JP2000296302A - Sewage treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewage treatment device capable of a continuous operation of filter units and also enabling to prevent deterioration of the water quality of treated water. SOLUTION: Sewage water is fed to the sewage treatment device provided with a biological reaction tank 1, plural filter units 3 in which at least one portion of a surrounding wall immersed and arranged along an inflow direction of the sewage in the inside comprises a water passing support body, partitioning walls 4 for partitioning respective filter units, an aeration means provided at the bottom of the biological reaction tank 1, a washing diffusion pipe arranged at the bottom of the filter units and a buffer tank having a lower water level than a water level of the biological reaction tank 1. Then the treated water is taken out from the filter units 3, and also the washing diffusion pipes are selectively operated, thus respective filtering units 3 are alternately washed along the arranging direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sewage treatment method for biologically treating sewage, and more particularly to a sewage treatment method for separating sludge biologically treated by a filtration unit immersed in a biological reaction tank from water.

[0002]

2. Description of the Related Art In a sewage treatment apparatus by an activated sludge method for decomposing organic matter in wastewater by a biological reaction, first, an organic substance in the wastewater is eaten by microorganisms in the presence of air in an aeration tank (biological reaction tank). The organic matter is removed, then the organic matter is eaten in the sedimentation basin, and the microorganisms propagated are settled as sludge and separated from the water, and the supernatant water is collected and sent to the next step,
On the other hand, the sludge settled in the sedimentation basin is scraped and sent to the next step (dehydration step, etc.). However, this sewage treatment apparatus has the following problems. That is, if the load of the water amount or the sludge concentration fluctuates, the treated water quality deteriorates, the concentration of the settled sludge is low, so the amount of the concentrated sludge sent to the next step increases. There is a problem that the size of the sedimentation basin needs to be increased because it must be extremely small.

[0003] In order to solve such problems and to separate sludge that has been biologically treated from water without installing a sedimentation tank, a water-permeable porous material for maintaining a distance is interposed between the sludge and the sludge. A bag-shaped filter body formed by sealing the periphery of the aqueous sheet is immersed and arranged above the aeration unit in the aeration tank, and the filtered water is suctioned at a low suction force and at a slow speed due to a lower head difference than the filter body. By doing so, an apparatus has been proposed in which the suction pipe is drawn out of the aeration tank (for example, see Japanese Patent Application Laid-Open No. 5-185078). According to this treatment apparatus, suspended solids in the sewage are filtered out by the filter, and when the filtration is continued, a cake layer of concentrated sludge is formed on the surface of the filter, and fine particles in the sewage are separated from the fine particles by this filter. Assisted by the filtering action of the cake layer. In this processing apparatus, by maintaining the above-mentioned low suction force and low filtration rate, the cake layer becomes weak and the adhesion and peeling to the filter are repeated, so that the thickness is kept constant, and thus the thickness is kept constant. Filtration speed can be maintained.

[0004]

According to the treatment apparatus having the above-mentioned specific filter, the sedimentation basin after the biological treatment can be omitted and the filtration performance is excellent.
From an industrial point of view, there is a problem when a plurality of filter bodies are immersed and installed in the biological reaction tank along the inflow direction of the wastewater to wash the filtration unit. That is, even in the above treatment apparatus, if filtration is continued for a long period of time, there is a problem that the filtration rate is reduced due to the consolidation of the filtration layer formed on the surface of the water-permeable support. As a countermeasure, a diffuser is provided below the filtration unit, and air is supplied from the diffuser to remove the filtration layer, thereby recovering the filtration speed. As a method of cleaning the filtration unit, for example, a plurality of filtration units arranged along the inflow direction of the wastewater in the biological reaction tank interrupts the sequential filtration operation, during which time air is supplied to the filtration unit by the cleaning air diffuser. It is conceivable to supply. However, in this method, when the air diffuser below the filtration unit to be cleaned is operated, the air bubbles released from the air diffuser are also supplied to the filtration unit adjacent to the filtration unit, and the filtration layer of the unit is formed. Since it is removed, the cake layer having a filter action around the filtration unit is also peeled off, and there is a problem that the quality of treated water taken out from the filtration unit is deteriorated. Therefore, an object of the present invention is to provide a sewage treatment method capable of continuously operating a plurality of filtration units and preventing a decrease in the quality of treated water.

[0005]

In order to achieve the above object, according to the present invention, at least a part of a biological reaction tank and a peripheral wall immersed therein along the flow direction of sewage flow through. A plurality of filtration units having a plurality of filtration bodies composed of an aqueous support, and a partition partitioning each filtration unit,
A sewage treatment apparatus provided with an aeration unit provided at a lower portion of a biological reaction tank, an aeration unit for washing disposed below the filtration unit, and a buffer tank having a water level lower than the water level of the biological reaction tank. And removing the treated water from the filtration unit, and selectively operating the cleaning aeration means to alternately wash the filtration units along the arrangement direction thereof, employing a technical means. .

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view of a sewage treatment apparatus according to one embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. In FIG. 1, reference numeral 1 denotes a biological reaction tank, and the biological reaction tank 1 is divided into two sections by a partition wall 2 provided at a central portion thereof, and water in the two sections is provided above and below the partition wall 2. Upper communication part 2A and lower communication part 2 so that
B is formed. In the right section of the biological reaction tank 1, a filtration unit 3 is disposed, and the discharge end of the water collecting pipe 7 communicating with the filtration unit 3 is dropped into a buffer tank (not shown).
An air diffuser 5 is arranged in the left section. Each filtration unit 3 is separated by a unit spacing wall 4. In addition, a cleaning air diffuser 6 is disposed below each filtration unit 3. In this case, since the water level of the buffer tank is set lower than the water level of the biological reaction tank 1, a negative pressure due to the head difference always acts in the filtration unit 3 due to the siphon effect of the water collecting pipe 7.

FIG. 3 is a plan view showing a part of a filtration module constituting the filtration unit 3 in a cut-away manner. FIG.
It is sectional drawing. In both figures, reference numeral 10 denotes a filtration module, which is a filtration plate 11 (spacing member) and a filtration membrane support member (spacer) 1 fixed to a surface thereof by a frame-shaped holding plate 18.
2 and a water-permeable supporting membrane (hereinafter referred to as a filtration membrane) 13 held on the surface thereof. As shown in FIG. 3, water collecting grooves 14 are formed on both sides of the filter plate 11 vertically and horizontally. Water collecting groove 14 on both sides located at the top of filter plate 11
And a screw hole 16 extending from the end surface of the filter plate 11 to the horizontal hole 15 is provided.
A suction pipe 17 for pulling out filtered water is screwed on. The suction pipe 17 is connected to a water collecting pipe (see FIG. 2), and the treated water extracted from the filtration module 10 is transported to a buffer tank (not shown) via the water collecting pipe 7.

As the filtration membrane 13, for example, a nonwoven fabric made of a polymer fiber such as polyester or polypropylene or a metal nonwoven fabric can be used. This metal nonwoven fabric has a thickness of 0.
1 to 4 mm, the cross-sectional direction has the same fiber structure as the surface direction, and the size of the opening in the surface direction is 10 μm
It is getting bigger. If the thickness of the filtration membrane is too large, sludge accumulates in the filtration membrane and clogging is likely to occur. On the other hand, if it is too small, the mechanical strength is reduced.
mm. The opening of the filtration membrane has a separation particle size of 10 μm or more (preferably 10 to 200 μm).
μm).

According to the sewage treatment apparatus having the above configuration, sewage is treated as follows. For example, the sewage (mixed water of activated sludge fine particles and water) flowing into the biological reaction tank 1 from the first sedimentation basin (not shown) becomes an ascending flow in the left compartment by air bubbling from the air diffuser 5, and the upper part of the partition 2 It flows to the right section through the communication section 2A, where it flows downward, passes through the lower communication section 2B, and circulates back to the left section again. During this circulation, the activated sludge fine particles in the mixed water are captured by the filtration unit 3 by the filtration unit 3 immersed in the right compartment. That is, the activated sludge fine particles pass through the opening of the filtration membrane in the early stage of filtration, but gradually adhere to the surface of the filtration membrane to close the opening, and a cake layer of the sludge fine particles is formed and grows. The activated sludge fine particles in the water are captured by the filter action of the cake layer composed of the sludge fine particles, and the filtration action proceeds. On the other hand, the treated water flows into a buffer tank (not shown) via a water collecting pipe 7 provided in the filtration unit 3. Filtration module 10
Inside, suction filtration is performed by the differential pressure due to the head difference, but since the head is proportional to the flux, this differential pressure is
By setting it within about 0 mm, the permeation flow rate becomes 1 to
About 3 m / day can be obtained.

If it is determined that the permeation flux has decreased and the filtration unit 3 has been clogged, the filtration unit 3 is washed as follows. By performing aeration by cleaning aeration tube 6 disposed on the lower filtration unit 3 ₁ on the upstream side is first along the inflow direction of the sewage, filtration layer formed on the surface of the filtration unit 3 ₁ of the filter membrane (cake Layer). By performing aeration by tracheal 6 next diffuser cleaning was installed in the lower filter unit 3 _2, filtration unit 3 ₂
Wash and remove the filtration layer (cake layer) formed on the surface of. In this way, since the washing is sequentially performed from the upstream of the filtration unit along the inflow direction of the sewage, the continuous operation of the filtration unit can be performed. In this case, since each filtration unit is separated by the unit spacing wall 4, the aeration effect of the air diffuser below any of the filtration units does not spread to the filtration unit adjacent thereto, and the processing removed from the filtration unit Water quality deterioration can be prevented.

[0011]

The present invention will be described more specifically with reference to the following examples. Sewage treatment was performed under the following conditions using the apparatus shown in FIGS. Sewage is BOD180mg / L, SS130
Using sewage of mg / L, continuous treatment was performed in a biological reaction tank having an effective volume of 1 m ³ under the conditions of standard aeration activated sludge in which the residence time in the aeration tank was 6 hours. In this case, five filtration units each having a filtration module with a side surface area of 40 cm × 40 cm were immersed in the biological reaction tank, and treated water was taken out under natural flow. As the filtration module, a net spacer is fixed to the surface (both sides) of an ABS resin filter plate, and a polyester nonwoven fabric (thickness: 0.12 mm, basis weight: 15 g / m ² , average opening size in the surface direction: 120 μm)
m) was used. At an interval of 30 min from the start of operation of the filtration unit, 10 m ³ from the cleaning air diffuser
/ ^M sequentially conducted 2 / hr of the aeration washing 3min at a flow rate from the filtration unit _{3 1} to _{3 5.} For comparison, a sewage treatment experiment was performed under the same conditions as above except that the unit spacing wall was removed.

As a result of the above experiment, when no unit spacing wall is provided between the filtration units, BOD 25 mg / L, SS
The treated water quality was about 20 mg / L. In contrast, in the case of the present invention, BOD 10 mg / L, SS 5 mg
/ L and treated water quality were improved.

[0013]

According to the present invention having the above-mentioned structure, a plurality of filtration units can be operated continuously, and a decrease in the quality of treated water can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic vertical plan view of a sewage treatment apparatus according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a partially broken plan view of a filtration module according to one embodiment of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Biological reaction tank, 2 partition walls, 3 filtration units, 4 unit interval walls, 5 diffuser tubes, 6 diffuser tubes for washing, 7 water collecting tubes, 10 filtration modules, 11 filtration plates, 12 filtration membrane support members, 13 filtration membranes

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B01D 29/04 510D 520A 530A (71) Applicant 000001063 Kurita Kogyo Co., Ltd. 3-4-1 Nishishinjuku, Shinjuku-ku, Tokyo No. 7 (71) Applicant 000006655 Nippon Steel Corporation 2-6-3, Otemachi, Chiyoda-ku, Tokyo (72) Inventor Hitoshi Daido 2-2-1, Nishishinjuku, Shinjuku-ku, Tokyo Inside the Tokyo Sewerage Bureau ( 72) Inventor Eiji Aso 2-2-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Tokyo Metropolitan Government Sewerage Bureau Mutsuro 5200 Sankajiri, Kumagaya City, Saitama Prefecture Hitachi Metals Co., Ltd.Environmental Engineering Division (72) Inventor Yoshinao Kishine Kurita Kogyo Co., Ltd., 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo (72) Inventor Shigeki Sawada Kurita Kogyo Co., Ltd., 3-4-2-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Morio Sakata 2-6-3 Otemachi, Chiyoda-ku, Tokyo Nippon Steel Corporation (72) Inventor Kazuhisa Fukunaga 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation F-term (reference) 4D028 BC12 BC17 BD17 4D029 AA01 AB06 BB10 DD01

Claims (1)

[Claims] 1. A biological reaction tank, a plurality of filtration units having at least a portion of a peripheral wall immersed and disposed in the interior thereof along the flow direction of sewage, and a plurality of filtration units each formed of a water-permeable support; A sewage treatment apparatus comprising: an aeration unit provided at a lower part of a biological reaction tank; a filtration unit cleaning aeration unit provided below the filtration unit; and a buffer tank having a water level lower than that of the biological reaction tank. Sewage, supplying treated water from the filtration unit, removing treated water from the filtration unit, and selectively operating the cleaning air diffuser to alternately wash the filtration unit along the arrangement direction thereof. Processing method.