JPH08141587A - Method and apparatus for treating waste water - Google Patents

Abstract

PURPOSE: To inexpensively provide a compact waste water treatment method and apparatus obtaining stable clear treated water of a tertiary treatment level by an activated sludge method and removing nitrogen in sewage. CONSTITUTION: Two or more treatment tanks are connected in series by a connection pipe and the air diffusion pipe 8 connected to an intermittently operated blower 10 is arranged to the bottom part of the front treatment tank 6 and a bacteria propagating stagnation zone is provided above the air diffusion pipe 8 while a filter bed 16 composed of a filter material of which the specific gravity is higher than 1 is formed to the bottom of the rearmost treatment tank 14 and the backwashing pipe/treated water collecting pipe 19 connected to a backwashing mechanism due to water and air is arranged to the bottom part of the filter bed 16 through a connection pipe 22. The air diffusion pipe 18 connected to a continuously operated blower 21 is arranged to the upper surface of the filter bed 16 and a bacteria propagating stagnation zone 15 is provided above the air diffusion pipe 18 to provide a sludge return pipe 7 returning the activated sludge of the bacteria propagating stagnation zone 15 in the rearmost treatment tank 14 to the bacteria propagating stagnation zone in the front treatment tank 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating wastewater for purifying human waste, gray water and the like discharged from houses, factories and the like.

[0002]

2. Description of the Related Art There are the following conventional methods and apparatuses for treating human waste and gray water. Japanese Patent Publication No. 56-14360, “Treatment device for household wastewater”, includes a lower filtration layer made of a filter material having a relatively large specific gravity at the bottom of the treatment tank and an upper filtration layer made of a filter material having a specific gravity smaller than that of the lower filtration layer. A filter layer is formed, and a water collecting pipe is installed near the bottom of the lower filtration layer, and air diffusers are arranged near the upper surface of the upper filtration layer and near the boundary between the upper filtration layer and the lower filtration layer, respectively. A method and an apparatus are described in which a microbial breeding retention zone for treating activated sludge of raw water is provided in a region above the upper surface of a filtration layer, and the filtered water is taken out from a water collecting pipe at the bottom of the filtration layer.

Further, the present inventors previously formed a filtration layer of a filter medium having a specific gravity of more than 1 at the bottom of the treatment tank, and installed a backwash pipe and a water collection pipe with water and air at the bottom of the filtration layer. In addition, by installing a water collection pipe on the upper surface of the filtration layer, connecting a blower to the water collection pipe, and intermittently operating the blower, the raw water in the region above the upper surface of the filtration layer is treated by the microorganisms for activated sludge treatment. Intermittently aerating the breeding retention zone to remove nitrogen compounds that are the cause of eutrophication in lakes, etc. in addition to organic matter,
A method and a device for obtaining treated water quality at a tertiary treatment level have been proposed (Japanese Patent Application No. 5-127093).

[0004]

However, in the above-mentioned Japanese Patent Publication No. 56-14360 "Treatment device for household wastewater", an air diffuser is installed near the upper surface of the upper filtration layer, and the upper surface of the filtration layer is installed. Since a method of continuously supplying air to the microbial propagation retention zone for the treatment of activated sludge of raw water above is used, organic substances can be sufficiently removed, but nitrogen compounds that cause eutrophication cannot be removed. . On the other hand, in the previously proposed “method and device for obtaining treated water quality at the tertiary treatment level”, raw water is eutrophied not only to organic matter but also to lakes and marshes by intermittently aerating the microbial breeding retention zone for activated sludge treatment. The nitrogen compounds that are the cause of the Sometimes overflowed outside.

The present invention has been made in view of the above-mentioned problems, and is a compact wastewater treatment method for removing nitrogen in wastewater while obtaining clear and treated water with a stable tertiary treatment level by the activated sludge method. It is also an object of the present invention to provide a processing device at low cost.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a method for treating wastewater in which wastewater is biochemically treated and filtered to purify the wastewater, and the microorganism breeding retention zone in which biochemical treatment with activated sludge is performed is made to be two or more. Separately connected in series, intermittently aerating the front microbial breeding retention zone, continuously aerating the last microbial breeding retention zone, and returning the activated sludge in the last microbial breeding retention zone to the front microbial breeding retention zone Water is biochemically treated with a filter bed filled with a filter medium having a specific gravity of more than 1 formed just below the rearmost microbial breeding retention zone, and the wastewater is treated biochemically. In a wastewater treatment device having a treatment tank for treating and filtering,
Two or more treatment tanks are provided, and each treatment tank is connected in series by connecting pipes, and in the front treatment tank, an air diffuser connected to an intermittently operating blower is installed at the bottom, and microbial propagation retention is above the air diffuser. A backwash pipe is provided with a zone, a filter layer made of a filter medium having a specific gravity of more than 1 is formed in the bottom of the last treatment tank, and the bottom of the filter layer is connected to a backwash mechanism with water and air through a connecting pipe. A treated water collecting pipe is installed, an air diffusing pipe connected to a continuously operating blower is installed on the upper surface of the filtration layer, a microbial breeding retention zone is provided above the diffusing pipe, and a microbial breeding retention zone in the last treatment tank. The present invention relates to a wastewater treatment device provided with a sludge return pipe for returning the activated sludge to the microbial propagation retention zone in the front treatment tank.

In the present invention, if the activated sludge in the rearmost microbial breeding retention zone is returned only when the aeration of intermittent aeration in the forward microbial breeding retention zone is stopped, the generated nitrite and nitrate ions are treated in the front treatment tank. It is preferable because nitrogen gas can be efficiently reduced and removed. In addition, the filter material does not float in the filter layer,
In order to support the sludge layer formed by the propagation of microorganisms which is effective in removing fine suspended solids, a filter medium having a specific gravity of more than 1 such as sand, crushed anthracite, crushed glass, and granular activated carbon is filled. The configuration of the present invention will be described below with reference to FIG. The following description is for the minimum number of microbial breeding retention zones divided into two, but the number of microbial breeding retention zones, that is, the number of treatment tanks may be two or more. When three or more processing tanks are provided, only the last processing tank is continuously aerated, and the processing tank in front of it is the same structure with intermittent aeration.

As shown in FIG. 1, there are two treatment tanks, a first treatment tank 6 and a second treatment tank 14. The first treatment tank 6 is provided with a raw water supply pipe 5 and a sludge return pipe 7, Is supplied, an air diffuser 8 is installed at the bottom of the tank, and an intermittent aeration blower 10 is connected to the air diffuser 8 via a connecting pipe 9, and the blower 10 is intermittently operated to generate activated sludge. Supplies the air required for biochemical treatment. At the lower part of the first treatment tank 6, an activated sludge mixed liquid outlet 1 is provided.
1, the outlet 11 is connected to the activated sludge mixed liquid inlet 13 in the upper part of the second treatment tank 14 via the connecting pipe 12, and the activated sludge mixed liquid in the first treatment tank 6 passes through them to the second It flows into the processing tank 14.

The second processing tank 14 has a filter layer 16 made of a filter medium having a specific gravity of more than 1 at the bottom, and the bottom of the filter layer 16 is connected to a backwashing mechanism with water and air through a connecting pipe 22. While installing the backwash pipe and treated water collecting pipe 19,
An air diffuser 18 is installed on the upper surface of the filter layer 16. An aeration blower 21 is connected to the air diffuser 18 through a connecting pipe 20, and the blower 21 is continuously operated to biochemically treat the activated sludge in the microbial propagation retention zone 15 above the filtration layer 16. Supply the required air. The backwash pipe / treated water collecting pipe 19 includes a connecting pipe 22, a check valve 25, and a backwash pump 2.
3 is connected to the backwash water tank 27 via the connection pipe 2
2 is a backwash blower 2 via a check valve 26 provided in a branched manner
4 is connected. A sludge return pump 17 for returning the activated sludge in the microbial propagation retention zone 15 is installed in the second treatment tank 14, and the sludge return pump 17 is continuously or when the aeration of intermittent aeration of the first treatment tank 6 is stopped. The activated sludge is returned to the first treatment tank 6 via the pipe 7.

[0010]

Next, the operation of the present invention will be described. The raw water flowing from the flow rate adjusting tank 1 into the first processing tank 6 is the second processing tank 14
It is mixed with the activated sludge returned from. By operating the blower 10 connected to the air diffuser 8 installed in the first processing tank 6, the inside of the tank is intermittently aerated. The inside of the tank is aerated by the blower 10, the raw water and the activated sludge are sufficiently aerated and stirred, the organic matter in the raw water is removed, and the activated sludge grows. Further, the ammoniacal nitrogen and the organic nitrogen in the raw water are nitrified by nitrifying bacteria in the activated sludge to be nitrite or nitrate ions.

When the blower 10 is stopped, the first processing tank 6
Inside, activated sludge settles, forming a thick sludge layer,
Raw water in the first treatment tank 6 passes through the thick sludge layer and flows into the second treatment tank 14. At that time, the thick sludge layer became anoxic and was generated during aeration or the second treatment tank 1
The nitrite and nitrate ions circulated from No. 4 are reduced to form nitrogen gas, which is diffused into the atmosphere and removed. At the same time, when reducing to nitrogen gas, organic substances are consumed and removed. As described above, by repeating the aeration and stopping of the blower 10, organic matter and nitrogen in the raw water are removed.

The activated sludge mixed solution from which most of the organic substances and nitrogen in the raw water have been removed in the first treatment tank 6 flows into the second treatment tank 14 and is aerated in the microbial breeding retention zone 15 in the upper part, Remaining organic matter is removed and ammoniacal nitrogen is nitrified. Then, the raw water is physically filtered by the filtration layer 16 immediately below the microbial breeding retention zone, and the connection pipe 22, check valve 25, and backwash pump 23 are connected from the backwash pipe / processed water collecting pipe 19 at the bottom of the filter layer 16 to the connection pipe 22, check valve 25, and backwash pump 23. After that, it is guided to the backwash water tank 27.
This physical filtration passes through a sludge layer which is dense and rich in absorptivity, which is caused mainly by the accumulation of sludge generated by the propagation of microorganisms in the vicinity of the surface layer of the filtration layer 16, and thus has an excellent water purification effect. Is exhibited, fine suspended solids are removed, and treated water with high clarity is obtained.

The sludge layer formed on the surface of the filtration layer 16 grows as the operation continues, and the filtration resistance increases proportionally. Therefore, the microbial propagation retention zone 1 of the second treatment tank 14 is increased.
The water level of 5 rises gradually. Therefore, the backwash blower 24 is operated for a certain period of time, and air is supplied to the backwash pipe / treated water collecting pipe 19 installed near the bottom of the filtration layer 16 to destroy the sludge layer and simultaneously filter the sludge layer. The lump of the filter medium generated inside the layer 16 is destroyed, and the treated water in the backwash water tank 27 is supplied to the backwash pipe / treated water collecting pipe 19 by the backwash pump 23 for a certain period of time, and the microorganism breeding retention zone 15 By returning the adhering substance to the sludge layer, the clogging of the sludge layer and the filtration layer 16 is released, and long-term operation is enabled.

Further, the activated sludge in the microbial propagation retention zone 15 of the second treatment tank 14 is continuously or intermittently returned to the first treatment tank 6 by the sludge return pump 17, and the first treatment tank 6 is discharged.
And the concentration of activated sludge in the microbial propagation retention zone of the second treatment tank 14 becomes substantially the same. In the case of intermittently returning the gas, nitrite and nitrate ions generated in the second processing tank 14 are efficiently converted into nitrogen gas in the first processing tank 6 by returning the gas during intermittent aeration of the first processing tank 6. Can be reduced and removed.

[0015]

EXAMPLE An example of the present invention will be described below with reference to FIG. In FIG. 1, raw water first flows into the flow rate adjusting tank 1,
Flow rate adjusting pump 2 via connection pipe 3 by flow rate adjusting pump 2
After being pumped up to, the flow rate of which is adjusted by the flow rate adjusting unit 4, the raw water supply pipe 5 quantitatively supplies it to the microbial breeding retention zone of the first treatment tank 6. An air diffuser 8 is installed at the bottom of the first processing tank 6, and an intermittent aeration blower 10 is connected to the air diffuser 8 via a connecting pipe 9. The intermittent aeration blower 10 is intermittently operated, and the first treatment tank 6 is intermittently aerated for 30 minutes and aeration stopped for 90 minutes. When the blower 10 for intermittent aeration is in operation, removal of organic substances and nitrification of ammonia nitrogen and organic nitrogen are performed, and when stopped, removal of organic substances is performed simultaneously with denitrification of nitrous acid and nitrate ions.

The sewage treated in the first treatment tank 6 is supplied from the activated sludge mixture outlet 11 at the bottom of the tank to the microbial breeding retention zone 15 formed at the top of the second treatment tank 14.
Immediately below the microbial breeding retention zone 15, a filtration layer 16 filled with crushed anthracite having a specific gravity of 1.4 is formed,
An air diffuser 18 is installed on the upper surface of the filter layer 16, and a backwash tube and treated water collecting tube 19 is installed on the bottom of the filter layer 16. Then, the aeration blower 2 is connected to the air diffuser 18 via a connecting pipe 20.
1 is connected to the backwashing pipe / processed water collecting pipe 19 through a connecting pipe 22 and check valves 25 and 26.
4 and the backwash pump 23 are connected.

The backwash blower 24 connected to the backwash pipe / treated water collecting pipe 19 is operated for 1 minute every 30 minutes, and the filtration layer 1
At the same time that the sludge layer formed on the surface of 6 is destroyed, the lumps of the filter media formed inside the filter layer 16 are kneaded and loosened.
Immediately after that, the backwashing pump 23 connected to the backwashing pipe / treated water collecting pipe 19 is operated for 10 seconds, and the treated water in the backwashing water tank 27 pushes up the sludge on the surface of the filtration layer 16 and in the filtration layer to prevent the microorganisms. Returning to the breeding retention zone 15 completes the backwash. In addition to the above, the backwash pump 23 operates once a day for 1 minute to wash the surface of the filtration layer 16 and the inside of the filtration layer with the treated water. Further, the activated sludge in the microbial propagation retention zone 15 of the second treatment tank 14 is continuously or intermittently returned to the first treatment tank 6 by the sludge return pump 17, and the first treatment tank 6 and the second treatment tank 14 are activated. The concentration of activated sludge in the microbial propagation retention zone is almost the same.

The return of the activated sludge in the microbial propagation retention zone 15 of the second treatment tank 14 by the sludge return pump can be carried out when the aeration of the intermittent aeration of the first treatment tank 6 is stopped.
The nitrite and nitrate ions generated in 4 can be efficiently reduced and removed into nitrogen gas in the first treatment tank 6. The sewage purified in the microbial propagation retention zone 15 of the second treatment tank 14 passes through the filter layer 16 and is treated as treated water from the backwash pipe / treated water collecting pipe 19 through the connecting pipe 22 and the backwash pump 23. It is stored in the backwash water tank 27. The treated water stored in the backwash water tank 27 contacts the disinfectant in the disinfecting cylinder 28, is stored in the disinfecting tank 29, and flows out. Excess sludge generated in the microbial breeding retention zone of the first treatment tank 6 and the second treatment tank 14 is drawn out by a sludge drawing pump or the like, and after concentrated storage, carried out and disposed of by a vacuum car.

Table 1 shows the water quality of the raw water and the treated water in the examples separately for continuous return and intermittent return. Each measured value was measured by the measuring method according to JIS0102. As is clear from Table 1, the treated water returned intermittently has a smaller amount of NH ₄ —N and TN. By intermittently returning, the nitrification time increases and NH ₄ -N decreases further, and the generated activated sludge mixed liquid with a high concentration of NO ₂ -N and NO ₃ -N and sewage with a high organic matter concentration are generated. By contacting with each other, NO ₂ -N and NO ₃ -N are efficiently removed, and as a result, T-N is reduced.

[0020]

[Table 1]

[0021]

According to the present invention, the following effects are exhibited. (1) By filtering the activated sludge in the filtration layer immediately below the microbial breeding retention zone, instability of solid-liquid separation due to swelling of the sludge can be eliminated, and stable and clear water can be obtained. (2) By dividing the microbial breeding retention zone into two or more zones, it is possible to form a high organic matter concentration state effective for denitrification in the forward microbial breeding retention zone, and nitrogen can be removed efficiently. (3) By continuously aerating the microbial breeding retention zone having the last filter layer, it is possible to prevent a decrease in the amount of treated water passing through the filter layer without increasing the installation area and cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of an apparatus in a wastewater treatment method of the present invention.

[Explanation of symbols]

1 ... Flow rate adjusting tank 1, 2 ... Flow rate adjusting pump, 3 ... Connection pipe,
4 ... Flow rate adjusting box, 5 ... Raw water supply pipe, 6 ... First treatment tank, 7
... Sludge return pipe, 8 ... Air diffuser pipe, 9 ... Connection pipe, 10 ... Blower, 11 ... Activated sludge mixed liquid outlet, 12 ... Connection pipe, 13
... activated sludge mixed liquid inlet, 14 ... second treatment tank, 15 ... microorganism breeding retention zone, 16 ... filtration layer, 17 ... sludge return pump, 18 ... air diffuser, 19 ... backwash pipe / treated water collection pipe, 20
... Connection pipe, 21 ... Blower, 22 ... Connection pipe, 23 ... Backwash pump, 24 ... Backwash blower, 25 ... Check valve, 26 ... Check valve, 27 ... Backwash water tank, 28 ... Disinfection cylinder, 29 … Disinfection tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 3/12 ZAB F 3/20 ZAB Z 3/30 ZAB A B01D 29/08 530 D 540 A

Claims (3)

[Claims] 1. A microbial breeding retention zone for performing biochemical treatment with activated sludge is divided into two or more and connected in series, the forward microbial breeding retention zone is intermittently aerated, and the rearmost microbial breeding retention zone is continuous. Aeration, activated sludge in the rearmost microbial breeding retention zone is returned to the forward microbial breeding retention zone to treat water biochemically, and the specific gravity formed directly below the last microbial breeding retention zone is greater than 1. A method for treating wastewater, which comprises filtering water through a filter layer filled with a filter material. 2. The method for treating wastewater according to claim 1, wherein the activated sludge in the rearmost microbial breeding retention zone is returned only when the aeration of intermittent aeration of the forward microbial breeding retention zone is stopped. 3. A plurality of treatment tanks are provided, each treatment tank is connected in series by a connecting pipe, and an air diffuser connected to an intermittently operating blower is installed at the bottom of the front treatment tank. A microbial breeding retention zone is provided above, a filtration layer made of a filter material having a specific gravity of more than 1 is formed at the bottom of the last treatment tank, and a backwashing mechanism with water and air is provided at the bottom of the filtration layer through a connecting pipe. Installed backwash pipe and treated water collecting pipe connected, installed diffuser pipe connected to continuously operating blower on the upper surface of the filtration layer, provided a microbial breeding retention zone above the diffuser pipe, and the last treatment tank Wastewater treatment equipment provided with a sludge return pipe for returning the activated sludge in the microbial breeding retention zone in the above to the microbial breeding retention zone in the front treatment tank.