JP3722084B2 - Membrane separation wastewater treatment method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a membrane separation wastewater treatment apparatus that is provided in a wastewater treatment facility and performs filtration treatment with a plurality of membrane units, and in particular, according to the situation of each membrane unit while keeping the total amount of treatment liquid constant. The present invention relates to a membrane separation wastewater treatment method and apparatus for controlling the filtration amount of a membrane unit.
[0002]
[Prior art]
In a wastewater treatment facility such as sewage, membrane separation wastewater treatment using a membrane unit is performed for filtration of a liquid to be treated introduced into a treatment tank for biological treatment or the like. In particular, biological treatment effectively utilizes membrane separation wastewater treatment. Biological treatment is a treatment for decomposing organic substances contained in sludge in the liquid to be treated by utilizing the metabolic action of microorganisms. In addition, in order to promote the metabolism of microorganisms, a blower is disposed at the bottom of the treatment tank into which the liquid to be treated is introduced, and by supplying air and performing aeration (aeration), oxygen is introduced into the treatment tank. Supply. Thereby, a circulation flow is generated and sludge and oxygen can be sufficiently suspended.
[0003]
A plurality of membrane units are disposed inside such a treatment tank, and membrane separation wastewater treatment of the liquid to be treated is performed. The treatment liquid subjected to the biological treatment is solid-liquid separated by permeating through the membrane unit. The membrane unit is coated with a membrane such as a polysulfone porous membrane on the outer periphery, and the liquid to be treated is filtered by permeating through the membrane, pumped out by a pump, subjected to activated carbon adsorption treatment, etc., and then discharged outside the system. The
[0004]
In general, the filtration in the membrane unit is performed by a pressure difference. That is, the processing liquid is sucked by the pump, and the liquid to be processed 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, permeate the membrane, but proteins with large molecular weight cannot permeate the membrane, causing gelation and the like to adhere to the membrane surface. There is. The aeration described above can remove some of the deposits on the membrane surface. However, if the membrane unit is used for a long period of time, the deposits will adhere and block the membrane surface, causing inconvenience in the filtering action. Come. Therefore, the membrane unit is cleaned and replaced at regular intervals.
[0005]
When multiple membrane units are installed in the treatment tank, the operation of the pumps is the same so that the membrane surface of each membrane unit is kept uniformly, and filtration can be performed under the same conditions. It is based on what to do. This is a measure for preventing the membrane surface from being clogged by applying an extreme load to a specific membrane unit, and making the life of the membrane in each membrane unit uniform.
[0006]
[Problems to be solved by the invention]
However, in reality, some membrane units may be stopped in operation, for example, when performing maintenance on the membrane unit or when the amount of liquid to be processed is small. Therefore, when a membrane unit is used over a long period of time, the operation history (integrated flow rate, operating time, etc.) of each membrane unit is greatly different. As a result, the clogging state of the membrane surface is different for each membrane unit, and a membrane unit with significant contamination and a membrane unit with a good membrane surface coexist. Therefore, maintenance cannot be performed on all the membrane units at the same time, and membrane unit replacement work is performed each time, increasing the burden on the operator.
[0007]
Even when the same operation is performed faithfully and the operation history is the same, the membrane surface may be clogged for each membrane unit depending on the dispersion state of substances in the liquid to be treated. Such a phenomenon is not caused by a permanent relationship such as the arrangement position of each membrane unit, but changes depending on the state of the liquid to be treated, such as a stirring state by aeration. It was very difficult to keep the occlusion state uniform.
[0008]
Therefore, in the present invention, focusing on the above problems, the membrane separation capable of controlling the amount of water filtered by the membrane unit in accordance with the contamination status and operating time of each membrane unit and maintaining the total throughput to be filtered. An object is to provide a wastewater treatment method and apparatus.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the membrane separation wastewater treatment method according to the present invention has a product of the filtration pressure and the suction water amount in each membrane unit when the liquid to be treated is passed through a plurality of membrane units for solid-liquid separation. The suction flow rate of each membrane unit pump is controlled according to the fluctuation of the filtration pressure so as to have a common value.
[0010]
In addition, the membrane separation wastewater treatment method allows the integrated flow rate so that the ratio between the integrated flow rate and the pumped water flow rate in each membrane unit has a common value when the liquid to be treated is passed through a plurality of membrane units for solid-liquid separation. It is also possible to control the suction flow rate of each membrane unit pump in accordance with the fluctuations of.
[0011]
A membrane separation wastewater treatment apparatus according to the present invention is a membrane separation wastewater treatment apparatus that introduces a liquid to be treated into a treatment tank and performs a solid-liquid separation treatment, and is a plurality of membranes that are installed inside the treatment tank and filter the liquid to be treated A unit and a plurality of pumps for sucking the treated water in each membrane unit, provided with a pressure measuring means for measuring the filtration pressure of the treated water for each membrane unit, and by the filtration pressure and the pump Control means for controlling the operation of each pump is provided so that the product of the suction water amount has a common value.
[0012]
Further, the membrane separation wastewater treatment apparatus comprises 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 the respective membrane units, A configuration in which a flow rate measuring unit that measures the integrated flow rate of treated water is provided for each membrane unit, and a control unit that controls the operation of each pump so that the ratio between the integrated flow rate and the amount of sucked water by the pump has a common value It is also possible.
[0013]
[Action]
With the above configuration, the present invention measures the filtration pressure for each membrane unit with a pressure gauge installed for each membrane unit. From these measured values, the state of contamination of the membrane surface of each membrane unit can be analyzed, and the amount of treated water can be distributed according to the capability of each membrane unit at that time without changing the total amount of treatment. For this reason, it is possible to prevent the membrane surface from being clogged in a specific membrane unit and to continue the stable operation of the membrane. Further, always maintaining each membrane surface in each membrane unit in a similar state has a positive effect on the lifetime of the membrane, and it is possible to eliminate waste of operations such as maintenance of only a specific membrane unit.
[0014]
It is also possible to arrange a flow meter for each membrane unit. By disposing the flow meter in this way, the amount of treated water that has passed through each membrane unit can be measured, and the contamination status of the membrane surface can be analyzed. Based on these measured values, it is possible to prevent a specific membrane unit from being loaded by changing the amount of treated water in each membrane unit according to the state of each membrane surface. By controlling the integrated flow rate of each membrane unit, the replacement time of each membrane unit can be matched, so that unnecessary membrane replacement and construction can be eliminated.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Below, the embodiment of the membrane separation wastewater treatment equipment concerning the present invention is described in detail. FIG. 1 is a schematic diagram showing the overall configuration of a biological treatment apparatus to which a membrane separation wastewater treatment apparatus is applied. In addition, what is described below is only one aspect | mode of embodiment of this invention, and this invention is not limited to these.
[0016]
In a wastewater treatment facility such as sewage, the liquid 10 to be treated is subjected to purification treatment inside the treatment tank 12. As shown in FIG. 1, a membrane separation wastewater treatment apparatus 20 composed of a plurality of membrane units 14 is disposed inside the treatment tank 12, and aeration is performed by supplying air to the liquid 10 to be treated at the bottom. An air diffusing tube 16 is provided. The treatment liquid 10 is introduced into the treatment tank 12 by a pipe 22 drawn from the treatment liquid storage tank 18 disposed outside the treatment tank 12 to the treatment tank 12, and biological treatment is performed inside the treatment tank 12. After being broken, it is filtered by a membrane separation wastewater treatment device 20 described later and discharged out of the system.
[0017]
The biological treatment of the liquid to be treated 10 is performed using the metabolic action of microorganisms. The microorganism adsorbs the organic substance in the liquid 10 to be treated and takes it into the cell as a storage substance, oxidizes the adsorbed organic substance, and uses it as energy for growth and living body maintenance. If the organic substance in the liquid to be treated disappears after being adsorbed by the microorganism, the microorganism can no longer take in nutrients and eventually dies. Using such an action, the biological treatment apparatus removes organic substances in the liquid to be treated.
[0018]
Since a large amount of oxygen is required when microorganisms oxidize organic substances, an aeration pipe 16 for supplying oxygen is disposed in the treatment tank 12 and aeration is performed. The diffuser tube 16 includes a porous tube that generates fine bubbles and a non-porous tube that generates large bubbles. In this embodiment, the porous tube 16 is used. This is because, for example, a long air pipe is used, a plurality of air diffusion holes are formed in a row on the outer periphery so as to be parallel to the axis, and the air diffusion cylinder is formed so that the air diffusion holes are orthogonal to the axis of the air pipe. It is set as the structure which provided. Such an air diffuser 16 is disposed at the bottom of the processing tank 12 and is connected to the blower 17 via the air supply pipe 15. When air is supplied from the blower 17, it diffuses as fine bubbles into the liquid 10 to be treated simultaneously from the plurality of air diffusers 16. Thus, by performing aeration that generates bubbles in the liquid 10 to be processed, the metabolism of microorganisms is promoted and the effect of stirring and mixing the liquid 10 to be processed can be obtained. The diffuser tube 16 is not limited to the above-described one, and a porous diffuser or tube, or a non-porous diffuser can be used.
[0019]
Inside the treatment tank 12, a membrane separation wastewater treatment apparatus 20 having a plurality of membrane units 14 is disposed. The apparatus is for solid-liquid separation of the liquid to be treated 10 inside the treatment tank 12 from sludge and water, and performs filtration by allowing the liquid to be treated 10 to pass 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 arranged in parallel at 5 locations inside the processing tank 12. One end of each membrane unit 14 is connected to a treated water pipe 24 for discharging treated water that has been filtered and flowed into the membrane unit 14 from the inside of the treatment tank 12. Each of these treated water pipes 24 is connected to a plurality of pumps 26 disposed outside the treatment tank 12. The treated water inside each membrane unit 14 is pumped up through each treated water pipe 24 by operating each pump 26. Moreover, a negative pressure is generated inside the membrane unit 14 by operating the pump 26 to pump out the treated water. Due to this pressure difference, the liquid 10 to be treated outside each membrane unit 14 tends to flow into the membrane unit 14, and thus filtration through the filtration membrane 28 is promoted. The treated water pumped up in this way is collected in the treated water tank 36 and subjected to activated carbon adsorption treatment and the like, and then discharged out of the system.
[0020]
The membrane unit 14 has a structure in which flat membrane membranes 28 are laminated in multiple layers. The filter membrane 28 uses a member such as a polysulfone porous membrane, and is formed into a disk shape. The membrane unit 14 is configured in a cylindrical shape by superposing such filtration membranes 28 in multiple layers. The liquid 10 to be processed outside the membrane unit 14 passes through the stacked filtration membranes 28 and flows into the cylindrical interior. At this time, solutes smaller than the holes provided in the filtration membrane 28 such as water and ions pass through the filtration membrane 28, and large substances such as gravel cannot pass through the filtration membrane 28 and remain inside the treatment tank 12. Thus, the liquid 10 to be processed in the processing tank 12 is filtered by the membrane unit 14 and subjected to solid-liquid separation processing. Here, sludge containing gravel and the like remaining in the treatment tank 12 without being filtered and solid-liquid separated is discarded by incineration. Note that the configuration of the membrane unit 14 is not limited to the multilayer film structure described above, and the outer periphery may be surrounded by a flat membrane.
[0021]
By the way, the substance that could not pass through the membrane unit 14 when the liquid 10 to be treated is filtered adheres to the membrane and the membrane surface is blocked. Such clogging of the membrane surface can be somewhat removed by stirring the liquid 10 to be treated inside the treatment tank 12 by the aeration described above. However, if the membrane unit 14 is used over a long period of time, Occlusion is widespread. When a plurality of membrane units 14 are used, the membrane surface clogging situation for each membrane unit 14 is different, and the membrane clogging situation for only a specific membrane unit 14 may deteriorate. Therefore, in the present embodiment, each membrane unit 14 is prevented from being subjected to an extreme operating load on a specific membrane unit 14 and all the membrane units 14 disposed in the treatment tank 12 are operated evenly. 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 treated water passing through the inside of each treated water pipe 24. Measurement values obtained from the respective pressure gauges 30 are sent as signals to the analysis control means 32.
[0022]
The analysis control unit 32 is connected to the operation control unit of each pump 26 described above and controls these operations. That is, by controlling the rotation speed of each pump 26A, 26B, 26C, 26D, 26E, the amount of the liquid 10 to be processed that passes through each membrane unit 14A, 14B, 14C, 14D, 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 becomes 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 amount of water sucked by the pump to be a common value in all the membrane units 14, even when the amount of treated water for each membrane unit 14 is changed, It can be maintained without changing the amount.
[0023]
The above control is performed according to the state of blockage of the membrane surface in each membrane unit. For example, when the membrane surface of the membrane unit 14B is significantly closed compared to the other membrane units 14A, 14C, 14D, and 14E, the treated water discharged from the membrane unit 14B is the other membrane units 14A, 14C, and 14D. The filtration pressure is higher than the treated water from 14E (see FIG. 2). Therefore, it can be seen that the membrane surface is blocked as the filtration pressure of the treated water in each treated water pipe 24 is higher. Therefore, in order to make the state of each membrane surface uniform, the analysis control means reduces the amount of treated water of the membrane unit 14B whose membrane surface is contaminated, and conversely increases the amount of treated water of the membrane surface having a good surface. The rotational speed of each pump 26 is controlled by 32.
[0024]
In this way, the analysis control unit 32 controls the output of each pump 26 so as to perform an appropriate operation in consideration of the difference in pressure for each membrane unit 14, and performs processing so as not to reduce the total processing amount. Allocate water volume. Moreover, since the state of blockage 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.
[0025]
In addition, 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 treated water flowing through the treated water pipe 24. For example, the integrating flow meter 34 is configured to form a throttle inside the pipe by using, for example, an orifice plate, and measure the flow rate from the change in the flow velocity flowing inside the pipe by measuring the pressure before and after the throttle. That's fine. Thereby, each amount of 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 treated water for each membrane unit 14 is calculated. Further, the pump 26 for pumping up the treated water is configured such that the operation control is performed by the analysis control means 32, and the treated water pump is controlled according to each integrated flow rate.
[0026]
When the integrated flow rate of each treated water pipe 24 is calculated by the integrated flow meter 34, the state of blockage of the membrane surface in each membrane unit 14 can be known from the measured value. That is, the membrane unit 14 having a large integrated flow rate has a good membrane surface state, and the filtration treatment of the liquid 10 to be treated is smoothly performed. On the other hand, when the membrane surface is blocked, the amount of treated water to be filtered decreases, so the integrated flow rate flowing into the treated water pipe 24 decreases. Based on this, the analysis control means 32 performs control so that the drive rate of the pump 26 is increased with respect to the membrane unit 14 with a large integrated flow rate and the drive rate of the membrane unit 14 with a low integrated flow rate is decreased.
[0027]
The amount of treated water for each membrane unit is controlled so that the ratio between the integrated flow rate and the treated water amount becomes a common value. That is, when the integrated flow rate is large, the amount of treated water is increased. Conversely, when the integrated flow rate is small, the amount of treated water is decreased. At this time, by controlling so that the ratio between the integrated flow rate and the treated water amount is the same in all the membrane units, the total treated amount is always constant even if the treated water amount for each membrane unit changes. Can be maintained.
[0028]
The operation of the membrane separation wastewater treatment apparatus 20 configured as described above will be described. A liquid 10 to be treated introduced into the treatment tank 12 is stored outside the membrane separation wastewater treatment apparatus 20. The liquid 10 to be processed is aerated by the air diffuser 16 provided at the bottom of the processing tank 12, whereby the organic substance contained in the liquid 10 to be processed is decomposed. In addition, the liquid 10 to be treated is filtered by a plurality of membrane units 14 provided in the membrane separation wastewater treatment apparatus 20. The treated water thus filtered is pumped up from each membrane unit 14 by each pump 26 and discharged out of the system through each treated water pipe 24.
[0029]
At this time, the pressure gauge 30 is installed in each treated water piping 24, and the pressure of the treated water which flows through each pipe line is measured. This measured value is transmitted as a signal to the analysis control means 32 for analysis. For example, when the pumps 26 are controlled equally for each membrane unit 14, the pressure of the treated water in the treated water piping 24 should show the same value if the membrane surface state of all the membrane units 14 is good. It is. If the closed state of the membrane surface is different for each membrane unit 14, it becomes difficult to filter the liquid 10 to be treated in the membrane unit 14 whose membrane surface is significantly closed, and the liquid of the treated water flowing through the treated water pipe 24. The amount is reduced. Therefore, only a small amount of treated water is sucked with respect to the suction force of the pump 26, and the pressure in the treated water pipe 24 is increased. Therefore, a difference in the pressure of the treated water means that the closed state of the membrane surface of the membrane unit 14 is different.
[0030]
Therefore, the analysis control means 32 reduces the filtration processing burden by lowering the rotational speed of the pump 26 for the high-pressure membrane unit 14. Accordingly, since it is not preferable that the total treated amount of treated water is reduced, the amount of treated water is increased by increasing the number of revolutions of the pump 26 for the membrane unit 14 having a low measured value of the pressure gauge 30. . FIG. 2 shows the water control of the individual membrane units 14 with respect to the total throughput. Here, a case is shown in which the membrane units 14B, A, C, D, and E are analyzed in order from the largest measured value by the pressure gauge 30. Conventionally, the output of the pump 26 is equally set to 20%, but in this embodiment, the rotational speed of the pump 26 is controlled to reduce the rotational speed of the membrane unit 14 having a high pressure. . That is, the amount of treated water in the membrane unit 14E having a low pressure (small amount of deposits) is increased, and conversely, the amount of treated water in the membrane unit 14B having a high pressure (large amounts of deposits) is decreased. At this time, it is preferable to perform control so that the same amount of treatment is performed in total so as not to change the total amount of treated water filtered by each of the membrane units 14A, 14B, 14C, 14D, and 14E.
[0031]
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 unit 14 is maintained while maintaining the total treated amount of the membrane separation wastewater treatment apparatus 20 substantially constant. A filtration process suitable for the closed state of the membrane surface can be performed. Moreover, the usage condition of each membrane unit 14 can be made uniform by changing the amount of treated water according to the membrane surface state of each membrane unit 14.
[0032]
When the integrated flow meter 34 is used, the membrane unit 14 having a smaller integrated flow rate is in a state where the membrane surface is blocked and the operating condition is severe, so the above-described control is performed by the analysis control means 32. That is, the number of treated water is reduced by reducing the number of rotations of the pump 26 of the membrane unit 14 having a small integrated flow rate, and conversely, the amount of treated water is increased for the membrane unit 14 having a high integrated flow rate.
[0033]
As described above, according to the membrane separation wastewater treatment apparatus 20 of the present embodiment, it is possible to prevent only specific membrane units 14 from being contaminated and to bias the integrated flow rate, and to make the operating status of all the membrane units 14 uniform. Therefore, it is possible to prevent accidental contamination of only the specific membrane unit 14 by accident. Therefore, in cleaning or replacing the contaminated membrane unit 14, it is possible to work at the same time 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. It becomes.
In the present embodiment, the membrane separation wastewater treatment apparatus 20 is installed in the treatment tank 12, but the same effect can be obtained even if it is installed in a nitrification treatment tank or a denitrification treatment tank.
[0034]
【The invention's effect】
Based on the above, according to the membrane separation wastewater treatment apparatus according to the present invention, by measuring the filtration pressure (or flow rate) for each membrane unit, the respective contamination statuses of each membrane unit are analyzed, and based on the analysis results. Therefore, the amount of water to be treated can be distributed according to the situation of each membrane unit, so that a specific membrane unit is not significantly contaminated more than necessary. Therefore, in the membrane separation wastewater treatment apparatus 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 the drawings]
FIG. 1 is a schematic diagram of a membrane separation wastewater treatment apparatus and peripheral devices in the present embodiment.
FIG. 2 is an explanatory view showing an example of control of the amount of treated water in each membrane unit.
[Explanation of symbols]
10... Treatment liquid, 12. ...... Pipe, 24 ...... Processed water pipe, 26 ...... Pump, 28 ...... Filtration membrane, 30 ...... Pressure gauge, 32 ...... Analysis control means, 34 ...... Integrated flow meter.

Claims (4)

Each membrane unit pump according to fluctuations in filtration pressure so that the product of filtration pressure and suction water volume in each membrane unit has a common value when the liquid to be treated is passed through multiple membrane units for solid-liquid separation. Membrane separation wastewater treatment method, characterized by controlling the suction flow rate. When the liquid to be treated is passed through multiple membrane units for solid-liquid separation, each membrane unit pump is adjusted according to the fluctuations in the integrated flow rate so that the ratio between the integrated flow rate and the pressure feed water amount in each membrane unit has a common value. Membrane separation wastewater treatment method, characterized by controlling the suction flow rate. A membrane separation wastewater treatment apparatus for introducing a liquid to be treated into a treatment tank and performing a solid-liquid separation treatment, a plurality of membrane units installed inside the treatment tank for filtering the liquid to be treated, and treated water in each of the membrane units A pressure measuring means for measuring the filtration pressure of the treated water for each of the membrane units, and the product of the filtration pressure and the amount of sucked water by the pump has a common value. A membrane separation wastewater treatment apparatus characterized by comprising control means for controlling the operation of each pump. A membrane separation wastewater treatment apparatus for introducing a liquid to be treated into a treatment tank and performing a solid-liquid separation treatment, a plurality of membrane units installed inside the treatment tank for filtering the liquid to be treated, and treated water in each of the membrane units A plurality of pumps for sucking water, and a flow rate measuring means for measuring the cumulative flow rate of treated water is provided for each of the membrane units, and the ratio between the cumulative flow rate and the suction water amount by the pump has a common value. A membrane separation wastewater treatment apparatus characterized by comprising control means for controlling the operation of each pump.

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