JP3637206B2 - Raw water treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a raw water treatment method for separating raw or industrial wastewater or other raw sludge-containing raw water into treated water and concentrated sludge using a membrane separator, and in particular, a plurality of the membrane separators are arranged side by side. The present invention relates to a raw water treatment method capable of suitably performing maintenance of the apparatus over a long period of time by alternately switching the operation / stop operation of a plurality of membrane separation apparatuses and performing cleaning and standby at the time of the stop.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, pressure-type membrane separation devices that separate raw or industrial wastewater or other raw sludge-containing raw water into treated water and concentrated sludge are known, and the operation control method of such a membrane separation device can be simply described based on FIG. To explain, 4 is a membrane raw water tank provided with a liquid level detecting device 3, and the raw water stored in the membrane raw water tank 4 is pumped to the membrane separation devices 2a and 2b by the membrane raw water pumps 1a and 1b, and treated water and After separation into concentrated sludge, the membrane treated water is fed to the membrane treated water tank 5 and the concentrated sludge is fed to, for example, a dehydrator in the next step.
[0003]
In such a system, when the liquid level in the membrane raw water tank 4 drops to an arbitrary level position R1, the liquid level detection device 3 detects it, and selectively stops the membrane raw water pumps 1a and 1b, while the membrane raw water tank 4 liquid level. Is increased to an arbitrary level position R2, the liquid level detection device 3 detects it, and the membrane raw water pumps 1a, 1b are controlled to be activated selectively, so that the liquid level in the membrane raw water tank 4 is always within a certain level range. It is controlled so that membrane separation is performed in the inside.
[0004]
On the other hand, the membrane separator generally feeds treated water to the outside of the membrane module by pumping the raw water into the membrane module consisting of a large number of ultrafiltration membranes formed in a tube element shape. Although it is configured so as to be fed to the membrane treatment water tank or the like of the process, it is necessary to periodically stop the operation for cleaning in order to remove the sludge adhered in the membrane module.
[0005]
For this reason, in the conventional apparatus, a plurality of membrane raw water pumps 1a and 1b for supplying raw water to the membrane separation devices 2a and 2b are provided, and the membrane separation devices 2a and 2b are respectively connected via liquid pumps 9a and 9b. The cleaning liquid can be supplied from the cleaning liquid tank 6. The membrane raw water pumps 1a and 1b and the liquid pumps 9a and 9b are configured to be manually activated / stopped by the operation panel 80.
[0006]
[Problems to be solved by the invention]
That is, in the conventional apparatus shown in FIG. 3, the operation switching, washing, operation stop, etc. of the membrane separation apparatus are performed by switching the washing, etc. while confirming the operation status (mainly the inlet pressure of the membrane separation apparatus is increased). As a result, the manual switching has a problem in that the inclination in the module is uneven and the life of only a certain membrane unit is reduced.
[0007]
In view of the technical problem, the invention according to claim 1 efficiently performs operation switching, washing, operation stop, etc. of the membrane separation device, and maintains the expected performance without causing deterioration of the membrane separation device. It aims at providing the raw water treatment method to obtain.
Further, the invention according to claim 2 efficiently performs switching, washing, operation stop, etc. of the membrane separator while switching the operation of the membrane separator according to the liquid level of the raw water tank. An object of the present invention is to provide a raw water treatment method capable of maintaining the desired performance without causing deterioration of the apparatus, and smoothly treating raw water without causing blockage of the membrane module in the membrane separation apparatus or flux reduction. To do.
[0008]
[Means for Solving the Problems]
In order to solve this technical problem, the present invention provides the raw water that has flowed into the raw water tank to each of the plurality of membrane separation devices via a pump, and each membrane separation device uses treated water. And raw water treatment method to separate into concentrated sludge,
Provided first calendar timer and the second calendar timer for outputting a switching instead signal every predetermined schedule period, switching the streams to stop with the first calendar timer by said plurality of operation to sequence for each set period, The series stopped by the switching is automatically subjected to water extrusion and water washing to the membrane separation apparatus of the series according to the period set by the second calendar timer during the stop period, and then enters a standby state until the next operation. As described above, the predetermined period of the second calendar timer is set.
[0009]
According to this invention, it is possible to perform operation control in which the operation of starting, stopping, cleaning, and stopping the operation of the plurality of membrane separation devices are alternately switched in a merry-go-round manner by the calendar timer. In other words, the calendar timer automatically switches the operation series of a plurality of membrane separation devices, and the stopped series automatically performs water extrusion and water washing, and then waits for the next operation, thereby separating the membrane separation. The expected performance can be maintained without causing deterioration of the apparatus.
[0010]
The invention according to claim 2 is to switch the operation of the membrane separation device in accordance with the liquid level of the raw water tank. The feature of the invention is that the raw water flowing into the raw water tank is supplied through a plurality of pumps. In the raw water treatment method of supplying to the membrane separator and separating into treated water and concentrated sludge in each membrane separator,
When the liquid level of the raw water tank is lowered, the series operated by the plurality of membrane separators is stopped for each series at the liquid level stage, and sludge is supplied with pressure water to the membrane separators of the stopped series In addition, the membrane separation device is washed with water and then put into a standby state until the next operation.
[0011]
That is, in the apparatus shown in FIG. 3, in order to examine the problem focusing on the raw water tank side, when the amount of membrane treated water is larger than the raw water tank inflow amount in the source water tank, the membrane raw water tank liquid level decreases, The MLSS concentration (activated sludge concentration) becomes high, which causes a blockage of the membrane module and a decrease in flux (processing amount per unit area). In addition, if the fluctuation of the membrane raw water pump inlet pressure due to the fluctuation of the liquid level is large, the supply amount of raw water to the membrane separation device cannot be kept constant, resulting in a decrease in the flow rate in the membrane separation device, etc. Similarly, the membrane module is blocked and the flux is reduced.
[0012]
In contrast, the present invention provides two or more liquid level detection level positions by the liquid level detection means under the condition that there is one raw water tank and two or more membrane separation devices. The operation of the second membrane separator (group) is stopped when the operation of the first membrane separator (group) is stopped and the liquid level further falls below the first set level and reaches the second set level. To stop. Since the liquid level can be kept constant by performing the operation (hereinafter the same applies to the third and fourth units), the zone control for keeping the membrane raw water tank liquid level within a certain range can be easily performed. It is possible to keep the MLSS concentration in the membrane raw water tank and the pressure at the inlet of the membrane raw water pump constant. As a result, the supply of the membrane raw water to the membrane separation device can be maintained at a constant amount. Thus, blockage in the membrane module and reduction in flux can be prevented.
[0013]
Further, according to the present invention, the operation sequence of the plurality of membrane separation devices is automatically synchronized with the control of the liquid level or in combination with the periodic operation / stop control by the calendar timer according to claim 1. In addition, the stopped system automatically performs water extrusion and water washing and then waits until the next operation. Can be maintained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Only.
[0015]
FIG. 1A shows a raw water treatment system according to a premise embodiment of the present invention, 4 is a membrane raw water tank provided with a liquid level detecting device 3, and the raw water stored in the membrane raw water tank 4 is a membrane raw water pump 1a. 1b, 1c is pumped to the membrane separators 2a, 2b, 2c and separated into treated water and concentrated sludge, then the membrane treated water is fed to the membrane treated water tank 5, and the concentrated sludge is fed to the dehydrator in the next step, for example. In addition, the cleaning liquid can be supplied from the cleaning liquid tank 6 to the membrane separation devices 2a, 2b, and 2c via the liquid pumps 9a, 9b, and 9c, respectively. The membrane raw water pumps 1a, 1b and 1c and the liquid pumps 9a, 9b and 9c are provided with the weekly timers 10a, 10b and 10c and the daily timers 19a, 19b and 19c provided in the controller 8 for starting and stopping, as well as washing and operation stop. It is configured to control in a merry-go-round shape.
[0016]
Next, the operation control method according to this embodiment will be described with reference to FIG. 1B. First, in the first membrane separation device 2a, the calendar timer 10a performs the first week, the third to fourth weeks, the sixth The run / stop cycle is configured to run ˜7 weeks and to cease operation in the second and fifth weeks. In the second and fifth week shutdown cycles, the daily timer 19a is activated, the liquid pump 9a is activated in the first two to three days, the cleaning liquid is supplied from the cleaning tank 6, and the water extrusion and water in the membrane module are supplied. After the cleaning is performed, the system is on standby (paused) until the next operation start cycle.
Thereafter, the second membrane separation device 2b is shifted by one week with respect to the first membrane separation device 2a and the same operation control is performed, and the third membrane separation device 2c is further controlled with respect to the first membrane separation device 2a for two weeks. The same operation control is performed by shifting.
[0017]
As a result, in the first week and the fourth week, the first and second membrane separation devices 2a, 2b are operated for membrane separation, the third membrane separation device 2c is stopped, and the water in the membrane module is stopped. After extruding and washing with water, it is on standby (paused).
In the second week and the fifth week, the second and third membrane separation devices 2b and 2c are operated for membrane separation, the first membrane separation device 2a is shut down, and water is pushed out in the membrane module. After being washed with water, it is waiting (paused).
Furthermore, in the third week and the sixth week, the first and third membrane separation devices 2a and 2c are operated for membrane separation, the second membrane separation device 2b is shut down, and water extrusion in the membrane module is performed. After washing with water, it is on standby (pause).
[0018]
Therefore, according to the present embodiment, the weekly timers 10a, 10b, and 10c and the daily timers 19a, 19b, and 19c automatically switch the operation series of the plurality of membrane separation devices, and the stopped operation series automatically After performing the extrusion and water washing, the expected performance can be maintained without causing deterioration of the membrane separation apparatus by waiting until the next operation.
[0019]
FIG. 2 is a membrane separation system showing a second embodiment corresponding to the present invention , and the explanation will focus on the differences from the previous embodiment.
According to the present embodiment shown in FIG. 2A, the membrane raw water pumps 1a, 1b, 1c perform operation and stop control at a cycle of 2 weeks / 1 week by weekly timers 10a, 10b, 10c provided in the controller 8. At the same time, the driving / stopping control of the membrane raw water pumps 1a and 1b can be controlled by liquid level control based on the detection signal from the liquid level detection device 3.
[0020]
That is, the selected two membrane raw water pumps 1a, 1b, and 1c are always driven by the weekly timers 10a, 10b, and 10c, but when the liquid level drops below the liquid level M2 during the driving, The first membrane raw water pumps 1a, 1b, 1c in the first week of the first week are stopped, and the other membrane raw water pumps 1a, 1b, 1c being stopped are returned to drive regardless of the weekly timers 10a, 10b, 10c. Has been.
The daily timers 19a, 19b, and 19c are operated in conjunction with the stop signal when the membrane raw water pumps 1a, 1b, and 1c are stopped by the weekly timers 10a, 10b, and 10c and the liquid level is lowered. Configured to do.
[0021]
And in this embodiment, while providing the return circuit 16A which isolate | separates the said treated water and returns to the said raw | natural water tank 4 in the exit side of the said membrane separation apparatus 2, detection from the liquid level detection apparatus 3 in the middle of this return circuit 16A A separation liquid return valve 16 that is controlled to open and close by the controller 8 based on the signal is provided.
[0022]
Next, the operation control method of this embodiment will be described. First, in the present embodiment, the weekly timers 10a, 10b, 10c are each weekly as in the first embodiment shown in FIG. The operation sequence of the plurality of membrane separation devices is automatically switched at, the two membrane separation devices are operated for membrane separation, the other membrane separation devices are stopped, and the stopped operation sequences are the daily timers 19a, 19b, 19c. After performing water extrusion and water washing automatically by the above, the point of waiting until the next operation is the same as in the above example, but the difference from the above embodiment is as shown in FIGS. 1 (C) and (B). For example, in the first week, when the two membrane raw water pumps 1a and 1b selected by the weekly timers 10a and 10b are lowered to the level M2 or less of the raw water tank during driving, the first week during the driving. Subsequent membrane source of 1a Pump 1b is stopped is that the other raw water pump 1c suspended drives restored regardless of the Week retimer 10c.
[0023]
That is, in more detail, as shown in FIG. 2C, first, in the first week, the first and second membrane separation devices 2a and 2b are operated for membrane separation, and the third membrane separation device 2c is operated. The operation is stopped, and after the water is pushed out and washed in the membrane module, it is on standby (paused).
In this state, despite the fact that the amount of raw water flowing into the raw water tank 4 is decreasing, both the membrane separation devices 2a and 2b are driven, and the liquid level in the raw water tank 4 is changed from M1. When the lower limit level M2 of 1 is reached, the membrane separation device 2b is first stopped by the control signal from the controller 8, and the other membrane separation device 2c that is stopped is driven in synchronism with this, and the stopped membrane separation is performed. The apparatus 2b automatically performs water extrusion and water washing by the daily timer 19b, and then waits until the next operation.
If the raw water inflow amount to the membrane raw water tank 4 and the raw water pumping amount of the membrane raw water pump 1b are balanced, a cycle by a weekly timer is performed.
[0024]
When the raw water inflow amount into the membrane raw water tank 4 is further reduced to lower than the second lower limit level L lower than the first lower limit level M2, any membrane separation device is controlled by a control signal from the controller 8. The operation of 2a and 2c is also stopped, the separation liquid return valve 16 is opened, the treated water after the membrane separation is returned to the raw water tank 4 from the return circuit 16A, and the liquid level in the raw water tank 4 is changed to M1. Maintain a level in the range of M2.
Thereafter, when the liquid level in the membrane raw water tank 4 increases to the range of the levels M1 to M2, the cycle operation by the weekly timer is performed by the control signal from the controller 8. When the raw water inflow amount to the membrane raw water tank 4 and the raw water pumping amount of the membrane raw water pump 1b are balanced and are between M1 and M2, that state continues.
[0025]
When the liquid level in the raw water tank 4 is lowered again from M1 to the first lower limit level M2, as shown in the second week of FIG. The other membrane separation device 2a that is stopped is driven in synchronization with this, and the stopped membrane separation device 2c automatically performs water extrusion and water washing by the daily timer 19b, and then waits for the next operation. To do.
The same operation is repeated thereafter.
[0026]
【The invention's effect】
As described above, in any of the above-described inventions, the operation of the membrane separation apparatus can be efficiently switched, washed, stopped, etc., and the expected performance can be maintained without causing the deterioration of the membrane separation apparatus.
The invention according to claim 2 efficiently performs the operation switching, washing, operation stop, etc. of the membrane separation device while switching the operation of the membrane separation device according to the liquid level of the raw water tank. The desired performance can be maintained without causing deterioration of the raw water, and the raw water can be treated smoothly without causing the membrane module in the membrane separation apparatus to be clogged or reduced in flux.
[Brief description of the drawings]
FIG. 1 is a membrane separation system showing a premise embodiment of the present invention, in which (A) is a control block diagram and (B) is a cycle operation diagram.
2A is a control block diagram, FIG. 2B is an operation diagram of a main circuit, and FIG. 2C is a cycle operation diagram in a membrane separation system showing another embodiment combined with liquid level control.
is there.
FIG. 3 is a configuration diagram showing a conventional membrane separation system.

Claims (2)

In the raw water treatment method, the raw water flowing into the raw water tank is supplied to a plurality of membrane separation devices through respective pumps, and separated into treated water and concentrated sludge by each membrane separation device,
Provided first calendar timer and the second calendar timer for outputting a switching instead signal every predetermined schedule period, switching the streams to stop with the first calendar timer by said plurality of operation to sequence for each set period, The series stopped by the switching is automatically subjected to water extrusion and water washing to the membrane separation apparatus of the series according to the period set by the second calendar timer during the stop period, and then enters a standby state until the next operation. The raw water treatment method is characterized in that the predetermined period of the second calendar timer is set as described above. In the raw water treatment method, the raw water flowing into the raw water tank is supplied to a plurality of membrane separation devices through respective pumps, and separated into treated water and concentrated sludge by each membrane separation device,
When the liquid level of the raw water tank is lowered, the series operated by the plurality of membrane separators is stopped for each series at the liquid level stage, and sludge is supplied with pressure water to the membrane separators of the stopped series The raw water treatment method is characterized in that after the membrane separation device is washed with water, it is put into a standby state until the next operation.

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