JP5269749B2 - Filtration device cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing method of a filtration apparatus surely and extremely efficiently separating and removing deposit accumulated on a filtration filter or a separation membrane. <P>SOLUTION: The washing method of a filtration apparatus is provided for washing the filtration apparatus equipped with the filtration filter or the separation membrane. An air chamber set on the filtrate side of the filtration apparatus is filled with gas, a valve on the filtrate outflow side is closed from a filtering operation state of obtaining the filtrate by feeding raw water containing super-fine bubbles to the filtration apparatus by a raw water feed pump, to increase the pressure in a flow path from a discharge side of the raw water feed pump to a filtrate outflow side valve up to a pump delivery pressure, making once the filtration apparatus a pressurized sealed state, then a concentrated liquid discharge side valve is opened to rapidly reduce the raw water side pressure, to thereby separate the deposit on the filter or separation membrane to the raw water side. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a cleaning method for a filtration device, and more particularly to a filtration method for a filtration device that can effectively peel off deposits deposited on the filtration filter or the separation membrane in a filtration device equipped with a filtration filter or a separation membrane.

  When a filtration device equipped with a filtration filter or a separation membrane is operated for a long period of time, turbid substances in raw water adhere to and accumulate on the filtration filter or the separation membrane, and the filtration ability of the filtration filter and the separation membrane decreases. Examples of methods for recovering the filtration performance of filtration filters and separation membranes with reduced filtration capability include, for example, intermittent flow of raw water, raw water flushing, air bubbling, mechanical vibrations of the membrane, and physical deposits on the membrane surface. There are known methods such as scrubbing or back-pressure cleaning (hereinafter sometimes referred to as “backwashing”) in which water or gas is passed through the membrane in the direction opposite to that during filtration.

  For example, Japanese Patent Application Laid-Open No. 63-111995 discloses an aseptic water production apparatus equipped with a raw water tank, a hollow fiber type ultrafiltration module, and a pump for supplying raw water to the module. A water production apparatus is disclosed. In this device, the valve of the module effluent permeate line is opened and the valve of the module effluent concentrate flushing line is closed, and the valve of the module effluent concentrate flushing line is closed according to the timer time-up signal, and the pressure of the module influent water is reduced. When the pressure rises and reaches a predetermined pressure, the switch is operated to open the valve of the module effluent concentrate flushing line and release it all at once to perform flushing for a predetermined time. However, in this method, since raw water mainly flows in parallel to the surface of the raw water supply side separation membrane, it cannot be said that the effect of removing turbid substances deposited on the separation membrane is sufficient.

  In JP-A-60-197206, the permeate side of a permeable membrane module is sealed with a gas body filled in advance with the permeate side, the raw water pressure on the raw water side is increased for a predetermined time, and then the raw water side A method for cleaning a permeable membrane module is disclosed in which the accumulated water in the permeable membrane is peeled to the raw water side by lowering the raw water pressure. According to this method, the permeated water flows from the permeate side to the raw water side due to the expansion force of the gas body compressed on the permeate side, and backwashing is performed. It is described that the turbid matter emerges from the membrane surface, is discharged out of the system along the flow of the raw water, and the membrane surface is washed. However, with this method, the deposit on the film surface is considerably peeled off, but it is not entirely satisfactory and is not necessarily a satisfactory method.

JP 63-111995 A JP-A-60-197206

  The objective of this invention is providing the washing | cleaning method of the filtration apparatus which can peel and remove the deposit deposited on the filtration filter or the separation membrane reliably and extremely efficiently.

  As a result of intensive studies to achieve the above object, the present inventor has provided an air chamber on the filtered water side of the filtration device, filled the gas in this air chamber, and contains ultrafine bubbles by the raw water supply pump. From the filtration operation state in which the raw water is supplied to the filtration device, the filtered water outlet side valve is closed, the inside of the filtration device is increased to the pump discharge pressure, the inside of the filtration device is once pressurized and sealed, and then the concentrate discharge port When the side valve is opened and the pressure on the raw water side is drastically reduced, the deposits deposited on the surface of the filtration filter or separation membrane can be peeled off to the raw water side in an extremely efficient and reliable manner in a finely pulverized state. As a result, the present invention has been completed.

  That is, the present invention is a method for washing a filtration device equipped with a filtration filter or a separation membrane, wherein an air chamber provided on the filtrate water side of the filtration device is filled with gas, and ultrafine bubbles are removed by a raw water supply pump. The filtration water outlet side valve is closed and the flow path from the raw water supply pump discharge side to the filtered water outlet side valve is increased to the pump discharge pressure from the filtration operation state in which the raw water contained is supplied to the filtration device to obtain filtered water. Once the inside of the filtration device is pressurized and sealed, the concentrate outlet port valve is opened, the pressure on the raw water side is drastically lowered, and the deposit on the filtration filter or separation membrane is peeled off to the raw water side. A filtering device cleaning method is provided.

  In this filtering apparatus cleaning method, the raw water containing ultrafine bubbles has a gas-liquid mixed fluid obtained by mixing gas in the raw water, and has a reduced portion, a most sandwiched portion, and an enlarged portion due to the high pressure by the raw water supply pump. It may be ultrafine bubble-containing raw water that is obtained by circulating a flow path and changing the flow velocity and pressure of the high-speed shear flow of the gas-liquid mixed fluid formed in the flow path to generate ultrafine bubbles.

  In the present specification, the filtered water that has passed through the filtration filter and the permeated water that has passed through the separation membrane are collectively referred to as “filtered water”. Further, the filtration filter and the separation membrane may be collectively referred to as “membrane”, and filtration through the filtration filter and filtration through the separation membrane may be collectively referred to as “membrane filtration”.

  According to the method for cleaning a filtration device of the present invention, the impact received by the filtration filter or the separation membrane due to a sudden change in pressure when the concentrate discharge port side valve is opened and the raw water side pressure is suddenly lowered, Accumulated flow of filtered water from the filtered water side to the raw water side due to rapid expansion of gas in the chamber (back flow), and deposition due to rapid expansion of ultrafine bubbles in the raw water soaked in the sediment of turbid material Due to a synergistic effect with the crushing of the object, the deposit on the surface of the filtration filter or the separation membrane can be peeled off and removed very efficiently and reliably and in a finely pulverized state.

It is a schematic explanatory drawing (schematic flowchart) which shows an example of the washing | cleaning method of the filtration apparatus of this invention. It is a fragmentary sectional view (sectional view of a liquid feeding dispersion part) showing an example of a device (water pump with a built-in ultrafine bubble generator) in which a water pump used in the method of the present invention and an ultrafine bubble generator are integrated. . It is the elements on larger scale (sectional drawing) of the storage chamber of the water pump with a built-in ultrafine bubble generator of FIG. It is sectional drawing which shows the other example of the apparatus (water pump with a built-in ultrafine bubble generator) with which the water pump used by the method of this invention and the ultrafine bubble generator were integrated. It is the elements on larger scale (sectional drawing) of the water pump with a built-in ultrafine bubble generator of FIG. It is sectional drawing which shows the further another example of the apparatus (water pump with a built-in ultrafine bubble generator) in which the water pump and the ultrafine bubble generator used by the method of this invention were integrated. It is sectional drawing which shows an example of the ultrafine bubble generator used by the method of this invention.

The filtration device to be cleaned by the method of the present invention includes a filtration filter or a separation membrane. The filtration filter is not particularly limited, and for example, filtration filters of various materials and shapes having a pore diameter of about 1 μm or more and less than 25 μm can be used. Examples of the material of the filtration filter include metal (metal mesh), plastic, paper, and the like. Examples of the shape of the filtration filter (element) include a cylindrical type and a plate & frame type element. The internal volume of the filtration filter (filter element) is, for example, about 50 to 5000 mL, preferably about 100 to 2000 mL. Further, filtration area of the filtration filter (filter media element), for example 0.001～1M ^2, preferably 0.005～0.5M ² approximately.

  The separation membrane is not particularly limited, and examples thereof include an ultrafiltration membrane, a microfiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane. The ultrafiltration (UF) membrane is a separation membrane for separating a substance having a molecular weight of 500 to 300,000 (molecular size of about 0.001 to 0.03 μm), and includes a category of a normal nanofiltration membrane. A microfiltration (MF) membrane is a separation membrane for separating particles having a particle size of 0.02 to 2 μm. Accordingly, the pore diameter of the ultrafiltration or microfiltration membrane is 0.001 to 2 μm, more preferably 0.01 to 1 μm. A reverse osmosis (RO) membrane is a separation membrane (with a molecular size of about 1 to 0.001 μm) for separation of salts and substances having a molecular weight of about 500, and is used for desalination of seawater, for example. Further, the permeated water of the ultrafiltration membrane may be passed through the reverse osmosis membrane.

  Examples of the material for the separation membrane include general materials such as cellulose acetate, polyacrylonitrile, polysulfone, polyethersulfone, polyacrylonitrile, aromatic polyamide, polyvinylidene fluoride, polyvinyl chloride, polyethylene, polypropylene, polyimide, and ceramic. Can be used. Among these, cellulose acetate, polysulfone, polyethersulfone, polyacrylonitrile, and aromatic polyamide are preferable as the material for the ultrafiltration membrane, and polyvinylidene fluoride, polyethylene, polypropylene, polysulfone, and ceramic are preferable as the material for the microfiltration membrane. . As a material for the reverse osmosis membrane, cellulose acetate, aromatic polyamide and the like are preferable.

  A membrane module is mentioned as a filtration apparatus provided with the separation membrane. The membrane module may be any of a hollow fiber filtration membrane module, a flat plate module, a tubular module, a spiral module, etc., but a hollow fiber filtration membrane module is preferable because it can be backwashed relatively easily. . The hollow fiber membrane inner diameter of the hollow fiber membrane module is such that fine bubbles having a bubble diameter of 50 μm or less are effectively passed through the inside of the hollow fiber membrane, while preventing the blocking of contaminants and improving the hollow fiber filling rate. Therefore, the range of about 0.1 to 2.0 mm is preferable, and the range of 0.5 to 1.0 mm is more preferable.

  Examples of the hollow fiber membrane include cellulose acetate-based hollow fiber membranes, polysulfone-based hollow fiber membranes, polyacrylonitrile-based hollow fiber membranes, and polyvinylidene fluoride hollow fiber membranes. The cellulose acetate-based hollow fiber membrane is preferable because it can be easily suppressed and fouling of the membrane is easily suppressed. In addition, a pore having a smaller pore diameter on the inner surface side than on the outer surface side is suitable as the internal pressure type.

  In addition, it does not specifically limit as raw water provided to a filtration apparatus, Fresh water (river water, lake water, etc.), seawater, etc. are mentioned. As the raw water, a mixture of the concentrated circulating water obtained through the filtration device can be used.

  In the present invention, gas is filled in an air chamber (air hold tank) provided on the filtered water side of the filtration device, and raw water containing ultrafine bubbles is removed by a raw water supply pump (sometimes referred to as a “water supply pump”). From the filtration operation state where the filtered water is supplied to the filtration device, the filtered water outlet side valve is closed, the flow path from the raw water supply pump discharge side to the filtered water outlet side valve is increased to the pump discharge pressure, and once filtered After the inside of the apparatus is pressurized and sealed, the concentrate discharge port side valve is opened, the raw water side pressure is rapidly lowered, and the filter filter or separation membrane deposit is peeled off to the raw water side.

  The shape, material, and size of the air chamber are not particularly limited, and can be appropriately selected in consideration of the size of the filtration device, the operability of the cleaning operation, safety, and the like. The shape of the air chamber may be any of, for example, a cylindrical shape, a balloon shape (a hollow spherical shape, an elliptical shape, etc.). The material of the air chamber may be any of metal (stainless steel, titanium, etc.), glass, plastic, etc., for example. As the size of the air chamber, in the case of a cylindrical shape, the diameter is, for example, 5 mm to 200 mm, preferably about 10 mm to 100 mm, and the height (length) of the internal space is, for example, 10 mm to 1000 mm, preferably about 20 mm to 500 mm. It is.

  The internal volume of the air chamber is, for example, about 20 mL to 30 L, preferably about 25 mL to 1 L, and more preferably about 25 mL to 500 mL. If the internal volume of the air chamber is too small, the peelability of deposits on the surface of the filter or separation membrane tends to be lowered, and if it is too large, waste is reduced in terms of drainage reduction and cost.

  The attachment position of the air chamber may be a place where the air can be stored on the filtered water side of the filtration device, but it is preferable that the air chamber is attached above the surface of the filtered water during the filtration operation.

  Examples of the gas that fills the air chamber include, but are not limited to, air, nitrogen, and argon. In the present invention, since an air chamber is provided on the filtered water side of the filtration device, when the pressure in the filtration device is suddenly lowered during cleaning, a strong impact is given to the filtration filter or the separation membrane, and the gas at the time of the pressure drop is reduced. Since the expansion is significantly larger than that of water, an effect of increasing the capacity of pushing the secondary side (filtrated water side) water to the primary side (raw water side, concentrated liquid side) can be obtained.

  Next, raw water containing ultrafine bubbles will be described.

  In the present specification, ultrafine bubbles refer to bubbles having a bubble diameter of 50 μm or less when they are generated. The bubble diameter is preferably 50 μm or less when generated, and more preferably 10 μm or less when generated. Even when the ultrafine bubbles are generated, for example, about 10 μm, there is a phenomenon that they gradually decrease with time. In the present invention, the number of bubbles having a bubble diameter of 2 to 50 μm (number measured by a particle counter) contained in the ultrafine bubble-containing raw water flowing into the filtration device is, for example, 100 / mL at 20 to 30 ° C. As mentioned above, Preferably it is 300 piece / mL or more, More preferably, it is 1000 piece / mL or more, Especially 2000 piece / mL or more is preferable. The ultrafine bubble-containing raw water that flows into the membrane module may contain bubbles having a bubble diameter of 50 μm or more.

  In the present invention, since raw water containing ultrafine bubbles is used, when the pressure in the filtration device is drastically reduced during cleaning, the ultrafine bubbles in the raw water soaked in the deposit on the filtration surface are rapidly expanded, Grind the deposit finely. For this reason, the filtration surface of a filtration filter or a separation membrane can be cleaned very efficiently. Note that the ultrafine bubbles not only remove and crush the dirt on the filtration surface, but also work to prevent the once-separated dirt from adhering to the membrane surface again due to electrostatic action.

  Raw water containing ultrafine bubbles gives high-speed shearing to a gas-liquid mixed fluid in which a gas as a source of ultrafine bubbles is mixed into the raw water, or causes the gas-liquid mixed fluid to flow through a flow path where the gap changes. , An ultra-fine bubble generator that generates bubbles mainly having a size of 50 μm or less by changing the flow velocity and pressure of the gas-liquid mixed fluid by changing the channel gap (for example, 70% or more of all generated bubbles are bubbles It can be prepared by an ultrafine bubble generator which is a bubble having a diameter of 50 μm or less. As a method for generating ultrafine bubbles, generally, a method using a chemical, a method in which a gas is dissolved in a supersaturated state and a pressure is reduced, a method in which a gas is mixed with a fluid to give high-speed shearing, a flow of a gas-liquid mixed fluid There is a method of changing the flow gap and pressure of the gas-liquid mixed fluid by changing the passage gap. It is generally known that the properties of the generated ultrafine bubbles differ greatly depending on the generation method of the ultrafine bubbles (Hirofumi Taisei: All of microbubbles, Nihon Jitsugyo Shuppan pp. 1-285, 2006).

  As a method for generating ultrafine bubbles, there are a method in which gas is mixed in raw water to give high-speed shearing, and a method in which the flow gap and pressure of the gas-liquid mixed fluid are changed by changing the flow gap of the gas-liquid mixed fluid. preferable. As a method for applying high-speed shearing, there are a method of generating bubbles by rotating a liquid and a gas at a high speed in a cylindrical shape, and a method of generating bubbles by passing a gas-liquid mixed fluid through an annular slit at a high speed. . In particular, an apparatus including an annular slit that generates ultrafine bubbles in the liquid by allowing the gas-liquid mixed fluid to pass through the annular slit and ejecting the fluid is suitable. This annular slit is preferably provided with a flow path expanding portion provided so as to expand from the minimum gap portion from the inner diameter side to the outer diameter side (in this case, the gas-liquid mixed fluid flows from the inner diameter side to the outer diameter. Flows towards the side). The annular slit may be provided with a flow passage expanding portion provided so as to expand from the smallest gap portion from the outer diameter side toward the inner diameter side (in this case, the gas-liquid mixed fluid is outside It flows from the diameter side toward the inner diameter side). When the gas-liquid mixed fluid is caused to pass through the annular slit to be ejected, the annular slit may be passed using high pressure generated by high-speed rotation of a rotating body provided with a centrifugal blade. Further, as a method of changing the flow velocity and pressure of the gas-liquid mixed fluid by changing the channel gap of the gas-liquid mixed fluid, for example, the gas-liquid mixed fluid can be reduced by using a high pressure to reduce the narrowing portion, Examples thereof include a method of circulating a flow path (for example, an annular slit).

  In the present invention, after pressurization by the raw water supply pump (more specifically, after pressurization by rotation of the pump impeller of the raw water supply pump), pressure membrane filtration by the raw water supply pump is performed while generating ultrafine bubbles. May be performed. Ultra-fine bubbles generated in a state where the pressure is increased by the raw water supply pump expands due to the pressure drop when passing through the membrane, and the pressure when the gas dissolved under high pressure flows through the membrane (and membrane pores) An extremely large number of ultrafine bubbles are generated by the descending. When a filtration filter is used, the pressure on the discharge side of the raw water supply pump (that is, the filtration pressure during membrane filtration) is, for example, 0.01 MPa (gauge pressure) or more [eg, 0.01 to 0.5 MPa (gauge pressure)]. It is. When using an ultrafiltration membrane or a microfiltration membrane module, the pressure on the discharge side of the raw water supply pump (that is, the filtration pressure during membrane filtration) is, for example, 0.01 MPa (gauge pressure) or more [eg, 0.01 to 0.1 MPa. (Gauge pressure)], preferably 0.02 MPa (gauge pressure) or more [for example, 0.02 to 0.08 MPa (gauge pressure)]. When a reverse osmosis membrane module is used as the membrane module, the pressure on the discharge side of the water supply pump is about 100 times higher than that of the ultrafiltration or microfiltration membrane module. This is [for example, 1 to 7 MPa (gauge pressure)], and a high-pressure pump is required.

If the introduction position of the gas (air, etc.) that is the source of ultrafine bubbles (installation location of the gas supply means) is upstream of the filtration device and the device that generates ultrafine bubbles (ultrafine bubble generator), there are no restrictions. However, it is preferably upstream of the raw water supply pump (before pressurization due to rotation of the pump impeller) in that the introduced gas and raw water can be efficiently mixed with the rotary blades of the raw water supply pump. It is preferable to be immediately before the raw water supply pump (immediately before pressurization by rotation of the pump impeller). The gas supply amount is, for example, 0.005 to 0.50 L / min (standard state), preferably 0.03 to 0.30 L / min (standard state) per 1 m ³ / h of the discharge flow rate of the raw water supply pump, Preferably, it is 0.05-0.30 L / min (standard state). If the amount of gas supplied is too small, the number of ultrafine bubbles will decrease, and if it is too large, the proportion of ultrafine bubbles with a size of 50 μm or more will increase, both effectively removing dirt and clogging of the filtration device. It cannot be prevented. Even if the gas supply amount is small, a certain degree of effect can be obtained if ultrafine bubbles are generated.

  Further, generation of ultrafine bubbles may be performed in the raw water tank. In this case, raw water containing ultrafine bubbles can be prepared by providing an ultrafine bubble generator in the raw water tank.

  In the filtration operation, the membrane filtration method can be appropriately selected according to the structure of the filtration device and the like, and may be either a full-volume filtration method or a cross-flow filtration method. In particular, an internal pressure type cross-flow filtration method is preferable in that it can suppress the phenomenon of accumulation on the surface. In the case of the cross-flow filtration method, the higher the linear velocity of the raw water membrane surface, the more the deposition of adhering substances on the membrane surface is suppressed, so that a higher filtration flux (flux) is obtained, which is preferable in terms of preventing membrane contamination. The running cost increases as the film surface speed increases. The film surface linear velocity (cross flow velocity) of the raw water in the cross flow filtration method is, for example, 0.02 m / s or more and less than 0.5 m / s, preferably 0.05 m / s or more and less than 0.2 m / s. .

  In the filtration operation, in general, in order to prevent deposition of adhering substances on the membrane surface and perform the membrane filtration operation for a long time, the filtration device is intermittently supplied with filtered water from the filtration device or separately supplied clean water. Or backwash regularly. By adopting the cleaning method of the present invention as this backwashing, the filtration device can be cleaned extremely efficiently. In addition, by employing the cleaning method of the present invention, the number of backwashes that have been conventionally performed can be greatly reduced.

  Hereinafter, the cleaning method for the filtration device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic explanatory diagram (schematic flow diagram) showing an example of a cleaning method for a filtration device of the present invention. In the figure, 8 is a valve, 9 is a flow rate adjusting valve, 28 is a pressure gauge, and 29 is a flow meter.

  The raw water (treated water) stored in the raw water tank 3 from the raw water supply line (raw water replenishment line) 1 is integrated with the ultrafine bubble generating pump (the water supply pump and the ultrafine bubble generating device) from the raw water supply line 4. Device) 6 and supplied to the filtration device 11. The ultrafine bubble generating pump 6 is provided with an air suction port (gas supply means; air supply port) 5 for introducing air into the raw water. The air suction port 5 may be provided either before or after pressurization by the pump impeller, but is preferably provided before pressurization by the pump impeller from the viewpoint that it can be self-sucked. A plurality of raw water supply lines 4 may be provided. A prefilter may be attached at an appropriate position for the purpose of removing impurities in the raw water. As the ultrafine bubble generating pump 6, those described later can be used.

  A number of ultrafine bubbles are generated in the raw water by the ultrafine bubble generation pump 6. The ultrafine-bubble-containing raw water prepared by the ultrafine-bubble generating pump 6 is provided on the side of the filtration device 11 installed vertically through a valve V-4 (raw water inlet valve) and a flow rate adjusting valve FCV. The raw water supply port 10 containing ultrafine bubbles is supplied to the filtration device 11.

  The filtration device 11 includes a cylindrical filtration filter 26 housed in a cylindrical housing, and has an ultrafine bubble-containing raw water supply port 10, a filtered water outlet 18, and a concentrate discharge port 12. It is sufficient that at least one ultrafine bubble-containing raw water supply port and filtered water outlet are provided. The ultrafine bubble eye oil raw water supply port may also serve as the concentrate discharge port. The filter 26 contains a filter element such as a sintered wire mesh cylindrical element.

  In the filtration device 11, the filtered water that has been membrane-filtered under a predetermined condition is recovered from the filtered water and the concentrate drainage line 16 through the filtered water outlet 18 and the valve V-6 (filtered water outlet valve).

  During the filtration operation, in order to maintain the filtration capacity, back pressure washing is periodically performed by the washing method of the present invention. That is, the air chamber 14 provided on the filtered water side of the filtering device 11 is filled with gas, and the raw water containing ultrafine bubbles is supplied to the filtering device 11 by the ultrafine bubble generating pump (raw water supply pump) 6 and filtered. From the filtration operation state to obtain water, V-6 (filtrated water outlet valve) is closed and the flow path from the raw water supply pump discharge side to V-6 (filtrated water outlet valve) is pump discharge pressure [for example, 0.01 MPa. (Gauge pressure) or more (for example, 0.01 to 0.5 MPa (gauge pressure)), preferably 0.05 MPa (gauge pressure) or more (for example, 0.05 to 0.5 MPa (gauge pressure))] Once the inside of the filtration device is pressurized and sealed, V-7 and V-8 (concentrate outlet valve) are opened to rapidly reduce the pressure on the raw water side, and the filter filter or separation membrane deposit is removed from the raw water. Peel to the side

  In the method of the present invention, the pressure in the filtration device is lowered at a stroke by opening the concentrate discharge side valve from a state where the inside of the filtration device is pressurized and sealed. When this sudden pressure drop occurs, the ultrafine bubbles present in the raw water that have saturated inside the filtration device (especially the turbidity accumulated in the filter element and separation membrane of the filtration filter) expand, Crush. In addition, since a pressure drop occurs from the raw water side (primary side), the pressure on the filtered water side (secondary side) also escapes to the primary side, resulting in a reverse flow of filtered water, and the crushed suspended matter is filtered. Alternatively, they are separated along the flow from the separation membrane surface. For this reason, the filtration surface is efficiently and reliably cleaned.

  In addition, about the discharge | emission of the turbidity accumulated by performing a membrane filtration operation for a long period, you may combine the washing | cleaning method of this invention, and the following method. That is, regularly, filtrate water is stored in the filtrate water tank 21 from the valve V-9 side through the filtrate water line 20, and then the valves V-1 and V-2 are switched and the valves V-7 and V-8 are opened. In this state, the filtered water is sent to the filtration filter or separation membrane 26 using the ultrafine bubble generating pump 6 to update the water on the primary side (concentrate side) inside the filter or separation membrane. , Preventing excessive increase in turbidity in raw water inside the filter or separation membrane. As for the route for sending filtrate to the filtration filter or separation membrane 26, two methods, a flushing method for feeding from the V-4 side and a backflow method for feeding from the V-5 side, can be used properly.

  Next, the ultrafine bubble generating pump will be described in detail.

  FIG. 2 is a partial cross-sectional view (cross-sectional view of a liquid-feeding dispersion unit) showing an example of a device (super-fine bubble generation pump or a water-feed pump with a built-in ultra-fine bubble generation device) in which a water feed pump and an ultra-fine bubble generation device are integrated It is. FIG. 3 is a partially enlarged view (cross-sectional view) of a storage chamber of an apparatus in which the liquid feed pump and the ultrafine bubble generating apparatus of FIG. 2 are integrated.

  This ultrafine bubble generating pump disperses the gas supplied in the liquid as ultrafine bubbles, and includes a canned motor and a liquid feed dispersion unit. In FIG. 2, the canned motor section is omitted. Reference numeral 30 denotes a rotating shaft of the canned motor, and reference numeral 31 denotes a front bearing box (front bearing housing fixing portion).

  The housing 34 is fastened and fixed in a liquid-tight manner to the front bearing box 31 with bolts 42. The housing 34 and the front bearing box 31 define a storage chamber 35. The casing 34 is provided with a liquid supply port 39 and a liquid outflow port 38. The liquid supply port 39 is provided at an extended position of the rotating shaft 30 of the rotor of the canned motor, and the liquid outlet 38 is provided on a surface located in a direction intersecting the rotating shaft 30 of the housing 34. .

  An impeller (pump impeller) 43 is stored in the storage chamber 35. The impeller 43 is fastened by a bolt 44 to the tip of the rotating shaft 30 of the canned motor. As shown in FIG. 2, the impeller 43 is formed of a closed type centrifugal impeller, and includes a centrifugal blade 46 for feeding liquid on the surface of a disk constituting a part of the impeller main body within the impeller main body 45. It becomes the composition. A circulation blade 47 is provided on the back side of the impeller body 45. The circulation blade 47 has a larger diameter than the centrifugal blade 46.

  The impeller 43 is configured such that a gap is generated between the facing surface 32 of the impeller main body 45 of the front bearing box 31 and the impeller 43 in the storage chamber 35. The interior of the storage chamber 35 is divided into a liquid feeding space 36 and a circulation space 37 by the impeller main body 45. The liquid feeding space 36 conveys the fluid in the storage chamber 35 to the liquid outlet 38 side by the centrifugal blades 46 of the impeller 43, and the supplied liquid is supplied to the centrifugal blades 46 and the circulating blades of the impeller 43 in the circulation space 37. Due to the pressure difference generated by 47, the impeller body 45 circulates in the centrifugal direction and the centripetal direction.

  A dispersion portion 48 is provided in the gap between the facing surface 32 of the impeller main body 45 of the front bearing box 31 and the impeller 43. The dispersion part 48 is disposed in contact with the facing surface 32 of the front bearing box 31. As shown in FIG. 3, the dispersion unit 48 includes a dispersion unit body composed of two disks 49 and 50, and the discs 49 and 50 are distributed over (almost) the entire circumference of the disks 49 and 50. A flow path 51 (annular slit) is formed.

  As shown in FIG. 3, taper portions are formed to face each other so as to expand from the inner diameter side toward the outer diameter side on the facing surfaces on the side where the two disks 49 and 50 face each other. The channel 51 is provided with a channel reducing portion 51a in which the gap of the channel 51 is reduced from the outer diameter side toward the inner diameter side. Further, a flow path enlargement part 51b is formed on the inner diameter side of the flow path reduction part 51a so that the gap of the flow path 51 expands from the outer diameter side toward the inner diameter side. A gap minimum portion 51c in which the gap of the flow path 51 is the smallest is provided between the portion 51b. Thus, it is also preferable that the annular slit is provided with a flow path expanding portion provided so as to expand from the minimum gap portion from the outer diameter side toward the inner diameter side.

  The gas supply flow path 40 provided as a pipe line penetrating the front bearing box 31 opens at a position close to the rotating shaft 30 in the circulation space 37.

  Next, the operation of the ultrafine bubble generating pump will be described with reference to FIGS.

  When the rotating shaft 30 of the canned motor rotates, the impeller 43 also rotates together to take in the liquid from the liquid supply port 39. As the impeller 43 rotates, the liquid is sent in the centrifugal direction from the rotating shaft, and a part flows out from the liquid outlet 38.

  A pressure distribution is generated in the storage chamber 35 by the rotation of the impeller 43. In the pressure distribution, the pressure increases as the distance from the rotation shaft 30 increases, and the region A2 far from the rotation shaft 30 has a higher pressure than the region A1 near the rotation shaft 30, as shown in FIG.

  The liquid that has not flowed out from the liquid outlet 38 moves to the circulation space 37 of the impeller 43. In the circulation space 37, air and liquid taken in from the gas supply channel 40 exist. Since the pressure in the circulation space 37 is higher than the pressure in the fluid region A3 in the vicinity of the rotating shaft 30, the fluid moves so as to approach the rotating shaft. At this time, the gas-liquid mixture sequentially passes through the flow path reducing section 51 a and the flow path expanding section 51 b provided in the dispersion flow path 51 of the dispersion section 48 and moves in a direction approaching the rotating shaft 30. When the gas-liquid mixture passes through the flow path enlargement part 51b via the flow path reduction part 51a, the flow rate of the gas-liquid mixture changes due to the change in the flow path gap, the pressure changes, the gas is refined, and the ultrafine Bubbles are generated. That is, after pressurization with the impeller 43 of the pump, ultrafine bubbles are generated.

  This gas refinement is mainly determined by the flow rate of the liquid, the amount of gas, the gap size of the gap minimum portion 51c and the flow path enlargement portion 51b, and the like. For example, if the gas flow rate is below a certain threshold value, the bubble diameter is not reduced and sufficient miniaturization is not performed. In this case, the diameter of the bubbles to be refined can be adjusted mainly by the gap size of the gap minimum portion 51c and the flow path expanding portion 51b. On the other hand, when the flow rate of the liquid is equal to or higher than the threshold value, the bubble diameter is reduced and sufficient miniaturization is performed. The flow path enlargement part 51b provided in the dispersion flow path 51 exhibits the same effect as the Venturi tube, and the liquid accompanying the gas passes through the flow path 51 of the dispersion part 48, so that the gas can be refined. it can. The expansion angle (expansion angle in the cross section) of the dispersion flow path (annular slit) 51 in the flow path expansion section 51b is the reduction angle (reduction angle in the cross section) of the flow path contraction section 51a from the viewpoint of the ultrafine bubble generation efficiency. Although often smaller, the spread angle may be the same as or greater than the shrink angle.

  The circulation blade 47 provided on the back side of the impeller main body 45 generates a radiant flow, and moves the gas-liquid dispersion fluid in the circulation space 37 from the rotating shaft 30 side in the centrifugal direction. As described above, in the vicinity of the rotation axis in the circulation space 37, there is a gas-liquid dispersion fluid that has been refined by passing through the dispersion portion 48. Therefore, this fluid moves in the centrifugal direction from the rotation axis 30 side. .

  Further, the rotation of the circulation blade 47 increases the pressure of the fluid in the region A3 near the rotation shaft 30 and the outer region A4 of the circulation blade 47, so that the fluid in the circulation space 37 of the impeller body 45 is in the centrifugal direction and centripetal. Circulate and flow in the direction. In addition, due to the formation of a centrifugal pressure field by the rotation of the circulation blade, the outlet of the gas supply flow path 40 has a negative pressure and air self-priming is promoted.

  In the present embodiment, in order to promote the circulation of the fluid in the circulation space 37, the disk 50 provided on the side close to the impeller of the dispersion part 48 is provided with a partition part 50a extending to the rotating shaft side. Yes. By partitioning the inside of the circulation space 37 by the disk 50 (37a, 37b), in the space between the disk 50 including the partition part 50a and the surface facing the main body of the impeller, that is, the dispersion channel 51, the fluid flows in the centripetal direction. In addition, the fluid easily moves in the centrifugal direction in the space between the impeller body 45 and the disk 50 where the circulation blade 47 is located. By adopting such a configuration, circulation of the fluid in the circulation space 37 is promoted, and the fluid passes through the dispersion portion 48 more efficiently, so that the generation of ultrafine bubbles can be promoted. it can.

  The ultrafine bubble generating pump according to the present embodiment has a mechanism in which a part of the fluid pressurized by the centrifugal blade 46 in the storage chamber 35 causes a circulation flow behind the centrifugal blade 46. Further, air can be self-primed into the circulation flow path, and the self-supplied air can be merged with the flow of the centrifugal blade 46 and can be discharged from the liquid outlet 38. In addition, since the dispersion part is provided in the middle of the circulation flow and the bubbles can be made finer, the liquid can be transported and the fine bubbles can be generated with one apparatus. In addition, by providing the circulation vane 47 in the storage chamber 35, even when used under a pressurized condition, a differential pressure can be generated, and bubbles can be made finer.

  In the above example, the circulation blade 47 is provided outside the region partitioned by the two disks 49 and 50, but the circulation blade 47 is provided inside the region partitioned by the two disks 49 and 50. In addition, a flow path into which a fluid flows can be provided in a region defined by the two disks 49 and 50. In such an embodiment, contrary to the above example, the fluid (fluid pressurized by the impeller 43 of the pump) that flows into the region defined by the two disks 49 and 50 is dispersed in the dispersion channel (annular slit). ) In the order of the channel reducing portion, the gap minimum portion, and the channel expanding portion, and is ejected to the outside of the region (in the centrifugal direction) to generate ultrafine bubbles.

  In the above example, the dispersion portion 48 is provided in the vicinity of the impeller 43. However, after being pressurized by the impeller 43, ultrafine bubbles are generated in the gas-liquid mixture (for example, passing through an annular slit). As long as it has a mechanism, the dispersion part 48 may be provided at a position separated from the impeller 43.

  FIG. 4 is a cross-sectional view showing another example of a device in which a water pump and an ultrafine bubble generator used in the method of the present invention are integrated (ultrafine bubble generator pump; water pump with a built-in ultrafine bubble generator). is there. FIG. 5 is a partially enlarged view (cross-sectional view) of a pump part and a dispersion part (ultrafine bubble generation part) of the water pump with a built-in ultrafine bubble generation apparatus of FIG. 4 and 5, arrows indicate the flow direction of the liquid and gas-liquid mixture. In FIG. 4, “MB generation part” means a dispersion part (ultrafine bubble generation part).

  This ultrafine bubble generating pump disperses the gas supplied in the liquid as ultrafine bubbles, and includes a motor part (canned motor part), a pump part, and an ultrafine bubble generating part. Reference numeral 230 denotes a rotating shaft of the canned motor.

  The pump unit is provided with a liquid supply port 239, a gas supply channel 240, and an air vent valve 260. The liquid supply port 239 is provided at an extension position of the rotating shaft 230 of the rotor of the canned motor, and the air vent valve 260 is provided on a surface located in a direction intersecting the rotating shaft 230. Reference numeral 259 denotes a valve.

  An impeller (pump impeller) 243 is accommodated in the pump unit. The impeller 243 is attached to the tip of the rotating shaft 230 of the canned motor. As shown in FIGS. 4 and 5, the impeller 243 is configured by a closed type centrifugal impeller, and a centrifugal blade 246 for feeding liquid to the surface of a disk constituting a part of the impeller main body within the impeller main body. It is the composition provided with. Due to the high speed rotation of the impeller 243, the vicinity of the liquid supply port 239 becomes negative pressure, and air is sucked from the gas supply channel 240.

  The liquid and gas (air) that flowed into the pump unit from the liquid supply port 239 and the gas supply channel 240 are mixed by the centrifugal blade 246 and moved in the centrifugal direction, and then ultrafine provided between the pump unit and the motor unit. It flows into the bubble generator. As shown in FIG. 5, the ultrafine bubble generating portion includes a dispersion portion main body composed of two discs 249 and 250, and between these discs 249 and 250, the discs 249 and 250 have a peripheral portion. Dispersion flow paths 251 (annular slits) are formed over (almost) the entire circumference. In addition, in a region defined by two disks 249 and 250, a rotating body 252 is provided on the rotating shaft 230, and the rotating body 252 is configured by a disk 252a and a plurality of centrifugal blades 252b.

  As shown in FIG. 5, taper portions are formed to face each other so that the two disks 249 and 250 face each other so as to expand from the inner diameter side toward the outer diameter side. The channel 251 is provided with a channel reducing portion 251a in which the gap of the channel 251 is reduced from the inner diameter side toward the outer diameter side. Further, a flow path enlargement part 251b is formed on the outer diameter side of the flow path reduction part 251a, and the gap of the flow path 251 expands from the inner diameter side toward the outer diameter side. A gap minimum portion 251c where the gap of the flow path 251 is the smallest is provided between the enlarged portion 251b.

  Next, the operation of the ultrafine bubble generating pump will be described with reference to FIGS.

  When the rotating shaft 230 of the canned motor rotates, the impeller 243 also rotates integrally to take in liquid from the liquid supply port 239 and gas (air) from the gas supply channel 240. As the impeller 243 rotates, the gas-liquid mixture is sent in the centrifugal direction from the rotating shaft, and further moves to the ultrafine bubble generating unit.

  In the ultrafine bubble generating unit, the gas-liquid mixture flows into the region defined by the two disks 249 and 250 by the high-speed rotation of the rotating shaft 230, and the dispersing unit 248 by the rotation of the centrifugal blade 252 b of the rotating body 252. The flow path reducing section 251a and the flow path expanding section 251b provided in the dispersion flow path 251 are sequentially passed. When the gas-liquid mixture passes through the flow path reduction section 251a and the flow path expansion section 251b, the flow rate of the gas-liquid mixture changes due to the change in the flow gap, the pressure changes, the gas is refined, and the ultrafine Bubbles are generated. That is, after pressurization with the impeller 243 of the pump, ultrafine bubbles are generated.

  As described above, this gas refinement is mainly determined by the flow rate of the liquid, the amount of gas, the gap size of the gap minimum portion 251c and the flow path enlargement portion 251b, and the like. The expansion angle (expansion angle in the cross section) of the dispersion flow path (annular slit) 251 in the flow path expansion section 251b is the reduction angle (reduction angle in the cross section) of the flow path reduction section 251a from the viewpoint of the generation efficiency of ultrafine bubbles. Although often smaller, the spread angle may be the same as or greater than the shrink angle.

  FIG. 6 is a cross-sectional view showing still another example of a device in which the water pump and the ultrafine bubble generator used in the method of the present invention are integrated (superfine bubble generator pump; water pump with a built-in ultrafine bubble generator). It is. In FIG. 6, the arrows indicate the flow direction of the liquid and gas-liquid mixture. Further, “MB generation part” means a dispersion part (ultrafine bubble generation part).

  This ultrafine bubble generating pump disperses the gas supplied in the liquid as ultrafine bubbles, and includes a motor part (canned motor part), a pump part, and an ultrafine bubble generating part. Reference numeral 330 denotes a rotating shaft of the canned motor. The pump part and the ultrafine bubble generating part are provided on both sides of the motor part.

  A liquid supply port 339 and a gas supply channel 340 are provided in the pump unit. The liquid supply port 339 is provided at the extended position of the rotating shaft 330 of the rotor of the canned motor. Reference numeral 359 denotes a valve.

  An impeller (pump impeller) 343 is accommodated in the pump unit. The impeller 343 is attached to the tip of the rotating shaft 330 of the canned motor. As shown in FIG. 6, the impeller 343 is constituted by a closed type centrifugal impeller, and a centrifugal blade 346 for feeding liquid is provided on the surface of a disk constituting a part of the impeller main body inside the impeller main body. It has a configuration. Due to the high speed rotation of the impeller 343, the vicinity of the liquid supply port 339 becomes negative pressure, and air is sucked from the gas supply flow path 340.

  The liquid and gas (air) that flowed into the pump unit from the liquid supply port 339 and the gas supply flow path 340 are mixed by the centrifugal blade 346, and a part thereof is used for cooling the canned motor (after circulating through the cooling line, After returning to the pump part), the rest moves in the centrifugal direction, and then flows into the ultrafine bubble generating part through the intermediate pipe 370. As shown in FIG. 6, the ultrafine bubble generating portion includes a dispersion portion main body constituted by two disks 349 and 350, and between these disks 349 and 350, the peripheral edges of the disks 349 and 350 are arranged. A dispersion channel 351 (annular slit) is formed over (almost) the entire circumference. Further, in a region partitioned by two disks 349 and 350, a rotating body 352 is provided on the rotating shaft 330, and the rotating body 352 is constituted by a disk 352a and a plurality of centrifugal blades 352b.

  As shown in FIG. 6, taper portions are formed to face each other on the facing surfaces on the side where the two disks 349 and 350 face each other so as to expand from the inner diameter side toward the outer diameter side, The channel 351 is provided with a channel reducing portion 351a in which the gap of the channel 351 is reduced from the inner diameter side toward the outer diameter side. Further, a flow path expanding portion 351b is formed on the outer diameter side of the flow path reducing portion 351a, and the gap of the flow path 351 expands from the inner diameter side toward the outer diameter side. A minimum gap portion 351c in which the gap of the flow path 351 is the smallest is provided between the enlarged portion 351b. Note that an air bleeding valve 360 is provided on a surface located in a direction intersecting the rotating shaft 330 in the ultrafine bubble generating unit.

  Next, the operation of the ultrafine bubble generating pump will be described with reference to FIG.

  When the rotating shaft 330 of the canned motor rotates, the impeller 343 also rotates integrally, and takes in liquid from the liquid supply port 339 and gas (air) from the gas supply flow path 340. As the impeller 343 rotates, the gas-liquid mixture is sent in the centrifugal direction from the rotating shaft, and moves to the MB generating section through the intermediate pipe 370.

  In the MB generator, the gas-liquid mixture flows into the region defined by the two disks 349 and 350 due to the high-speed rotation of the rotating shaft 330, and the dispersion of the dispersion part 348 is caused by the rotation of the centrifugal blade 352 b of the rotating body 352. It passes through the flow path reduction part 351a and the flow path enlargement part 351b provided in the flow path 351 in order. When the gas-liquid mixture passes through the flow path reduction part 351a and the flow path enlargement part 351b, the flow rate of the gas-liquid mixture changes due to the change in the flow path gap, the pressure changes, the gas is refined, and the ultrafine Bubbles are generated. That is, after pressurization with the impeller 343 of the pump, ultrafine bubbles are generated.

  As described above, this gas refinement is mainly determined by the flow rate of the liquid, the amount of gas, the gap size of the gap minimum portion 351c and the flow path expanding portion 351b, and the like. The expansion angle (expansion angle in the cross section) of the dispersion flow path (annular slit) 351 in the flow path expansion section 351b is the reduction angle (reduction angle in the cross section) of the flow path contraction section 351a in terms of the efficiency of generating ultrafine bubbles. Smaller is preferred.

  When the apparatus in which the water pump and the ultrafine bubble generator shown in FIGS. 2 to 6 are integrated is used, at 20 to 30 ° C., for example, 100 / mL or more (preferably 300 / mL or more, more preferably Can obtain raw water containing ultrafine bubbles of 1000 / mL or more, particularly 2000 / mL or more), and the number of bubbles having a bubble diameter of 2 to 5 μm (number measured by a particle counter) is 20 to 30. At 0 ° C., for example, an ultrafine bubble mixed liquid of 100 / mL or more (preferably 300 / mL or more, more preferably 1000 / mL or more, particularly 2000 / mL or more) can be obtained.

  In the above example, a device in which a water pump and an ultrafine bubble generator are integrated (ultrafine bubble generator pump; water pump with a built-in ultrafine bubble generator) is used. Can also be used as separate devices and devices. For example, the ultrafine bubble generator 7 may be provided on the downstream side (discharge side) of a normal water pump. In this case, an air suction port (gas supply means; air supply port) for introducing gas (air) into the raw water is provided at an appropriate location, for example, upstream of the water pump.

  The ultrafine bubble generator 7 will be described in detail below.

  FIG. 7 is a cross-sectional view showing an example of the ultrafine bubble generator 7. In this example, the ultrafine bubble generating device 7 includes a cylindrical casing 71 having a low height compared to its diameter, and two upper and lower disks 74 and 75 installed horizontally inside the casing 71. It consists of A gas-liquid mixed flow inlet 72 is provided at the lower portion of the casing 71, and a gas-liquid mixed flow outlet 73 is provided at the upper portion. The disc 74 located below the two discs is donut-shaped and is installed on the bottom surface inside the casing 71. The disc 75 located above the two discs has a disk shape with substantially the same diameter as the disc 74 and is installed so as to cover the disc 74. In the circumferential direction of the peripheral portions of the opposing surfaces of the disks 74 and 75, an annular slit is formed through which the gas-liquid mixture pressurized by the water pump 6 is passed and ejected outward. The jet direction of the gas-liquid mixture is a direction orthogonal to the inflow direction of the gas-liquid mixture flowing into the region partitioned by the disk 74 and the disk 75 from the gas-liquid mixture flow inlet. When the pressurized gas-liquid mixture passes through the annular slit, a large number of ultrafine bubbles are generated, and the gas-liquid mixture (ultrafine bubble mixture) containing the ultrafine bubbles flows out from the gas-liquid mixture flow outlet 73. And supplied to the membrane module 11. The arrows in FIG. 7 indicate the flow of the gas-liquid mixture. Since the gas-liquid mixture distribution outlet 73 is provided in the upper part of the housing 71, the gas does not stay and the ultrafine bubble mixture is smoothly supplied to the membrane module 6.

  In the ultrafine bubble generator 7, for example, by adjusting the structure of the annular slit, the passage speed of the gas-liquid mixture in the annular slit, the supply ratio of gas and liquid, etc., the (ultra) fine bubbles in the ultrafine bubble mixture are adjusted. The bubble diameter, bubble diameter distribution, and number of bubbles can be controlled. The number of bubbles, bubble diameter, bubble diameter distribution, and the like can be measured using a particle counter as described above.

  It is preferable that the annular slit includes a flow path expanding portion 78 provided so as to expand from the gap minimum portion 77 from the inner diameter side toward the outer diameter side. When the annular slit has such a structure, the gas-liquid mixture passes through and ejects at a high speed, so that ultrafine bubbles are generated in the gas-liquid mixture due to a change in the gap between the channels. This is because the flow rate of the gas-liquid mixture changes when the gas-liquid mixture passes through the flow path (flow path expanding portion 78) continuously expanding from the gap minimum portion 77 from the inner diameter side toward the outer diameter side. This is because the pressure changes.

  The preferable structure of the annular slit is not particularly limited as long as it has the flow path expanding portion 78 provided so as to expand from the minimum gap portion 77 at least from the inner diameter side to the outer diameter side. On the inner diameter side of the portion 77, there may be provided a flow path reducing portion 76 in which the flow path is continuously reduced toward the smallest gap portion. In addition, the annular slit has a structure in which the channel cross-sectional area increases stepwise from the inner diameter side to the outer diameter side, a structure in which the channel cross-sectional area decreases stepwise from the inner diameter side to the outer diameter side, You may have the structure where a flow-path cross-sectional area increases continuously toward an outer diameter side, and the structure where a flow-path cross-sectional area decreases continuously from an inner diameter side toward an outer diameter side. In the present invention, from the viewpoint of efficiently generating ultrafine bubbles, it is preferable that the annular slit includes a flow channel expanding portion in which the flow channel cross-sectional area continuously increases from the smallest gap portion from the inner diameter side toward the outer diameter side. .

  When the expansion angle (expansion angle in the cross section) θ2 of the annular slit in the flow path expansion portion 78 is made smaller than the reduction angle (reduction angle in the cross section) θ1 in the flow path reduction portion 76 from the viewpoint of the generation efficiency of the ultrafine bubbles. However, θ2 may be equal to or greater than θ1.

  By using the ultrafine bubble generator 7 having the above structure, the number of bubbles having a bubble diameter of 2 to 50 μm (number measured by a particle counter) is, for example, 100 / mL or more at 20 to 30 ° C. The raw water containing ultrafine bubbles can be obtained (preferably 300 / mL or more, more preferably 1000 / mL or more, particularly 2000 / mL or more). Further, when the ultrafine bubble generating device 7 having the above structure is used, the number of bubbles having a bubble diameter of 2 to 5 μm (the number measured by a particle counter) is, for example, 100 / It is possible to obtain a mixture of ultrafine bubbles that is mL or more (preferably 300 / mL or more, more preferably 1000 / mL or more, particularly 2000 / mL or more).

  The method for cleaning a filtration device of the present invention includes a filtration device having a filtration filter or a separation membrane therein, a raw water inlet, a filtered water outlet, and a concentrate outlet, and raw water supply for supplying raw water to the filtration device. The present invention can be applied to a water purification apparatus including a pump, an ultrafine bubble generating device that generates ultrafine bubbles in raw water supplied to the filtration device, and an air chamber provided on the filtered water side of the filtration device. The raw water supply pump and the ultrafine bubble generator may be integrated.

  As an ultrafine bubble generator in this water purification device, a gas-liquid mixed fluid obtained by mixing gas in raw water is circulated through a flow path having a reduced portion, the most sandwiched portion, and an enlarged portion by high pressure by a raw water supply pump. It is preferable that the apparatus generate ultrafine bubbles by changing the flow velocity and pressure of the high-speed shear flow of the gas-liquid mixed fluid formed in the flow path.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.

Example 1
In the water purification system (equipment) shown in FIG. 1, the filtration device 11 was washed. As a filtration filter 26 in the filtration device 11, a cylindrical element made of SUS special sintered wire mesh (manufactured by Central Filter Industry Co., Ltd., trade name “PM-A-C65 * 40 * 250-GL”, filter medium size Φ65 / Φ40 × 250L, A filter housing with a filtration area of 0.05 m ² and an element internal volume of 829 cc) packed in a cylindrical housing was used. As the air chamber 14, a stainless steel cylinder (diameter: 1 inch, length: 100 mm) having an internal volume of 88 cc was attached. As the ultrafine bubble generating pump 6, the pump shown in FIG. 6 (water pump with a built-in ultrafine bubble generator) was used. Moreover, as raw water, water added with 100 ppm by weight of kaolin for biochemistry (manufactured by Wako Pure Chemical Industries, Ltd.) (pseudo sludge) was used. The filtration pressure is 0.2 MPa (gauge pressure). The procedure for washing the filter is as follows. In addition, the filter surface of the filter before cleaning is in a state where a cake of pseudo sludge is accumulated on one surface.
(1) The air chamber 14 provided on the filtered water side of the filtration device 11 in advance is filled with air, and the raw water containing ultrafine bubbles by the ultrafine bubble generating pump 6 is supplied to the valve V-4 (raw water inlet valve). Filter with a special element in the filtration filter 26 from the side, and obtain filtered water from the valve V-6 (filtrated water outlet valve) (valves V-2, V-5, V-7, V-8 are closed) [ Filtration operation]. This filtration operation was performed for a predetermined time.
(2) The inside of the filtration filter 26 is increased to the pump discharge pressure by closing the valve V-6 in the state of the filtration operation [pressurization step].
(3) After completion of pressurization, the valve V-4 (raw water inlet valve) is closed, and the filtration filter 26 is sealed in a pressurized state [pressure maintaining step].
(4) Valves V-7 and V-8 (concentrate outlet valve) are opened at once, the pressure inside the filtration filter 26 is depressurized toward the primary side (concentrate drainage side), and special element cleaning is performed [depressurization step. ].
After performing said operation, the filtration filter was taken out and the peeling condition of pseudo sludge was observed visually. As a result, the pseudo sludge cake was crushed very finely and the filtration surface was renewed very cleanly.

Example 2
The same operation as in Example 1 was performed except that a stainless steel cylinder (diameter 1 inch, length 60 mm) having an internal volume of about 29 cc was used as the air chamber 14.
After washing, the filtration filter was taken out and the peeling state of the pseudo sludge was visually observed. As a result, the pseudo sludge cake was finely pulverized and the filtration surface was renewed cleanly.

Comparative Example 1
The same as in Example 1 except that the air chamber 14 was not attached and a normal water supply pump was used as the raw water supply pump instead of the ultrafine bubble generating pump (raw water containing no ultrafine bubbles was supplied). The operation was performed.
After cleaning, the filtration filter was taken out, and when the pseudo sludge peeling state was visually observed, the pseudo sludge cake floated from the filtration surface, but there was almost no peeling, and when this was attached to the filtration device again and restarted, The floated cake was pressed against the filtration surface by the pump pressure and became almost the same as before washing.

Comparative Example 2
The same operation as in Example 1 was performed except that the air chamber 14 was not attached.
After washing, the filtration filter was taken out and the peeling state of the pseudo sludge was visually observed. As a result, the pseudo sludge cake was broken and the cake on the filtration surface was peeled off, but there was a portion where the cake remained. Further, the peeled cake was scaly and was not finely pulverized.

Comparative Example 3
The same operation as in Example 1 was performed except that a normal water supply pump was used as the raw water supply pump instead of the ultrafine bubble generating pump (raw water containing no ultrafine bubbles was supplied).
After washing, the filtration filter was taken out, and when the artificial sludge was peeled off visually, the pseudo cake was peeled off at a considerable part, but it was not entirely, and the peeled cake was plate-like and finely pulverized. It was not in the state that was done.

1 Raw water supply line (raw water replenishment line)
3 Raw Water Tank 4 Raw Water Supply Line 5 Air Suction Port 6 Ultrafine Bubble Generation Pump (Raw Water Supply Pump)
7 Ultra Fine Bubble Generator 8 Valve 9 Flow Control Valve 10 Raw Water Inlet (Ultra Fine Bubble Containing Raw Water Supply Port)
DESCRIPTION OF SYMBOLS 11 Filtration apparatus 12 Concentrate discharge port 13 Concentrate drainage line 14 Air chamber 16 Filtrated water and concentrate drainage line 17 Filtration water circulation line 18 Filtration water outlet 20 Filtration water line 21 Filtration water tank 26 Filtration filter (or separation membrane)
27 Raw water return line 28 Pressure gauge 29 Flow meter 30, 230, 330 Rotating shaft of canned motor 31 Front bearing box 32 Opposing surface of impeller body 45 of front bearing box 33 Lubricant discharge port 34 Housing 35 Storage chamber 36 Liquid feeding space 37 Circulating space 38, 238, 338 Liquid outlet 39, 239, 339 Liquid supply port 40, 240, 340 Gas supply passage 41 Lubricating liquid pipe 42 Bolt 43, 243, 343 Impeller 44 Bolt 45 Impeller main body 46,246,346 Centrifugal blade 47 Circulating blade 48,248,348 Dispersion part 49,249,349 Disc 50,250,350 Disc 50a Partition part 51,251,351 Dispersion channel 51a, 251a, 351a Channel reduction part 51b , 251b, 351b Channel enlarged portion 51c, 251c, 351c Minimum gap 259,359 valves 260 and 360 vent valve 370 intermediate pipe 71 housing 72 gas-liquid mixture flow inlet 73 gas-liquid mixture flow outlet 74 disk 75 disk 76 the flow path reduction portion 77 gap minimum unit 78 enlarged flow path portion

Claims (2)

  A method for washing a filtration device provided with a filtration filter or a separation membrane, wherein a gas is filled in an air chamber provided on the filtrate water side of the filtration device, and raw water containing ultrafine bubbles is filtered by the raw water supply pump The filtration water outlet side valve is closed and the flow path from the raw water supply pump discharge side to the filtrate water outlet side valve is increased to the pump discharge pressure from the filtration operation state where the filtrate is obtained by supplying Of the filtration device characterized in that after the pressure is sealed, the concentrate outlet port valve is opened and the pressure on the raw water side is drastically lowered to separate the filtration filter or separation membrane deposit to the raw water side. Cleaning method.   The raw water containing ultrafine bubbles is mixed with a gas-liquid mixed fluid obtained by mixing gas in the raw water, and the flow path having the reduced portion, the most sandwiched portion, and the enlarged portion is circulated by the high pressure by the raw water supply pump. The cleaning method for a filtration device according to claim 1, which is raw water containing ultrafine bubbles obtained by changing the flow velocity and pressure of the high-speed shear flow of the gas-liquid mixed fluid formed in the inside to generate ultrafine bubbles.

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