JP3933320B2 - Operation method of water treatment apparatus equipped with membrane separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating a water treatment apparatus equipped with a membrane separation device that performs activated sludge treatment and membrane separation on organic sewage, sewage, and the like that have a large amount of water fluctuation.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a membrane separation activated sludge treatment that treats organic sewage, sewage, etc. (hereinafter referred to as sewage) using a membrane is known. In this process, usually, as shown in FIG. 6, the inflowing sewage 41 is removed in the pretreatment facility 42, and then stored in the flow rate adjustment tank 43 and sent to the aeration tank 44 at a constant flow rate. The organic substance in the sewage 41 is decomposed and removed by activated sludge, and denitrified as necessary. On the other hand, the activated sludge mixed liquid in the tank is filtered by a membrane separator 45 installed in the tank and permeated through the membrane. 46 is led out and discharged through the treated water tank 47. At this time, the excess sludge 48 is continuously or intermittently extracted and stored in the sludge storage tank 49 so that the activated sludge concentration in the aeration tank 44 does not become extremely high.
[0003]
Such membrane-separated activated sludge treatment has begun to spread widely since the quality of treated water is stable and system maintenance is easy.
[0004]
[Problems to be solved by the invention]
However, the submerged membrane separation device is usually susceptible to the influence of the aeration device because the membrane is disposed above the aeration device so that the bubble flow of the aeration is used for cleaning the membrane surface and generating the liquid flow. .
[0005]
In other words, if the aeration tube is used to uniformly aerate the air with an appropriate amount of air, the membrane surface is evenly cleaned and the filtration is stable, but if the aeration tube is clogged, deposits are deposited on the membrane surface immediately above it. Is likely to occur. In this regard, even if continuous aeration is performed, air is not always ejected uniformly from all the diffuser holes. For example, if the diffuser pipes are not arranged horizontally, there are diffuser holes with a large amount of ejection. On the other hand, the air diffuser located at the opposite electrode has a negative pressure, and there is a local phenomenon such as sludge entering the air diffuser through the air diffuser, and the sludge that has entered the air diffuser is Within a long period of time, there is a problem in that it is dried by the supplied air, becomes a scab, and the diffuser tube becomes clogged.
[0006]
In addition, even when filtration is stopped to balance the amount of influent sewage and the amount of filtration, since a slight filtration is performed due to the pressure difference caused by aeration, a separation membrane with an organic filtration membrane disposed on the surface of the filter plate is used. In a membrane separation apparatus arranged in a row, the filtrate may stay on the permeate side of the filtration membrane, and the filtration membrane may swell. It is easy to get tired by vibration and may break.
[0007]
An object of the present invention is to solve the above-mentioned problems and to prevent blockage of an aeration device (aeration device) and fatigue breakage of a filtration membrane.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention performs activated sludge treatment of water to be treated flowing into a biological treatment tank in a state where aeration air is ejected from an air diffuser communicating with an air supply source via an air supply pipe. with the activated sludge mixture in the tank, diffusing over the air device is filtered by membrane separation apparatus arranged EXTRA-permeate outlet communicating with the permeate that has passed through the membrane surface to the permeate side of the separation membrane When the activated sludge mixed liquid in the tank is at the normal water level, the permeated water is sent to the treated water tank through the permeated water deriving system, and the water level of the activated sludge mixed liquid in the tank is set to a predetermined level. When the water level drops to the lower limit water level, the permeated water derived through the permeated water deriving system is injected into the tank along the supply pipe by the return pipe and returned to the tank together with the aerated air ejected from the diffuser , and then the activated sludge mixed liquid Water level rises to a certain upper water level And when, to provide a method of operating as the membrane separation unit water treatment device provided with a stop injection of permeate.
[0009]
The above operating method can be performed more advantageously in a water treatment apparatus equipped with a membrane separation device using a flat membrane cartridge having a filtration membrane on the surface of a membrane support as a separation membrane.
[0010]
With the above arrangement, the active each time the water level of the sludge mixture is reduced to a predetermined lower limit level, the permeate, is removed to the outside of the diffuser diffusing the gas apparatus sludge adhering to the inside or diffusing pores of the gas apparatus, residual since sludge can anti-sticking as wet state, dusting can be prevented clogging of a gas device, thereby preventing deposition on the membrane surface of the separation membrane.
[0011]
At that time, since the filtration is continuously performed regardless of the water level, in a membrane separation apparatus using a flat membrane cartridge in which a filtration membrane is disposed on the surface of the membrane support as a separation membrane, the filtration membrane is stretched on the membrane support. In this state, there is no problem of fatigue fracture due to the swelling of the conventional filter membrane.
[0012]
The filtration method may be a suction filtration method in which a suction pressure is applied to the permeation side of the separation membrane through a permeate discharge system, or a gravity filtration method in which the head of the activated sludge mixed liquid is used as a filtration driving pressure.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
The water treatment apparatus according to the first embodiment shown in FIG. 1 includes a pretreatment facility 2 for pretreatment of inflowing raw water 1, a flow rate adjusting tank 4 communicated with the pretreatment facility 2 via a raw water supply system 3, and a flow rate. A biological treatment tank 7 communicating with the adjustment tank 4 via the raw water supply system 5 and having a membrane separation device 6 installed therein; a treatment water tank 9 communicating with the membrane separation apparatus 6 via the permeate discharge system 8; A sludge storage tank 11 communicated with the treatment tank 7 via a sludge transfer system 10 is provided. In the treated water tank 9, a discharge pipe 12 reaching the discharge channel is opened, and in the sludge storage tank 11, a sludge extraction pipe 13 is opened.
[0014]
Specifically, the pretreatment facility 2 includes a screen 2a and a foreign matter storage tank 2b for storing foreign matter and sand.
The raw water supply system 3 is interposed in a raw water supply pipe 3a having one end opened inside the foreign substance storage tank 2b on the screen transmission side and the other end opened inside the flow rate adjusting tank 4, and the raw water supply pipe 3a. And raw water supply pump 3b.
[0015]
The raw water supply system 5 has a raw water supply pipe 5a having one end opened inside the flow rate adjusting tank 4 and the other end opened inside the biological treatment tank 7, and a raw water supply pump 5b interposed in the raw water supply pipe 5a. It consists of.
[0016]
The biological treatment tank 7 is provided with a level meter 15 for detecting the water level of the activated sludge mixed liquid 14 in the tank.
The membrane separation device 6 is immersed in the activated sludge mixed solution 14 and, as shown in FIG. 2, a plate-like membrane cartridge 17 is placed inside a box-shaped case 16 opened at the top and bottom. Are arranged along the vertical direction and with an appropriate membrane gap (6 to 10 mm), and below the membrane cartridge 17 is connected to an air supply source such as a blower 18 outside the tank or a compressor via an air supply pipe 19. A diffuser device 20 communicating with each other is provided. The air diffuser 20 has a plurality of air holes 20a.
[0017]
The membrane cartridge 17 has organic filtration membranes 17b disposed on the front and back surfaces of the filter plate 17a, and is connected to the permeate channel formed between the filter plate 17a and the filtration membrane 17b and inside the filter plate 17a. A water nozzle 17 c is formed on the filter plate 17 a, and a water collecting pipe 22 communicating with the permeated water nozzle 17 c of each membrane cartridge 17 through the tube 21 is attached to the case 16.
[0018]
The permeated water lead-out system 8 communicates at one end with the water collecting pipe 22 of the membrane separation device 6, the other end opens into the treated water tank 9, and a permeated water lead-out pipe 24 with a pump device 23 interposed therebetween, and the permeated water lead-out pipe. 24 has a return pipe 26 that communicates with the discharge side of the pump device 23 through a valve device 25 and that is led in the middle of the air supply pipe 19. Further, a control device 27 is provided which is electrically connected to the valve device 25 and the above level meter 15 and opens and closes the valve device 25 in accordance with an electric signal from the level meter 15.
[0019]
The sludge transfer system 10 includes a sludge transfer pipe 10a having one end opened in the lower part of the biological treatment tank 7 and the other end opened inside the sludge storage tank 11, and a sludge pump provided in the sludge transfer pipe 10a (preferably Is an air lift pump) 10b and a valve device 10c.
[0020]
The operation of the above configuration will be described.
The raw water 1 flows into the pretreatment facility 2, the contaminants in the raw water 1 are separated by the screen 2 a and the sand etc. settles and remains in the foreign matter storage tank 2 b, and the raw water at the end is fed by the raw water supply system 3. It is sent to the flow rate adjustment tank 4.
[0021]
The raw water 1 flowing into the flow rate adjusting tank 4 is stored and sent to the biological treatment tank 7 by the raw water supply system 5.
In the biological treatment tank 7, the raw water 1 from the flow rate adjustment tank 4 flows in, and the aerated air is ejected from the air diffuser holes 20 a of the air diffuser 20, so that the BOD in the raw water 1 is oxidized and decomposed by the activated sludge.
[0022]
At this time, in the case 16 of the membrane separation device 6, the bubble flow of the aerated air and the rising liquid flow generated thereby pass upward through the gap between the membrane cartridges 17 and 17, and thereby the filtration membrane 17b In a state where the membrane surface is washed and concentration polarization is prevented, the activated sludge mixed liquid 14 is filtered by the membrane surface of the filtration membrane 17b by the suction pressure acting from the pump device 23, and the permeated water 28 that has permeated the membrane surface is obtained. It flows into the permeated water outlet pipe 24.
[0023]
At this time, the water level of the activated sludge mixed liquid 14 is measured by the level meter 15, and the measured value is sent as an electric signal to the control device 27, while the electric signal indicating the normal water level is being sent. 28 is sent to the treated water tank 9 through the permeated water outlet tube 24. And it discharges through the discharge pipe 12 suitably.
[0024]
On the other hand, when an electric signal indicating a predetermined lower limit water level LL is sent, the control device 27 opens and closes the valve device 25 to open the return pipe 26 side, and the permeated water 28 is diffused through the return pipe 26 and the air supply pipe 19. 20 and flows into the biological treatment tank 7 through the air holes 20a.
[0025]
Thereafter, when the water level of the activated sludge mixed liquid 14 rises and an electric signal indicating a predetermined upper water level HL is sent by the level meter 15, the valve device 25 is opened and closed by the control device 27, and the return pipe 26 side is opened. The permeated water 28 is blocked and sent to the treated water tank 9.
[0026]
In this way, every time the water level of the activated sludge mixed liquid 14 in the biological treatment tank 7 is lowered to the predetermined lower limit water level LL, the diffuser 20 is washed by the permeated water 28. It is difficult to occur, and deposits on the film surface of the film cartridge 17 due to this hardly occur.
[0027]
At that time, since the activated sludge mixed liquid 14 does not fall below the predetermined lower limit water level LL, the membrane cartridge 17 is not exposed and the membrane cartridge 17 is continuously filtered. There is no problem of fatigue rupture due to the swelling of the conventional filter membrane because it is stuck to the plate 17a.
[0028]
The sludge 29 accumulated at the bottom in the biological treatment tank 7 is appropriately transferred to the sludge storage tank 11 by the sludge transfer system 10 and extracted through the sludge extraction pipe 13.
The water treatment apparatus according to the second embodiment shown in FIG. 3 has a configuration substantially similar to that of the first embodiment.
[0029]
However, the membrane permeated water outlet pipe 24 is not provided with a pump device, and is located in the treated water tank 9 at a position corresponding to the predetermined lower limit water level LL of the activated sludge mixed liquid 15 (even at a position slightly higher than the upper end of the membrane cartridge 17). In the biological treatment tank 7, gravity filtration is performed using the head of the activated sludge mixed liquid 15 as a filtration driving pressure, and the filtration is stopped at the lower limit water level LL.
[0030]
According to such an apparatus configuration, the permeated water 28 by gravity filtration is led out to the treated water tank 9 through the permeated water outlet pipe 24, and the permeated water 28 in the treated water tank 9 depends on the water level of the activated sludge mixed liquid 15. It is sent to the aeration device 20 through the return pipe 30. In this case as well, it is possible to prevent the air diffuser 20 from being blocked, deposits on the membrane surface of the membrane cartridge 17, and fatigue of the filtration membrane 17b.
[0031]
The water treatment apparatus in the third embodiment shown in FIG. 4 has a configuration substantially similar to that of the second embodiment.
However, the biological treatment tank 7 is divided into a denitrification section 7a where the raw water supply pipe 5a is opened and a nitrification section 7b communicating with the denitrification section 7a, and the membrane separation device 6 is installed in the nitrification section 7b. Yes. And the circulation system 32 which circulates the activated sludge mixed liquid 14 about 2 to 5 times the amount of raw water inflow between the denitrification part 7a and the nitrification part 7b is provided, and the level meter 15 is provided in the nitrification part 7b. Yes.
[0032]
According to such an apparatus configuration, the same effects as those of the second embodiment can be obtained, and a high nitrogen removing effect can be obtained.
As long as the denitrification unit 7a and the nitrification unit 7b are balanced, the level meter 15 may be provided in either the denitrification unit 7a or the nitrification unit 7b.
[0033]
Such an apparatus configuration for the purpose of removing nitrogen may be applied to the water treatment apparatus of the first embodiment.
Further, as shown in FIG. 5, an overflow channel 7 c that guides the activated sludge mixed liquid 14 in the biological treatment tank 7 to the flow rate adjustment tank 4 is provided, and a level meter 15 is provided in the flow rate adjustment tank 4, thereby providing a biological treatment tank. 7, the water level in the flow rate adjusting tank 4 is maintained constant, and the injection of the permeated water 28 is started and stopped at the predetermined lower limit water level LL and the predetermined upper water level HL in the flow rate adjusting tank 4. The same effect as in the embodiment can be obtained.
[0034]
As the membrane separation device 6, a flat membrane cartridge type having an organic filtration membrane as described above can effectively utilize the advantages of the present invention that can prevent fatigue of the filtration membrane and blockage of the diffuser. Even if a membrane separation device of a type including a membrane made of another shape or material, such as a tubular ceramic membrane or a hollow fiber membrane, is installed, the advantage that the air diffuser can be blocked can be utilized.
[0035]
Each of the above-described embodiments is intended to exemplify the biological treatment tank 7 and the permeated water lead-out system 8 which are characteristic configurations of the present invention, and various modifications can be made without departing from the scope of the present invention. It is.
[0036]
【The invention's effect】
As described above, according to the method of the present invention, every time the activated sludge mixed liquid is lowered to the predetermined lower limit water level, the aeration apparatus is washed with permeated water. It is possible to prevent deposition on the surface. Therefore, it is possible to reduce the frequency of membrane cleaning by means other than aeration, and it is possible to omit only the water backwashing and cope with the chemical cleaning alone.
[0037]
At that time, since the filtration is continuously performed regardless of the water level, in the membrane separation apparatus having the flat membrane cartridge in which the filtration membrane is arranged on the surface of the membrane support, the filtration membrane sticks to the membrane support. The problem of fatigue fracture due to the swelling of the conventional filtration membrane is not caused. Therefore, the film life is increased.
[Brief description of the drawings]
FIG. 1 is an apparatus configuration diagram illustrating a method for operating a water treatment apparatus including a membrane separation apparatus according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing the overall configuration of the membrane separation apparatus.
FIG. 3 is an apparatus configuration diagram illustrating an operation method of a water treatment apparatus including a membrane separation apparatus according to a second embodiment of the present invention.
FIG. 4 is an apparatus configuration diagram illustrating an operation method of a water treatment apparatus including a membrane separation apparatus according to a third embodiment of the present invention.
FIG. 5 is an apparatus configuration diagram illustrating an operation method of a water treatment apparatus including a membrane separation apparatus according to a fourth embodiment of the present invention.
FIG. 6 is a block diagram showing a processing flow in a water treatment apparatus equipped with a conventional membrane separation apparatus.
[Explanation of symbols]
1 Raw Water 6 Membrane Separator 7 Biological Treatment Tank 8 Permeate Derivation System 9 Treated Water Tank
14 Activated sludge mixture
15 level meter
17 Membrane cartridge (separation membrane)
17a filter plate
17b Filtration membrane
20 Aeration equipment
26 Return tube
27 Control unit

Claims (2)

In the state in which aeration air is ejected from an air diffuser communicating with an air supply source through an air supply pipe, the water to be treated flowing into the biological treatment tank is treated with activated sludge , and the activated sludge mixed liquid in the tank is When the permeated water filtered through the membrane separator with the external pressure type separation membrane above the diffuser and permeated through the membrane surface is led out of the tank through the permeate outlet system connected to the permeate side of the separation membrane , While the water level of the activated sludge mixed liquid is normal, the permeated water derivation system is used when the permeated water is sent to the treated water tank through the permeated water deriving system and the water level of the activated sludge mixed liquid in the tank is lowered to the predetermined lower limit water level. When the permeated water derived through the air is injected into the air supply pipe through the return pipe and returned to the tank together with the aerated air ejected from the diffuser , the water level of the activated sludge mixture rises to a predetermined upper water level. Stop permeate injection How the operation of the water treatment apparatus having a membrane separation device according to claim.   The operation method of the water treatment apparatus provided with the membrane separation apparatus according to claim 1, wherein a flat membrane cartridge having a filtration membrane on the surface of the membrane support is used as the separation membrane.

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