JP3688979B2 - Water level difference type membrane filtration device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water level difference type membrane filtration device, and in particular, feeds raw water at a constant flow rate to a riser pipe with an overflow weir or a pump, and sets the free water surface position of the riser pipe to the filtration resistance water level of the permeable membrane module. The present invention relates to a novel improvement for performing a smooth constant flow filtration that is equal to or higher than the sum of the outlet side pipe resistance water level and preventing membrane breakage at the start of refiltration.
[0002]
[Prior art]
Conventionally, as this type of membrane filtration device, the total amount filtration method shown in FIG. 5, the cross flow filtration method shown in FIG. 6, and industrial water No. 497 issued by Japan Industrial Water Association in February 2000 were used. The water level difference utilization type of FIG. 7 and the suction type of FIG. 8 disclosed on pages 31 and 32 of FIG.
First, in the case of the total amount filtration method of FIG. 5, the raw water from the raw water tank 1 is filtered through the raw water supply pump 2 by the membrane filtration device 3 composed of a permeable membrane module, and supplied to the treated water tank 5 through the pipe 4. Was configured.
When the membrane filtration device 3 is backwashed, the backwash pump 6 provided between the treated water tank 5 and the pipe 4 is driven to supply raw water to the membrane filtration device 3 in the direction opposite to that during filtration. Backwashed and drained.
[0003]
In the case of the cross flow filtration method of FIG. 6, the configuration is basically the same as that of FIG. 5, but a part of the treated water of the membrane filtration device 3 is fed into the raw water tank 1 through the reverse feed pipe 7. I was returning.
[0004]
In the case of the water level difference utilization type of FIG. 7, the raw water in the raw water tank 1 is sent from the membrane module type membrane filtration water tank 3a to the membrane filtration water tank 3aA via the suction pump 2a and taken out as membrane filtration water. The membrane filtration water tank 3a is provided with a cleaning blower 10 for cleaning.
[0005]
In the case of the suction type shown in FIG. 8, the tank to which raw water is supplied is formed by the membrane soaking tank 3b and sent to the membrane filtration water tank 3aA via the suction pump 2a to obtain the membrane filtrate.
[0006]
[Problems to be solved by the invention]
Since the conventional membrane filtration apparatus was comprised as mentioned above, the following subjects existed.
That is, in both cases of FIGS. 5 and 6, there is no difference in water level between the raw water tank and the membrane filtration device, and the raw water must be supplied to the membrane filtration device by a pump.
Moreover, in the case of FIG.7 and FIG.8, since the raw | natural water has a water level difference with respect to a membrane filtration apparatus in a position where a raw | natural water tank is higher than a membrane filtration apparatus, the above pumps for raw water supply are unnecessary. Since the membrane filtration water tank is a submerged membrane module type, it needs a sufficient volume to be stored in the tank, and this tank must have a pressure resistant / sealed structure that can withstand the pressure of the water level, The amount of water held in the tank was large, and the weight of the tank when water was held was extremely large, and the installation work for the tank required a large amount of expenses for foundation work.
Moreover, if this tank was a square type, a pressure resistance design was required.
In addition, when the inside of the tank is air-cleaned (air scrubbing) in this method, since the water level difference acts on the membrane filtration water tank, the air supply pressure required for air cleaning must be greater than this water level difference. In order to generate large power for sending compressed air, a large pump or motor is required, which is economically disadvantageous.
[0007]
The present invention has been made to solve the above-described problems. In particular, the raw water at a constant flow rate is supplied to the rising pipe by the overflow weir or the pump, and the free water surface position of the rising pipe is set to the permeable membrane. Provide a water level difference type membrane filtration device that performs smooth constant flow filtration that is equal to or higher than the sum of the filtration resistance water level of the module and the outlet side pipe resistance water level, and prevents membrane breakage at the start of refiltration. With the goal.
[0008]
[Means for Solving the Problems]
The water level difference type membrane filtration device according to the present invention supplies raw water from the raw water tank to the permeable membrane module via the overflow weir or pumping pump and the rising pipe, and performs filtration operation by the permeable membrane module using the water level difference. to perform, free water surface height position of the launch tube is, the water level difference utilizing the at permeation membrane module filtration resistance level and above the sum of the filtered water tube resistance level of the outlet-side filtration water pipe of the permeation membrane module In the mold membrane filtration apparatus, the backwash drainage branch pipe is connected to the lower part of the permeable membrane module and communicates with the rising pipe, and the upper end position of the backwash drainage branch pipe is the permeable membrane. Ri configuration der substantially corresponds to the upper height position of the module, also the permeation membrane module is a construction which is a casing accommodating hollow element membrane module.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a water level difference utilization type membrane filtration device according to the present invention will be described with reference to the drawings. The same or equivalent parts as those in the conventional example will be described using the same reference numerals.
FIG. 1 is a configuration diagram showing a form of a total amount filtration system according to the present invention.
In FIG. 1, reference numeral 1 denotes a raw water tank (which may not be a raw water tank). The raw water in this raw water tank 1 passes through an overflow weir 20A provided in this raw water tank 1 or a pumping pump (not shown). It is configured to be sent to a rising pipe 20 that is vertically raised.
[0010]
Connected to the lower portion of the rising pipe 20 is a permeable membrane module 3 which is provided vertically and is formed of a well-known casing housing type hollow membrane membrane module.
The permeable membrane module 3 is connected to a drain drain valve V _B1 and an electromagnetic part B at a lower portion thereof, and to an exhaust exhaust valve V _{B2 at} an upper portion thereof.
[0011]
A siphon type branch pipe for backwash drainage 21 as an exhaust pipe is connected to the lower part of the permeable membrane module 3, and a drain valve 23 is connected to the backwash drainage branch pipe 21.
A filtered water pipe 4 having a filtered water valve 26 for sending filtered treated water to the filtered water tank 5 is connected to the upper part of the permeable membrane module 3.
A backflow cleaning pipe 31 communicating with the lower part of the filtered water tank 5 is provided at a position before the filtered water valve 26 of the filtered water pipe 4, and the backflow cleaning pump 6 and the backwash opening / closing valve 30 are provided in the backflow cleaning pipe 31. Is provided. The upper end position 21 a of the backwash drainage branch pipe 21 substantially corresponds to the upper height position 3 a of the permeable membrane module 3.
[0012]
Next, the operation will be described. First, the raw water flows into the constant flow rising pipe 20 by the overflow weir 20A which is a constant inflow device. The required transmembrane pressure difference of the permeable membrane module 3 is generally about 1 m / d with a water level difference of several meters at the start of filtration. Therefore, the water level during the start-up 20 starts filtration at a water level difference H1 which is a difference from the water level WL1 which is several meters higher than the filtered water pipe 4, that is, the upper end position WL0 ′ of the filtered water pipe 4. At this time, the filtered water valve 26 is open and the drain valve 23 is closed.
If the above-mentioned membrane filtration is continued, the membrane becomes clogged, so it is necessary to carry out backwashing every several tens of seconds for several tens of seconds. Backwashing is performed by the backwash on / off valve 30 with a timer. This is done by closing the filtered water valve 26, opening the drain valve 23, and starting the backwash pump 6. At this time, since the raw water in the rising pipe 20 is also drained together, the water level in the rising pipe 20 is lowered to WL0.
Next, the backwash pump 6 is stopped, the drain valve 23 is closed, and the filtered water valve 26 is opened, so that the filtration is resumed, but the water level in the rising pipe 20 starts from WL0.
At this time, the differential pressure applied to the membrane of the permeable membrane module 3 is extremely small, and the filtration rate is low. If this state is continued, the filtered water amount is smaller than the raw water inflow amount, so that the water level in the rising pipe 20 gradually rises and stops at a water level where the raw water inflow amount and the filtered water amount are balanced.
As the above-described cycle is continued, dirt that cannot be removed by backwashing accumulates in the membrane, the water level in the riser 20 gradually rises, and after several months, the upper limit of the transmembrane pressure difference is reached. Reach WL2. In this case, it is necessary to clean the membrane with chemicals and return it to the initial state.
[0013]
FIG. 2 shows a temporal filtration process in the above operation. That is, as described above, when the filtration time elapses, the clogged state of the membrane of the permeable membrane module 3 deteriorates (that is, the filtration resistance increases) despite the regular backwashing operation. The water level WL1 rises as indicated by WL1 ′.
Therefore, the free water surface height position in the riser pipe 20 when the permeation membrane module 3 is used by using the above water level difference is the filtration resistance water level of the permeation membrane module 3 and the filtration water tube on the outlet side of the permeation membrane module 3. It is necessary to set it to be equal to or higher than the sum of the filtered water pipe resistance level of 4.
[0014]
In the case of the casing housing type membrane module, the backwashing may be performed only by air washing, but it is preferable to backwash with water in order to ensure completeness. In this case, the filtered treated water is backwashed using the backwash pump 6, but in order to reduce the power of the backwash pump 6 as much as possible, the water level on the primary side (raw water supply side) of the permeable membrane module 3. It is preferable to perform backwashing in a state where the pressure is lowered.
The lowering level of the water level may be a position near the upper part of the permeable membrane module 3, that is, WL0. By doing so, after backwashing, pressure more than necessary is applied at the start of filtration, and an extremely fast filtration rate is prevented so that the membrane is not damaged or clogging of the membrane is not promoted. Therefore, the backwash drainage branch pipe 21 of the permeable membrane module 3 is a siphon pipe.
Moreover, the smaller the pipe diameter of the starting water introduction pipe 20 on the primary side of the permeable membrane module 3, the smaller the amount of accumulated water and the less waste water during pumping, and less waste, and the filtration resistance of the permeable membrane module 3. Whether the response to the change in the water level of the rising pipe 20 may be fast or not, it is practically preferable to set the flow velocity in the pipe to 0.3 to 0.5 m / second.
[0015]
Next, the configuration shown in FIG. 3 is a configuration diagram showing a cross flow filtration system which is another form of FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted to avoid duplication.
A branch valve 21 for backwash drainage connected to the permeable membrane module 3 is connected to a drain valve 23 that performs a variable on-off valve driven by a motor 22, and a cross-flow drain pipe connected to the upper part of the permeable membrane module 3. 7 is provided with a cross flow drain valve 24.
At the downstream position of the filtered water pipe 4, a filtered water valve 26 that performs a variable on-off valve driven by a motor 25 in conjunction with a filtered water flow meter 26a is provided.
[0016]
Accordingly, the filtration operation of FIG. 2 is basically the same as that of FIG. 1, but since it is a cross flow filtration system, the opening degree of the filtrate water valve 26 is made variable by the motor 25 as shown in FIG. Only the opening and closing of the valve 24 is different.
[0017]
【The invention's effect】
Since the water level difference utilizing membrane filtration device according to the present invention is configured as described above, the following effects can be obtained.
That is, since raw water is supplied to the permeable membrane module using a difference in water level with the overflow weir, a conventionally used raw water supply pump is not required, and the apparatus configuration is simplified.
In addition, since a permeable membrane module, that is, a casing housing type hollow core membrane module is used as a filtration device, the filtration device itself is small, so it is necessary to use a large and high-cost filtration tank like a conventional water level difference type. Therefore, a low-cost and highly reliable filtration device can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a water level difference type membrane filtration device according to the present invention.
FIG. 2 is an explanatory diagram showing the operation of FIG. 1;
FIG. 3 is a configuration diagram showing another embodiment of FIG. 1;
4 is an explanatory diagram showing the operation of FIG. 3. FIG.
FIG. 5 is a block diagram showing a conventional total filtration method.
FIG. 6 is a configuration diagram showing a conventional cross-flow filtration method.
FIG. 7 is a configuration diagram showing a conventional water level difference type configuration.
FIG. 8 is a configuration diagram showing a configuration of a conventional suction type.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Raw water tank 3 Permeation membrane module 3a Upper part height position 4 Filtration water pipe 20 Startup pipe 20A Overflow weir 21 Branch pipe 21a for backwash drainage Upper end position

Claims (2)

Raw water is supplied from the raw water tank (1) to the permeable membrane module (3) through the overflow weir (20A) or the pumping pump and the rising pipe (20), and the permeable membrane module (3) uses the water level difference. to perform the filtration operation, the free water surface height position of the launch tube (20) is, the permeation membrane module (3) outlet filtered water tubes of the filtration resistance level and the permeable membrane module (3) of ( in the water level difference-using membrane filtration apparatus which der so that more than the sum of the filtered water tube resistance level of 4), communicating with the permeable membrane module (3) is connected to the lower of and the rising pipe (20) siphon Type backwash drainage branch pipe (21), the upper end position (21a) of the backwash drainage branch pipe (21) substantially corresponds to the upper height position (3a) of the permeable membrane module (3) A water level difference type membrane filtration device characterized by   The water level difference type membrane filtration device according to claim 1, wherein the permeable membrane module (3) is a casing housing type hollow core membrane module.

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