JP2003290766A - Method and apparatus for treating waste water by membrane separation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating waste water by membrane separation, in which the amount of the water which is to be treated and is filtered by membrane units can be controlled correspondingly to the contaminated state of each of the membrane units. <P>SOLUTION: A pressure gauge 30 or an integrating flowmeter 34 is arranged in each of several membrane units 14 arranged in a treating tank 12. The measured value is sent to an analyzing/controlling means 32. The contaminated state of membrane surface of each of the units 14 is analyzed from the measured value of the corresponding unit. The amount of the water to be treated is distributed properly to each of the units 14 according to its capacity at that time without changing the total amount of the water to be treated in this apparatus as a whole. As a result, the units 14 can be operated stably without interruption by preventing the membrane surface of the specified one of the units 14 from being clogged extremely. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separation wastewater treatment apparatus which is installed in a wastewater treatment facility and performs a filtration treatment with a plurality of membrane units, and in particular, each membrane unit while maintaining a constant total treatment liquid treatment amount. The present invention relates to a membrane separation wastewater treatment method and apparatus for controlling the filtration amount of each membrane unit according to each situation.

[0002]

2. Description of the Related Art In a wastewater treatment facility such as sewage, for filtering treatment of a liquid to be treated introduced into a treatment tank for biological treatment,
We are conducting membrane separation wastewater treatment using a membrane unit. In particular, biological treatment makes effective use of membrane separation wastewater treatment. The biological treatment is a treatment for degrading organic substances contained in sludge in a liquid to be treated by utilizing metabolic action of microorganisms. Also,
In order to promote the metabolism of microorganisms, a blower is installed at the bottom of the treatment tank for introducing the liquid to be treated, and by this, air is supplied to perform aeration, thereby supplying oxygen to the inside of the treatment tank. ing. This creates a circulating flow,
Sludge and oxygen can be sufficiently suspended.

A plurality of membrane units are arranged inside such a treatment tank to carry out membrane separation and drainage treatment of the liquid to be treated.
The treatment liquid subjected to the biological treatment is solid-liquid separated by passing through the membrane unit. The membrane unit is covered with a membrane such as a polysulfone porous membrane, and the liquid to be treated is filtered by passing through the membrane and is pumped out by a pump to perform activated carbon adsorption treatment, etc., and then discharged to the outside of the system. It

Filtration in the membrane unit is generally performed by a pressure difference. That is, the treatment liquid is sucked by the pump, and the liquid to be treated outside the membrane unit is introduced through the membrane unit by the negative pressure generated at this time. At this time, solutes smaller than the membrane of the membrane unit, such as water and ions, can permeate the membrane, but proteins with large molecular weight cannot permeate the membrane, causing gelation phenomenon, etc. to adhere to the membrane surface. There is. By the aeration mentioned above,
Although the deposits on the membrane surface can be removed to some extent, when the membrane unit is used for a long period of time, the deposits adhere to the membrane surface and block the membrane surface, which causes a disadvantage in the filtering action. Therefore, the membrane unit is cleaned and replaced at regular intervals.

When a plurality of membrane units are arranged in the treatment tank, the membrane surface of each membrane unit is kept in a closed state so that each membrane unit can perform filtration under the same conditions.
Basically, the pumps are operated in the same way. This is a measure for preventing an extreme load from being applied to a specific membrane unit to cause clogging of the membrane surface and making the membrane life in each membrane unit uniform.

[0006]

However, in reality, the operation of some membrane units may be stopped when the membrane units are maintained or when the inflow of the liquid to be treated is small. Therefore, if a membrane unit is used for a long period of time, the operation history (integrated flow rate, operating time, etc.) of each membrane unit will be greatly different. As a result, the membrane surface is closed differently for each membrane unit, and a membrane unit having significant contamination and a membrane unit having a favorable membrane surface are mixed. Therefore, maintenance cannot be performed on all the membrane units at the same time, and replacement work of the membrane units and the like must be performed each time, which increases the burden on the operator.

Further, even if the same operation is faithfully performed and the operation history is the same, the clogging condition of the membrane surface is different for each membrane unit due to the dispersion state of the substance in the liquid to be treated. There is. Such a phenomenon does not originate from a constant relationship such as the arrangement position of each membrane unit, but changes depending on the condition of the liquid to be treated such as the agitation state due to aeration. It was very difficult to keep the occlusion state uniform.

Therefore, in the present invention, focusing on the above problem, it is possible to control the amount of water filtered by the membrane unit in accordance with the pollution status and operating time of each membrane unit and maintain the total amount of filtered treatment. It is an object of the present invention to provide a method and an apparatus for treating a membrane separation wastewater.

[0009]

In order to achieve the above object, the membrane separation wastewater treatment method according to the present invention provides a method for passing a liquid to be treated through a plurality of membrane units for solid-liquid separation. It is characterized in that the suction flow rate of each membrane unit pump is controlled according to the fluctuation of the filtration pressure so that the product of the filtration pressure and the suction water amount in 1 has a common value.

Further, in the membrane separation wastewater treatment method, when the liquid to be treated is caused to flow through a plurality of membrane units for solid-liquid separation, the ratio of the integrated flow rate and the pressure-fed water amount in each membrane unit has a common value. It is also possible to control the suction flow rate of each membrane unit pump according to the fluctuation of the integrated flow rate.

The membrane separation wastewater treatment apparatus according to the present invention is a membrane separation wastewater treatment apparatus for introducing a liquid to be treated into a treatment tank to perform solid-liquid separation treatment, and is installed inside the treatment tank to filter the liquid to be treated. A plurality of membrane units and a plurality of pumps for sucking the treated water in each of the membrane units are provided, and pressure measuring means for measuring the filtration pressure of the treated water is provided for each of the membrane units. It is characterized in that control means for controlling the operation of each of the pumps is provided so that the product of the amount of water sucked by the pump and the amount of suction water by the pump has a common value.

Further, the membrane separation wastewater treatment apparatus has a plurality of membrane units installed inside the treatment tank for filtering the liquid to be treated, and a plurality of pumps for sucking the treated water in each of the membrane units. A control means is provided for each of the membrane units, the flow rate measuring means for measuring the integrated flow rate of the treated water is provided, and the operation means controls the operation of each pump so that the ratio of the integrated flow rate to the suction water amount by the pump has a common value. It is also possible to adopt a configuration in which.

[0013]

With the above-mentioned structure, the present invention measures the filtration pressure for each membrane unit by the pressure gauge installed for each membrane unit. From these measured values, the contamination status of the membrane surface of each membrane unit can be analyzed, and the amount of treated water can be distributed according to the capacity of each membrane unit at that time without changing the total amount of treatment. Therefore, it has become possible to prevent extreme clogging of the membrane surface of a specific membrane unit and continue stable operation of the membrane. Further, always maintaining the respective film surfaces in the respective film units in the same state has a favorable effect on the life of the film, and it is possible to eliminate the waste of the work of maintaining only a specific film unit.

It is also possible to arrange a flow meter for each membrane unit. By arranging the flowmeter in this way, the amount of treated water that has permeated each membrane unit can be measured and the contamination state of the membrane surface can be analyzed. By changing the amount of treated water of each membrane unit according to the state of each membrane surface based on these measured values, it is possible to prevent a load from being applied to a particular membrane unit. By controlling the integrated flow rate of each membrane unit, it is possible to match the replacement time of each membrane unit and the like, so that wasteful membrane replacement and construction can be eliminated.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a membrane separation wastewater treatment apparatus according to the present invention will be described in detail below. FIG. 1 is a schematic diagram showing the overall configuration of a biological treatment device to which a membrane separation wastewater treatment device is applied. In addition, what is described below is only one aspect of the embodiment of the present invention, and the present invention is not limited thereto.

In a wastewater treatment facility such as sewage, the liquid to be treated 10 is purified inside a treatment tank 12.
As shown in FIG. 1, a membrane separation / effluent treatment device 20 including a plurality of membrane units 14 is arranged inside the treatment tank 12, and air is supplied to the liquid to be treated 10 at the bottom to perform aeration. An air diffuser 16 is provided for this purpose.
The liquid to be treated 10 is introduced into the treatment tank 12 by a pipe 22 drawn from the liquid to be treated storage tank 18 arranged outside the treatment tank 12 to the treatment tank 12, and biological treatment is performed inside the treatment tank 12. After being removed, it is filtered by the membrane separation wastewater treatment device 20 described later and discharged to the outside of the system.

The biological treatment of the liquid to be treated 10 is carried out by utilizing the metabolic action of microorganisms. The microorganism adsorbs the organic substance in the liquid to be treated 10 and takes it into the cell as a storage substance,
It oxidizes the adsorbed organic substances and uses them as energy for growth and living body maintenance. When the organic substances in the liquid to be treated are absorbed by the microorganisms, the nutrients cannot be ingested by the microorganisms and eventually die. Utilizing such an action, the biological treatment apparatus removes organic substances in the liquid to be treated.

Since a large amount of oxygen is required when a microorganism oxidizes an organic substance, an aeration pipe 16 for feeding oxygen is provided in the treatment tank 12 for aeration. The air diffuser 16 includes a porous one that generates fine bubbles and a non-porous one that generates large bubbles. In this embodiment, the porous air diffuser 16 is used. For example, a long air pipe is used, and a plurality of air diffuser holes are formed in a row on the outer periphery so as to be parallel to the axis, and the air diffuser cylinder is arranged so that the air diffuser holes are orthogonal to the axis of the air pipe. Is provided. Such an air diffuser 16 is used in the processing tank 12
It is arranged at the bottom of, and is connected to the blower 17 via the air supply pipe 15. When the air is supplied from the blower 17, the air diffuses into the liquid 10 to be treated all at once from the plurality of diffusers 16 as fine bubbles. Thus, by performing aeration for generating bubbles in the liquid to be treated 10,
The effect of accelerating the metabolism of microorganisms and stirring and mixing the liquid to be treated 10 can be obtained. The air diffuser 16 is not limited to the one described above, and it is also possible to use a porous diffuser, a tube, or a non-porous diffuser.

Inside the treatment tank 12, a membrane separation wastewater treatment device 20 having a plurality of membrane units 14 is arranged. This apparatus separates the liquid to be treated 10 in the treatment tank 12 into solid and liquid of sludge and water, and filters the liquid to be treated 10 through each membrane unit 14. In the present embodiment, each membrane unit 14 is formed in a vertical cylindrical shape, and such membrane units 14 are vertically arranged in parallel at five locations inside the processing tank 12. Each membrane unit 1
A treated water pipe 24 for discharging the treated water, which has been filtered and flowed into the membrane unit 14 from the inside of the treatment tank 12, is connected to one end of 4. Each of these treated water pipes 2
4 are connected to a plurality of pumps 26 arranged outside the processing tank 12. The treated water inside each membrane unit 14 is activated by operating each pump 26.
It is pumped up through each treated water pipe 24. Further, by operating the pump 26 to pump out the treated water, a negative pressure is generated inside the membrane unit 14. This pressure difference causes
The liquid to be treated 10 outside each membrane unit 14 is the membrane unit 14
Since it tries to flow into the inside, filtration by the filtration membrane 28 is promoted. The treated water thus pumped is collected in the treated water tank 36, subjected to activated carbon adsorption treatment and the like, and then discharged out of the system.

The membrane unit 14 is a flat membrane filtration membrane 28.
It is a structure in which is laminated in multiple layers. For the filtration membrane 28, a member such as a polysulfone porous membrane is used and is formed into a disc shape. The membrane unit 14 is formed in a cylindrical shape by stacking such filtration membranes 28 in multiple layers. The liquid to be treated 10 outside the membrane unit 14 permeates through the stacked filtration membranes 28 and flows into the cylindrical inside. At this time, solutes such as water and ions smaller than the pores provided in the filtration membrane 28 pass through the filtration membrane 28, and large substances such as gravel cannot pass through the filtration membrane 28 and remain inside the processing tank 12. In this way, the liquid to be treated 10 in the treatment tank 12 is filtered by the membrane unit 14 and subjected to solid-liquid separation treatment. Here, the sludge containing the gravel and the like that has been subjected to the solid-liquid separation treatment and is not filtered and remains in the treatment tank 12 is discarded by the incineration treatment. The structure of the membrane unit 14 is not limited to the above-described multilayer film structure, and the outer periphery may be surrounded by a flat film.

By the way, the substance that could not permeate the membrane unit 14 when the liquid 10 to be treated is filtered adheres to the membrane, resulting in clogging of the membrane surface. Such clogging of the membrane surface can be removed to some extent by stirring the liquid to be treated 10 inside the treatment tank 12 by the aeration described above, but if the membrane unit 14 is used for a long period of time, The obstruction is widespread. When a plurality of membrane units 14 are used, the membrane surface clogging situation differs for each membrane unit 14, and the membrane surface clogging situation may worsen only for a specific membrane unit 14. Therefore, in the present embodiment, each membrane unit 14 is provided so as to avoid applying an excessive operating load to the particular membrane unit 14 and to uniformly operate all the membrane units 14 arranged in the treatment tank 12. A pressure gauge 30 is provided as a pressure measuring means for measuring the situation. The pressure gauge 30 is provided in the middle of each treated water pipe 24 from each membrane unit 14 to each pump 26, and measures the filtration pressure of the treated water passing through the inside of each treated water pipe 24. The measurement value obtained from each pressure gauge 30 is sent to the analysis control means 32 as a signal.

The analysis control means 32 includes the pumps 2 described above.
It is connected to the operation control unit 6 and controls these operations. That is, each pump 26A, 26B, 26C, 26
By controlling the rotation speeds of D and 26E, the liquid amount of the liquid to be treated 10 that permeates each of the membrane units 14A, 14B, 14C, 14D and 14E is controlled. At that time, the amount of treated water to be filtered is controlled so that the product of the filtration pressure measured in a certain membrane unit and the amount of treated water has a common value. That is, when the filtration pressure is high, the amount of treated water decreases, and conversely, when the filtration pressure is low, the amount of treated water increases. At this time, by controlling the product of the filtration pressure and the suction water amount by the pump to be a common value in all the membrane units 14, even if the treated water amount of each membrane unit 14 changes, the total total treatment The amount can be maintained unchanged.

The above-mentioned control is performed according to the closed state of the membrane surface of each membrane unit. For example, when the membrane surface of the membrane unit 14B is another membrane unit 14A,
In the case where it is severely blocked as compared with 14C, 14D, 14E, the treated water discharged from the membrane unit 14B has a higher filtration pressure than the treated water from the other membrane units 14A, 14C, 14D, 14E ( See FIG. 2). Therefore, it is understood that the higher the filtration pressure of the treated water in each treated water pipe 24 is, the more the membrane surface is closed. Therefore, in order to make the state of each membrane surface uniform, the amount of treated water in the membrane unit 14B with the membrane surface contaminated is reduced, and conversely, the amount of treated water of a good membrane surface is increased, so that the analysis control means The number of revolutions of each pump 26 is controlled by 32.

As described above, the analysis control means 32 controls the output of each pump 26 so as to perform an appropriate operation in consideration of the difference in pressure between the membrane units 14, and does not reduce the total processing amount. The amount of treated water is distributed as follows. Also,
Since the closed state of the membrane surface changes every moment, it is preferable to control the amount of treated water on time by the measurement value obtained from the pressure gauge 30.

It is also possible to provide an integrated flow meter 34 as a flow rate measuring means instead of the pressure gauge 30 and measure the integrated flow rate of the treated water flowing through the treated water pipe 24. The integrating flowmeter 34 may be configured such that an orifice plate is used to form a throttle inside the pipe and the pressure before and after the throttle is measured to measure the flow rate from the change in the flow velocity flowing inside the pipe. Good. As a result, the amount of each treated water filtered by each membrane unit 14 can be measured. The measured value is sent to the analysis control means 32, and the integrated flow rate of the treated water for each membrane unit 14 is calculated. Further, the pump 26 for pumping the treated water is configured to be operated and controlled by the analysis control means 32, and the treated water pump is controlled according to each integrated flow rate.

By the integrated flow meter 34, each treated water pipe 2
When the integrated flow rate of No. 4 is calculated, it is possible to know the blockage state of the membrane surface in each membrane unit 14 from the measured value.
That is, the membrane unit 14 having a large integrated flow rate has a good membrane surface condition, and the filtration treatment of the liquid 10 to be treated is smoothly performed. On the contrary, if the membrane surface is closed, the amount of treated water to be filtered decreases, so that the integrated flow rate flowing into the treated water pipe 24 decreases. Based on this, the analysis control means 32 controls the membrane unit 14 having a large cumulative flow rate so as to increase the driving rate of the pump 26 and decrease the driving rate of the membrane unit 14 having a small cumulative flow rate.

The amount of treated water for each membrane unit is controlled so that the ratio between the integrated flow rate and the amount of treated water becomes a common value. That is, when the integrated flow rate is high, the amount of treated water is increased, and conversely, when the integrated flow rate is low, the amount of treated water is decreased. At this time, in all the membrane units, by controlling so that the ratio of the integrated flow rate to the treated water amount is the same, even if the treated water amount of each membrane unit changes, the total total treated amount is always constant. Can be maintained.

The operation of the membrane separation wastewater treatment device 20 configured as described above will be described. Membrane separation wastewater treatment equipment 2
The liquid to be treated 10 introduced into the treatment tank 12 is stored outside the 0. The liquid to be treated 10 is aerated by the air diffuser 16 provided at the bottom of the treatment tank 12, whereby the organic substance contained in the liquid to be treated 10 is decomposed. The liquid to be treated 10 is a membrane separation wastewater treatment device 20.
It is filtered by the plurality of membrane units 14 provided in. The treated water filtered in this way is pumped up from each membrane unit 14 by each pump 26 and discharged to the outside of the system through each treated water pipe 24.

At this time, a pressure gauge 30 is attached to each treated water pipe 24.
Is installed to measure the pressure of treated water flowing through each pipeline. This measured value is transmitted as a signal to the analysis control means 32 and analyzed. For example, when the pumps 26 are controlled equally for each membrane unit 14, if the membrane surface conditions of all the membrane units 14 are good, the pressure of the treated water in the treated water pipe 24 should show the same value. Is.
When the membrane surface is closed differently for each membrane unit 14, the liquid to be treated 1 is treated in the membrane unit 14 where the membrane surface is significantly closed.
It becomes difficult to filter 0, and the amount of treated water flowing through the treated water pipe 24 is reduced. Therefore, only a small amount of treated water is sucked with respect to the suction force of the pump 26,
The pressure in the treated water pipe 24 increases. Therefore, the difference in the pressure of the treated water means that the membrane surfaces of the membrane units 14 are in different closed states.

Therefore, the analysis control means 32 reduces the rotation speed of the pump 26 for the membrane unit 14 having a high pressure to reduce the load of the filtration process. Since it is not preferable that the total amount of treated water be reduced in connection with this, the rotation speed of the pump 26 is increased to increase the amount of treated water for the membrane unit 14 for which the measured value of the pressure gauge 30 was low. . Figure 2
Shows the water volume control of the individual membrane units 14 relative to the total throughput. Here, the membrane units 14B, A, C, and
The case where it is analyzed as D and E is shown. In the past, the output of the pump 26 was equivalently set to 20%, while
In the present embodiment, the rotation speed of the pump 26 is controlled to reduce the rotation speed for the membrane unit 14 having a high pressure. That is, the amount of treated water of the membrane unit 14E having a low pressure (low adherence) is increased, and conversely, the amount of treated water of the membrane unit 14B having a high pressure (high adherence) is reduced. At this time, each membrane unit 14A, 14B, 14C, 14
In order not to change the total treatment amount of the treated water filtered by D and 14E, it is preferable to control so as to treat the same amount in total.

In this way, by controlling the amount of treated water according to the pressure of the treated water discharged from each membrane unit 14, each membrane is maintained while keeping the total treated amount of the membrane separation wastewater treatment device 20 substantially constant. The unit 14 can perform a filtration process suitable for the closed state of the membrane surface. Moreover, by changing the amount of treated water according to the state of the membrane surface of each membrane unit 14, the usage status of each membrane unit 14 can be made uniform.

When using the integrating flow meter 34,
Since the membrane unit 14 having a smaller cumulative flow rate is in a state in which the membrane surface is closed and the operating condition is severe, the above-mentioned control is performed by the analysis control means 32. That is, the rotation speed of the pump 26 of the membrane unit 14 having a small cumulative flow rate is reduced to reduce the amount of treated water, and conversely, the membrane unit 14 having a large cumulative flow rate is controlled to increase the treated water amount.

As described above, according to the membrane separation / effluent treatment apparatus 20 of the present embodiment, it is possible to prevent the fouling of the specific membrane unit 14 and the deviation of the integrated flow rate from occurring, and to check the operation status of all the membrane units 14. Since it can be made uniform, it is possible to prevent the particular membrane unit 14 from being violently contaminated. Therefore, the contaminated membrane unit 14
In the cleaning or replacement of the above, it is possible to perform the work at once under the same conditions without causing a significant difference in the usage status of each membrane unit 14, and it is possible to reduce the burden on the operator. In this embodiment, the membrane separation wastewater treatment device 20 is installed in the treatment tank 12, but the same effect can be obtained by installing it in the nitrification treatment tank or the denitrification treatment tank.

[0034]

As described above, according to the membrane separation / effluent treatment apparatus of the present invention, by measuring the filtration pressure (or flow rate) of each membrane unit, the contamination status of each membrane unit is analyzed, Since the amount of water to be treated can be distributed according to the situation of each membrane unit based on this analysis result,
It does not contaminate a particular membrane unit more than necessary. Therefore, in a membrane separation wastewater treatment device provided with a plurality of membrane units, the usage status of each membrane unit can be made uniform, and excellent membrane separation performance can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a membrane separation wastewater treatment device and peripheral equipment in the present embodiment.

FIG. 2 is an explanatory diagram showing an example of treated water amount control in each membrane unit.

[Explanation of symbols]

10 ... Liquid to be treated, 12 ... Treatment tank, 14 ... Membrane unit, 16 ... Diffuser, 18 ... Liquid storage tank, 20 ... Membrane separation wastewater treatment device, 22 ……… Pipes, 24 ………… Processed water piping, 26 ……… Pumps, 28…
...... Filtration membrane, 30 ...... Pressure gauge, 32 ...... Analysis control means, 34 ...... Integrated flow meter.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4D006 GA06 GA07 HA41 HA93 JA31Z                       JA53Z KA31 KA44 KB22                       KE03P KE03Q KE08P KE08Q                       KE23Q MA03 MC62 PA01                       PB08 PB24                 4D028 BC03 BC12 BD06 BD16 CA00                       CC00

Claims (4)

[Claims] 1. When a liquid to be treated is caused to flow through a plurality of membrane units to perform solid-liquid separation, the filtration pressure and suction water amount in each membrane unit have a common value so that they can be adjusted according to variations in the filtration pressure. A method for treating membrane separation wastewater, which comprises controlling the suction flow rate of each membrane unit pump. 2. When the liquid to be treated is caused to flow through a plurality of membrane units to perform solid-liquid separation, it is possible to adjust the accumulated flow rate so that the ratio of the integrated flow rate to the pressure-fed water amount in each membrane unit has a common value. A method for treating membrane separation wastewater, which comprises controlling the suction flow rate of each membrane unit pump. 3. A membrane separation wastewater treatment apparatus for introducing a liquid to be treated into a treatment tank to perform solid-liquid separation treatment, wherein a plurality of membrane units installed inside the treatment tank to filter the liquid to be treated, and each of the membranes. A plurality of pumps for sucking the treated water in the unit are provided, and a pressure measuring means for measuring the filtration pressure of the treated water is provided for each of the membrane units, and the product of the filtration pressure and the suctioned water amount by the pump is obtained. A membrane separation wastewater treatment apparatus comprising a control means for controlling the operation of each pump so as to have a common value. 4. A membrane separation wastewater treatment apparatus for introducing a liquid to be treated into a treatment tank to perform solid-liquid separation treatment, comprising a plurality of membrane units installed inside the treatment tank for filtering the liquid to be treated, and each of the membranes. A plurality of pumps for sucking the treated water in the unit are provided, and a flow rate measuring means for measuring an integrated flow rate of the treated water is provided for each of the membrane units, and the ratio of the integrated flow rate to the suction water amount by the pump is A membrane separation wastewater treatment apparatus comprising a control means for controlling the operation of each pump so as to have a common value.