JP3859402B2 - Filtration basin washing wastewater treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating filtration basin washing wastewater in a water purification treatment facility.
[0002]
[Prior art]
Conventionally, as a water purification treatment facility, for example, there is one shown in FIG. In FIG. 4, raw water 1 is received by a landing well 2 and then led to a coagulating sedimentation basin 3, and a coagulant is added to coagulate and precipitate suspended components in the raw water. The supernatant water of the coagulation sedimentation basin 3 is guided to the sand filtration basin 4, and the filtered treated water is guided to the sterilization tank 5 and supplied as tap water after chlorination.
[0003]
At the time of backwashing the sand filtration basin 4, the backwashing is performed using the treated water as washing water, and the washing drainage returns the drainage basin 6 to the landing well 2. When there are a plurality of sand filtration ponds 4, use wash water from other sand filter ponds 4 or store the wash water from the sand filter pond 4 in a wash water tank provided separately. Use. In many cases, the drainage basin 6 is constantly stirred by a stirrer in order to prevent sedimentation of sludge.
[0004]
[Problems to be solved by the invention]
In the above-described configuration, when the washing wastewater stored in the drainage basin 6 is returned to the landing well 2, the return water has high turbidity and a high concentration of manganese, etc., which may temporarily adversely affect the water purification system. is there. Furthermore, since pathogenic microorganisms such as Cryptosporidium removed in the sand filtration pond 4 are also returned to the receiving well together with the return water, these pathogenic microorganisms may circulate and concentrate in the water purification system.
[0005]
On the other hand, when membrane filtration water is used as tap water after membrane filtration of washing wastewater, there is a possibility that washing water with high turbidity may be mixed into tap water when there is a membrane breakage or the like. When this membrane filtrate is returned to the landing well 2, the raw water turbidity is temporarily lowered, which may affect the optimum injection rate of the coagulant in the coagulation sedimentation basin 3. Furthermore, it is wasteful as a water purification treatment system to return the membrane filtered water having a quality which can be used as tap water to the landing well and mix it with raw water.
[0006]
The present invention solves the above-mentioned problems, and provides a method for treating the filtration basin washing wastewater in a water purification treatment facility that filters the washing effluent of the filtration basin and reuses this membrane filtrate as the washing water of the filtration pond. The purpose is to do.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention according to claim 1 is to temporarily store the washing drainage of the filtration pond in the water treatment facility in the drainage basin, and filter the washing drainage of the drainage pond with a membrane filtration device. Is stored in a wash water tank as wash water, the wash water of the wash water tank is supplied to the filter basin to wash the filter basin, and the wash wastewater is returned to the drain basin for circulation reuse.
[0008]
With the configuration described above, since the washing water system is separated from the water purification system, pathogenic microorganisms in the washing wastewater are completely separated from the water purification system by membrane filtration, and are not returned to the water purification system. Since the pond is washed once every 1 to 2 days, even if the membrane is damaged, the washing is temporarily stopped, and leakage into the tap water can be prevented by taking measures during that time. Since the washing water is membrane filtration water, it becomes washing water with lower turbidity than when using normal sand-filtered treated water, and since the washing effect is high and the turbidity remaining in the filtration pond is less, Turbidity leakage in the water purification process immediately after washing can be reduced.
[0009]
The filtration basin is washed once or twice a day, and since a large amount of washing wastewater is generated during washing, the washing wastewater is temporarily stored in the drainage basin and the washing wastewater is processed at a predetermined constant flow rate in the membrane filtration device. Thus, the cleaning water regenerated from the cleaning wastewater can be secured in the cleaning water tank in an amount necessary for the next cleaning, and the cleaning water can be recycled and reused.
The present invention according to claim 2 uses the discharge pressure of a membrane filtration pump that applies a driving pressure to the membrane filtration device to pump the membrane filtrate into the washing tank as washing water, and uses the washing water in the washing tank as the head of the washing tank. The pressure is supplied to the filtration basin by pressure, and the filtration basin is washed. The washing wastewater is returned to the drainage basin and recycled.
[0010]
With the configuration described above, the head pressure of the washing water tank can be used as the driving force for supplying cleaning water to the filtration pond, and the discharge pressure of the membrane filtration pump can be used as the driving force for supplying filtered water to the washing water tank. Can be used effectively.
According to a third aspect of the present invention, the membrane filtration apparatus includes an external pressure membrane module immersed in a drainage basin, a membrane filtration pump that applies a negative pressure as a driving pressure to the external pressure membrane module, and a lower portion of the external pressure membrane module. The air diffuser is arranged and a blower connected to the air diffuser.
[0011]
With the above configuration, a membrane filtration device can be configured by immersing an external pressure membrane module in an existing drainage pond, and a separate site for performing membrane filtration is not required. Also, the upward flow of gas-liquid mixing caused by the air diffused from the diffuser acts as a sweep on the membrane surface of the external pressure membrane module, and the sweep for this membrane surface cleaning becomes a bubble swirl flow. Since the drainage pond is agitated, there is no need for a drainage agitator.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, in a water purification system that purifies raw water 11, raw water 1 is received by a landing well 12 and then guided to a coagulation sedimentation basin 13. A coagulant is added to the coagulation sedimentation basin 13 and suspended components in the raw water. Flocculate and precipitate.
[0013]
Thereafter, the supernatant water separated in the coagulation sedimentation basin 13 is guided to the sand filtration basin 14 and subjected to sand filtration, and the treated water subjected to the sand filtration is guided to the disinfection tank 15 and supplied as tap water after chlorination.
The sand filtration basin 14 is washed once or twice a day. In the washing water system, a large amount of washing wastewater generated during backwashing of the sand filtration basin 14 is temporarily stored in the drainage basin 16, and a driving pressure is applied to the membrane filtration device 17 by the membrane filtration pump 18. Process by suction filtration at a predetermined constant flow rate. A membrane filtration pump 18 that applies a driving pressure to the membrane filtration device 17 may be provided in front of the membrane filtration device 17 so that the washing wastewater in the drainage basin 16 is pressure filtered and processed.
[0014]
This membrane filtered water is stored in the washing water tank 19 as washing water, and the washing water in the washing water tank 19 is supplied to the sand filtration pond 14 by the washing pump 20 or by the head difference of the washing water tank without providing the washing pump 20. The filtration basin 14 is washed. At this time, if necessary, a cleaning chemical is added to the cleaning water. The washing wastewater is returned to the drainage basin 16 and the washing wastewater is regenerated into washing water, and only the amount necessary for the next washing is secured in the washing water tank 19 to recycle and reuse the washing water.
[0015]
Thus, since the washing water system is separated from the water purification system, the pathogenic microorganisms contained in the washing drainage of the sand filtration pond 14 are completely separated from the water purification system by membrane filtration. Even if the membrane is broken, it can be treated while washing is stopped, and there is no leakage into tap water.
Further, since the washing water supplied to the sand filtration pond 14 is membrane filtration water, the washing water has a lower turbidity than when the sand-filtered treated water is used as washing water, and the washing effect is enhanced. Therefore, since the turbidity remaining in the sand filtration pond 14 is reduced, turbidity leakage in the water purification system immediately after washing can be reduced.
[0016]
FIG. 2 shows another embodiment of the present invention. In FIG. 2, the washing water tank 19 is provided higher than the sand filtration basin 14 or its lower limit water level is higher than the sand filtration basin 14, and the membrane filtration water of the membrane filtration device 17 is discharged from the membrane filtration pump 18. The water is pumped to the washing water tank 19 using the pressure.
The sand filtration basin 14 is washed by supplying the wash water composed of the membrane filtration water of the wash water tank 19 to the sand filtration basin 14 using the head pressure of the washing water tank 19. The washing wastewater is returned to the drainage basin 16 and recycled.
[0017]
With this configuration, the head pressure of the washing water tank 19 is used as the driving force for supplying the washing water to the sand filtration pond 14, and the discharge pressure of the membrane filtration pump 18 is used as the driving force for supplying the membrane filtration water to the washing water tank 19. And can use energy effectively.
In any of the above-described embodiments, various types of membrane filtration devices 17 can be used. However, as a preferable configuration, as shown in FIG. An external pressure membrane module 21 immersed in the membrane, a membrane filtration pump 18 that applies a negative pressure to the external pressure membrane module 21 as a driving pressure, an air diffuser 22 disposed below the external pressure membrane module 21, and an air diffuser 22 The one provided with the blower 23 connected to is used. The external pressure membrane module 21 is made of a ceramic membrane or an organic membrane having a pore diameter of about 0.1 μm or less.
[0018]
In this structure, the membrane filtration apparatus 17 can be comprised by immersing an external pressure type membrane module in the existing drainage pond 16, and the site for performing a membrane filtration process is not required separately. Further, the upward flow of the gas-liquid mixture caused by the air diffused from the diffuser 22 acts as a sweep on the membrane surface of the external pressure membrane module 21, and the sweep for cleaning the membrane surface is a bubble swirl flow. Since the drainage basin 16 is stirred, the stirrer for the drainage basin 16 becomes unnecessary.
[0019]
【The invention's effect】
As described above, according to the present invention, the washing water system is formed separately from the water purification system, and the pathogenic microorganisms in the washing waste water are completely separated from the water purification system by membrane filtration of the washing water. By using membrane filtered water as washing water, the effect of washing can be enhanced and leakage of turbidity in water purification treatment immediately after washing can be suppressed. A large amount of washing wastewater once stored in the drainage basin is treated with a membrane filtration device at a predetermined constant flow rate and regenerated into washing water, and only the amount necessary for the next washing is secured in the washing water tank, thereby circulating the washing water. Can be reused.
[0020]
Moreover, energy can be used effectively by supplying wash water to the filtration basin using the head pressure of the wash water tank and supplying filtered water to the wash water tank using the discharge pressure of the membrane filtration pump. By using an external pressure membrane module immersed in the tank, it is possible to configure a membrane filtration device in an existing drainage pond, eliminating the need for a separate site for membrane filtration treatment, and the membrane of the external pressure membrane module Since the sweep acting on the surface becomes a bubble swirl flow and stirs the drainage basin, a stirrer for the drainage basin becomes unnecessary.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a flow sheet showing a method for treating filtration basin washing wastewater in an embodiment of the present invention.
FIG. 2 is a flow sheet showing a method for treating filtration basin washing wastewater according to another embodiment of the present invention.
FIG. 3 is a schematic diagram showing the configuration of a membrane filtration device.
FIG. 4 is a flow sheet showing a conventional water purification treatment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Raw water 12 Landing well 13 Coagulation sedimentation tank 14 Sand filtration tank 15 Disinfection tank 16 Drainage tank 17 Membrane filtration apparatus 18 Membrane filtration pump 19 Washing water tank 20 Washing pump

Claims (3)

The washing drainage of the filtration pond in the water treatment facility is temporarily stored in the drainage basin, the washing drainage of the drainage pond is filtered with a membrane filtration device, the membrane filtrate is stored in the washing tank as washing water, and the washing water in the washing tank is filtered. A method for treating filtration basin wastewater, which is supplied to a pond to wash the filtration basin, and the washing wastewater is returned to the drainage basin for recycling. Using the discharge pressure of the membrane filtration pump that gives the driving pressure to the membrane filtration device, the membrane filtration water is pumped up as washing water to the washing tank, and the washing water from the washing tank is supplied to the filtration basin at the head pressure of the washing tank and filtered. 2. The method for treating filtration basin washing wastewater according to claim 1, wherein the pond is washed, and the washing wastewater is returned to the drainage pond and recycled. The membrane filtration apparatus includes an external pressure membrane module immersed in a drainage basin, a membrane filtration pump that applies a negative pressure to the external pressure membrane module as a driving pressure, an air diffuser disposed below the external pressure membrane module, The processing method of the filtration basin washing waste water of Claim 1 or 2 which consists of a blower connected to the apparatus.

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