JPS6354407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a supertank in which a flocculant is added to raw water and the raw water is allowed to flow directly into the supertank to remove suspended matter in the raw water and clarify the raw water. It is.

Conventionally, in supertanks with high turbidity trapping capacity, such as multilayer supertanks and two-way supertanks that have multiple packed layers with different filler particle sizes, a flocculant is added to the raw water and only rapid stirring is performed. After that, the raw water is directly flowed into a filter tank to remove suspended matter in the raw water and clarify the raw water. However, while this type of supertank has the advantage of requiring only a small amount of flocculant to be used, if the raw water has a high turbidity, for example, if the raw water turbidity is 20 degrees or higher, suspended solids cannot be removed completely. , it is not possible to obtain clear water, and the overtank may become clogged quickly.If the turbidity of the raw water reaches 20 degrees or higher, even if it is temporary, only the overtank is used. I couldn't process it.

In addition, when treating such raw water, a coagulation sedimentation device is installed before the overtank, and when the turbidity in the raw water is low, a coagulant is added to the raw water and then the water is allowed to flow directly into the overtank for overtreatment. When the turbidity of the raw water is high, the flocs are precipitated in a coagulation-sedimentation device, and then the effluent is treated in a filtration device. However, when comparing the processing capacity of coagulation sedimentation equipment with the same installation area, it is smaller than that of filtration equipment, and therefore the installation scale is larger and a large amount of construction cost is required. It is extremely uneconomical to install a coagulation-sedimentation device only for the purpose of using it when the amount increases, and the coagulation-sedimentation device requires a high injection rate of flocculant, which increases maintenance costs and the amount of sludge generated. It has its drawbacks.

The present invention solves these drawbacks of conventional overtanks, and by attaching a special contact sedimentation tank before the overtank, it is possible to convert raw water with large fluctuations in turbidity to water with high turbidity. A new technology that enables efficient treatment by switching the flow path depending on turbidity fluctuations, such as flowing into the contact sedimentation tank, then into the supertank, and directly into the supertank when the turbidity is low. The purpose is to provide a suitable overtank.

That is, the present invention includes a mixing tank in the upper part of the tank, a pair of screens vertically dividing the inside of the tank into three chambers, and a space between the screens filled with a filler having a diameter of at least 25 mm. A settling tank is provided, the mixing tank and the overtank are connected, for example, by a bypass pipe, the mixing tank and the contact settling tank are connected, for example, with a mixing tank outlet pipe, and the contact settling tank and the overtank are connected, for example, by a mixing tank outlet pipe. For example, when connecting with a contact sedimentation tank outlet pipe, and when the amount of suspended solids present in the raw water is small, raw water to which a flocculant has been added is mixed in the mixing tank, and then the mixed water is passed through a bypass pipe and directly filtered by the water head difference. When the amount of suspended solids present in the raw water is large, the mixed water is passed horizontally through the mixing tank outlet pipe to the packing layer in the contact sedimentation tank to remove the filling. The structure is such that flocs are allowed to grow in the material layer and flocs with a relatively large particle size are precipitated, and then the effluent water is passed through the contact sedimentation tank outlet pipe and flowed into the overtreatment tank with a water head difference for overtreatment. This invention relates to an overtank equipped with a characteristic contact sedimentation tank.

The present invention will be explained in detail below with reference to the drawings.

The figure is a longitudinal cross-sectional view showing an example of an embodiment of a tank equipped with a contact sedimentation tank according to the present invention. Layer the sand layer 4. The gravel layer 3 may be configured such that the lower part thereof is filled with gravel having a relatively large diameter, and the upper part thereof is filled with gravel having a relatively small diameter. Further, a lower water collection pipe 6 is inserted into the upper part of the gravel layer 3, and the water collection pipe 6 is connected to the upper part of the filter tank 1 above the sand layer 4 via a communication pipe 7. In addition, an upper water collection pipe 8 is located in the middle of the sand layer 4.
is inserted, and the treated water outflow pipe 9 is connected to the water collection pipe 8. Further, a liquid level detector 14 is provided above the overflow tank 1, and a cleaning drain pipe 10 is connected thereto. Furthermore, a wash water inflow pipe 13 is located below the floor plate 5 of the cleaning tank 1.
At the same time, insert the air distribution pipe 11,
An air inflow pipe 12 is connected to the pipe 11.

Further, a mixing tank 16 and a contact settling tank 18 are provided above the filter tank 1. A stirrer 17 is installed in the mixing tank 16.
At the same time, a raw water pipe 31 to which a flocculant injection pipe 30 is connected is connected.

In addition, a pair of screens 19 and 19' that allow water to pass through but not fillers 22 and 23, which will be described later, are vertically installed in the contact sedimentation tank 18 at intervals, vertically dividing the tank into three chambers, The two chambers at both ends constituted by the side walls and screens 19 and 19' of the tank 18 are defined as an inflow passage 27 and an outflow passage 28, respectively, and further below the space between the screens 19 and 19', For example, a perforated plate or slit that allows water to pass through but is filled with 2
In addition to providing a support plate 24 that supports 2 and 23, the space is further vertically divided into two chambers by a screen 20, and one chamber on the inflow path 27 side has a diameter
Fill the other chamber with a filling material 22 with a diameter of 50 mm or more.
A filling material 23 of 25 to 30 mm is filled.

Further, the mixing tank 16 and the overtank 1 are connected, for example, by a bypass pipe 21, so that the mixed water from the mixing tank 16 can flow into the overtank 1 with a water head difference.

Further, the mixing tank 16 and the inflow passage 27 of the contact sedimentation tank 18 are connected, for example, by the mixing tank outlet pipe 15, and the outflow passage 28 of the tank 18 and the overflow tank 1 are connected, for example, by the contact sedimentation tank outlet pipe 2. , contact settling tank 1
The structure is such that the outflow water from 8 can flow into the overtank 1 with a water head difference.

Further, a cleaning nozzle 25 is attached above the fillers 22 and 23 of the contact sedimentation tank 18, and a cleaning drain pipe 29 is attached to the bottom of the tank 18. Further, a liquid level detector 26 is attached above the mixing tank 16.

A supertank 1 equipped with such a contact sedimentation tank 18
When treating raw water containing suspended solids, for example, when the raw water has a high turbidity of 20 degrees or more, a coagulant selected from, for example, van sulfate or polyaluminum chloride is added to the raw water from the flocculant injection pipe 30. For example, add a flocculant of 10 to 20 ppm.
The raw water is injected into the mixing tank 16 through the raw water pipe 31, and the raw water is rapidly stirred by the stirrer 17 in the mixing tank 16 to form small flocs. This mixed water is caused to flow from the mixing tank 16 through the mixing tank outlet pipe 15 into the inflow path 27 of the contact sedimentation tank 18, and is passed horizontally through the fillings 22 and 23.

By passing the mixed water through the gaps between the fillers 22 and 23, the mixed water flows through the fillers 22 and 23.
and 23, the flocs can be further grown, and relatively large flocs can be precipitated in the voids of the fillers 22 and 23.

By passing the mixed water horizontally through the contact sedimentation tank 18 in this way, relatively large flocs can be precipitated and the turbidity in the raw water can be reduced to, for example, about 20 degrees.
load can be reduced. In addition, filling 2
For 2 and 23, it is recommended to use chestnut stone or crushed stone with a diameter of 25 mm or more. Also, the fillings 22 and 23
Although it is possible to achieve the intended purpose by using fillers 22 having the same diameter, as in this embodiment, the filler 22 has a relatively large diameter, preferably a diameter of 50 mm.
mm or more, and the filler 23 has a relatively small diameter, preferably 25 to 30 mm.
In this way, the filling material 22 mainly performs slow stirring to allow the flocs to grow sufficiently, and the filling material 23 mainly performs the role of efficiently settling large flocs that are relatively easy to settle. can be done and become more effective.

The contact sedimentation tank 18, which is a requirement of the present invention, is
The structure is such that the mixed water passes horizontally through the packings 22 and 23 in the tank.The reason for this is that when the mixed water is passed through in an upward flow, the diameter of the packings is large and the gaps between them are large, so that flocs do not form. The problem is that the flocs float to the surface without settling on the packing and flow into the overtank, and even if the mixed water is passed in a downward flow, the flocs tend to fall down the packing layer and flow into the overtank. This is because it occurs.

When the contact sedimentation tank 18 is filled with the fillers 22 and 23 and the mixed water is passed horizontally as in the present invention, floc separation efficiency is high, and the mixed water is processed at a high flow rate of, for example, 30 to 80 m/h. Therefore, the contact settling tank 18 can have an extremely small capacity.

Next, the effluent water, which has been passed through the fillers 22 and 23 to reduce the turbidity in the raw water, is caused to flow from the outflow path 28 through the contact sedimentation tank outlet pipe 2 to the bottom of the overtank 1 with a difference in water head. In the filter tank 1, the water flowing out from the contact settling tank 18 is slowly stirred again by raising the gravel layer 3 at a flow rate of, for example, 10 to 20 m/h, and the small blocks flowing out from the contact settling tank 18 are grown. At the same time, relatively large flocs are passed through the contact Hz in the gravel layer 3. Next, about half of the water that has risen through the gravel layer 3 is allowed to rise directly to the sand layer 4, and the other half is transferred to the lower water collection pipe 6 and the communication pipe 7.
Water is passed downward from above the sand layer 4 through the sand layer 4, and small flocs flowing out from the gravel layer 3 are removed while water is passed through the sand layer 4 from two opposite directions.
Water from these two directions is collected through the upper water collection pipe 8, and treated water is obtained through the treated water outflow pipe 9.

Next, when the turbidity of the raw water is low concentration, for example, 20 degrees or less, a flocculant as described above is added to the raw water through the flocculant injection pipe 30 in advance, for example, several times.
ppm is injected, and the raw water is passed through the raw water pipe 31 into the mixing tank 1.
6, the raw water and flocculant are rapidly stirred by the stirrer 17 to form small flocs, and then the mixed water from the mixing tank 16 is directly flowed into the bottom of the mixing tank 1 via the bypass pipe 21. Then, perform overtreatment in the same manner as described above to obtain clear treated water.

Furthermore, when the fillers 22 and 23 in the contact sedimentation tank 18 become clogged, the water level in the mixing tank 16 rises, but when the water level reaches position B on the liquid level detector 26, the inflow of raw water is interrupted. The water in the tank 18 is drained from the cleaning drain pipe 29, and then cleaning water is injected from the cleaning nozzle 25 to wash the fillers 22 and 23, and the flocs precipitated on the fillers 22 and 23 are removed from the cleaning drain pipe 29. Remove.

Furthermore, if the gravel layer 3 and sand layer 4 in the tank 1 become clogged and the water level in the tank 1 rises and reaches position A on the liquid level detector 14, the inflow of raw water is interrupted and air is injected. Pipe 12 and air distribution pipe 11
At the same time, the washing water is made to flow upward through the washing water inflow pipe 13 at a high flow rate to remove the suspended solids trapped in the gravel layer 3 and the sand layer 4, and the washing water is discharged from the washing drainage pipe 10. . Although any type of tank 1 can be used, it is preferably a two-way tank, a multilayer tank, an upflow tank, etc. as in this embodiment, which has a relatively high ability to capture suspended solids. It is best to use a large tank.

As explained above, the present invention is equipped with a mixing tank and a special contact sedimentation tank before the overtank, and when the turbidity of the raw water is relatively low, a flocculant is added to the raw water and it is directly transferred to the overtank. It is possible to obtain clear treated water by passing water through and over-treating it, as well as
When the raw water has high turbidity, the raw water with a coagulant added is passed through a contact sedimentation tank, and the suspended solids are precipitated and removed in that tank to a predetermined concentration to reduce the load on the overtank. Since overtreatment is carried out in the overtank, suspended matter can be efficiently removed and clear treated water can be consistently obtained even if the raw water has a large turbidity fluctuation.

In addition, the contact sedimentation tank of the present invention has a special structure in which it has a packing material and raw water is passed horizontally through the packing material, so flocs can be precipitated efficiently and treated at a high flow rate. It has the advantage of requiring a smaller device and lower construction costs than conventional coagulation-sedimentation equipment.Furthermore, the amount of flocculant injected is smaller than that of coagulation-sedimentation equipment, which reduces the amount of sludge produced. It has the advantage of being small in quantity.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view showing an example of an embodiment of a supertank equipped with a contact sedimentation tank according to the present invention. 1...Target tank, 2...Contact sedimentation tank outlet pipe, 16
... Mixing tank, 18 ... Contact sedimentation tank, 19 ... Screen, 21 ... Bypass pipe, 22, 23 ... Filler, 24 ... Support plate, 31 ... Raw water pipe.

Claims (1)

[Claims] 1. In the upper part of the tank, there is a mixing tank, the inside of the tank is vertically divided into three chambers by a pair of screens, and the space between the screens is filled with a filler having a diameter of at least 25 mm. At the same time, the mixing tank is connected to the contact sedimentation tank and the overtank, and the mixing tank is connected to the contact sedimentation tank and the overtank in order, and when the amount of suspended solids present in the raw water is small, flocculation After mixing the raw water to which the agent has been added in a mixing tank, the mixed water is directly flowed into a supertank with a difference in water head for overtreatment, and when there is a large amount of suspended solids in the raw water, the mixed water is The water is allowed to pass horizontally through a packed layer in a sedimentation tank, allowing flocs to grow in the packed layer and flocs with a relatively large particle size are precipitated, and then the effluent water is allowed to flow into a sedimentation tank using a head difference. An overtank equipped with a contact sedimentation tank, characterized in that it is configured to carry out treatment. 2 The space between the screens of the contact sedimentation tank is further vertically divided into two chambers with a screen, and one chamber has a diameter of 50 mm.
Claim 1, characterized in that the other chamber is filled with a 25-35 mm filler, and the mixed water is passed horizontally from one chamber to the other chamber. An overtank equipped with a contact sedimentation tank.