JP6529238B2 - Sand filter - Google Patents

Description

The present invention relates to a sand filtration equipment.

  DESCRIPTION OF RELATED ART The purification apparatus which purify | cleans the to-be-processed water polluted by VOC (volatile organic compound) etc. is known (for example, refer patent document 1, 2).

  There is also known a membrane filtration apparatus provided with a membrane-like filter medium (temperature responsive membrane) which expands and contracts depending on temperature (see, for example, Patent Document 3).

JP 2004-105905 A JP, 2009-056355, A JP, 2011-152544, A

  By the way, the sand filtration apparatus which filters and processes to-be-processed water through a filtration sand layer is known. In this sand filtration apparatus, for example, biofilms and the like in the water to be treated are accumulated in the filter sand layer along with the filtration treatment, so that the treatment efficiency of the filtration treatment gradually decreases (clogging). As a countermeasure, in the sand filtration apparatus, backwashing is periodically performed (about several times a day) to wash the filtered sand layer by passing washing water through the filtered sand layer in the opposite direction to the filtering process.

  However, since the filtration process is interrupted during the backwashing, it is desirable to make the backwashing efficient.

  In view of the above facts, the present invention aims to improve the cleaning efficiency of backwashing.

The sand filtration apparatus according to the first aspect is pumped from the contaminated soil to which biostimulation is applied , filters treated water containing a biofilm through a filter sand layer, and is reverse to the filtration process. The sand filter, which backwashes the sand layer through washing water through the sand layer, and a washing water heater, which heats the washing water passing through the sand layer, the washing water heater sets the washing water to 40 ° C. Above, it heats to 70 degrees C or less.

According to the sand filtration apparatus which concerns on a 1st aspect , the biofilm in to-be-processed water is accumulate | stored in a filter sand layer with filtration treatment. The biofilm thus accumulated in the filter sand layer is removed from the filter sand layer by backwashing.

  Here, in the present invention, since the washing water heated by the washing water heater is passed through the filter sand layer at the time of reverse washing, bacteria and the like forming a biofilm are easily killed. This makes it easier to remove the biofilm attached to the filtered sand layer as compared to the case where the filtered sand layer is backwashed with the non-heated washing water. Therefore, the cleaning efficiency of the backwashing of the filter sand layer can be improved.

Also, by passing washing water heated to 40 ° C. or more and 70 ° C. or less at the time of reverse washing through a filter sand layer, bacteria forming a biofilm are more likely to be killed. Therefore, the removal efficiency of the biofilm attached to the filter sand layer is further improved.

A sand filtration apparatus according to a second aspect is the sand filtration apparatus according to the first aspect, further comprising a pumping line connected to the sand filter to supply the ground water pumped from the contaminated soil to the sand filter.

  As described above, according to the present invention, the cleaning efficiency of the backwashing can be improved.

It is a schematic diagram which shows the water treatment system which concerns on one Embodiment of this invention. It is a schematic diagram which shows the aeration apparatus shown by FIG. It is a longitudinal cross-sectional view which shows the aeration tank shown by FIG. (A) And (B) is a longitudinal cross-sectional view which shows the diffuser and membrane filter which are shown by FIG. It is a partially expanded view of FIG. 4 (B). (A) And (B) is a longitudinal cross-sectional view which shows the modification of the aeration tank shown by FIG. It is a longitudinal cross-sectional view which shows the modification of the aeration tank shown by FIG. It is a schematic diagram which shows the liquid centrifugation apparatus shown by FIG. It is a schematic diagram which shows the sand filtration apparatus shown by FIG. It is a longitudinal cross-sectional view which shows the sand filter shown by FIG. 9 typically. (A) is a graph which shows the relationship between the temperature of groundwater, and the formation amount of a biofilm, (B) is a graph which shows the relationship between the temperature of groundwater and the treated water volume (processing capacity) of a sand filter.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[Water treatment system]
The water treatment system 10 which concerns on this embodiment is shown by FIG. The water treatment system 10 purifies the groundwater pumped up from the contaminated ground (soil) 12.

  The ground 12 includes a low permeability layer 12A and an aquifer 12B deposited on the low permeability layer 12A. In addition, the groundwater level of the aquifer 12B is shown by S in FIG.

  The aquifer 12B has higher water permeability than the low water permeability layer 12A, and groundwater is likely to flow. In the aquifer 12B, contaminated soil 12B1 containing a contaminant such as VOC (volatile organic compound) is present, and iron and manganese are contained as in the conventional soil. Iron and manganese in soil particles are usually insoluble in many cases, but they become soluble when the pH drops or under reducing conditions, and become soluble iron and soluble manganese and elute in groundwater .

  In addition, as VOC, a trichloroethylene, benzene, a vinyl chloride monomer etc. are mentioned, for example.

  The water treatment system 10 according to the present embodiment includes the temporary water tank 22, the aeration device 30, the liquid centrifugal separator 76, the sand filtration device 90, and the injection tank 100, and the groundwater pumped up from the aquifer 12B Water) is treated and purified in an aerator 30, a liquid centrifugal separator 76, and a sand filter 90. Then, the ground water (treated water) purified by the water treatment system 10 is again injected to the aquifer 12B. By repeating such water treatment and circulating ground water between the aquifer 12B and the water treatment system 10, the contaminated soil 12B1 is purified.

  In addition, the flow of groundwater is shown by the arrow in FIG. In addition, a water blocking wall 16 is formed in the aquifer 12B. The water blocking wall 16 is formed so as to surround the contaminated soil 12B1, and its lower end is embedded in the low water permeability layer 12A. This prevents the spread of contaminated ground water and the like.

  In addition, biostimulation (anaerobic biostimulation) is adopted in the water treatment system 10 according to the present embodiment, and organic matter is contained in groundwater (treated water) injected to the aquifer 12B. Is added. Thereby, the purification efficiency (decomposition efficiency) of pollutants such as VOCs in the contaminated soil 12B1 is enhanced.

  With biostimulation, for example, organic substances (nutrients) such as polylactic acid ester, amino acids, yeast extract and the like are injected into the aquifer 12B and inhabited in the aquifer 12B (contaminated soil 12B1). It is a method to promote the purification of pollutants (VOC) by growing and activating microorganisms. On the other hand, the amount of elution of soluble iron and soluble manganese is increased by reducing the soil.

  Next, a schematic configuration of the water treatment system 10 according to the present embodiment will be described.

  A pumping well 18 is connected to the temporary water receiving tank 22 via a pumping line 20. The pumping line 20 is formed of, for example, a pipe or a hose. In addition, the various lines mentioned later are also formed by piping, a hose, etc. similarly to the pumping line 20, for example.

  The pumping well 18 is formed by excavating the ground 12 and reaches the aquifer 12B. Moreover, the pumping line which is not shown in figure is provided in the pumping line 20. As shown in FIG. By operating the pumping pump, contaminated underground water from the aquifer 12B is pumped up to the temporary receiving water tank 22.

  The groundwater pumped up to the temporary water receiving tank 22 is supplied to the aeration device 30 via the water distribution line 24 and is aerated. As a result, the VOCs in the ground water are volatilized and the VOCs are removed from the ground water. The gas containing the volatilized VOC is supplied to an adsorption device 48 (see FIG. 2) described later, and after the VOC is removed, the gas is released to the atmosphere.

  Ground water subjected to aeration treatment in the aeration apparatus 30 is supplied to the liquid centrifugal separator 76 via the water distribution line 74, and is further supplied to the sand filtration apparatus 90 via the water distribution line 84.

  Here, along with the aeration processing in the aeration apparatus 30, soluble metals (soluble iron, soluble manganese, etc.) in the ground water are oxidized and deposited in the ground water. In addition, a microorganism is formed in the ground water to form a biofilm. These precipitates and biofilms are collectively referred to as scale W.

  As shown in FIG. 3, the scale W precipitates as a precipitate on the bottom wall 32 L of the aeration tank 32 and is discharged to the outside of the aeration tank 32 via a suction unit 70 described later. In addition, the scale W remaining in the ground water is gradually removed from the ground water by the liquid centrifugal separator 76 and the sand filter 90 which follow.

  In addition, as the scale W, for example, an iron salt, a manganese scale, a silica scale, a biofilm (slime) and the like can be mentioned. Examples of iron salts and manganese scales include iron hydroxide, iron oxide and manganese oxide. Moreover, as a silica scale, calcium silicate, magnesium silicate, aluminum silicate etc. are mentioned. Furthermore, examples of the biofilm (slime) include algae, bacteria and the like.

  An injection tank 100 is connected to the sand filter 90 via a water distribution line 98. Furthermore, a water injection well 104 is connected to the injection tank 100 via a water injection line 102.

  The water injection well 104 is formed by excavating the ground 12, and reaches the aquifer 12B. The water injection line 103 is provided with a water injection pump 103 (see FIG. 9) described later. Then, when the water injection pump 103 is operated, the groundwater filtered by the sand filter 90 is injected into the aquifer 12B through the water injection well 104.

  Next, the aerator 30, the liquid centrifugal separator 76, and the sand filter 90 which constitute the water treatment system 10 will be described in detail.

[Aeration device]
First, the aeration device 30 will be described.

  As shown in FIG. 2, the aeration apparatus 30 includes an aeration tank 32, a treated water heater 38, and a plurality of injectors 54. The aeration tank 32 stores underground water as treated water. The temporary water tank 22 (see FIG. 1) described above is connected to the aeration tank 32 via the water distribution line 24. The water distribution line 24 is provided with a water supply pump (not shown). Groundwater is supplied from the temporary water receiving tank 22 to the aeration tank 32 by operating the water supply pump.

  Further, in the aeration tank 32, a circulation water distribution line 34 is provided. The circulation water distribution line 34 is provided with a circulation pump 36 and a water heater 38. And, by operating the circulation pump 36, the ground water is circulated between the aeration tank 32 and the water heater 38.

  The treated water heater 38 is formed of, for example, an electric heater, a gas water heater, or the like, and heats the groundwater flowing through the circulation water distribution line 34 to a temperature at which VOCs are easily volatilized. Specifically, the treated water temperature control unit 40 is electrically connected to the treated water heater 38. Further, a water temperature sensor (not shown) is electrically connected to the water temperature control unit 40.

  The treated water temperature sensor detects the temperature of the groundwater stored in the aeration tank 32 or the groundwater flowing through the circulating water distribution line 34, and outputs the temperature to the treated water temperature control unit 40. The treated water temperature control unit 40 controls the operation of the treated water heater 38 such that the temperature of the ground water detected by the treated water temperature sensor is equal to or higher than a predetermined value.

  In addition, as temperature of the underground water (to-be-processed water) which volatilizes VOC, 25 to 50 degree (degreeC) is preferable, and 35 to 45 degree is more preferable. Moreover, you may provide the to-be-processed water heater 38 not only in the circulation water distribution line 34, but in the water distribution line 24 which supplies underground water to the aeration tank 32, for example from the aeration tank 32 or the temporary water receiving tank 22.

  Further, a gas-liquid separation tank 44 is connected to the upper part of the aeration tank 32 via an exhaust line 42A. A gas containing VOCs volatilized from the aeration tank 32 is supplied to the gas-liquid separation tank 44 through the exhaust line 42A. Then, in the gas-liquid separation tank 44, the gas and the liquid in the gas are separated.

  An adsorption device 48 is connected to the gas-liquid separation tank 44 via an exhaust line 42B. A gas containing VOC from the gas-liquid separation tank 44 is supplied to the adsorption device 48 through the exhaust line 42B. The exhaust line 42B is provided with a blower 46 for feeding the gas from the gas-liquid separation tank 44 to the adsorption device 48.

  The adsorption device 48 includes, for example, an adsorbent such as activated carbon. The adsorbent adsorbs contaminants such as VOCs in the gas supplied from the gas-liquid separation tank 44. Then, the gas from which contaminants such as VOCs have been removed is discharged to the atmosphere through the exhaust line 42C.

  As shown in FIG. 3, the bottom wall 32 </ b> L of the aeration tank 32 is provided with a plurality of legs 50 for supporting the bottom wall 32 </ b> L of the aeration tank 32 with respect to the installation surface 49. An installation space 51 for an injector 54 described later is formed below the bottom wall 32L of the aeration tank 32 by the legs 50.

  Furthermore, in the bottom wall portion 32L of the aeration tank 32, a plurality of intake ports 52 penetrating the bottom wall portion 32L in the thickness direction are formed. The plurality of air inlets 52 are formed in a circular shape, and are arranged in two horizontal directions. Diffuser 56 of injector 54 mentioned below is installed in these air intakes 52, respectively.

  The injector 54 is a diffuser for injecting air from the bottom wall portion 32L of the aeration tank 32 into the groundwater to aerate the groundwater. The injector 54 includes a diffuser 56, a blower 60, an air heater 62, and a membrane filter 66 (see FIG. 4A).

  The diffuser 56 is in the form of a disc formed in a disk shape in a plan view, and is respectively fitted into a plurality of air inlets 52 formed in the bottom wall portion 32L of the aeration tank 32. An intake line 58 is connected to each diffuser 56.

  The diffuser 56 is not limited to a disk shape in plan view, and may be, for example, a rectangular shape in plan view. Further, instead of the diffuser 56, a diffuser may be installed under the bottom wall 32L of the aeration tank 32.

  The intake line 58 is laid in the installation space 51 described above. A blower 60 and an air heater 62 are provided in the intake line 58. The intake line 58 is a collective line (collective pipe) connected to the plurality of diffusers 56.

  The blower 60 is, for example, a fan or a compressor. By operating the blower 60, air is supplied to the diffuser 56 through the intake line 58. Then, the air supplied to the diffuser 56 is blown out into the aeration tank 32 from an air outlet 56A (see FIG. 4A) formed in the central portion of the diffuser 56.

  The air heater 62 is formed, for example, by a heater or the like, and heats the air supplied to the aeration tank 32 to a temperature at which the VOCs easily evaporate. Specifically, an air temperature control unit 64 is electrically connected to the air heater 62. Further, an air temperature sensor (not shown) is electrically connected to the air temperature control unit 64.

  The air temperature sensor detects the temperature of the air flowing through the outside air or the intake line 58 and outputs the temperature to the air temperature control unit 64. The air temperature control unit 64 controls the operation of the air heater 62 such that the temperature of the air detected by the air temperature sensor becomes equal to or higher than a predetermined value.

  In addition, as temperature of the air for volatilizing VOC, 25 to 50 degree (degreeC) is preferable similarly to the ground water (to-be-processed water) mentioned above, and 35 to 45 degree is more preferable. Also, the air heater 62 can be omitted as appropriate.

  As shown in FIG. 4A, the upper surface of the diffuser 56 is covered by a membrane filter 66. The membrane filter 66 as an example of the elastic cover is formed of, for example, a film-like rubber or the like. The membrane filter 66 covers the upper surface of the diffuser 56 and the outer peripheral portion thereof is fixed to the outer peripheral portion of the diffuser 56 so as to close the outlet 56A of the diffuser 56.

  Thereby, when air is blown out from the blow out port 56A, as shown in FIG. 4 (B), the pressure that the membrane filter 66 receives from the air expands in a hemispherical shape (dome shape) into the aeration tank 32 (elastic deformation ). On the other hand, when the air blowoff from the blowout port 56A is stopped, the membrane filter 66 is contracted and the upper surface of the diffuser 56 is covered by the contracted membrane filter 66, as shown in FIG. 4 (A).

  Here, the membrane filter 66 is formed with a plurality of injection holes 66A that open and close in accordance with expansion and contraction (expansion and contraction). Specifically, as shown in FIG. 4A, the plurality of injection holes 66A are formed in a slit shape, and are closed in a contracted state (natural state) of the membrane filter 66.

  On the other hand, as shown in FIGS. 4B and 5, when the membrane filter 66 expands, the plurality of injection holes 66A are opened. As a result, the air blown out from the air outlet 56A of the diffuser 56 is injected into the underground water through the respective injection holes 66A.

  The outlet 56A of the diffuser 56 may be closed by another filter having the same function as the membrane filter 66. Also, the membrane filter 66 can be omitted as appropriate.

  As shown in FIG. 3, the aeration tank 32 is connected to a discharge line 68 for discharging the precipitate such as the scale W to the outside of the aeration tank 32. At the front end portion of the discharge line 68, a suction portion 70 facing the bottom wall portion 32L of the aeration tank 32 is provided. Further, a suction pump 72 is provided in the discharge line 68. By operating the suction pump 72, the precipitate such as the scale W deposited on the bottom wall 32L of the aeration tank 32 is sucked from the suction unit 70 and discharged to the outside of the aeration tank 32 through the discharge line 68. Be done.

  Next, the operation and effects of the aeration apparatus 30 will be described.

  As shown in FIGS. 2 and 3, a plurality of injectors 54 are provided below the bottom wall 32 </ b> L of the aeration tank 32. The diffusers 56 of the injector 54 are respectively installed in a plurality of intake ports 52 formed in the bottom wall portion 32 </ b> L of the aeration tank 32. Then, when the blower 60 is operated, as shown in FIG. 4B and FIG. 5, air is supplied to the diffuser 56 through the intake line 58 and air is blown out from the outlet 56 A of the diffuser 56. .

  As a result, the membrane filter 66 that blocks the air outlet 56A of the diffuser 56 is expanded, and the plurality of injection holes 66A are opened. As a result, air is injected from the plurality of injection holes 66A into the groundwater stored in the aeration tank 32, and the groundwater is aerated. With this aeration, VOCs in the groundwater are volatilized.

  Further, as shown in FIG. 2, the gas containing the volatilized VOC is supplied to the gas-liquid separation tank 44 via the exhaust line 42A, separated from the liquid, and then to the adsorption device 48 via the exhaust line 42B. It is supplied and the VOC is removed. Then, the gas from which the VOC has been removed is released to the atmosphere via the exhaust line 42C.

  Here, in the present embodiment, air is jetted from the intake port 52 formed in the bottom wall portion 32L of the aeration tank 32 into the ground water. Therefore, the whole groundwater stored in the aeration tank 32 can be efficiently aerated.

  In addition, since the groundwater pumped up from the aquifer 12B is generally at a low temperature, VOCs in the groundwater are less likely to be volatilized, but in the present embodiment, the groundwater stored in the aeration tank 32 is predetermined by the water heater 38 Heated to temperature. As a result, VOCs in the ground water are easily volatilized, and the volatilization efficiency of the VOCs is improved. In addition, the amount of air supplied from the injector 54 to the aeration tank 32 can be reduced along with the improvement of the volatilization efficiency of the VOC.

  Furthermore, in the present embodiment, the air supplied from the injector 54 to the aeration tank 32 is heated by the air heater 62 to a predetermined temperature. This makes VOCs in the underground water more volatile. Therefore, the volatilization efficiency of VOC is further improved.

  By the way, in the bottom wall portion 32L of the aeration tank 32, there is a possibility that deposits such as the scale W may be deposited along with the aeration processing of the ground water. And if a deposit accumulates on the bottom wall part 32L of the aeration tank 32, the inlet 52 will be closed and the jet efficiency of the air from the injector 54 may fall. Therefore, it is necessary to stop the blower 60 periodically, that is, to interrupt the aeration treatment periodically to remove the sediment deposited on the bottom wall 32L of the aeration tank 32. Therefore, it is desirable to improve the removal efficiency of the precipitate deposited on the bottom wall 32 L of the aeration tank 32.

  In particular, in the present embodiment, the above-described biostimulation is adopted, and the aquifer 12B is injected with an organic substance that causes microorganisms to grow and activate. Since the aquifer 12B has a reducing atmosphere due to the organic matter, soluble metals in the aquifer 12B are easily eluted into groundwater. As a result, since the concentration of the soluble metal in the groundwater supplied to the aeration tank 32 becomes high, the amount of deposition of the scale W in the aeration tank 32 is large, and the precipitate is deposited on the bottom wall 32 L of the aeration tank 32 It is easy to do.

  Furthermore, the groundwater injected to the aquifer 12B is heated by the above-described water heater 38, and its temperature is high. In this case, the microorganisms in the aquifer 12B easily grow, and the decomposition rate of the VOC is increased, and at the same time, the soluble metal is further easily eluted in the ground water. Therefore, the deposition amount of scale in the aeration tank 32 is likely to be further increased.

  Here, as in the conventional case, when an injector such as a diffuser is installed on the bottom wall portion 32L of the aeration tank 32, the injector becomes an obstacle and it becomes difficult to remove the precipitate such as the scale W .

  On the other hand, in the present embodiment, since the injector 54 is provided below the bottom wall 32L of the aeration tank 32, no obstacle exists on the bottom wall 32L of the aeration tank 32. Thereby, since it becomes easy to remove precipitates, such as scale W, from the upper surface of bottom wall part 32L of aeration tank 32, the removal efficiency of precipitates improves.

  Further, in the present embodiment, as described above, the underground water stored in the aeration tank 32 is heated to a predetermined temperature by the water heater 38, and the air supplied from the injector 54 to the aeration tank 32 is air. The heater 62 heats to a predetermined temperature. This improves the volatilization efficiency of VOCs in the groundwater. As a result, the amount of air supplied from the injector 54 to the aeration tank 32 can be reduced. That is, in the present embodiment, VOCs in groundwater can be volatilized with a small amount of air. Therefore, the amount of treated water (processing capacity) of the aeration device 30 is improved. As an example, at normal groundwater temperature (15 ° C to 20 ° C), aeration volume of 100 times the treatment water volume is required (If the treatment water volume is 10L / min, the aeration volume is 1000L / min) However, if the groundwater temperature is raised by about 30 ° C., it is possible to treat with an aeration volume of 50 times (500 L / min if the treated water volume is 10 L / min).

  Furthermore, when the amount of air supplied from the injector 54 to the aeration tank 32 is reduced, the amount of oxygen supplied to the ground water is also reduced, so that the oxidation of the soluble metal is suppressed. Therefore, the deposition amount of scale W such as iron oxide can be reduced.

  By the way, when removing a deposit, the air blower 60 is stopped. Therefore, sediment such as ground water and scale W may flow back to the outlet 56A of the diffuser 56, but in the present embodiment, the upper surface of the diffuser 56 is covered by the membrane filter 66.

  Therefore, when the blower 60 is stopped, as shown in FIG. 4A, the membrane filter 66 is contracted to close the plurality of injection holes 66A. As a result, the outlet 56A of the diffuser 56 is blocked by the membrane filter 66, so that the backflow of ground water or sediment to the outlet 56A is suppressed. Therefore, clogging or the like of the outlet 56A of the diffuser 56 can be suppressed.

  Furthermore, as shown in FIG. 3, the aeration tank 32 is provided with a discharge line 68 and a suction pump 72. Then, when the suction pump 72 is operated, the precipitate such as the scale W precipitated on the bottom wall 32 L of the aeration tank 32 is sucked from the suction unit 70 and discharged to the outside of the aeration tank 32 through the discharge line 68. Be done. Therefore, the removal efficiency of the precipitate is improved.

  Furthermore, the load of water treatment in the subsequent liquid centrifugal separator 76 and sand filter 90 is reduced with the improvement of the removal efficiency of the precipitate.

  Next, a modification of the aeration apparatus will be described.

  In the modification shown in FIG. 6A, on one side of the aeration tank 32, a suction unit 70 for suctioning sediment such as the scale W is provided. In such a case, for example, when the injection amount of the air of a part of the injectors 54 on the suction unit 70 side among the plurality of injectors 54 is relatively reduced, the groundwater flows as indicated by the arrow F. The deposit easily moves to the suction unit 70 side. Therefore, the removal efficiency of precipitates such as scale W is improved.

  Note that, as shown in FIG. 6B, the groundwater flows as indicated by an arrow F by relatively reducing the size of a portion of the injector 54 (diffuser 56) on the suction portion 70 side. It is also possible to make it easy to move the deposit to the suction unit 70 side.

  Further, for example, as in the modification shown in FIG. 7, the upper surface of the bottom wall portion 32L of the aeration tank 32 is inclined toward the suction portion 70, whereby the bottom wall portion 32L of the aeration tank 32 is precipitated. The precipitate such as the scale W or the like may be easily moved to the suction unit 70.

  The shape and arrangement of the suction unit 70 can be changed as appropriate. Further, the suction unit 70 may be provided as needed, and can be omitted as appropriate.

[Liquid centrifuge]
Next, a liquid centrifugal separator will be described.

  As shown in FIG. 1, a liquid centrifugal separator 76 is connected to the aerator 30 via a water distribution line 74. As shown in FIG. 2, the water distribution line 74 is provided with a water supply pump 75. As the water supply pump 75 is operated, underground water is supplied from the aeration tank 32 to the liquid centrifugal separator 76 through the water distribution line 74.

  As shown in FIG. 8, the liquid centrifugal separator 76 is a hydrocyclone that uses centrifugal force to separate ground water and the scale W and the like remaining in the ground water. In the liquid centrifugal separator 76, precipitates such as iron salts and manganese scale having a large specific gravity are drained from the lower end to the settling tank 78 through the drain line 77. On the other hand, ground water containing no iron salt or the like having a large specific gravity is supplied from the upper part of the liquid centrifugal separator 76 to the filtration raw water tank 82 through the drainage line 80.

  By using the liquid centrifugal separator 76 in this manner, the scale W or the like having a large specific gravity can be efficiently removed from the ground water. Further, the liquid centrifugal separator 76 is excellent in durability and maintainability because its structure is simple.

  The groundwater overflowing from the settling tank 78 is supplied to the filtration raw water tank 82 as shown by the arrow G. In addition, a sand filter 92 described later is connected to the filtration raw water tank 82 via a water distribution line 84. In addition, a water supply pump 86 is provided in the water distribution line 84. As the water supply pump 86 is operated, underground water is supplied from the filtration raw water tank 82 to the sand filter 92 through the water distribution line 84.

[Sand filter]
Next, the sand filtration device will be described.

  As shown in FIG. 9, the sand filtration apparatus 90 removes the biofilm V (see FIG. 10) and the like remaining in the ground water, and includes a sand filter 92 and a washing water heater 118. .

  As shown in FIG. 10, the sand filter 92 includes a filtration tank 94 and a filter sand layer 96 provided in the filtration tank 94. The filter sand layer 96 is formed of filter sand as a filter medium. For this filtration sand, for example, a porous body such as ceramic sand is used. The filtration sand is not limited to the porous body, and, for example, normal sand may be used.

  Here, when filtering ground water, the feed water pump 86 (refer to FIG. 8) is operated to allow the bottom 94 L of the filtration tank 94 to be treated water (filtration raw water) from the filtration raw water tank 82 via the water distribution line 84 Groundwater is supplied. This groundwater passes through the sand filter layer 96 (white arrow), and after the biofilm V and the like are removed, it is drained from the upper part 94U of the filtration tank 94 through the water distribution line 98 to the injection tank 100 (see FIG. 9) Ru. Groundwater is thus filtered.

  As shown in FIG. 9, a water injection well 104 (see FIG. 1) is connected to the injection tank 100 via a water injection line 102. The water injection line 103 is provided with a water injection pump 103. As the water injection pump 103 is operated, the groundwater stored in the injection tank 100 is supplied to the water injection well 104 via the water injection line 102. At this time, the aforementioned organic material for biostimulation and the like are appropriately added to the ground water.

  In addition, a backwash water tank 108 is connected to the injection tank 100 via a water distribution line 106. In the backwash water tank 108, wash water (groundwater) for backwashing the filter sand layer 96 is stored.

  In addition, a filtration tank 94 is connected to the backwash water tank 108 via a water supply line 112. The water supply line 112 is provided with a cleaning pump 110. When the washing pump 110 is operated, as shown in FIG. 10, groundwater in the form of washing water is supplied from the backwash water tank 108 to the upper part 94U of the filtration tank 94 through the water supply line 112.

  The washing water supplied to the filtration tank 94 passes through the filter sand layer 96 (black arrow) in the opposite direction to the filtration processing (black arrow), and after removing the biofilm V attached to the filter sand layer 96, the bottom 94L of the filtration tank 94 The water is drained to the backwash tank 116 (see FIG. 9) through the drainage line 114. During the backwashing, the feed water pump 86 (see FIG. 8) is stopped to interrupt the filtration process.

  Here, the water supply line 112 is provided with a washing water heater 118. The wash water heater 118 heats the wash water flowing through the water supply line 112 to a predetermined temperature at which bacteria forming the biofilm V are likely to be killed. Thereby, the biofilm V is easily removed from the filter sand layer 96.

  Next, the operation and effects of the sand filtration device 90 will be described.

  As shown in FIG. 10, in the sand filter 92, the biofilm V in the groundwater is accumulated in the filter sand layer 96 along with the filtering process. The biofilm V accumulated in the filter sand layer 96 is removed from the filter sand layer 96 by backwashing.

  Here, in the present embodiment, since the washing water heated by the washing water heater 118 is passed through the filter sand layer 96 at the time of back washing, the bacteria forming the biofilm V and the like are easily killed. This makes it easier to remove the biofilm V attached to the filtered sand layer 96 as compared to the case where the filtered sand layer 96 is backwashed with the non-heated washing water. Therefore, the cleaning efficiency of the backwashing of the filter sand layer 96 can be improved.

  Moreover, the relationship between the temperature of groundwater and the formation amount of a biofilm is shown by FIG. 11 (A). As can be seen from FIG. 11, when the temperature of the groundwater reaches 40 ° C. (° C.) or more, the amount of biofilm formation decreases. This is because when the temperature of the groundwater reaches 40 degrees or more, the bacteria forming the biofilm are easily killed.

  Therefore, it is preferable to heat the temperature of washing water to 40 degrees or more, and 50-70 degrees is more preferable. The washing water heater 118 may have the temperature of the washing water at least higher than the temperature of the ground water (water to be treated) to be subjected to the filtering treatment.

  Further, FIG. 11B shows the relationship between the temperature of the ground water and the amount of treated water (processing capacity) of the sand filter 92. The graph 120 in FIG. 11 (B) shows the amount of water treated by the sand filter 92 when the filter sand layer 96 is not in use. Further, the graph 122 shows the amount of treated water of the sand filter 92 when the filter sand layer 96 is blocked by the biofilm.

  Furthermore, the graph 124 shows the amount of treated water of the sand filter 92 when the filter sand layer 96 clogged by the biofilm V is backwashed with the washing water of 30 degrees, and the graph 126 is a clogged filter by the biofilm V It shows the amount of water treated by the sand filter 92 when the sand layer 96 is backwashed with 60 ° washing water.

  As shown in the graphs 124 and 126, it can be seen that the amount of treated water in the sand filter 92 increases as the temperature of the washing water rises. That is, it can be seen that the removal efficiency of the biofilm attached to the filter sand layer 96 is improved.

  Next, the modification of the water treatment system concerning the above-mentioned embodiment is explained.

  Although the above-mentioned embodiment showed the example using biostimulation, it does not restrict to this. For example, bioaugmentation in which an externally cultured microorganism is injected into the aquifer 12B together with a nutrient or the like may be used. Moreover, the said embodiment is suitable also for purification | cleaning of the original ground with comparatively high density | concentrations, such as organic substance in a ground water, and a soluble metal. Furthermore, the water treatment system 10 which concerns on the said embodiment is applicable also to water treatment, such as factory drainage.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to such Embodiment, You may use it combining suitably one Embodiment and various modifications, The summary of this invention Of course, various modifications can be made without departing from the scope of the invention.

Reference Signs List 30 aeration device 32 aeration tank 32 L bottom wall 52 intake 54 injector 56 diffuser 56 A blowout 60 blower 66 membrane filter 66 A injection hole 70 suction unit 90 filtration device 92 filter 96 filter sand layer 118 washing water heater V biofilm

Claims (2)

The water is pumped from the contaminated soil to which biostimulation is applied, and the groundwater containing the biofilm is filtered through a filter sand layer, and the filter sand layer is reversed through the washing water through the filter sand layer in the opposite direction to the filter processing. Sand filter to wash,
A wash water heater for heating wash water to be passed through the filter sand layer;
Equipped with
The washing water heater heats the washing water to 40 ° C. or more and 70 ° C. or less,
Sand filtration device. And a pumping line connected to the sand filter to supply the sand filter with the groundwater pumped from the contaminated soil.
The sand filtration apparatus of Claim 1.