JP4614188B2 - Immersion flat membrane filtration device - Google Patents

Description

  The present invention relates to an immersion flat membrane filtration device, and more particularly to an immersion flat membrane filtration device that is immersed in a treatment tank filled with water to be treated such as sewage and industrial wastewater, and filters the treated water after treatment.

  In sludge and industrial wastewater, activated sludge treatment is generally used in which wastewater containing organic components is decomposed by microorganisms. As one method of this activated sludge treatment, there is a membrane separation activated sludge method. In the membrane separation activated sludge method, a submerged flat membrane filtration apparatus is used for membrane separation of water to be treated and activated sludge after reaction treatment. Moreover, also when processing by solid-liquid separation without using activated sludge, the immersion flat membrane filtration apparatus which uses an immersion flat membrane as a solid-liquid separation means is used. As disclosed in Patent Documents 1 and 2, the immersion flat membrane filtration device is arranged in parallel in a state where a plurality of membrane elements are immersed in a treatment tank filled with water to be treated, and each membrane element is disposed from the inside. Filtration water is obtained by sucking the water to be treated. Each membrane element is vertically installed in the processing tank with a predetermined interval, and below that, an aeration means for aeration is provided. For the purpose of aeration, (1) to obtain a cleaning effect that suppresses clogging of the membrane by removing solid matter such as sludge cake deposited on the membrane surface, (2) to cause a swirling flow in the treatment tank (3) When the water to be treated in the treatment tank contains microorganisms such as activated sludge, supply oxygen for aerobic treatment. And so on. Thereby, the filtration process by a membrane element can be performed efficiently.

The conventional immersion flat membrane filtration device has a problem that the power cost of air diffusing for maintaining the filtration performance of the membrane is large. In order to solve this problem, the membrane elements are stacked on the top and bottom of the tank and supported by the frame. Air is first supplied to the lower membrane element from the diffuser disposed below, and then the air used in the lower stage is supplied to the upper stage. An apparatus that can be used with a membrane element is disclosed in Patent Document 3. As a result, the amount of air used per membrane module can be greatly reduced. Also, Patent Document 4 discloses a structure in which a cylindrical spacer is provided between the upper and lower membrane elements so that the diffused air used in the lower stage can be used for the upper membrane element without escaping to the outside of the membrane element. Has been.
JP 2001-162141 A JP 2000-237551 A JP-A-8-57269 JP-A-11-57426

  However, in the case of the upper and lower multistage membrane elements as shown in Patent Documents 3 and 4, first, the water to be treated is filtered by the lower membrane module, but the sludge after filtration and separation along with the diffused air was not separated. The treated water is supplied to the upper membrane element, so that the treated water filtered by the upper membrane module has an increased amount of sludge in the treated water compared to the lower membrane module, that is, the treated water is concentrated. Therefore, the higher the membrane module in the upper stage, the higher the concentration of the water to be treated, and the contamination by the sludge tends to proceed, and there is a difference in how the membrane is soiled between the upper and lower membrane modules. The membrane element / module has a problem that the filtration performance of the water to be treated decreases.

  In view of the above, an object of the present invention is to reduce the concentration of water to be treated in a cylindrical spacer in order to solve the above-described problems of the prior art. Moreover, this invention aims at preventing the fall of the membrane filtration performance as the whole immersion flat membrane filtration apparatus.

The immersion flat membrane filtration device of the present invention has a plurality of membrane elements for membrane filtration of water to be treated in a treatment tank arranged in parallel vertically in the treatment tank and a plurality of layers arranged in the vertical direction in the treatment tank. In the submerged flat membrane filtration device provided with a cylindrical spacer surrounding the gap between the upper and lower membrane elements, the cylindrical shape extends from the treatment tank to the side of the cylindrical spacer on the side intersecting the membrane plane of the membrane element. A water passage hole for taking in the water to be treated is provided inside the spacer, and the water passage hole is arranged only above half of the side surface of the cylindrical spacer.

In this case, the ratio of the opening area of the water flow hole for a side area of the cylindrical spacer provided with the water flow hole is preferably 1% to 30%.
Further, a ridge that is inclined outwardly and downwardly from the side surface of the cylindrical spacer may be provided at the upper portion of the water passage hole. An auxiliary air diffuser may be provided on the side surface of the membrane element below the ridge.

  According to the present invention, a water passage hole for taking in water to be treated from the outside to the inside of the cylindrical spacer is provided in a part of the cylindrical spacer installed between the upper and lower membrane elements. For this reason, even if the membrane modules of the submerged flat membrane filtration device are stacked in multiple stages, the treated water concentrated by the lower membrane module is diluted and the treated water filtered by the upper membrane module is concentrated. Can be reduced. Therefore, the fall of the membrane filtration performance as the whole immersion flat membrane filtration apparatus can be prevented.

By providing the water passage hole above half of the side surface of the cylindrical spacer, the upper membrane without disturbing the diffused air that has risen uniformly from the air diffuser due to the flow of water to be treated flowing from the water passage hole Can be supplied to the module. Further, the diffused air that has passed through the lower membrane module does not leak outside the cylindrical spacer through the vent hole. Therefore, aeration air can be effectively provided to the upper membrane module.

The opening ratio of the water passage hole is 1% to 30%, and this opening ratio is an amount capable of diluting the water to be treated concentrated by the lower membrane module, for example, an amount equivalent to the treated water collected by the lower membrane module It is set so that water can be supplied into the spacer. For this reason, the to-be-processed water concentrated without being membrane-filtered by the lower-stage membrane module can be diluted effectively. Further, according to the opening ratio, even if the water to be treated outside the cylindrical spacer flows into the inside from the water passage hole, the flow of the diffused air uniformly diffused by the diffuser means is not disturbed, and the upper membrane module Aeration air can be supplied uniformly.

A trough that is inclined outward and downward from the side surface of the cylindrical spacer is provided at the upper part of the water passage hole . For this reason, air diffused air rising along the outer side surface of the lower membrane module is taken into the cylindrical spacer from the water hole, and the amount of air diffused supplied to the upper membrane module is increased to enhance the cleaning effect of the membrane module. Can do.

In addition to the configuration in which a ridge is provided in the upper portion of the opening , auxiliary air diffusion means is provided below the ridge and on the side surface of the membrane element, that is, the lower membrane module. For this reason, the amount of diffused air supplied from the vent hole to the inside of the cylindrical spacer can be increased, and the cleaning effect of the upper membrane element can be further enhanced.

It surrounds the gap between the membrane elements of the upper and lower, are provided a cylindrical spacer is expanded in a tapered shape toward the lower side of the side intersecting the film plane of the membrane element from above. For this reason, the water to be treated outside the cylindrical spacer can flow upward into the cylindrical spacer along the side surface of the lower membrane module. Therefore, the water to be treated in the cylindrical spacer can be diluted and supplied to the upper membrane module while being uniformly distributed without disturbing the diffused air that has passed through the lower membrane module.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an immersion flat membrane filtration device according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of an immersion flat membrane filtration device of the present invention. FIG. 1A shows a sectional view of the submerged flat membrane filtration apparatus in the direction of arrow B, and FIG. 2B shows a perspective view.

The immersion flat membrane filtration device 10 of the present invention is immersed in a treatment tank filled with water to be treated such as sewage and industrial wastewater, and includes a plurality of membrane elements 14.
The membrane element 14 is a flat filter membrane, and the membrane modules 16 are formed by arranging the membrane surfaces of the plurality of membrane elements 14 in parallel at predetermined intervals so as to be parallel to each other.

  In the submerged flat membrane filtration apparatus 10 of the present invention, the membrane modules 16 are stacked (stacked) in the vertical direction of the treatment tank to form a multistage formation of an upper membrane module 16a and a lower membrane module 16b.

  Further, an air diffuser 20 is disposed below the lower membrane module 16b. The diffuser means 20 has a plurality of diffuser tubes arranged in parallel on a straight line along the lower side of the membrane element 14 like the membrane elements 14 arranged in parallel. The air diffuser 20 supplies cleaning air to the membrane module 16 to prevent solid matter such as sludge from adhering to the membrane surface and blocking it. Further, the air diffuser 20 can be configured so that the amount of air diffused can be arbitrarily adjusted.

  A cylindrical spacer 30 is installed between the membrane modules 16 arranged in the vertical direction in the submerged flat membrane filtration device 10. The cylindrical spacer 30 is a space in which the lower membrane module 16b and the upper membrane module 16a are separated by a predetermined interval.

  The cylindrical spacer 30 is provided with a water passage hole 40. As shown in FIG. 1 (1), the water passage holes 40 are formed on a pair of side surfaces of the membrane module 16, that is, on the side surfaces of the cylindrical spacer 30 facing the side (arrow A) intersecting the membrane plane of the flat membrane element 14. Forming. The water passage hole 40 is an opening through which water to be treated in the treatment tank can be supplied into the cylindrical spacer 30.

The operation of the submerged flat membrane filtration device having the above configuration will be described below.
Water to be treated that has been biologically treated or coagulated with activated sludge in the treatment tank is subjected to a lower stage by air lift by aeration air supplied by the aeration means 20 of the submerged flat membrane filtration device 10 disposed in the treatment tank. It flows from the lower surface of the membrane module 16b. That is, the water to be treated flows upward between the plurality of membrane elements 14b of the lower membrane module 16b and flows between the lower membrane modules 16b. At this time, filtration separation is performed by the membrane element 14b, and it is separated from water to be treated such as activated sludge to obtain treated water. The treated water is discharged out of the reaction tank through a water collecting pipe (not shown) provided at the upper part of the membrane element. On the other hand, the water to be treated that has not been filtered and separated, such as activated sludge that has passed through the lower membrane module 16b, flows into a cylindrical spacer 30 formed on the upper portion of the lower membrane module 16b.

  A water passage hole 40 is opened on the side surface of the cylindrical spacer 30, that is, the side intersecting the membrane plane of the flat membrane element 14, and water to be treated outside the cylindrical spacer 30 passes through the water passage hole 40. Flows into the inner spacer 30. For this reason, the to-be-processed water concentrated by the filtration separation of the lower stage membrane module 16b can be diluted before reaching the upper stage membrane module 16a.

  By the way, the air diffused by the air diffuser 20 needs to be uniformly dispersed and supplied to the membrane module 16 in order to effectively wash the membrane element, for example, as shown in the background art. . Therefore, in order to supply the water to be treated from the water passage hole 40 into the cylindrical spacer 30, this point must be taken into consideration. Hereinafter, in this embodiment, the attachment position of the water passage holes will be described from the viewpoint of the amount of water flow between the membrane elements and the state of the flow of the diffused air.

  FIG. 2 is an explanatory diagram of the amount of aeration air passing between the membrane elements. The plurality of membrane elements constituting the membrane module are immersed in the treatment tank with the membrane surfaces arranged in parallel at predetermined intervals so as to be parallel to each other. At this time, air diffused air is difficult to hit at both edges of the membrane element, and contamination of this portion is relatively easy to proceed as compared with the central portion of the membrane element.

  Therefore, four cases of upper opening, lower opening, both upper and lower openings, and no opening are set on the side surface of the cylindrical spacer 30, and between the membrane elements 14 constituting the membrane module 16 as shown in FIG. Thus, the amount of air diffused in the edge regions 1 to 9 was measured.

FIG. 2 (2) is a graph showing the air flow rate at the edge of the membrane element. The graph shows the vertical axis: air flow rate (L / min) and the horizontal axis: edge regions 1 to 9, respectively.
First, the air flow rate of the membrane element tube of the cylindrical spacer without an opening provided with no water flow hole is 0.4 to 0.6 (L / min), except for the edge regions 1 and 9, as shown by the curve a. The diffused air is supplied substantially uniformly over the entire upper end region. This is presumably because the diffused air from the lower membrane module flows almost uniformly into the upper membrane module without being affected by the inflow of water to be treated from the opening (water passage hole).

  Next, the cylindrical spacers of both the upper and lower openings and the lower opening are shown by curves b and c, respectively. As shown in the figure, the air flow rate of each of the edge regions 1 to 9 is 0.3 (L / min) or less, and the air flow rate of the diffused air passing through the edge region of the membrane element is significantly higher than that without the opening. You can see that it is decreasing.

  Here, the flow state of the diffused air in the lower opening will be described with reference to a partially enlarged view of the cylindrical spacer of the submerged flat membrane filtration device of FIG. FIG. 1A shows the flow of diffused air in a water passage hole opened at the bottom of the cylindrical spacer. When the water passage hole 40 is opened at the lower part of the cylindrical spacer 30, the water to be treated flows into the cylindrical spacer 30 from the water passage hole 40 as indicated by an arrow b. At this time, when the water to be treated passes through the water passage hole 40, the water to be treated flows from the direction intersecting the side surface of the cylindrical spacer 30. The treated water that has flowed in pushes the flow of diffused air that has passed through the lower membrane module 16 b into the center of the spacer as indicated by the arrow c, and forms a vortex in the space above the cylindrical spacer 30. Then, the diffused air that has passed through the lower membrane module 16b is concentrated in the center of the spacer, and the diffused air does not flow in the region indicated by the lower end d of the upper membrane module 16a, and activated sludge adheres in the filtration separation of the lower end d. It becomes easy. In this way, the dispersion of the diffused air is biased, the diffused air is concentrated and passed through the central part rather than the edge of the membrane element, and the amount of air diffused at both edges is reduced. Conceivable.

  Here, the state of the air diffused in the upper opening will be described below. FIG. 3 (2) shows the flow of diffused air in the water passage hole opened at the top of the cylindrical spacer. As shown in the drawing, when the water passage hole 40 is opened in the upper part of the cylindrical spacer 30, the water to be treated flows into the cylindrical spacer 30 from the water passage hole 40 as indicated by an arrow e. At this time, when the water to be treated passes through the water passage hole 40, the water to be treated flows from the direction intersecting the side surface of the cylindrical spacer 30. And the to-be-processed water which flowed in from the water flow hole 40 flows in into the upper stage membrane module 16a immediately with the flow of the flow f of to-be-processed water which passed the lower stage membrane module 16b. Therefore, the phenomenon that the diffused air is concentrated at the center of the cylindrical spacer 30 as shown by the arrow c in (1) does not occur, and the diffused air that has passed through the lower membrane module 16b is dispersed in a uniformly dispersed state. It can be supplied to the upper membrane module 16a without disturbing the state. Therefore, it is considered that the diffused air is uniformly dispersed when the water flow holes are provided in the upper part of the cylindrical spacer.

  In the present invention, it is necessary to dilute the water to be treated by the water flow holes opened in the cylindrical spacer and supply the water to be treated so as not to disturb the flow of the diffused air. The position of the hole 40 is specifically specified as follows.

  First, the attachment position of the water passage hole 40 opens on the side surface of the cylindrical spacer 30 on the side intersecting the membrane plane of the membrane element, and the position is set above half of the side surface. More preferably, it is effective to form 1/3 or more. As a result, the air diffused uniformly from the air diffuser can be supplied to the upper membrane module without being disturbed. Also, the diffused air that has passed through the lower membrane module does not leak outside through the water passage hole.

  The opening ratio of the water passage hole 40 is such that the opening area of the water passage hole is 1% to 30% with respect to the side surface area of the cylindrical spacer provided with the water passage hole. If this is below the above range, sufficient treated water is not supplied into the cylindrical spacer, and the concentrated treated water cannot be sufficiently diluted. Above the above range, excessive water to be treated is supplied into the cylindrical spacer, and the flow of the diffused air is offset.

  Further, the shape of the water passage hole 40 is a rectangular opening on the side surface of the cylindrical spacer 30. In addition, it is not necessary to stick to the shape shown in FIG. 4 if the water to be treated can be diluted while taking into account the aperture ratio described above and the flow of the diffused air in the cylindrical spacer 30 is not disturbed. As shown, a plurality of rectangular openings 40 </ b> A that are rectangular openings may be arranged on the side surface of the cylindrical spacer 30 side by side on a straight line in the horizontal direction. Further, the water passage hole may be designed so as to minimize the processing cost while maintaining the strength required for the cylindrical spacer.

  Drawing 5 is an explanatory view of the 1st modification of an immersion flat membrane filtration device concerning an embodiment. FIG. 5 shows a front cross section of the submerged flat membrane filtration device 10A. As shown in the figure, an air diffuser 20 for cleaning the membrane module 16 is provided below the submerged flat membrane filtration device 10A. Part of the diffused air from the diffuser means 20 is diffused air that flows along the outer side surface of the lower membrane module 16b. In order to take the diffused air flowing outside the lower membrane module 16 b into the cylindrical spacer 30, a gutter 50 is provided above the water passage hole 40. The flange 50 is inclined obliquely downward from the side surface of the cylindrical spacer 30 to the outside. By providing the jar 50, the water to be treated is diluted, more aeration air is supplied to the upper membrane module 16a, and the membrane filtration performance of the upper membrane module 16a can be stabilized.

  Drawing 6 is an explanatory view of the 2nd modification of an immersion flat membrane filtration device concerning an embodiment. FIG. 6 shows a front cross section of the submerged flat membrane filtration device 10B. As shown in the figure, the configuration different from the submerged flat membrane filtration device 10B of the second modification and the submerged flat membrane filtration device 10A of the first modification is that an auxiliary air diffuser 60 is provided below the tub 50. 5 is inclined obliquely downward in order to take in diffused air flowing along the outer side surface of the lower membrane module 16 b into the cylindrical spacer 30. Since the diffused air flowing along the lower membrane module 16b varies depending on the processing conditions, the amount of diffused air supplied into the cylindrical spacer 30 may not be constant. Therefore, the submerged flat membrane filtration device 10B of the second modified example is provided with the auxiliary air diffusion means 60 below the trough 50 and on the side surface of the lower membrane module 16b. Thereby, the diffused air from the auxiliary diffuser 60 floats along the outer side surface of the lower membrane module 16 b and is supplied from the ridge 50 into the cylindrical spacer 30. Therefore, more aeration air is supplied to the upper membrane module 16a, and the membrane filtration performance of the upper membrane module 16a can be stabilized.

  Drawing 7 is an explanatory view of the 3rd modification of an immersion flat membrane filtration device concerning an embodiment. FIG. 7 shows a front cross section of the submerged flat membrane filtration device 10C. As shown in the figure, the cylindrical spacer 30A of the submerged flat membrane filtration device 10C is formed in a trapezoidal shape in cross section by expanding the pair of side surfaces on the side intersecting the membrane plane of the membrane element downward in a taper shape. Yes. A water passage hole 40B is formed on the lower surface of the cylindrical spacer 30A. Other configurations are the same as those of the apparatus configuration of FIG. As a result, the water to be treated flows into the cylindrical spacer 30A from the lower surface of the cylindrical spacer 30A as shown by the arrow g, and the water to be treated in the cylindrical spacer 30A can be diluted. The treated water that flows in at this time flows from the water passage hole 40B on the lower surface of the cylindrical spacer 30A along the side surface of the lower membrane module 16b as shown by the arrow g, and thus the flow of diffused air in the cylindrical spacer 30A (Arrow h) is not disturbed.

  According to such an immersion flat membrane filtration device, the water to be treated that has passed through the lower membrane module can be effectively diluted, and the distribution of the diffused air flowing into the upper membrane module can be made uniform. . Accordingly, it is possible to reduce the local progress of dirt on the upper membrane module or the progress of dirt on the entire membrane.

It is explanatory drawing of the immersion flat membrane filtration apparatus of this invention. It is explanatory drawing of the ventilation | gas_flowing amount of the diffused air which passes between membrane elements. The partial enlarged view of the cylindrical spacer of an immersion flat membrane filtration apparatus is shown. It is explanatory drawing of a water flow hole. It is explanatory drawing of the 1st modification of an immersion flat membrane filtration apparatus. It is explanatory drawing of the 2nd modification of an immersion flat membrane filtration apparatus. It is explanatory drawing of the 3rd modification of an immersion flat membrane filtration apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ......... Immersion flat membrane filtration apparatus, 14 ......... Membrane element, 16 ......... Membrane module, 20 ......... Air diffuser, 30 ......... Cylindrical spacer, 40 ......... Water passage hole, 50 ... …… 庇, 60 ……… Auxiliary air diffuser.

Claims (4)

A plurality of membrane elements for membrane filtration of water to be treated in the treatment tank are arranged vertically in parallel in the treatment tank, and a plurality of layers are arranged in the vertical direction in the treatment tank, and a gap between the upper and lower membrane elements is formed. In the submerged flat membrane filtration device provided with a surrounding cylindrical spacer,
Provided on the side surface of the cylindrical spacer on the side intersecting the membrane plane of the membrane element is a water passage hole for taking in the treated water from the treatment tank to the inside of the cylindrical spacer, and the water passage hole is the cylindrical shape. An immersion flat membrane filtration device, which is disposed only above half of the side surface of the spacer.   The submerged flat membrane filtration device according to claim 1, wherein a ratio of an opening area of the water passage hole to a side surface area of the cylindrical spacer provided with the water passage hole is 1% to 30%.   The submerged flat membrane filtration device according to claim 1 or 2, wherein a ridge that is inclined outward and downward from a side surface of the cylindrical spacer is provided at an upper portion of the water passage hole.   The submerged flat membrane filtration device according to claim 3, wherein auxiliary air diffusion means is provided on a side surface of the membrane element below the ridge.

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