JP5368142B2 - Overflow water treatment system in combined sewers. - Google Patents

Description

  The present invention relates to a system for treating overflow water of a combined sewer, and more particularly, to an overflow water treatment system that can improve the water quality of combined sewage overflow (CSO) by high-speed filtration.

  Conventionally, as sewer systems, there are known a segregated sewer that flows rainwater and sewage through separate pipes and a combined sewer that flows rainwater and sewage through the same pipe, especially in urban areas. Many combined sewers are used.

  And in the combined sewerage, the planned interception amount nQ of the interceptor pipe is usually different according to the capacity of the sewage treatment plant (where “n” is a numerical value that varies depending on the city, for example, n = 3 in Tokyo, Osaka City has n = 2.2, and "Q" is the maximum amount of sewage time in fine weather.) And cannot be treated at the sewage treatment plant exceeding the planned interception amount. Overflow water is discharged into public water areas such as rivers without any treatment. Specifically, as shown in FIG. 5, when the amount of rainwater and sewage flowing into the combined sewer pipe 51 exceeds the planned interception amount nQ (sometimes referred to as “the maximum amount of sewage during rainy hours”), Overflow moisture (excess nQ) flows over the overflow weir (not shown) of the rainwater spout 52 installed between the combined sewage pipe 51 and the interception pipe 53 and flows into the river 54 and the like. ing.

  Here, as described above, overflow water that cannot be treated at the sewage treatment plant in the combined sewer is discharged into a river or the like as it is untreated, but the overflow water contains sewage. There was a risk of rivers being contaminated by the discharge of overflow water. Therefore, a technique for improving the quality of overflow water (BOD, SS, etc.) discharged into rivers and the like has been demanded.

  On the other hand, a technique for filtering overflow water of a combined sewer using a filter provided with a filter provided rotatably and a cleaning device that injects a high-temperature fluid onto the filter is known (for example, patents). Reference 1). However, in such a filter, there is a risk that the filter will eventually become clogged even if it is washed repeatedly with a hot fluid, and it is necessary to always prepare a hot fluid for washing the filter. There was a problem that there was.

  In addition, in high-speed filtration technology using floating filter media such as those used in sewage treatment plants, the filtered media stored in the upper part of the filter media packed bed was washed down naturally, so in the design, The height of the water tank is limited to a height at which a desired backwash line speed (line speed of filtered water flowing during backwashing) can be obtained, and in order to ensure sufficient amount of filtered water necessary for washing the filter medium Needed to install a plurality of filtration tanks in parallel and provide a common treated water (filtrated water) tank, and required a large installation area (see, for example, Patent Document 2 and Patent Document 3). Therefore, it is difficult to install a filtration device to which the high-speed filtration technology is applied between a rainwater discharge and a river or the like, and it is not suitable as a means for improving the quality of combined sewage overflow (CSO).

JP 2004-305902 A Japanese Patent No. 3853738 Japanese Patent No. 3824583

  Therefore, there is a need for a combined sewage overflow treatment system that can be installed on-site in a space-saving manner and that is easy to maintain and does not become unfilterable due to clogging.

This invention aims to solve the above-mentioned problem advantageously, and the overflow water treatment system of the present invention is a system for treating overflow water of a combined sewer, comprising a first vertical hole, An overflow water channel for connecting the combined sewage pipe and the first vertical hole to flow the overflow water from the combined sewage pipe to the first vertical hole, a filter medium layer made of a filter medium, and supporting the filter medium Screen, a water collecting device installed below the filter medium layer, a second vertical hole provided with a filtered water discharge pipe provided above the filter medium layer, the first vertical hole, and the second A connecting flow path that connects to the vertical hole, a backwash pump connected to the water collecting device, and the overflow water provided in the connection flow path to the second vertical hole when the filter medium layer is backwashed. comprising a connection channel valve to stop the flow, contact between the overflow water passage and the confluent sewage pipe And at least one of the connection part between the first vertical hole and the overflow water flow path is located above the filtrate discharge pipe, and the connection part between the second vertical hole and the connection flow path Is located below the filter medium layer.
According to such an overflow water treatment system, at least one of the connection portion between the combined sewer pipe and the overflow water passage and the connection portion between the first vertical hole and the overflow water passage is located above the filtrate discharge pipe. And the connecting portion between the second vertical hole and the connecting flow path is located below the filter medium layer, so that the head pressure of the overflow water in the first vertical hole is used as a propulsive force in the filter medium layer. Overflow water can be filtered (removal of contaminants, BOD, SS, etc.). In addition, since the overflow water treatment system of the present invention uses a filter medium layer instead of a filter for the filtration of overflow water, the filter medium can be easily washed (backwashed) by downflow using a backwash pump. There is no worry about clogging. Furthermore, since the vertical hole has a higher degree of freedom in designing in the depth direction than the aquarium, the overflow water treatment system of the present invention makes it easy to adjust the depth of the vertical hole to reduce the amount of filtered water required for cleaning the filter media. And the area necessary for installation can be reduced. That is, the overflow water treatment system of the present invention can be installed on-site. In addition, since the overflow water treatment system of the present invention uses a backwash pump to clean the filter medium, unlike the above-described conventional filtration apparatus that cleans the filter medium by the natural flow of filtered water, it is limited to the depth of the vertical hole. The backwash line speed can be kept constant without receiving water, and it is not necessary to provide a backwash water tank for allowing the water used for washing (backwash water) to flow down naturally at the bottom of the overflow water treatment system. Further, the overflow water treatment system of the present invention can perform backwashing with the connection flow path valve closed, and the backwash pump does not suck in overflow water in the first vertical hole during backwashing. The desired backwash line speed can be obtained without using a large discharge pump as the backwash pump.

  Here, in the overflow water treatment system of the present invention, the distance a from the lower part of the filtered water discharge pipe to the upper part of the filter medium layer, the thickness b of the filter medium layer, and the lower part of the filter medium layer to the bottom of the second vertical hole. It is preferable that the distance c satisfies the relationship of a ≧ b + c. This is because when the distance a is equal to or greater than the sum of the thickness b and the distance c, the amount of filtered water necessary for washing the filter medium can be sufficiently secured. In addition, in this invention, a, b, and c point out the distance and thickness in the state which is filtering the overflow water in an overflow water treatment system.

  The overflow water treatment system of the present invention includes a distance a from the lower portion of the filtrate discharge pipe to the upper portion of the filter medium layer, a thickness b of the filter medium layer, an apparent porosity α of the filter medium layer, and the filter medium layer. It is preferable that the distance c from the lower part to the bottom of the second vertical hole satisfies a relationship of a ≧ α × b + c. This is because the filter medium can be more reliably washed when a, b ′, which is obtained by multiplying the porosity α by b, and c satisfy the relationship of a ≧ b ′ + c. Here, the apparent porosity α (0 <α <1) of the filter medium layer refers to the ratio (volume ratio) occupied by the voids in the filter medium layer in the state where filtration of the overflow water is started. That is, α = 1−β when expressed using the ratio (volume ratio) β occupied by the filter medium in the filter medium layer. In the case where the filter medium itself has voids, such as when the filter medium is a porous material, the presence of the voids is not considered in the calculation of the porosity α (that is, the voids present in the filter medium are not included in the filter medium layer). Not considered a void).

  In the overflow water treatment system of the present invention, it is preferable that a flow rate adjusting valve capable of adjusting an inflow amount of the overflow water into the first vertical hole is provided in the overflow water flow path. In this way, it is possible to adjust the inflow of the overflow water according to the filtration capacity of the filter medium layer regardless of the level of the combined sewage pipe (rainfall), and the first vertical hole during backwashing This is because unnecessary inflow of overflow water into the water can be stopped.

  Here, in the overflow water treatment system of the present invention, it is preferable that the filter medium is a floating filter medium, and the screen is provided above the filter medium layer. This is because if a floating filter medium is used as the filter medium, there is no need to install a screen below the filter medium layer, and therefore there is no possibility of clogging the lower screen, which is difficult to clean and maintain.

Moreover, in the overflow water treatment system of the present invention, the floating filter medium is made of a foamed polymer having an apparent density of 0.1 to 0.4 g / cm ³ and a 50% compression hardness of 0.1 MPa or more, It is preferable to perform backwashing of the filter medium layer at a backwash line speed of 1.2 to 4.0 m / min by downward flow using the backwash pump. When the apparent density of the floating filter medium is less than 0.1 g / cm ³ , the desired compression hardness cannot be obtained, and the filter medium layer is used during backwashing at a backwash line speed of 1.2 to 4.0 m / min. Because it is impossible to deploy. On the other hand, if the apparent density exceeds 0.4 g / cm ³ , the filter medium may flow out during backwashing. Moreover, the reason why the 50% compression hardness is set to 0.1 MPa or more is that if it is softer than this, the filter medium will be compacted during high-speed filtration, so that a large amount of SS cannot be captured, and the filtration duration time will be shortened. is there. Furthermore, the backwash line speed is set to 1.2 to 4.0 m / min. The trapping material can be smoothly discharged by developing the filter medium downward by the downward flow while preventing the floating filter medium from flowing out. This is because backwashing can be performed in a short time. Here, 50% compression means the pressure required to crush a polymer sheet for forming filter media particles until its height is halved. In the present invention, the apparent density and 50% compression hardness can be measured by the methods defined in JIS K6767.

  Furthermore, in the overflow water treatment system of the present invention, a pretreatment screen is provided at a connection portion between the combined sewage pipe and the overflow water flow path, and the pretreatment screen washing line for backwashing the pretreatment screen. Is preferably further provided. In this way, it is possible to prevent clogging troubles in the overflow water treatment system due to inflow of large contaminants, for example, contaminants having a size of 25 mm or more, and early clogging of the filter medium layer, and the pretreatment screen eyes. This is because it is possible to prevent the stoppage of the overflow water into the overflow water treatment system due to clogging. In the present invention, a contaminant refers to a solid having a size of 2 mm or more, and a suspended substance refers to a solid having a size of less than 2 mm.

  And the overflow water treatment system of this invention WHEREIN: It is preferable that the said 2nd vertical hole is a column shape, and the said water collection apparatus is stretched around radially. This is because the backwash water containing suspended solids can be collected evenly during backwashing.

  According to the present invention, it is possible to provide a combined sewage overflow treatment system that can be installed on-site in a space-saving manner and that is easy to maintain and does not require cleaning due to clogging. .

It is explanatory drawing which shows an example of the combined sewer which applied the overflow water treatment system of this invention. It is explanatory drawing which shows the overflow water treatment system of 1st Embodiment of this invention. It is a top view which shows the shape of the water collecting apparatus which can be used for the overflow water treatment system of this invention. It is explanatory drawing which shows the overflow water treatment system of 2nd Embodiment of this invention. It is explanatory drawing which shows the conventional merge type sewer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing an example of a combined sewer system to which the overflow water treatment system of the present invention is applied, and FIG. 2 is an explanatory view showing the overflow water treatment system of the first embodiment of the present invention. . Moreover, FIG. 3 is a top view which shows the shape of the water collecting apparatus which can be used for the overflow water treatment system of this invention, FIG. 4 is explanatory drawing which shows the overflow water treatment system of 2nd Embodiment of this invention. is there. In addition, what attached | subjected the same code | symbol in each figure shall show the same component.

  As shown in FIG. 1, the overflow water treatment system of the present invention treats overflow water (nQ excess) that exceeds the planned interception amount nQ and cannot be treated at the sewage treatment plant. That is, in the combined sewer system to which the overflow water treatment system of the present invention is applied, overflow water is provided in the combined sewer pipe 11 when the amount of rainwater and sewage flowing into the combined sewer pipe 11 exceeds the planned interception amount. It flows into the overflow water treatment system 100 beyond the overflow part 15 and is processed. Here, the overflow part 15 is desirably provided upstream of the existing rainwater spout 12. However, when installation on the upstream side of the rainwater spout 12 is difficult, the rainwater spout 12 may be provided. Then, the overflow water (filtered water) that has been filtered by the overflow water treatment system 100 and improved in water quality is discharged into the river 14 and the like. The filtered water may be discharged after optionally adding a disinfectant such as hypochlorous acid. In this case, the filtered water to which the disinfectant is added is greatly reduced in SS by the overflow water treatment system of the present invention. Therefore, the amount of the disinfectant added can be reduced as compared with the case of adding the disinfectant directly to the overflow water.

  And as shown in FIG. 2, the overflow water treatment system 100 of 1st Embodiment of this invention is the overflow water flow path 120 which connects the 1st vertical hole 110, the merged sewer pipe 11, and the 1st vertical hole 110. As shown in FIG. And the second vertical hole 130, the connecting flow path 140 connecting the first vertical hole 110 and the second vertical hole 130, the overflow bypass path 150, and the backwash pump 160.

  Here, an automatic scraping screen 121 of, for example, 4 mm mesh is installed at the connecting portion between the combined sewage pipe 11 and the overflow water flow path 120, so that foreign matters such as dust existing in the overflow water can be removed. Has been. As the automatic scraping screen 121, a known automatic scraping screen with a screen scraping device that prevents the screen from being blocked can be used. Further, the overflow water flow path 120 is provided with a flow rate adjustment valve 122 for adjusting the inflow amount of overflow water from the combined sewage pipe 11.

  For the first vertical hole 110, a new structure such as a manhole can be used. In this embodiment, the first vertical hole 110 is formed by providing the manhole 170 with the partition wall 111. Further, a level switch (not shown) is provided in the first vertical hole 110 so that the rise of the overflow water level in the first vertical hole 110 can be detected.

  The second vertical hole 130 uses an existing manhole. The second vertical hole 130 includes a screen 131, a filter medium layer 132 made of a dispersion-type filter medium supported by the screen 131, and a lower part than the filter medium layer 132. And a filtrate drainage pipe 134 provided above the filter medium layer 132. And in this 2nd vertical hole 130, the distance a from the lower part of the filtered water discharge pipe 134 to the upper part of the filter medium layer 132 is 2 m, the thickness b of the filter medium layer 132 is 0.8 m, and the filter medium layer 132, for example. The distance c from the lower part to the bottom of the second vertical hole is 1.2 m. The porosity α of the filter medium layer 132 is 0.5. The second vertical hole 130 may optionally include a blower (not shown) for improving the fluidity of the filter medium when the filter medium layer 132 is backwashed.

Here, the dispersion type filter medium means a particulate filter medium that develops and flows during backwashing. A known filter medium can be used as the dispersion type filter medium. For example, the floating filter is made of a foamed polymer having an apparent density of 0.1 to 0.4 g / cm ³ and a 50% compression hardness of 0.1 MPa or more. Filter media can be used. Here, examples of the foamed polymer having such physical properties include polypropylene, polystyrene, polyethylene, and the like. In particular, it is preferable to use closed-cell foamed polyethylene with a controlled degree of foaming as the foamed polymer. . This is because closed-cell foamed polyethylene has excellent heat resistance, chemical resistance, and weather resistance. The apparent density and 50% compression hardness can be measured by the methods defined in JIS K6767. And it is preferable that the above-mentioned floating filter medium is 4-10 mm in size, and it is preferable that a shape is uneven | corrugated shape (different shape provided with some unevenness | corrugation in the outer surface) or a cylinder shape.

  Note that a screen that can prevent the outflow of the filter medium can be used as the screen 131, and the filter medium layer 132 is charged with the above-mentioned floating filter medium after the water is poured into the second vertical hole 130 to a predetermined height. By installing the screen 131 on the upper side of the floated filter medium, it can be provided in the second vertical hole 130.

  The water collecting device 133 can collect backwash water containing suspended solids when the filter medium layer 132 is backwashed. Specifically, the linear velocity of the water collection section during backwashing is 0.5 m / s. As described above, a known one can be used as long as it is designed to be 1.0 m / s or more, but a water collecting device having a radially extending pipe as shown in FIG. 3 is used. Is preferred. The water collecting device 133 is connected to the backwash pump 160 installed in the space (pump chamber 171) opposite to the first vertical hole 110 in the manhole 170 through the water collecting device line 136. As shown in FIG. 1, the backwash water generated during the backwashing of the filter medium layer 132 is sent to the water shielding pipe 13 or the combined sewage pipe 11 by using the backwash pump 160. This is because backwash water contains suspended solids, and if discharged into the river 14 as it is, it causes water pollution. In addition, the water shielding pipe 13 is preferable as the destination of the backwash water.

  Here, as the backwash pump 160, a known manhole pump can be used. The installation position of the pump may be in a third vertical hole excavated separately or on the ground, but is preferably in the manhole 170 from the viewpoint of space saving and ease of pipe installation.

  In the overflow water treatment system 100 according to the first embodiment, the lower portions of the first vertical hole 110 and the second vertical hole 130 are connected to each other by the connecting flow path 140, and the upper portions thereof are overflow bypass. They are connected by a path 150. Moreover, the connection part of the merging sewer pipe 11 and the overflow water flow path 120 is located above the filtered water discharge pipe 134, and the connection part of the 1st vertical hole 110 and the overflow water flow path 120 is filtered water. The connection portion between the second vertical hole 130 and the connecting flow path 140 is located below the filter medium layer 132 in a substantially horizontal position with the discharge pipe 134. Furthermore, the overflow bypass 150 is above the water level at the design maximum filtration loss head of the overflow water treatment system 100. In addition to the present embodiment, the connecting portion between the first vertical hole 110 and the overflow water flow channel 120 may be located above the filtered water discharge pipe 134 and a substantially horizontal position.

  According to the overflow water treatment system 100 of the first embodiment, the overflow water is filtered by the filter medium layer 132 of the second vertical hole 130 by using the head pressure of the overflow water in the first vertical hole 110 as a driving force. be able to. Therefore, the overflow water can be discharged into the river 14 as filtered water with improved water quality by reducing impurities, biochemical oxygen demand (BOD) and suspended solids (SS). The water flow rate to the filter medium layer 132 can be adjusted by controlling the opening degree of the flow rate adjusting valve 122 with a control device (not shown), and can be set to, for example, 1500 m / day or less. Moreover, in the overflow water treatment system 100 of this 1st Embodiment, when the overflow water of a fixed amount or more enters, the flow regulating valve 122 can be closed and the overflow water processing can be stopped temporarily.

  And in this overflow water treatment system 100, the automatic scraping type screen 121 is installed in an entrance part, and failure of the overflow water treatment system 100 by the inflow of a big foreign material is prevented. Moreover, when obstruction | occlusion of the filter medium layer 132 arises by continuous filtration, the filter medium layer 132 can be back-washed and the filtration performance of the overflow water treatment system 100 can be recovered. Specifically, the overflow water treatment system 100 uses a level switch (not shown) installed in the first vertical hole 110 so that the water level of the overflow water in the first vertical hole 110 exceeds that of the first vertical hole 110. For example, when the height is 60 cm to 1 m higher than the connection with the flowing water flow path 120, that is, the filtration differential pressure is increased, and the difference between the water level of the first vertical hole 110 and the water level of the second vertical hole 130 becomes a certain level or more. It is possible to control so that the filter medium 132, which will be described later in detail, is backwashed. Note that the backwashing of the filter medium layer 132 in the overflow water treatment system 100 is automatically performed when the amount of rainwater and sewage flowing through the combined sewage pipe 11 becomes nQ or less, or when the rain has ended. It may be controlled or backwashing may be started manually.

  Here, an example of the backwashing procedure of the filter medium layer 132 in the overflow water treatment system 100 will be described below. First, when the level switch of the first vertical hole 110 detects an increase in the level of overflow water in the first vertical hole 110, a control device (not shown) closes the flow rate adjustment valve 122 and stops the inflow of overflow water. Then, if necessary, the water below the filter medium layer 132 is drawn out by the backwash pump 160 while air is pulsed with a blower (not shown), and the overflow and filtration of the first vertical hole 110 and the second vertical hole 130 are performed. Water is sent out to the interception pipe 13, and the backwashing is started by bringing the filtrate into contact with the floating filter medium at a downward flow of, for example, a linear velocity (backwashing linear velocity) of 1.2 to 4.0 m / min. Thereby, SS and the like captured by the floating filter medium is separated from the floating filter medium, and is sent to the collecting pipe 13 through the water collecting device 133 and the backwash pump 160, so the filter medium layer 132 is cleaned, Filtration loss head is recovered. The backwashing time can be set by a timer as an arbitrary time. For example, the time until the water level of the second vertical hole 130 becomes the position of the screen 131 can also be set. Specifically, when the backwashing operation is completed, a level switch (not shown) is installed in the second vertical hole 130, and the level switch indicates that the water level of the second vertical hole 130 is the position of the screen 131. The control device (not shown) can also be controlled by stopping the backwash pump 160 and opening the flow rate adjustment valve 122.

  In the overflow water treatment system 100 of the present embodiment, the overflow bypass passage 150 is provided. Therefore, even if the water level of the first vertical hole 110 suddenly rises due to a failure of the control device, It can be discharged into the river 14 via the overflow bypass 150 and the filtered water discharge pipe 134.

  In addition to the embodiment described above, the overflow water treatment system of the present invention may include a plurality of overflow water flow paths. This is because when there are a plurality of overflow water flow paths, filtration can be continued using other flow paths even if the automatic scraping screen is closed in one flow path. In addition, a means for supplying tap water, medium water, and industrial water to the upper part of the second vertical hole is provided, and the filter medium layer is back-washed using tap water, intermediate water, and industrial water. Also good. In this way, when it rains, it is backwashed with filtered water, and after raining, the filter media layer is backwashed with tap water, medium water, or industrial water, and the overflow treatment system is It is possible to keep waiting. Further, when the position of the combined sewage pipe is below the first vertical hole, a pump is installed in the overflow water flow path, and the overflow water is pumped up by the pump and flows into the first vertical hole. good.

  Next, the overflow water treatment system of 2nd Embodiment of this invention is demonstrated. As shown in FIG. 4, this overflow water treatment system 100 is provided with a pretreatment screen 123 having a mesh size of 25 to 50 mm, for example, at the connection portion between the combined sewage pipe 11 and the overflow water flow path 120. A path 140 passes through the pump chamber 171 and includes a connecting flow path valve 141, and a pretreatment screen washing line 180 for washing the pretreatment screen 123 using the backwash pump 160 is provided. In other respects, the second embodiment is different from the first embodiment, and is otherwise configured in the same manner as the first embodiment.

  In the overflow water treatment system 100 according to the second embodiment, not only the flow rate adjustment valve 122 but also the connection flow path valve 141 is preferably closed at the time of backwashing, so that there is no direct relationship with backwashing of the filter medium layer 132. It is not necessary to feed the overflow water in one vertical hole 110 by the backwash pump 160. Therefore, a desired backwash line speed can be obtained even with the backwash pump 160 having a small discharge amount. In addition, it is preferable that the connection flow path valve 141 is located in the pump chamber 171 from a viewpoint of ease of maintenance.

  Moreover, in this overflow water treatment system 100, since the pretreatment screen washing line 180 is provided, even if the pretreatment screen 123 is blocked by impurities contained in the overflow water, the pretreatment screen is cleaned. 123 can be washed and filtration can continue. The pretreatment screen 123 may be cleaned automatically when a flow sensor (not shown) is installed in the overflow water flow path 120 and the flow rate of the overflow water becomes a predetermined value or less. Alternatively, control may be performed so that it is automatically performed when the amount of rainwater and sewage flowing into the merging sewer pipe 11 becomes nQ or less, or when the rain has ended. Here, the pretreatment screen is cleaned by closing the valve 182 and opening the valve 181.

  The overflow water treatment system according to the first and second embodiments as described above can be installed on-site in a small space, is easy to maintain, and does not become unfilterable due to clogging.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Example 1
A pilot test machine for an overflow water treatment system having the same configuration as the overflow water treatment system of the first embodiment described above was produced. Here, as for the size of the pilot testing machine, the first vertical hole has a bottom area of 4 m ² and a height of 5 m, the second vertical hole has a bottom area of 7 m ² and a height of 5 m (a = 2 m, b = 0.8 m, c = 1.2 m). In addition, a screen having a mesh size of 3 mm is installed in the second vertical hole, and a windmill having a size of 7.5 × 7.5 × 4 mm and a 50% compression hardness of 0.5 MPa is provided below the screen. The shape of the floating filter medium is filled (α = 0.5). The apparent density and 50% compression hardness were measured according to the methods defined in JIS K6767.

Then, the combined sewage exceeding 3Q was passed through the pilot test machine at 7000 m ³ / day for one year, and the annual BOD and SS throughput and the contaminant removal rate were measured and calculated by the following methods. The results are shown in Table 1.

(Comparative Example 1)
The following method is used to create a reservoir with an area of 105 m ² , a height of 5 m, and an effective volume of 525 m ^3. It was calculated by measuring with. The results are shown in Table 1.

(Comparative Example 2)
Combined sewage exceeding 3Q is passed through an automatic scraping screen (4 mm bar screen, filtration area 3 m ² ) at 7000 m ³ / day for 1 year, and the annual BOD and SS throughput and contaminant removal rate are as follows: It was calculated by measuring by the method. The results are shown in Table 1.

[BOD processing amount]
The BOD concentration of treated water was measured according to JIS K0102, and the annual treated amount was calculated.
[SS throughput]
The SS concentration of treated water was measured according to Circular No. 59 (December 28, 1971) -Appendix Table 8, and the annual treated amount was calculated.
[Contaminant removal rate]
For both the combined sewage exceeding 3Q and the treated water, the dry weight of the residue remaining on the net when passing through a 2 mm mesh net was measured. Then, the concentration of impurities was calculated by dividing the dry weight by the amount of water circulated, and the removal ratio was calculated.

  From Example 1 and Comparative Examples 1-2, the overflow water treatment system of Example 1 can be installed in a space-saving manner (same BOD treatment performance and required area of 12%) compared to the reservoir in Comparative Example 1. Thus, it can be seen that the power required for the processing can be reduced to 1/10 or less. This is because, in the reservoir, it is necessary to treat the water once stored by biological reaction (high-grade treatment), whereas the overflow water treatment system only needs to perform the filtration treatment. Moreover, according to the overflow water treatment system of Example 1, it turns out that all of BOD, SS, and a contaminant can be reduced equivalent to the comparative example 1. FIG. Furthermore, it can be seen that according to the overflow water treatment system of Example 1, impurities can be reliably removed as compared with the automatic scraping screen of Comparative Example 2.

DESCRIPTION OF SYMBOLS 11 Combined sewage pipe 12 Rain spout 13 Intercept pipe 14 River 15 Overflow part 51 Combined sewer pipe 52 Rain spout 53 Intercept pipe 54 River 100 Overflow water treatment system 110 First vertical hole 111 Bulkhead 120 Overflow water flow path 121 Automatic scraping Take-type screen 122 Flow control valve 123 Pretreatment screen 130 Second vertical hole 131 Screen 132 Filter medium layer 133 Water collecting device 134 Filtration water discharge pipe 136 Water collecting device line 140 Connection flow path 141 Connection flow path valve 150 Overflow bypass 160 Backwash pump 170 Manhole 171 Pump chamber 180 Pretreatment screen cleaning line 181 Valve 182 Valve

Claims (8)

A system for treating overflow water from a combined sewer,
A first vertical hole;
An overflow water flow path for connecting a merged sewer pipe and the first vertical hole to flow overflow water from the merged sewer pipe to the first vertical hole;
A second vertical hole including a filter medium layer made of a filter medium, a screen that supports the filter medium, a water collecting device installed below the filter medium layer, and a filtrate discharge pipe provided above the filter medium layer. ,
A connecting flow path connecting the first vertical hole and the second vertical hole;
A backwash pump connected to the water collector;
A connection flow path valve provided in the connection flow path to stop the overflow of the overflow water into the second vertical hole when the filter medium layer is backwashed;
With
At least one of the connecting portion between the combined sewage pipe and the overflow water flow channel and the connecting portion between the first vertical hole and the overflow water flow channel is located above the filtered water discharge pipe, and An overflow water treatment system in which a connection portion between the second vertical hole and the connection channel is located below the filter medium layer.   The distance a from the lower part of the filtered water discharge pipe to the upper part of the filter medium layer, the thickness b of the filter medium layer, and the distance c from the lower part of the filter medium layer to the bottom part of the second vertical hole satisfy the relationship of a ≧ b + c. The overflow water treatment system according to claim 1, wherein the overflow water treatment system is satisfied.   Distance a from the lower part of the filtered water discharge pipe to the upper part of the filter medium layer, thickness b of the filter medium layer, apparent porosity α of the filter medium layer, and from the lower part of the filter medium layer to the bottom of the second vertical hole The overflow water treatment system according to claim 1, wherein the distance c satisfies a relationship of a ≧ α × b + c. The overflow water treatment system according to any one of claims 1 to 3 , wherein a flow rate adjustment valve capable of adjusting an inflow amount of the overflow water into the first vertical hole is provided in the overflow water flow path. The filter medium is a floating filter medium;
The overflow water treatment system according to any one of claims 1 to 4 , wherein the screen is provided on an upper portion of the filter medium layer. The floating filter medium is made of a foamed polymer having an apparent density of 0.1 to 0.4 g / cm ³ and a 50% compression hardness of 0.1 MPa or more,
The overflow water treatment system according to claim 5 , wherein the backwashing of the filter medium layer is performed at a backwash line speed of 1.2 to 4.0 m / min by downward flow using the backwash pump. A pretreatment screen is provided at a connection portion between the combined sewage pipe and the overflow water flow path,
Further comprising overflow running water processing system according to any one of claims 1 to 6 pretreatment screen cleaning line for backwashing the pretreatment screen. The overflow water treatment system according to any one of claims 1 to 7 , wherein the second vertical hole has a cylindrical shape, and the water collecting device is stretched radially.

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