JPH05208104A - Apparatus for removing suspensible solid - Google Patents

Abstract

PURPOSE:To simplify and miniaturize the title apparatus and to extend a filtration lasting time. CONSTITUTION:An upper filter bed with a porosity of 60-80% composed of a filter material with specific gravity of 1.01-1.2 being a foamed material having through-holes and a lower filter bed 3 composed of a granular filter material with specific gravity of 1.4-2.6 are formed in one filter tank 1. Since this apparatus is constituted so as to efficiently remove large SS and fine SS, the treatment capacity of the filter tank 1 is extremely high in spite of one tank and the removal ratio of SS is also high. A large amount of SS can be caught and a filtration lasting time can be extremely extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for primary treatment of organic wastewater such as municipal wastewater and industrial wastewater, which is used in wastewater containing a large amount of suspending solids (hereinafter referred to as SS). Of SS by rapid filtration.

[0002]

2. Description of the Related Art In the primary treatment for removing SS in waste water, an apparatus by a precipitation method has been conventionally used. However, since the precipitation method can only apply a water surface load of 25 to 50 m ³ / m ² · day, the installation area of equipment is very large, and the removal rate of SS is only about 40%. I can't get it.

In order to solve the problem of the precipitation method, an SS removal device for primary treatment by the filtration method has recently been developed (26th Sewer Research Conference Lecture, p.232-).
234, 1989). FIG. 2 is an explanatory diagram of the device disclosed in the above document. This device is based on a two-stage filtration method,
Upflow moving bed filter 20 and downflow fixed bed filter 21
Is equipped with. The upflow moving bed filter 20 and the downflow fixed bed filter 21 include fine sand (particle size 0.6 mm,
The evenness factor 1.4) is filled.

When removing SS in wastewater with this device,
Raw water is introduced into the lower part of the upward flow moving bed filter 20 by the pump 22 and the pipe 23 to remove SS to some extent.
Next, the outflow water from the upper portion of the upward flow moving bed filter 20 is introduced into the upper portion of the downward flow fixed bed filter 21 by the pipe 24, and the filtered water is discharged from the pipe 25. 26 in the figure
Is a treated water tank, 27 and 28 are backwash water pumps, 29 is a backwash air compressor, and 30 and 31 are backwash water discharge pipes.

In the processing result by the device at this time,
When the filtration speed is 100m / day for the upflow moving bed filter and 75m / day for the downflow fixed bed filter, and 200m / day for the upflow moving bed filter and the downflow fixed bed filter. Filter 17
It is described that the case is 5 m / day.

[0006]

However, the above-mentioned conventional apparatus has some problems. First, the conventional device is complicated and large because it has a configuration including two filters, and it is insufficient to achieve the original purpose of reducing the installation area. Further, since the fixed bed type filter 21 is filled with very fine filter media (0.6 mm of sand), it is pretreated by the moving bed type filter 20. The degree of clogging of the filter layer is large, and the duration of filtration (the time during which filtration can be continued) is short.

The present invention is simple and compact,
An object of the present invention is to provide a device for removing suspended solids, which can prolong the duration of filtration.

[0008]

In order to achieve the above-mentioned object, in the present invention, S in the drainage which is passed through a filter layer is used.
In the device for removing S, the specific gravity is 1.0 in the filtration tank.
An upper filter layer having a porosity of 60% to 80% filled with a filter medium of 1 to 1.2 and a lower filter layer filled with a granular filter medium having a specific gravity of 1.4 to 2.6 are formed. The filter material to be filled in the upper filter layer is a foam or the like and preferably has a shape having irregularities on the surface and having through holes.

In the present invention, the specific gravity of the filter medium, the through holes of the filter medium,
The porosity of the foam and filter layer is defined as follows. The specific gravity of the filter medium is the specific gravity of water content, and is the value measured with water in the voids except closed cells. The porosity of the filter layer is the porosity of the entire filter layer formed by filling the filter material. The through-holes of the filter medium do not include even the pores of the porous material, but refer to the large pores such as a cylindrical hollow portion. The foam refers to, for example, a product obtained by molding a synthetic resin or the like in a foamed state.

[0010]

In the present invention, two filter layers filled with different filter media are provided in the same tank so that waste water having a high SS concentration can be efficiently filtered. That is, two filter layers in the same tank are mainly an upper filter layer filled with a filter medium suitable for capturing large SS and a lower filter layer filled with a filter medium suitable for capturing fine SS. It is a combination with.

The filter medium filled in the upper filter layer must have a shape capable of forming a filter layer having a high porosity. The upper filter layer formed of such a filter material that can increase the porosity is
Even if the amount of attached SS increases, the degree of increase in water resistance does not increase so much. Therefore, it is possible to continue the passage of the high SS concentration raw water for a long time and also to pass the water at a high filtration rate.

As the shape of the filter medium which allows the filter layer to exhibit the above-mentioned performance, it is preferable that the filter medium has through holes. The filter medium having the through holes as described above can form a filter layer having a large porosity, and a large amount of SS can be captured with a small water resistance. Further, since a filter medium having a large number of irregularities on the surface such as a foam easily attaches SS, the removal rate of SS is also good.

The porosity of the upper filter layer is preferably in the range of about 60% to 80%. If the porosity is less than 60%, the amount of SS that can be captured is small, and the filterable time is shortened due to an increase in water flow resistance. When the porosity exceeds 80%, the amount of trapped SS increases and the filterable time also increases, but the removal rate of SS decreases, which is not preferable.

The lower filter layer is for removing fine SS which could not be captured by the upper filter layer, and is filled with a granular filter medium which forms a dense filter layer. The porosity of this filter layer is small, usually about 50%. Therefore, SS is sufficiently removed from the outflow water that has passed through the lower filter layer. Since a large amount of SS is captured in the upper filter layer, the load on the lower filter layer is significantly reduced. Therefore, even if the lower filter layer is filled with the granular filter medium having a small porosity, the degree of clogging is small and the filtration can be continued for a long time at a high filtration rate.

Further, the filter medium filled in the upper filter layer and the filter medium filled in the lower filter layer are not only different in shape but also different in specific gravity. As described above, the specific gravity of the filter medium filled in the upper filter layer is 1.01 to 1.2, and the specific gravity of the filter medium filled in the lower filter layer is 1.4 to 2.6. There is a clear difference. This difference in specific gravity is due to consideration for facilitating the backwashing operation of the filter layer. When backwashing the filter layer, backwash water or air for backwashing is supplied from the lower side of the filter layer to cause the filter medium to flow, and the SS is peeled and removed, but at the end of the backwash, it sediments. In this case, the sedimentation speed varies depending on the specific gravity of the filter medium, the sediment of the filter medium having a large specific gravity is fast, and the sedimentation of the filter medium having a small specific gravity is slow, so that the two filter layers are restored to the original arrangement state.

The filter material of the upper filter layer needs to be able to sink into water to form a fixed layer, but when backwashing the filter layer, backwashing water and air for backwashing are required as little as possible. It is desirable to finish. In order to satisfy these two conditions, the specific gravity of the filter medium is limited to the above range.

The specific gravity of the filter material filled in the lower filter layer is set to be at least 0.2 higher than the specific gravity of the filter material in the upper filter layer in order to clarify the difference from the specific gravity of the filter material in the upper filter layer. However, if the specific gravity becomes too large, the required amount of the utility to be supplied at the time of backwashing increases, so the upper limit of the specific gravity is 2.6.
I made it to the degree.

[0018]

FIG. 1 is a diagram schematically showing an embodiment of the present invention. 1 is a vertical type filter tank, in which two different filter layers are provided. That is, an upper filter layer 2 filled with a filter medium having a specific gravity of 1.01 to 1.2 is formed above, and a lower filter layer 3 filled with a granular filter medium having a specific gravity of 1.4 to 2.6 is formed below. Has been done. Reference numeral 4 is a supporting gravel layer, 5 is a perforated plate for receiving the supporting gravel layer 4, and 6 is a wire mesh for preventing outflow of the filter medium during backwashing of the filter tank. Further, 7 is an inflow pipe for supplying raw water to the upper part of the filtration tank 1, 8 is a discharge pipe for filtered water, 9 is a supply pipe for backwash water, 10 is a supply pipe for backwash air,
Reference numeral 11 is a backwash water discharge pipe. The wire mesh 6 is provided at a predetermined distance from the upper filter layer 2 so that the filter material filled when backwashing the filter layer can properly flow. This interval is usually 20 to the filling height of the filter medium.
Make it about 50%.

The filter material forming the upper filter layer 2 has a size of 5
Approximately 20 mm, and a filter layer 2 having a porosity of approximately 60% to 80% at the time of filling is used. As one of the filter media satisfying such a condition, it is preferable to use a synthetic resin foam whose specific gravity is adjusted to the above range and which has a through hole such as a cylindrical shape.

As the filter material forming the lower filter layer 3, anthracite, synthetic resin particles, zeolite, sand, various ceramic particles, etc. are used. The size thereof is determined by the SS concentration of the raw water to be filtered and the particle size distribution of SS, but is usually about 1 to 5 mm. When the size of the filter medium is less than 1 mm, there is an advantage that fine SS can be captured, but it is not preferable because the pressure loss is large and the frequency of clogging increases. If the size exceeds 5 mm, the frequency of clogging decreases, but the removal rate of fine SS decreases, which is not preferable.

A method of filtering waste water by the thus constructed apparatus will be described. For example, raw sewage containing a large amount of SS just after passing through the screen is used as raw water, and the raw water is supplied from the inflow pipe 7 to the upper part of the filtration tank 1. In this filtration tank 1, a large amount of SS and SS BOD contained in the raw water is removed, and the filtered water is discharged from the discharge pipe 8. If the above-mentioned operation is continued for a long time, the filter layer is clogged, so when the pressure loss of the filter tank 1 rises to a predetermined value, the operation is stopped and the filter layer is backwashed.

Next, an example of an experiment conducted to confirm the effect of the present invention will be described. (Embodiment) With the structure shown in FIG. 1, a filter layer of the condition shown in Table 1 is provided in an acrylic resin filter tank having an inner diameter of 10 cm and a height of 4 m, and the inflow water of the first sedimentation tank of the sewage treatment plant is supplied as raw water. , A filtration experiment was conducted. The operating conditions at this time are as shown in Table 1. The results are shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2]

According to Table 2, the filtration speed is 120 m / day,
The SS removal rate when performing at 180 m / day is 7
The values were 8% and 72%, which were comparable to those when the conventional device equipped with two filters was used. Further, the filtration duration at this time is 37 hours and 27 hours, and even if there is only one filtration tank, backwashing of the filter layer only needs to be carried out once a day to 1.5 days, It has been found that continuous filtration for a long time is possible.

The results of the above embodiment will be compared with the results of processing by the above-mentioned two-stage type passing device which is a conventional technique. The respective filtration rates were as follows. The present invention: 120 m / day 180 m / day Conventional technology: Moving bed type filter 100 m / day Fixed bed type filter 75 m / day Moving bed type filter 200 m / day Fixed bed type filter 175 m / day

Respective devices based on the above filtration rate
In the case of the present invention, the required filtration area of (1) formula- (2) formula
And in the case of the prior art, equations (3) to (4)
Calculated by the formula. In the above formula, the required filtration surface
The product is expressed as a ratio to the unit wastewater treatment amount, and Q is the treatment of wastewater.
Rational, S_a1, S_a2Is the required filtration area of the present invention, S_b1, S _b2
Indicates the required filtration area of the prior art.

[0028]

[Equation 1]

[0029]

[Equation 2]

[0030]

[Equation 3]

[0031]

[Equation 4]

Based on the above results, the ratio of the required filtration area of the present invention to the prior art is calculated, and S _a1 / S _b1 ≈
0.52, S _a2 / S _b2 ≈0.35. That is, the device of the present invention has a required filtration area of 1
It is a very compact device with only / 2-1 / 3.

[0033]

As described above, according to the present invention, two filter layers filled with different filter media are formed in one filter tank to efficiently remove large SS and fine SS respectively. Has been done. Therefore, even if there is only one filtration tank, the treatment capacity is very large and the removal rate of SS is high, so that the apparatus is downsized and the filtration duration is very long.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional device.

[Explanation of symbols]

 1 Filter tank 2 Upper filter layer 3 Lower filter layer 7 Raw water inflow pipe 8 Filtered water discharge pipe

[Procedure amendment]

[Submission date] March 25, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction content]

In the processing result by the device at this time,
When the filtration speed is 100m / day for the upflow moving bed filter and 70m / day for the downflow fixed bed filter, and 200m / day for the upflow moving bed filter and the downflow fixed bed type. Filter 17
It is described that the case is 5 m / day.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

Further, the filter medium filled in the upper filter layer and the filter medium filled in the lower filter layer are not only different in shape but also different in specific gravity. As described above, the specific gravity of the filter medium filled in the upper filter layer is 1.01 to 1.2, and the specific gravity of the filter medium filled in the lower filter layer is 1.4 to 2.6. There is a clear difference. This difference in specific gravity is due to consideration for facilitating the backwashing operation of the filter layer. When backwashing the filter layer, backwash water or air for backwashing is supplied from the lower side of the filter layer to cause the filter medium to flow, and the SS is peeled and removed, but at the end of the backwash, it sediments. In this case, the sedimentation speed varies depending on the specific gravity of the filter medium, the sediment of the filter medium having a large specific gravity is fast, and the sedimentation of the filter medium having a small specific gravity is slow, so that the above two filter layers are restored to the original arrangement state.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026] the results of the prior art in the above embodiment the two
The results are compared with the results obtained by the step filter . The respective filtration rates were as follows. The present invention: 120 m / day 180 m / day Conventional technology: Moving bed type filter 100 m / day Fixed bed type filter 70 m / day Moving bed type filter 200 m / day Fixed bed type filter 175 m / day

Claims (3)

[Claims] 1. An apparatus for removing suspended solids in wastewater by passing through a filter layer, wherein the specific gravity is 1.01 in a filter tank.
.About.1.2 filter medium is filled and the porosity is 60% to 80%, and an upper filter layer is formed, and a specific gravity is 1.4 to 2.6. A device for removing suspended solids. 2. The device for removing suspended solids according to claim 1, wherein the filter medium with which the upper filter layer is filled has a shape having irregularities on the surface and having through holes. 3. The device for removing suspended solids according to claim 1 or 2, wherein the filter medium filled in the upper filter layer is a foam.