JPH08281082A - Washing method of immersion type membrane cartridge - Google Patents

Abstract

PURPOSE: To efficiently and economically wash an immersion type membrane cartridge without taking it out from a treating tank. CONSTITUTION: In the state that the immersion type membrane cartridge is immersed into an activated sludge mixture liquid 12 and filtering and aeration are stopped, a chemical liquid is poured into a permeated water flow path of the membrane cartridge 17 under low pressure to be held for a proper time, and next clean water is poured into the permeated water flow path while the chemical liquid is permeated to a liquid side to be treated, to replace the inside of the permeated water flow path with the clean water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a submerged membrane cartridge used for solid-liquid separation in activated sludge treatment of organic wastewater, sludge flocculation treatment and the like.

[0002]

2. Description of the Related Art Conventionally, in facilities that perform activated sludge treatment or sludge flocculation treatment of organic waste water, as a solid-liquid separation device for separating activated sludge or flocculated sludge, for example, it is immersed in a liquid to be treated in a treatment tank. A submerged membrane separator is installed. The immersion type membrane separation device is as shown in FIG. 2, in which a flat plate-shaped membrane cartridge 2 arranged vertically is arranged in parallel in a box-shaped casing 1 having an opening at the top and the bottom to form a membrane. Below the cartridge 2, an air diffuser 3 connected to an air supply means (not shown) such as a blower is arranged. In the membrane cartridge 2, the organic filtration membranes 5 and 5 are arranged on both sides of the membrane support 4, and the surface and the inside of the membrane support 4 covered with the filtration membrane 5 serve as a permeate flow channel 6. The passage 6 communicates with a suction means (not shown).

When solid-liquid separation is carried out, a suction pressure is applied to the permeate flow path 6 of the membrane cartridge 2 by a suction means so that suspended substances such as activated sludge are captured by the filtration membrane 5, and the filtration membrane is filtered. The permeated water that has passed through 5 and flowed into the permeated water channel 6 is taken out. At this time, aeration air is supplied through the air diffuser 3, and the surface of the filtration membrane 5 is washed by the piercing force of the bubbles of the aeration air and the upward flow of the liquid to be treated caused by the air lift action of the bubbles. There is.

[0004]

In the membrane cartridge 2 as described above, solid-liquid separation can be performed without applying a large suction pressure, so that energy can be saved, but chemical cleaning is necessary for various reasons such as a rapid change in concentration. When
Cleaning is difficult because it is immersed in the liquid to be treated.

Therefore, a method of taking out the whole of the immersion type membrane separation device (hereinafter referred to as a membrane separation device) from the treatment tank and immersing it in the chemical cleaning tank, or after discharging all the liquid to be treated in the treatment tank, Although a method of filling a chemical solution has been proposed, all of them require a large-scale device and are not economical. Moreover, such an outside of the filtration membrane (processing liquid side)
Since it is difficult to remove dirt such as sludge adhered to the surface of the filtration membrane in the chemical cleaning from the above, it is also necessary to perform physical cleaning with a sponge or the like.

Further, a cleaning method has also been proposed in which the membrane cartridge is immersed in the liquid to be treated, and the chemical liquid is injected into the inside of the filtration membrane (permeate flow path) and is leached to the outside (the side of the liquid to be treated). However, although this cleaning method has a high cleaning effect,
Since the chemical solution is injected while aerating, the leached chemical solution quickly diffuses into the liquid to be treated, and the chemical solution consumption increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to enable an immersion type membrane cartridge to be effectively and economically cleaned with a chemical solution.

[0008]

In order to solve the above-mentioned problems, a method for cleaning an immersion type membrane cartridge of the present invention comprises immersing the immersion type membrane cartridge in a liquid to be treated, stopping filtration, and aeration. In the stopped state, a chemical solution is injected into the permeate flow path of the membrane cartridge at a low pressure and held for an appropriate time, and then fresh water is injected into the permeate flow path to leach the chemical solution to the liquid to be treated side. The inside of the permeate flow channel is replaced with fresh water.

Further, in the method for cleaning a submerged membrane cartridge of the present invention, when two or more types of chemicals are used, the chemicals for each chemical are injected into the permeate passage of the membrane cartridge at a low pressure and held for an appropriate time. Next, a step of injecting fresh water into the permeate flow channel to allow the chemical solution to leaching to the liquid to be treated and replacing the permeate flow channel with fresh water is performed.

[0010]

According to the above construction, the chemical liquid is supplied to the permeate side at a low pressure and held for an appropriate period of time while the pressures on the treated liquid side and the permeated water side maintain a constant balance across the filtration membrane. Therefore, the chemical solution is evenly leached into the liquid to be treated from the entire membrane surface of the filtration membrane, and the entire surface of the filtration membrane is washed with the chemical solution. At this time, since the aeration is stopped, the chemical liquid leached to the side of the liquid to be treated does not immediately diffuse into the liquid to be treated, the cleaning effect by the liquid chemical is enhanced, and the consumption amount of the liquid chemical is reduced. After that, since the inside of the permeate flow channel is replaced with fresh water, the chemical liquid present in the permeate flow channel or in the filtration membrane is extruded toward the treated liquid side when the fresh water permeates into the treated liquid side. Therefore, the filtration membrane can be effectively and economically washed without taking out the entire immersion type membrane separation device or the membrane cartridge from the treatment tank, and the chemical liquid is prevented from being mixed with the permeated water after the filtration is restarted.

Further, for each chemical solution, the step of injecting and retaining the chemical solution in the permeated water channel and the step of replacing this chemical solution with fresh water are carried out, so that only the cleaning utilizing the characteristics of each chemical solution is performed. Instead, the reaction between the chemicals is avoided.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (Example 1) In FIG. 1, the activated sludge tank 11 is
Activated sludge mixed liquid 12 obtained by mixing activated sludge with water to be treated
Is stored and immersed in the activated sludge mixed liquid 12 to install the immersion type membrane separation device 13. 14 is a treated water supply pipe, 1
5 is a sludge drawing pipe.

In the submerged membrane separation device 13, flat plate-like membrane cartridges 17 arranged in the vertical direction are installed in parallel inside a box-shaped casing 16 having upper and lower openings at appropriate intervals, and below the membrane cartridge 17. In addition, the air diffuser 19 connected to the blower 18 is installed. In this embodiment, 100 membrane cartridges 17 each having a length of 1 m, a width of 0.5 m and a thickness of 6 mm are installed at 14 mm intervals.

The membrane cartridge 17 is constructed in the same manner as the conventional one described with reference to FIG. 2, and is provided with a suction pipe 20 which communicates with the permeate passage inside the filtration membrane. The suction pipe 20 of each membrane cartridge 17 is connected to a header pipe 21, and the permeate pipe 22 having the header pipe 21 as the starting end side.
Is led to a permeated water tank (not shown) outside the activated sludge tank 11. The permeate pipe 22 is provided with a switching valve 23 and a suction pump 24 that applies a suction pressure into the permeate flow path of the membrane cartridge 17 via the header pipe 21 and the suction pipe 20.

Reference numerals 25, 26, and 27 denote a first chemical liquid tank, a second chemical liquid tank, and a fresh water tank, respectively, that store the chemical liquids. These first chemical liquid tank 25, second chemical liquid tank 26, and fresh water tank 27, respectively. Are installed outside and above the activated sludge tank 11, and the chemical liquid supply pipe 25 is provided with control valves 25a, 26a, 27a.
It is connected to the switching valve 23 via b, 26b and a fresh water supply pipe 27b.

In the above-mentioned activated sludge tank 11, while the solid-liquid separation was carried out while the activated sludge treatment was being carried out, the permeated water amount decreased to 60% of the initial amount due to the contamination of the filtration membrane. Was washed.

The introduction of the water to be treated into the activated sludge tank 11 is stopped, the suction pump 24 is stopped to stop the filtration by the membrane separator 13, and the blower 18 is stopped to stop the air diffuser 1.
Aeration from 9 was stopped.

Then, with the membrane cartridge 17 immersed in the activated sludge mixed solution 12, the switching valve 23 is switched and the control valve 25a is opened so that the chemical solution in the first chemical solution tank 25 is 1% hypochlorous acid. The acid soda solution is supplied to the chemical solution supply pipe 25b, the permeate water pipe 22, the header pipe 2
1. Through the suction tube 20, it was injected into the permeate flow path of the membrane cartridge 17. The sodium hypochlorite solution was injected in an amount of 4 to 5 liters per one membrane cartridge 17 under natural flow in 4 to 5 minutes. After the injection was completed, the solution was left for about 1 hour to hold the sodium hypochlorite solution in the permeate flow channel.

Then, the control valve 25a is closed,
The control valve 27a is opened, and the fresh water in the fresh water tank 27 is allowed to spontaneously flow through the fresh water supply pipe 27b into the permeate flow path of the membrane cartridge 17 so that the sodium hypochlorite solution 1
It was injected in an amount of ˜3 times, whereby the sodium hypochlorite solution was extruded toward the activated sludge mixed solution 12 side, and the permeate flow channel was filled with fresh water.

Thereafter, the blower 18 is driven to drive the air diffuser 19
After starting the aeration from, the switching valve 23 was switched, the suction pump 24 was driven, and the filtration was restarted, and the amount of permeated water recovered to the initial value.

This is a mixture 1 of activated sludge with a filter membrane sandwiched between them.
The pressure on the 2 side and the permeate side maintains a constant balance, and the pressure difference between the activated sludge mixture 12 side and the permeate side is constant at any part of the filtration membrane. Since the chemical solution is supplied at a low pressure and held for an appropriate time, the chemical solution is evenly leached from the entire membrane surface of the filtration membrane, and the entire surface of the filtration membrane is effectively washed by the chemical solution to eliminate clogging of pores. Is. Here, since the clogging substances seemed to be mainly organic pollutants, sodium hypochlorite solution was used to decompose or dissolve the organic pollutants.
At this time, since the aeration from the air diffuser 19 is stopped, the chemical solution leached through the filter membrane does not immediately diffuse into the activated sludge mixed solution 12, and the chemical solution stays near the surface of the filter membrane and is washed. The effect is enhanced and the consumption of the chemical solution is smaller than before. When a high pressure is applied to the permeate side or a chemical solution is supplied at a large flow rate as in the past, pressure loss occurs in the permeate channel and only the upper part of the filtration membrane is washed or the filtration membrane peels off. The cleaning method of this embodiment is preferable also from this point.

After the chemical solution is washed, the inside of the permeate flow passage is replaced with fresh water, so that the fresh water permeates from the permeate flow passage side to the treated water side through the filtration membrane, and this clear water is passed through the permeate flow passage and the filtration membrane. The existing chemical liquid is pushed out to the activated sludge mixed liquid 12 side. In addition, since aeration is started prior to restarting filtration, deposits that were not completely separated from the membrane surface due to the leaching of the chemical solution and fresh water are physically separated by the bubble flow of aerated air, which results in a cleaning effect. Is more enhanced.

In this way, the filtration membrane of the membrane cartridge 17 is effectively washed with the chemical liquid without taking out the entire membrane separation device 13 or the membrane cartridge 17 from the activated sludge tank 11, and the chemical liquid is filtered in the permeated water channel and filtered. It can be removed from the membrane. However, if the permeated water for a certain period of time after the restart of filtration is returned to the previous treatment step and retreated,
It is possible to reliably prevent the permeated water containing the chemical liquid remaining in the permeated water channel and the filtration membrane from being taken out as treated water. (Embodiment 2) Activated sludge tank 11 constructed in the same manner as in Embodiment 1.
In the above, since the amount of permeated water decreased to 60% of the initial amount due to the contamination of the filtration membrane during the solid-liquid separation while performing the activated sludge treatment, the membrane was treated with the 1% sodium hypochlorite solution in the same manner as in Example 1. After cleaning the cartridge 17,
Since the amount of permeated water recovered only to the initial 75%,
It was judged that the inorganic pollutant remained, and further washing was performed. That is, chemical cleaning with a 1% sodium hypochlorite solution was performed, the sodium hypochlorite solution was replaced with fresh water, and then the following cleaning was performed.

While switching the switching valve 23 and opening the control valve 26a, the 1N hydrochloric acid as the chemical liquid in the second chemical liquid tank 25 is supplied to the chemical liquid supply pipe 26b, the permeate water pipe 22,
Through the header tube 21 and the suction tube 20, the membrane cartridge 17
Was injected into the permeate flow channel. 1N hydrochloric acid was injected in an amount of 4 to 5 liters per one membrane cartridge 17 under natural flow in 4 to 5 minutes. After the injection was completed, the mixture was left for about 1 hour to hold 1N hydrochloric acid in the permeate flow channel.

Then, the control valve 26a is closed,
The control valve 27a is opened, and the fresh water in the fresh water tank 27 is injected through the fresh water supply pipe 27b into the permeate flow path of the membrane cartridge 17 in a flow rate of 1 to 3 times that of 1N hydrochloric acid, whereby 1N hydrochloric acid is added. It was extruded to the outside of the filtration membrane and the inside of the permeate flow channel was filled with fresh water.

Thereafter, the blower 18 is driven to drive the air diffuser 19
After starting the aeration from, the switching valve 23 was switched, the suction pump 24 was driven, and the filtration was restarted, and the amount of permeated water recovered to the initial value.

As described above, when the substance for pore clogging is an organic pollutant, sodium hypochlorite or a detergent is used, and when it is an inorganic pollutant, an acid such as oxalic acid or hydrochloric acid is used. It is effective to wash the chemical solution in multiple stages if necessary.

In the above-mentioned embodiment, the membrane separation device for performing solid-liquid separation by using the suction pressure of the suction pump as a driving force is exemplified. However, the natural head of the liquid to be treated such as the activated sludge mixed liquid in the tank is The membrane cartridge can be washed in the same manner in a membrane separation device that performs solid-liquid separation as a driving force. Further, the membrane cartridge is not limited to the one described above, and if the inner side of the filtration membrane is used as the permeate flow channel, the membrane cartridge can be washed in the same manner, such as one having only the surface of the membrane support as the permeate flow channel.

[0029]

As described above, according to the present invention, the membrane cartridge is immersed in the liquid to be treated, and the chemical solution is washed while the aeration is stopped. Not only can it be washed, but the consumption of chemicals can be reduced.

Further, the chemical solution cleaning step of cleaning the chemical solution with the chemical solution and the fresh water substitution step of substituting the chemical solution with fresh water are performed for each chemical solution to be used, so that the chemical solution according to the pore clogging substance is effective. Not only can it be cleaned, but also efficient cleaning that avoids the reaction between chemicals can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of an immersion type membrane separation device to which a cleaning method for an immersion type membrane cartridge of the present invention is applied and an activated sludge tank in which the device is arranged.

FIG. 2 is a perspective view showing an overall configuration of a conventional immersion type membrane separation device.

[Explanation of symbols]

 11 Activated sludge tank 12 Activated sludge mixed solution 13 Immersion type membrane separator 17 Membrane cartridge 19 Air diffuser 25 First chemical liquid tank 26 Second chemical liquid tank 27 Fresh water tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Yata 1-47 Shikazu East, Naniwa-ku, Osaka City, Osaka Prefecture Kubota Co., Ltd. 1-chome 2-47 Kubota Co., Ltd.

Claims (2)

[Claims] 1. A submerged membrane cartridge is immersed in a liquid to be treated, filtration is stopped, and aeration is stopped, while a chemical solution is injected into the permeate flow path of the membrane cartridge at a low pressure and kept for an appropriate time. Then, a method for cleaning an immersion type membrane cartridge is characterized in that fresh water is injected into the permeated water channel to allow the chemical solution to leached to the liquid to be treated and the permeated water channel is replaced with fresh water. 2. When using two or more types of chemical liquids, for each chemical liquid, the chemical liquid is injected into the permeated water channel of the membrane cartridge at a low pressure and held for an appropriate time, and then fresh water is injected into the permeated water channel. 2. The method for cleaning an immersion type membrane cartridge according to claim 1, further comprising the step of leaching the chemical liquid to the side of the liquid to be treated and replacing the inside of the permeated water channel with fresh water.