane inner diameter of the membrane module in the membrane processing apparatus to two or more types.

According to a fourth aspect of the present invention, in the membrane-based wastewater treatment method according to the first, second or third aspect, the membrane treatment by the membrane treatment apparatus is performed by an internal pressure type cross flow system. This is a wastewater treatment method that can be used. With this configuration, it is possible to prevent the film clogging from occurring in a short period of time.

[0014] The invention of claim 5 is based on claims 1 and 2,
5. The membrane-based wastewater treatment method according to 3 or 4, wherein the membrane filtered water obtained from the membrane treatment device is used as tap water. In this configuration, even if the membrane filtration water by the membrane treatment device has achieved the standard of tap water, and the filtration pond is sufficiently washed,
A decrease in water recovery can be prevented.

A sixth aspect of the present invention is a water purification apparatus wherein the membrane-based wastewater treatment method according to any one of the first to fifth aspects is used for wastewater treatment in a water supply system. In this configuration, the sludge pond can be omitted to mix the settled sludge and the backwash wastewater, so that the site area can be reduced and the mixed sludge is subjected to membrane treatment by the membrane treatment device. In addition, it is not affected by seasonal fluctuations, and it is possible to obtain concentrated sludge of high concentration that is almost constant at all times. Since the quality and quantity of the concentrated sludge injected into the dehydrator is almost constant, the capacity of the dehydrator has to be reduced after the conventional sludge concentration treatment, which had to accept low-concentration and large-volume concentrated sludge in winter. It is economical because it can be made smaller than the capacity of the machine. Furthermore, since the membrane treatment by the membrane concentrator is performed by the internal pressure type cross flow method, the sedimentation sludge does not cause clogging in a relatively short period of time, and is effective in extending the interval between chemical washings. In addition, since the supernatant water that has been conventionally returned to the landing well is subjected to membrane treatment, the membrane filtered water can be used as tap water, and the water recovery rate can be improved.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a system diagram showing an embodiment of a membrane-based wastewater treatment method of the present invention and a water purification apparatus using the membrane-based wastewater treatment method. FIG. 2 is a diagram showing a film processing apparatus.

In FIG. 1, the water purification apparatus mainly includes a landing well 1 for receiving raw water, a chemical mixing pond 2 for adding and mixing a flocculant to the raw water, a floc forming pond 3 for performing a flocculation reaction, and a sediment sludge. The sedimentation basin 4 for solid-liquid separation into clear water, the filtration basin 5 for completely removing fine flocs that are not solid-liquid separated in the sedimentation basin 4, the sedimentation sludge drawn from the bottom of the sedimentation basin 4, and the filtration basin 5 periodically. It comprises a drainage pond 6 for receiving the backwash wastewater discharged by the backwashing operation to be performed, a membrane treatment device 7 for condensing sludge and obtaining clear membrane filtered water, and a dehydrator 8 for dewatering the membrane-concentrated sludge. Have been. As shown in FIG. 2, the membrane processing device 7 includes a circulation tank 9, a stirrer 10, a circulation pump 11, and a membrane module 12, and includes a backwash unit 20 that sends backwash water to the membrane module 12. . 13 to 19 indicate piping, and V indicates a valve.

First, water purification treatment will be described with reference to FIG. 1. After raw water is received by a landing well 1, the raw water is guided to a chemical mixing pond 2 to which a flocculant is added, and suspended in raw water in a floc forming pond 3. Aggregate the components. The water to be subjected to the coagulation treatment is supplied to the sedimentation basin 4 and solid-liquid separated into sedimentation sludge and supernatant water. The supernatant water obtained in the sedimentation basin 4 passes through the filtration basin 5 and is further subjected to chlorination to be supplied as tap water.

In this water purification treatment, a membrane-based wastewater treatment using a membrane module is performed.
Settling sludge pulled out from the bottom of the settling tank 4 and the filtration tank 5
The mixed sludge with the backwash wastewater discharged by the backwash operation periodically performed in the above is sent to the drainage pond 6, and the mixed sludge water in the drainage pond 6 is sent to the membrane treatment device 7 for treatment, and the sludge and the membrane are treated. It is separated into filtered water. The membrane filtered water obtained from the membrane treatment device 7 is subjected to chlorination and supplied as tap water, and the membrane concentrated sludge obtained intermittently or continuously from the membrane treatment device 7 is sent to the dehydrator 8 to be dewatered. You.

Further, referring to FIG. 2, the membrane-based wastewater treatment will be described in detail. In the figure, first, settling sludge is supplied from a drainage pond 6 to a circulation tank 9 having a stirrer 10 via a pipe 13. The settled sludge is sent to the membrane module 12 through the pipe 14 by the circulation pump 11 and subjected to membrane filtration, and then the circulating water is returned to the circulation tank 9 through the pipe 15. On the other hand, the membrane filtered water is sent to the chlorination treatment step through the pipe 16. Further, in a backwashing operation that is periodically performed, membrane backwash water obtained by washing the inside of the membrane module 12 through the pipe 17 by the backwash means 20 is returned to the circulation tank 9 through the pipe 18. You. In this way, the sludge concentrated in the circulation tank 9 is intermittently or continuously extracted by the valve V via the pipe 19 and then sent to the dehydrator 8. The membrane module 12 of the membrane treatment device 7 uses an organic membrane of a microfiltration membrane or an ultrafiltration membrane. As the backwashing means 20, it is preferable to perform backflow water washing using raw water or membrane filtered water, backpressure washing using pressurized gas, or a combination thereof.

When the filtration method in the membrane treatment apparatus is an external pressure type or internal pressure type dead end filtration (total filtration), clogging occurs in a relatively short period of time due to concentrated sludge adhering to the membrane surface, and frequently occurs. It is necessary to perform chemical cleaning with acid or alkali, which is not economical. Therefore, the cross-flow system in which the concentrated sludge adhering to the membrane surface is separated and circulated, the clogging of the membrane module 12 is suppressed, and the frequency of chemical cleaning can be reduced. At that time, when water is passed using an external pressure type or internal pressure type membrane module, when the power of the circulation pump 11 is the same, the internal pressure type can set the membrane surface flow rate higher than the external pressure type. In addition, sludge deposits on the membrane surface are reduced, and clogging of the membrane is suppressed. From the above, the internal pressure type cross flow method is adopted as the filtration method in the membrane concentrator 7.

Further, in the membrane concentrator 7 of the present embodiment,
When the concentration of sludge supplied to the membrane concentrator 7 is as high as 2% or more as the membrane module 12, the membrane filtration is performed by a single-stage system using one type of organic membrane. When the concentration of the sludge is as low as 2% or less, in order to reduce the power cost of the circulation pump 11 as much as possible, two or more types of organic membranes having different membrane filling rates and membrane inner diameters are used. Is subjected to a membrane filtration treatment in a multistage system in which the solid concentration of sludge is increased stepwise. Membrane module 1 at this time
2 is a membrane module in which the membrane filling ratio is 20 to 70% and the membrane inner diameter is 1 to 4 mm.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to these examples.

(Embodiment 1) This embodiment will be described with reference to the processing flow shown in FIG. Raw water is subjected to coagulation sedimentation / filtration treatment as described above, and is used as tap water. In this treatment step, the settling sludge from the sedimentation basin 4 and the backwash wastewater from the filtration basin 5 are sent to the drainage basin 6,
After being temporarily stored in the drainage pond 6, it is sent to the membrane processing apparatus 7 and filtered by the internal pressure type cross flow method. In this membrane-based wastewater treatment method, the treatment is carried out by a membrane treatment device 7 based on the specifications shown in Table 1 below, and the concentration of the sludge treated by the membrane treatment device 7 is 2.1%. It is. Note that PVDF in Table 1 is a fluororesin-based polyvinylidene fluoride, and the film processing apparatus 7 is an organic-based film module. The following PVDF is a similar substance.

[0025]

[Table 1]

FIG. 3 shows the daily change of the average filtration pressure in the membrane processing apparatus 7 of this embodiment. In the figure, the horizontal axis indicates the number of days of water passage, and the vertical axis indicates the average filtration pressure. Here, the average filtration pressure represents a pressure obtained by subtracting the membrane outlet pressure from the average value of the membrane inlet pressure and the circulating water pressure. Table 2
Shows the dewatering performance of the membrane-concentrated sludge obtained by the membrane treatment device 7 of the present example and the concentrated sludge obtained by the existing equipment in a dehydration test using a dehydrator 8. In addition, Table 3 shows the results of water quality analysis of the membrane filtered water obtained by the membrane treatment device 7 of this example.

[0027]

[Table 2]

[0028]

[Table 3] *) Is the target value of the comfortable water quality item

As is clear from the above results, as shown in Table 2, in the conventional example, the dewatering time required 11 hours and the water content of the dewatered cake was 52.3%. In the membrane-concentrated sludge by the membrane treatment device 7, the dewatering time is 5 hours and the moisture content of the dewatered cake is 52.2%. According to the membrane treatment device 7 of the present embodiment, the sludge concentration is good. This shows that the membrane-concentrated sludge has a stable solid substance concentration. Further, as is clear from Table 3, the quality of the membrane filtered water discharged from the membrane treatment device 7 satisfies the tap water quality standard.

(Embodiment 2) This embodiment will be described with reference to the processing flow shown in FIG. Raw water is subjected to coagulation sedimentation / filtration treatment as described above, and is used as tap water. In this treatment step, the settling sludge from the sedimentation basin 4 and the backwash wastewater from the filtration basin 5 are sent to the drainage basin 6,
After being temporarily stored in the drainage pond 6, it is sent to the membrane processing apparatus 7 and filtered by the internal pressure type cross flow method. In this membrane-based wastewater treatment method, membrane treatment is performed by a membrane treatment device 7 based on the specifications shown in Table 4 below, and the concentration of sludge treated by the membrane treatment device 7 is 0.4%.
Mixed sludge.

[0031]

[Table 4]

FIG. 4 shows the daily change of the average filtration pressure by the membrane treatment apparatus 7 according to the second embodiment. The horizontal axis of the figure shows the number of days of water passage, and the vertical axis shows the average filtration pressure. . Table 5 shows the results obtained by performing a dehydration test on the membrane-condensed sludge obtained by the present example and the concentrated sludge obtained by the existing equipment as dewatering performance. Table 6 shows the results of water quality analysis of the membrane filtered water obtained in this example.

[0033]

[Table 5]

[0034]

[Table 6] *) Is the target value of the comfortable water quality item

As is clear from the above results, Table 5 shows that in the conventional example, the dewatering time was 16 hours and the water content of the dewatered cake was 51.5%, whereas the concentrated sludge by the membrane treatment device 7 was used. The dehydration time was 5 hours, and the water content of the dehydrated cake was 53.3%. Thus, according to the membrane processing apparatus 7 of the present embodiment, it is shown that the sludge concentration is good. Further, the water quality of the membrane filtered water discharged from the membrane treatment device 7 satisfies the tap water quality standard, as is clear from Table 6.

(Embodiment 3) This embodiment will be described with reference to the processing flow shown in FIG. Raw water is subjected to coagulation sedimentation / filtration treatment as described above, and is used as tap water. In this treatment step, the settling sludge from the sedimentation basin 4 and the backwash wastewater from the filtration basin 5 are sent to the drainage basin 6,
After being temporarily stored in the drainage pond 6, it is sent to the membrane processing apparatus 7 and filtered by the internal pressure type cross flow method. In this membrane-based wastewater treatment method, membrane treatment is performed by the membrane treatment device 7 based on the specifications shown in Table 7 below, and the sludge concentration treated by the membrane treatment device 7 is 0.3%.
Mixed sludge.

[0037]

[Table 7]

FIG. 5 shows the change over time of the average filtration pressure in the membrane treatment apparatus 7, where the horizontal axis represents the number of days of water passage and the vertical axis represents the average filtration pressure. Table 8 shows the dehydration performance obtained by performing a dehydration test on the membrane concentrated sludge obtained by the method of the present invention and the concentrated sludge obtained by existing equipment. In addition, Table 9 shows the results of the water quality analysis of the membrane filtered water obtained in this example.

[0039]

[Table 8]

[0040]

[Table 9] *) Is the target value of the comfortable water quality item

As is clear from the above results, Table 8 shows that the conventional example requires 15 hours for the dehydration time and the moisture content of the dewatered cake is 50.3%, while the concentrated sludge by the membrane treatment apparatus 7 is used. The dehydration time was 4 hours, and the water content of the dehydrated cake was 52.6%. Thus, according to the membrane processing apparatus 7 of the present embodiment, it is shown that the sludge concentration is good. Further, as is clear from Table 9, the quality of the membrane filtered water discharged from the membrane treatment device 7 satisfies the tap water quality standard.

As described above, as is clear from FIGS. 3 to 5, by using the method of the present invention, it is possible to stably pass water without increasing the average filtration pressure in the membrane treatment apparatus. It was revealed. Further, as is clear from Tables 2, 5 and 8, the sludge concentration obtained by the method of the present invention is 2.0 to 3.6 as compared with the existing equipment.
The dewatering time by the dehydrator is reduced by 27-45% compared to the case of existing equipment, and it is possible to obtain concentrated sludge having excellent dewatering properties. Further, as is clear from Tables 3, 6, and 9, according to the method of the present invention, the membrane filtered water quality satisfies the tap water quality standard, and the membrane filtered water can be used as tap water. Indicates that you can do it.

[0043]

As described above, according to the membrane-based wastewater treatment method of the present invention, the wastewater sludge pond can be omitted because the mixed sludge and the backwash wastewater are treated. In addition, the site area can be reduced and the solid matter concentration (5
(~ 10%) sludge can be driven into the dehydrator, which has the advantage of greatly reducing the dehydration time in the dehydrator. Accordingly, there is an effect that the capacity of the dehydrator in the case of the conventional gravity concentration method can be reduced.

Further, according to the present invention, in the membrane treatment apparatus, the mixed sludge is subjected to the membrane filtration by the internal pressure type cross flow method, so that the average filtration pressure can be continuously passed without an abrupt increase in the average filtration pressure. Since clogging does not occur in a relatively short time and the interval between chemical cleaning operations is long, there is an advantage that the cost and labor for the chemical cleaning operation can be reduced. Furthermore, by treating the supernatant water, which has been conventionally returned to the landing well, with membrane treatment, it becomes possible to use the membrane filtered water as tap water, thereby improving the water recovery rate. Have. Furthermore, even if the backwashing step of the filtration pond is performed frequently, since the backwash water is recovered, the purification of the filtration pond is effectively performed, and the water quality of the tap water has an effect of making the quality of the tap water comfortable. .

[Brief description of the drawings]

FIG. 1 is a system diagram for explaining a water purification apparatus and a membrane-based wastewater treatment method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a film processing apparatus according to an embodiment of the present invention.

FIG. 3 is a view showing an average filtration pressure of the membrane processing apparatus of Example 1.

FIG. 4 is a view showing an average filtration pressure of the membrane processing apparatus of Example 2.

FIG. 5 is a view showing an average filtration pressure of the membrane processing apparatus of Example 2.

FIG. 6 is a system diagram for explaining a conventional water purification apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Landing well 2 Chemical mixing pond 3 Floc formation pond 4 Sedimentation pond 5 Filtration pond 6 Drainage pond 7 Membrane treatment device 8 Dehydrator 9 Circulation tank 10 Stirrer 11 Circulation pump 12 Membrane module

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C02F 1/44 C02F 1/44 H 1/52 1/52 Z

Claims (6)

[Claims] Claims 1. Raw water taken from a river or the like is subjected to coagulation and sedimentation.
Upon purification by filtration, the sedimentation sludge settled at the bottom of the sedimentation basin in the treatment process and backwash wastewater discharged from the filtration basin are mixed and supplied to the membrane treatment device, and the membrane is treated by the membrane treatment device. A membrane-based wastewater treatment method comprising separating filtrated water and sludge, using the membrane filtered water as tap water, and concentrating the solid content of the sludge to 5 to 10%. 2. The membrane-based wastewater treatment method according to claim 1, wherein two or more types of organic membranes having different membrane filling rates are used as membrane modules used in the membrane treatment apparatus. Wastewater treatment method. 3. The membrane-based wastewater treatment method according to claim 1, wherein two or more types of organic membranes having different membrane inner diameters are used as a membrane module specified in the membrane treatment apparatus. Processing method. 4. The membrane-based wastewater treatment method according to claim 1, 2 or 3, wherein the membrane treatment by the membrane treatment device is performed by an internal pressure type cross-flow method. 5. The membrane-based wastewater treatment method according to claim 1, wherein the membrane filtered water obtained from the membrane treatment device is used as tap water. Processing method. 6. A water purification apparatus, wherein the membrane-based wastewater treatment method according to claim 1 is used for wastewater treatment in a water supply system.