WO2018033997A1

WO2018033997A1 - Active sludge treatment method, and method for improving existing waste water treatment equipment by using active sludge treatment method

Info

Publication number: WO2018033997A1
Application number: PCT/JP2016/074192
Authority: WO
Inventors: 藤野　清治
Original assignee: 日本アルシー株式会社
Priority date: 2016-08-19
Filing date: 2016-08-19
Publication date: 2018-02-22

Abstract

The purpose of the present invention is to provide: an active sludge treatment method which is capable of, in a waste water treatment in a combined sewage system, treating waste water using space-saving equipment with substantially no bad smell being generated in association with treatment, even in a waste water treatment for waste water containing a large amount of inorganic sludge; and a method for improving existing waste water treatment equipment by using the active sludge treatment method. The method comprises (1) step 1 for separating sludge-containing treated water which is generated in a microorganism reaction tank 1, into inorganic sludge and treated raw water 2, using a sludge separation device 15 provided between the microorganism reaction tank 1 and a raw water aeration adjustment tank 14, (2) step 2 for supplying the separated treated raw water 2 to the raw water aeration adjustment tank 14, (3) step 3 for aerating, in the raw water aeration adjustment tank 14, raw water mixed with the treated raw water 2 to adjust the oxidation-reduction potential of the raw water to become positive, and supplying the adjusted treated raw water 1 to the microorganism reaction tank 1, and (4) step 4 allowing water discharged from the microorganism reaction tank 1 to be effluent.

Description

Activated sludge treatment method and repair method of existing wastewater treatment equipment using the method

The present invention relates to an activated sludge treatment method and a method for renovating an existing wastewater treatment facility using this activated sludge treatment method, and in particular, a rejuvenation method for activated sludge and a water treatment facility in a combined wastewater treatment facility including wastewater containing a large amount of inorganic sludge. Regarding the method.

Since the activated sludge treatment method is an extremely excellent wastewater treatment method, it is widely used for wastewater treatment, and various treatment methods have been proposed depending on the type of raw water.
In the conventional activated sludge treatment method, various microorganisms are used from soil bacteria to large protozoa using a food chain. However, activated sludge treatment has the following problems. (1) Enormous aeration tank (lagoon method / oxidation ditch) requires a large volume of aeration tank, and (2) Hydrogen ion concentration in the inflowing raw water (below) (3) When a harmful substance that sterilizes the activated sludge flows, the activated sludge is damaged and loses the purification function of the raw water or filamentous bacteria. (4) When the fluctuation of the pollutant component of the inflow raw water is large, or when the high-speed aeration activated sludge treatment is performed, the bulking is likely to occur.

In order to solve the above problems, the present applicant has developed a microbial reaction tank and a wastewater treatment method (Patent Document 1), and has made achievements in wastewater treatment in many fields.
Moreover, as one of the methods for reducing excess sludge, a method is disclosed in which the excess sludge is subjected to ozone treatment and then returned to the aeration tank (Non-Patent Document 1). In addition, there is known a method of returning to an aeration tank after treating with thermophilic bacteria, mechanically crushing, or chemically treating.
However, as diversification of wastewater treatment proceeds and regulations on environmental loads become stricter, it may be difficult to reduce excess sludge even in wastewater treatment by the above methods.

In order to solve the above problem, as shown in FIG. 9, the present applicant is provided with a raw water aeration adjusting tank 14 ′ and a microbial reaction tank 1 ′, and sludge generated in the microbial reaction tank 1 ′ is removed from the raw water aeration adjusting tank 14. In the activated sludge treatment method of treating wastewater by a circulation system that circulates to the process 1 for supplying the sludge 1 generated from the microorganism reaction tank 1 ′ to the raw water aeration adjusting tank 14 ′ to which raw water before treatment is supplied; The step of supplying the adjusted treated raw water 1 to the microorganism reaction tank 1 ′ after adjusting the aeration of the raw water mixed with the sludge 1 in the raw water aeration adjusting tank 14 ′ so that the oxidation-reduction potential becomes a positive value. 2 and an activated sludge treatment method characterized by having a step 3 in which discharged water from the microorganism reaction tank 1 ′ is discharged water (Patent Document 2).

However, this activated sludge treatment method also has the following problems.
(1) The sewage drainage treatment system has a separate sewage pipe and rainwater pipe, and sewage for household use discharged from the sewage pipe is drained and discharged. There are two types: a sewer system that divides water into the sea, and a combined sewer system that sends sewage and rainwater for household use to a wastewater treatment facility through a single pipe. The combined sewer system is less expensive than the split sewer system because only one pipe is required. For this reason, the combined sewerage system is widely adopted especially in developing countries. In the case of this combined sewer system, even if the sludge circulation system is employed, if the amount of inorganic sludge that cannot be decomposed in the microorganism reaction tank increases, the sludge treatment becomes difficult in many cases. In addition, when the amount of sludge increases, it becomes difficult to install the activated sludge treatment apparatus in an urban area where residents are crowded due to the generation of malodor associated with the treatment.
(2) It is difficult to secure a space for installing a wastewater treatment facility using a combined sewer system containing a large amount of inorganic sludge.
(3) In the case of wastewater treatment by the combined sewer system, since it contains a large amount of inorganic sludge, sludge discharged from the microbial reaction tank is often generated, and the treatment is costly due to the generation of malodor.
(4) When a wastewater treatment device is installed in an urban area, space is often saved, and much experience and technology are required for the operation of a small wastewater treatment device.

Japanese Patent No. 4142138 International publication WO2013 / 132611

The present invention has been made to address the above-described problems. In the wastewater treatment method using the activated sludge treatment method, particularly in the wastewater treatment in the combined sewer system, even in wastewater treatment containing wastewater containing a large amount of inorganic sludge. An object of the present invention is to provide an activated sludge treatment method that can generate wastewater treatment in a space-saving facility with almost no bad odor accompanying the treatment, and a method for refurbishing existing wastewater treatment equipment using this activated sludge treatment method.

The activated sludge treatment method of the present invention comprises a raw water aeration adjusting tank and a microorganism reaction tank, and an activated sludge treatment for treating wastewater by a circulation system that circulates sludge-containing treated water generated in the microorganism reaction tank to the raw water aeration adjusting tank. The method includes the following steps.
(1) The process of separating the sludge containing treated water generated from the microbial reaction tank into the inorganic sludge and the treated raw water 2 by the sludge separation device provided between the microbial reaction tank and the raw water aeration control tank. 1,
(2) Step 2 of supplying the treated raw water 2 separated to the raw water aeration control tank,
(3) The raw water mixed with the treated raw water 2 is aerated in the raw water aeration adjusting tank so that the oxidation-reduction potential becomes a positive value, and the adjusted treated raw water 1 is then added to the microbial reaction tank. Step 3 of supplying, and (4) Step 4 of using discharged water from the microbial reaction tank as discharged water.

The microorganism reaction tank used in the activated sludge treatment method of the present invention is provided in an outer tank, a cylindrical inner tank that is disposed inside the outer tank and has upper and lower openings, and an upper part of the cylindrical inner tank. A circulation rate control device for controlling the circulation rate of the water to be treated, a control cylinder provided on the outer periphery of the upper part of the cylindrical inner tank, and settling outside the inner side of the cylindrical inner tank. A water quality measuring device provided; a raw water supply port provided in a circulation path of water to be treated that circulates in the outer tank and the inner tank; and a treated water discharge port provided in an upper portion of the outer tank. is doing.
The cylindrical inner tank is divided into a cylindrical upper part and a cylindrical lower part by a partition wall having a communication hole in the center part, and the cylindrical upper part has a truncated cone-shaped top part having an open top surface and a bottom surface. The inclination angle of the cross section in the height direction passing through the center is 40 to 60 degrees, and a plurality of air blowing ports are provided around the communication hole in the upper part of the cylinder and the peripheral edge of the partition wall, and are arranged in the outer tank. The aerobic microorganism treatment tank is disposed inside the outer tank with the partition walls supported by a plurality of support pillars, and the cylindrical lower part is an anaerobic microorganism treatment tank having an opening on the bottom surface,
A stirring device is provided for stirring the inside of the aerobic microorganism treatment tank and the inside of the anaerobic microorganism treatment tank.

At least one selected from the hydrogen ion concentration (hereinafter referred to as pH), oxidation-reduction potential (hereinafter referred to as ORP), and dissolved oxygen amount (hereinafter referred to as DO) measured by the water quality measuring apparatus. Means for detecting the measured value and the level of the water to be treated provided in the circulation rate control device arranged at the upper part of the cylindrical inner tank in accordance with the detected measured value Opening and closing of the liquid level control valve that adjusts to the lowest level sometimes, up and down movement of the liquid level control control plate that adjusts the level of the water to be treated to the lowest level at the lowest level of the liquid level control plate, and from the air inlet The microorganism reaction tank includes means for controlling the in-tank circulation rate of the water to be treated to 3 to 20 by controlling at least one amount selected from the amount of air to be blown. Here, the to-be-processed water circulation rate in a reaction tank means the quantity defined by following Formula.

Rate of treated water circulation = amount of treated water discharged from the upper part of the inner tank (m ³ / day) / raw water supply (m ³ / day)

In the microbial reaction tank, the raw water supplied from the raw water supply port passes through the activated sludge and the inside of the cylindrical inner tank, the outer peripheral surface of the cylindrical inner tank, and the activated sludge settled at the lower part of the outer tank. The anaerobic microorganism treatment and the aerobic microorganism treatment are continuously performed by circulating in the tank.

The sludge separator used in the activated sludge treatment method of the present invention is a centrifugal dehydrator.

The microorganism reaction tank used in the activated sludge treatment method of the present invention is characterized in that a settling and fixing prevention device for preventing settling and fixing of sludge is provided inside and outside the outer tank and the inner layer constituting the microorganism reaction tank. To do.
In particular, this settling prevention device is (1) a scraper provided on the inner wall of the lower part of the outer tank where the sludge settles. (2) An agitated flow generator for generating a stirred flow of sludge along the inner wall of the lower part of the outer tank It is one of these.

The method for repairing an existing wastewater treatment facility of the present invention is a method for repairing an existing wastewater treatment facility that reduces the amount of sludge generated in the wastewater treatment facility from the amount of sludge generated in the existing wastewater treatment facility, the repair method Is a step of newly installing the microorganism reaction tank and the sludge separation device described above, and a circulation step of circulating the sludge-containing treated water by the activated sludge treatment method of the present invention through the newly installed microorganism reaction tank and the sludge separation device. It is characterized by providing.

In the method of the present invention, the following effects can be obtained by circulating sludge-containing treated water generated in a microbial reaction tank used as a wastewater treatment facility by the method of claim 1.
(1) Since the inorganic sludge separated using the sludge separator is circulated in the microbial reaction tank, almost no odor is generated in the dehydrated cake. For this reason, wastewater treatment facilities can be installed in urban areas.
(2) Since the sludge-containing treated water is circulated in the microorganism reaction tank, the dehydrated cake can be landfilled with a low content of organic sludge. Moreover, the amount of excess sludge discharged from the microorganism reaction tank can be greatly reduced except for inorganic sludge.
(3) In the wastewater treatment in the combined sewer system, a space-saving microbial reaction tank is newly installed, so the installation area of the wastewater treatment facility can be reduced.

It is a block diagram of the activated sludge processing method. It is sectional drawing of a microbial reaction tank. It is sectional drawing of the microorganisms reaction tank provided with the scraper. It is sectional drawing of the microorganisms reaction tank provided with the fluid spray nozzle. It is sectional drawing of the microorganisms reaction tank provided with the other fluid spray nozzle. It is sectional drawing of the microorganisms reaction tank provided with the discharge pump. It is sectional drawing of the microorganisms reaction tank provided with the other discharge pump. It is a figure which shows the to-be-processed water and the circulation path | route of activated sludge in a microbial reaction tank. It is a block diagram of the existing activated sludge processing method.

A block diagram of the activated sludge treatment method of the present invention is shown in FIG.
Waste water from the sewer is circulated through the microorganism reaction tank 1. Sludge-containing treated water containing sludge generated in the microorganism reaction tank 1 is separated into the inorganic sludge and the treated raw water 2 by the sludge separation device 15, and the treated raw water 2 passes through the raw water aeration adjusting tank 14 and is again returned to the microorganism reaction tank 1. Circulate to. Organic sludge is digested in this circulation process. Hereafter, each process accompanying a circulation is demonstrated in order.

Step 1:
Step 1 separates the sludge-containing treated water generated from the microbial reaction tank 1 into the inorganic sludge and the treated raw water 2 by the sludge separation device 15 provided between the microbial reaction tank 1 and the raw water aeration control tank 14. It is a process to do.
The sludge separation device 15 is provided mainly for discharging inorganic sludge, and a dehydrator, a sedimentation tank, or the like can be used. Examples of the dehydrator include, for example, a centrifugal dehydrator that uses centrifugal force generated by high-speed rotation, a screw press dehydrator that uses a screw to squeeze, a belt press dehydrator that uses a belt-like filter cloth, and a vacuum dehydration that dehydrates in a vacuum. Machine, filter press dehydrator for pressure filtration, multiple disk dehydrator and the like. Examples of the precipitation tank include a single-stage or multi-stage gravity precipitation separation tank. Among the dehydrators, a centrifugal dehydrator is preferable. Since the inorganic sludge and the treated raw water 2 are supplied to the sludge separation device 15 after circulating through the microorganism reaction tank 1, it is not necessary to add a flocculant or the like to the sludge separation device 15. Moreover, the inorganic sludge discharged is almost free from bad odor.

Step 2:
Step 2 is a step of supplying raw raw water 2 generated in the microorganism reaction tank 1 to the raw water aeration control tank 14.
The raw water aeration tank 14 can be obtained by adding air blowing equipment to an existing raw water tank when the existing wastewater treatment equipment is to be repaired.
A large solid content in the wastewater to be treated is removed by a filtration screen or the like, and stored in the raw water aeration adjusting tank 14 as raw water to be treated. The raw raw water aeration tank 14 is supplied with the raw raw water 2 generated in the microbial reaction tank 1 and mixed with the raw water to treat activated sludge such as refractory substances in the raw water and harmful substances that destroy the activated sludge. The pollutant that tends to give an abnormality is adsorbed to the organic sludge in the treated raw water 2. Since the organic sludge in the treated raw water 2 is treated in the microorganism reaction tank 1, it is an activated sludge suitable for the wastewater to be treated. For this reason, by supplying the treated raw water 2 to the raw water, the activity of the activated sludge is maintained at a high level, so that the occurrence of abnormal phenomena during the activated sludge treatment in the microbial reaction tank is reduced and the treatment can be stabilized. it can.

The treated raw water 2 supplied to the raw water aeration adjustment tank 14 is supplied to the raw water aeration adjustment tank 14 in a range where the sludge concentration in the raw water aeration adjustment tank 14 is 500 to 8000 mg / L as MLSS. Preferably, it is supplied in a range of 1000 to 5000 mg / L. When the MLSS is less than 500 mg / L, the activated sludge treatment becomes unstable because the pollutant that adversely affects the activated sludge cannot be adsorbed. Moreover, when MLSS exceeds 8000 mg / L, the biochemical oxygen demand (henceforth BOD) contained in the treated raw water 1 will decrease.

Step 3:
In step 3, the raw water mixed with the treated raw water 2 is aerated in the raw water aeration adjusting tank 14 so that the ORP of the raw water becomes a positive value, and then the treated raw water 1 is supplied to the microorganism reaction tank 1. It is. By adjusting the aeration so as to have a positive value, activated sludge treatment can be performed in which hydrogen sulfide, ammonia, mercaptan, etc., which cause bad odor, are oxidized and odor is hardly emitted.
The aeration process in the raw water aeration adjusting tank 14 is performed by an aeration process in which the residence time of the raw water is 3 hours or longer, preferably 5 hours or longer. Aeration treatment is performed in the presence of treated raw water 2, and raw water containing sludge is supplied to the microbial reaction tank.

Step 4:
Step 4 is a step in which the discharged water from the microbial reaction tank 1 is discharged water. The treated raw water 1 is subjected to aeration treatment in the raw water aeration adjusting tank 14 so that the pH is naturally adjusted by the pH buffering action of microorganisms, so that an existing pressurized flotation concentration separation tank is not required. Can be used effectively, and the installation area can be reduced.
In the present invention, the anaerobic microbial treatment in the microbial reactor 1 refers to a treatment in a state where DO is less than 0.05 mg / L, and the aerobic microbial treatment refers to DO of 0.05 mg / L or more, preferably 0.1 mg. / L or more, more preferably treatment in a state of 0.2 mg / L or more. Furthermore, it means an operation in which the ORP is less than −80 mV in the anaerobic microorganism treatment and the ORP is −80 mV or more in the aerobic microorganism treatment, preferably in a positive state.
The microorganism reaction tank 1 anaerobically and aerobically digests the organic sludge contained in the treated raw water 1 to decompose most of the pollutants adsorbed by the sludge into gases such as carbon dioxide gas, water, nitrogen gas and methane gas. In addition, since organic sludge is used for the growth of microorganisms and most of it becomes digested sludge that has been transformed into cells, the amount of organic sludge is significantly reduced.

A microbial reactor is shown in FIG. FIG. 2 is a cross-sectional view of the microbial reaction tank.
The microbial reaction tank 1 includes an outer tank 2, a cylindrical inner tank 3 disposed in the outer tank 2, a circulation rate control device 4 provided on the upper part of the cylindrical inner tank 3, and a cylindrical shape A control cylinder 5 provided on the outer peripheral side of the inner tank 3, a treated water quality measuring device 6, a raw water supply port 10 provided in the circulation path of the treated water circulating in the outer tank 2 and the inner tank 3, and the outside The treatment water discharge port 11 provided in the upper part of the tank 2 and the sludge extraction port 13 are comprised. The water tank volume of the microbial reaction tank 1 is not limited and can be adapted from a small scale to a large scale, but the effect is remarkably exhibited when the microbial reaction tank 1 is 20 m ³ or more, preferably This is a case where the present invention is applied to a microbial reaction tank having an internal volume of 30 to 6000 m ³ . When the volume of the treatment tank exceeds 6000 m ³ , it becomes difficult to create a circulating flow. Moreover, in the case of a small scale of less than 20 m ³ , the advantage of circulating the sludge up and down in the microorganism reaction tank 1 is reduced.

The outer tub 2 has a true cylindrical appearance including a cylindrical side surface 2b and an upper surface portion 2c on a base 2a serving as a bottom surface. A rotating shaft 7 for attaching a stirring blade or the like is provided at the center of the cylinder. The rotary shaft 7 is rotatably fixed by a frame 2d provided at the center of the circle of the base 2a and a bearing 2e provided at the center of the circle of the upper surface portion 2c. The rotating shaft 7 is rotated by the driving device 2f. The upper surface portion 2c fixes the rotating shaft 7 rotatably, and holds the cylindrical inner tank 3 with a support or the like.
A raw water supply port 10 is provided at the bottom of the outer tub 2. The raw water supply port 10 includes a plurality of discharge ports 10b or slits provided in the annular raw water supply unit 10a, which are disposed below the lower opening 3f of the cylindrical inner tank 3. By disposing the raw water supply port 10 in this way, the anaerobic sludge is sufficiently stirred. The raw water supply port 10 can be provided in addition to the lower part of the cylindrical inner tank 3 as long as it is a circulation path of the water to be treated.
In addition, a purified treated water discharge port 11 is provided at the upper part of the outer tub 2, and a settling immobilization prevention device 12 for preventing sedimentation and fixation of settled sludge is provided on the inner surface of the outer tub. Yes.

Examples of the anti-settling device include (1) a scraper provided on the inner wall of the lower part of the outer tank where the sludge settles, and (2) an agitating flow generator that generates an agitated flow of sludge along the inner wall of the lower part of the outer tank. . The stirring flow generator includes a movable fluid spray nozzle that sprays fluid while moving the inclined surface of the inner wall, a fluid spray nozzle that is fixed to the inclined surface of the inner wall at a predetermined interval, and moves to the inclined surface or lower surface of the inner wall. While pumping the sludge that has settled in the lower part of the outer tank and discharging it into the anaerobic microorganism treatment tank, or by fixing the sludge that has settled in the lower part of the outer tank at a predetermined interval and sucking the sludge that has settled in the lower part of the outer tank The pump etc. which discharge in a microorganisms processing tank can be mentioned.

FIG. 3 shows an example of a cross-sectional view of a microbial reaction tank provided with a self-propelled scraper for a scraper provided on the inner wall of the lower part of the outer tank in which sludge settles. A moving device 12e capable of moving along the upper peripheral edge of the outer tub is attached to the upper peripheral edge of the outer tub, and a scraper 12d is attached to the tip of the moving device 12e. By making this scraper 12d self-propelled along the inner wall of the lower part of the outer tub, the settled sludge is loosened to give fluidity. Sludge that is given fluidity will not settle and settle.

FIGS. 4 to 7 show an agitation flow generator that generates an agitation flow of sludge along the inner wall of the lower part of the outer tank. 4 is a cross-sectional view of a microorganism reaction tank provided with a movable fluid spray nozzle that sprays fluid while moving on the inclined surface of the inner wall, and FIG. 5 is fixed to the inclined surface of the inner wall at a predetermined interval. It is a figure which shows the example of the fluid spray nozzle. FIG. 6 and FIG. 7 are diagrams showing an example of a discharge pump replacing the nozzle.
The nozzle 12f arranged on the inclined surface at the lower part of the inner wall of the outer tank shown in FIG. 4 sprays the fluid sent from the blower or pump mounted on the moving device 12e attached to the upper peripheral edge of the outer tank to the accumulated sludge. be able to. Examples of the fluid include air, water, and sludge. By spraying a fluid from the nozzle 12f on the accumulated sludge, it is possible to impart fluidity to the deposited sludge and prevent sedimentation and fixation of the sludge.
The nozzle 12g shown in FIG. 5 is fixed at a predetermined interval, for example, a fixed interval, in the circumferential direction and the inclined direction of the inclined surface of the inner wall lower portion of the outer tub inner wall where the fluid is uniformly sprayed on the previously accumulated sludge. Arranged. By continuously or intermittently spraying fluid from the nozzle 12g, it is possible to impart fluidity to the deposited sludge and prevent sedimentation and fixation of the sludge. It is important that the fixed nozzle 12g has a structure in which a nozzle is provided above the inclined surface of the lower inner wall of the outer tank and the piping is installed in the direction of the circulating flow so as not to inhibit the circulating flow of sludge as much as possible.

The movable discharge pump 12h arranged on the inclined surface or the lower surface of the lower inner wall of the outer tub shown in FIG. 6 can self-run the lower inner wall of the outer tub by a moving device 12e attached to the upper peripheral edge of the outer tub. The discharge pump 12h includes a suction nozzle 12i that sucks sludge that has settled in the lower part of the outer tank, and a discharge port 12j that discharges the sucked sludge into the anaerobic microorganism treatment tank. By running the lower part of the inner wall of the outer tub while sucking and discharging the sludge, it is possible to impart fluidity to the deposited sludge and prevent sedimentation and fixation of the sludge.
The fixed discharge pump 12h, which is fixed to the inclined surface or the lower surface of the lower inner wall of the outer tub shown in FIG. 7, is fixedly disposed at a place where sludge is likely to accumulate. The discharge pump 12h includes a suction nozzle 12i that sucks sludge that has settled in the lower part of the outer tank, and a discharge port 12j that discharges the sucked sludge into the anaerobic microorganism treatment tank. It is important that the discharge pump 12h that is fixedly installed be installed by a method that does not impede the sludge circulation. For example, all the pump pipes are installed in parallel with the flow direction of the sludge circulation.

As shown in FIG. 2, the cylindrical inner tank 3 is arranged in the outer tank in which the settling and fixing prevention device 12 is provided.
The cylindrical inner tank 3 having a substantially circular cross section is divided into a cylindrical upper part 3c and a cylindrical lower part 3d by a partition wall 3a. A communication hole 3b is provided in the central portion of the partition wall 3a to connect the cylindrical upper part 3c and the cylindrical lower part 3d.
Even when the volume of the microorganism reaction tank is increased due to the presence of the partition wall 3a, the cylindrical upper part 3c and the cylindrical lower part 3d are sufficiently separated, and activated sludge treatment can be performed in each tank. The aerobic microorganism treatment reaction can be sufficiently performed in the cylindrical upper portion 3c, and the anaerobic microorganism treatment reaction can be sufficiently performed in the cylindrical lower portion 3d. When the area of the partition wall 3a becomes large, it is reinforced with a support member 3g or the like.
The communication hole 3b has a diameter that allows the activated sludge treated with anaerobic microorganisms to move from the cylindrical lower part 3d to the cylindrical upper part 3c, which is an aerobic microorganism treatment tank. The diameter of the communication hole 3b is adjusted by the volume of the microorganism reaction tank, the nature and amount of raw water to be treated, and the like.

The cylindrical upper portion 3c has a truncated cone-shaped top portion whose upper surface and bottom surface are open. That is, it is a shape in which the tip of the cylindrical portion is reduced in diameter by a predetermined angle in the height direction. The inclination angle of the cross section in the height direction passing through the center of the truncated cone is 40 to 60 degrees, preferably 45 degrees. By making the inclination angle within this range, the sludge contained in the water to be treated discharged from the upper part of the aerobic tank is likely to aggregate by flowing down the frustoconical outer surface, and the sludge can be rapidly forced to settle. Moreover, when sludge aggregates, separation of the sludge and the purified treated water becomes easy.
The cylindrical upper portion 3c is an aerobic microorganism treatment tank in which

air blowing ports

8 and 8a are provided. The air blowing port 8 is provided around the central shaft 7 and around the communication hole 3b, and can be fixed on the partition wall 3a by a support pillar (not shown). It is preferable that the air outlet of the air inlet 8 is preferably disposed downward because it can contribute to the agitation of the water to be treated and sludge in the aerobic tank.
The air blowing port 8a has a plurality of air holes 8c or air blowing portions 8b provided in the air blowing portion 8b. It can be made into the slit formed in the upper surface or side surface of this.
The amount of water to be treated is varied within the range of 3 to 20 without using a circulation pump, depending on the amount of air blown from the

air blowing ports

8 and 8a and the control amount of the circulation rate control device described later. Can do. Thereby, the aerobic microorganism treatment by an appropriate nitrification condition and the anaerobic microorganism treatment by an appropriate denitrification condition can be easily set. Furthermore, because the sludge solid-liquid separation is made very efficient by the forced sedimentation principle on the outer peripheral surface of the aerobic microorganism treatment tank having the above-mentioned inclination angle, the aerobic / anaerobic microorganism treatment reaction is efficiently carried out in the same vertical tank. Can be done.
In the aerobic tank, an alkali supply port or an acid supply port (not shown) can be provided.

The cylindrical lower part 3d is an anaerobic microorganism treatment tank having a volume that is 1/10 to 1 times the volume of the upper part of the cylinder. Within this volume range, for example, an aerobic microbial treatment reaction and an anaerobic microbial treatment reaction of raw water containing a high-concentration nitrogen-containing pollutant can be efficiently performed. In the anaerobic microorganism treatment tank, a denitrifying nutrient supply port (not shown) can be provided.
In addition, when there are few hydrogen donors in the raw water and nitrogen is denitrified by supplying a nitrogen donor such as methanol or acetic acid, the volume of the anaerobic microorganism treatment tank is made larger than that of the aerobic microorganism treatment tank. It is preferable.
The shape of the cylindrical lower portion 3d is a shape having an inverted truncated cone shape having an opening 3f having a larger area than the opening 3e of the cylindrical upper portion 3c at the lower portion of the cylinder. That is, it is a shape in which the tip of the cylindrical portion is reduced in diameter by a predetermined angle in the lower direction. By increasing the area of the opening 3f, the sludge can be easily stirred in the anaerobic microorganism treatment tank.
When the shape of the cylindrical lower portion 3d is the inverted truncated cone shape, it is preferable that the lower inner surface 2g of the outer tub 2 has the same angle as the predetermined angle because it is possible to prevent sludge from being settled and fixed.

The cylindrical inner tank 3 is provided with a stirring device for sufficiently carrying out the treatment reaction between the water to be treated and the activated sludge in the aerobic microorganism treatment tank as the cylinder upper part 3c and in the anaerobic microorganism treatment tank as the cylinder lower part 3d. Is provided.
The stirring device is preferably stirring

blades

7 a and 7 b fixed to a rotating shaft 7 attached to the center of the cylindrical inner tank 3. The stirring blade 7a is preferably provided in the cylindrical upper part 3c, and a turbine blade capable of sufficiently performing the aerobic microorganism treatment reaction is preferable. In addition to the turbine blade, any shape can be used as long as the number of rotations at which the aeration performance is not significantly lowered by the amount of air blown is relatively small and the air and water can be mixed.
The stirring blade 7b is a propeller blade that is provided in the cylindrical lower portion 3d and can sufficiently perform the anaerobic microorganism treatment reaction.

The partition wall 3 a provided in the cylindrical inner tub 3 is supported by a plurality of support columns 9 that are fixed and erected on the base 2 a that is the bottom surface of the outer tub 2.
The cylindrical inner tank 3 is held in the outer tank by a support by the support column 9 and a support tool bridged to the upper part of the outer tank 2. By providing the plurality of support columns 9, the indicator column 9 functions as a buffer column when the sludge is stirred, and the stirring becomes more efficient.

A circulation rate control device 4 for controlling the circulation rate in the reaction tank of the water to be treated is provided on the upper part of the cylindrical inner tank 3. Specifically, the control of the circulation rate of the water to be treated in the reaction tank by the circulation rate control device 4 is performed by opening and closing the liquid level control valve or vertically moving the liquid level control plate. The liquid level control valve allows the inner and outer cylinders to contact each other so that they can rotate freely. The liquid level can be adjusted by opening and closing the slit-shaped window on the side of the inner and outer cylinders. Is the lowest. The liquid level adjusting plate can adjust the surface by moving up and down in the outer cylinder provided with the slit-shaped window without providing the slit-shaped window in the inner cylinder, and at the lowest position of the liquid level adjusting plate, that is, the above-mentioned When the inner cylinder is lowered to the lowest level, the level of the water to be treated becomes the lowest. In FIG. 2, the water level is indicated by A.
Control of the circulation rate in the reaction tank can also be controlled by the amount of air blown from the air blowing port 8 and / or 8a. Increasing the amount of air blown increases the circulation rate. It is also possible to combine the opening and closing of the liquid level control valve and the air amount control.

As the anaerobic microorganism treatment tank and aerobic microorganism treatment tank increase in size, maintaining the circulating flow rate of sludge is not sufficient with aeration air alone, or harmful effects due to excessive air blowing may occur. There is. In preparation for such a case, the air inlet shown by 8a of FIG. 2 is needed. Due to the air blowing port 8a having poor aeration efficiency, there is an advantage that the adjustment of the air blowing amount and the ORP is much easier to adjust. For example, the air blowing port 8a is provided with an air blowing portion 8b having an annular shape in plan view, which is in communication with an external blower or the like around the stirring blade 7a in an aerobic portion which is the upper surface of the partition wall 3a. The part 8b is provided with a hole or a slit. This not only simply increases the amount of air, but also exhibits a baffle effect of the stirring blade 7a, and exhibits a synergistic effect that allows efficient stirring.

By adjusting the opening and closing of the liquid level control valve and / or the air blowing amount, the circulation rate of the water to be treated can be changed without using a pump. As will be described later, the water to be treated is transferred from the aerobic microorganism treatment tank 3c to the anaerobic microorganism treatment tank 3d through the control cylinder 5 disposed outside the tank, and from the anaerobic microorganism treatment tank 3d to the aerobic microorganism treatment tank 3c. Denitrification, dephosphorization, and the like are performed by circulating the water. Therefore, optimal denitrification, dephosphorization, etc. can be performed by controlling the circulation rate of the water to be treated based on a predetermined control program according to the detected value.

A control cylinder 5 is disposed on the upper outer periphery of the cylindrical inner tank 3. The control cylinder 5 is a cylinder whose upper surface and lower surface are open, and the lower surface 5 a of the control cylinder 5 is disposed close to the inclined surface of the cylindrical inner tank 3. A sludge sedimentation portion is formed in the inclined surface portion disposed close to the slurry, and sludge is concentrated and treated water is separated. Moreover, the rapid forced sedimentation of sludge is attained by arrange | positioning the lower surface 5a close. The distance between the lower surface 5a and the inclined surface of the cylindrical inner tub 3 is preferably adjustable. Further, the shape of the control cylinder 5 can be a right cylindrical shape in which the opening surfaces of the upper surface and the lower surface are the same area, or an inverted truncated cone shape in which the opening area of the upper surface is larger than the opening area of the lower surface.
In the microorganism reaction tank, a water quality measuring device 6 to be treated is provided inside and outside the cylindrical inner tank 2. This to-be-processed water quality measuring apparatus 6 is an apparatus which measures pH, ORP, and DO of to-be-processed water.

The circulation rate of water to be treated in the microorganism reaction tank is 3 to 20, preferably 5 to 20. If the circulation rate of the treated water is less than 3, the aerobic microbial treatment reaction is more likely to occur, and if it exceeds 20, the balance between the aerobic microbial treatment reaction and the anaerobic microbial treatment reaction is lost, and the raw water is denitrified and dehydrated. Unable to perform phosphorus. That is, by setting the treated water circulation rate within this range, the ORP of the treated water measured by the treated water quality measuring device is −10 mV or less, preferably −50 mV or less, and the aerobic microorganism treatment in the anaerobic microorganism treatment reaction tank. In the reaction vessel, it can be maintained at +10 mV or more, preferably +100 mV or more. As a result, the aerobic microorganism treatment reaction and the anaerobic microorganism treatment reaction are sufficiently performed, and denitrification and dephosphorization are continuously performed. Under such conditions, the pH in the aerobic microorganism treatment reaction tank is in the range of 4.5 to 8.5, preferably 5.5 to 7.5.

The wastewater treatment method using the microbial reaction tank 1 has the following excellent characteristics as compared with the conventional wastewater treatment method.
In the conventional wastewater treatment method, raw water and return sludge are mixed in a certain ratio and flow into the aeration tank, and then the returned sludge in contact with the sludge and treated water are separated in the sedimentation tank, which is the next step. The raw water is pushed out and flows until it is done.
The waste water treatment method using the microbial reaction tank 1 is a method in which a circulating flow of activated sludge circulating up and down is formed, and raw water is added to the circulating flow. It is an energy-saving wastewater treatment method because the sludge circulation flow is formed by using the upflow by aeration air used for microbial treatment without using a circulation pump to make the circulation flow of activated sludge. Furthermore, it is the processing method which can implement aeration of an aerobic microorganism processing tank efficiently.
The raw water may be added anywhere in the circulation flow path, but is preferably an aerobic microorganism treatment tank. More preferably, an anaerobic microorganism treatment tank is suitable. In the case of the treatment using the circulating flow in the wastewater treatment method of the present invention, even the raw water having at least BOD of 800 mg / L and the total nitrogen amount (hereinafter referred to as TN) of 40 mg / L or more is treated. The BOD is usually extremely low, 20 mg / L or less, and generally the water quality of the discharged water can be operated at a BOD of 10 mg / L or less.
In addition, if raw water is added to the sludge sedimentation part in the circulation flow path formed on the outer peripheral surface of the cylindrical inner tank that is an aerobic microorganism treatment tank, the contact between the sludge and the raw water becomes insufficient, and Adsorption may be insufficient. In that case, contaminated substances in the raw water which is partially untreated may be mixed with the treated water, resulting in deterioration of the treated water. However, when the water quality regulation value is loose, raw water can be added to the sludge sedimentation part in the circulation flow path, for example, as a primary treatment facility such as sewage discharge with a BOD of 300 mg / L or less or 600 mg / L or less. There is a case.

Hereinafter, the circulation of the water to be treated and the activated sludge in the microorganism reaction tank 1 will be described with reference to FIG. FIG. 8 is a diagram showing a circulation path of water to be treated and activated sludge in the microorganism reaction tank 1. In FIG. 8, the hatched portion is a portion where the concentration of activated sludge is high, and the arrow represents the circulation direction of the treated water and activated sludge.

The microorganism reaction tank 1 contains activated sludge in an amount of 5,000 to 12,000 mg / L in terms of solid content, and the treated raw water 1 first comes into contact with the activated sludge in an anaerobic state within the cylindrical lower part 3d to denitrify it. Reaction takes place. The treated raw water 1 supplied from the raw water supply port 10 and the circulated activated sludge are circulated in the lower part 3d of the cylinder by the rotation of the stirring blades or the air jet from the air diffuser to cause an anaerobic microorganism treatment reaction.
Next, the raw water and the activated sludge move through the communication hole 3b to the cylindrical upper portion 3c into which air is blown, and in contact with the activated sludge in the cylindrical upper portion 3c in an aerobic state, the rotation of the stirring blade or the air blowing port As a result of more air ejection, the nitrification reaction, which is an aerobic microorganism treatment reaction, proceeds in the cylindrical upper part 3c. As the nitrification reaction proceeds, the pH of the treated water decreases. The pH, ORP, and DO of the liquid to be treated are measured by the treated water quality measuring device 6, and the circulation amount of the raw water or the water to be treated is determined based on these values. Specifically, the amount of air blown is adjusted so that the ORP can be maintained at +10 mV or more in an aerobic reaction treatment tank where nitrification reaction is performed, and -10 mV or less in an anaerobic reaction treatment tank where denitrification reaction is performed. Circulate treated water. The circulation amount can be easily achieved by controlling the air amount and / or the circulation rate control device without using a circulation pump or the like. For this reason, the wastewater treatment method of the present invention is an energy-saving wastewater treatment method. In addition, since the equipment including the microbial reaction tank can adjust each unit of the microbial reaction, it is easy to program these controls in advance and automatically operate unattended, and has a feature as a labor-saving plant. Yes.

The circulation rate is controlled by the circulation rate control device 4, and the treated water and a part of the activated sludge discharged from the upper part of the cylindrical upper part 3c flow down on the frustoconical outer peripheral surface having an inclination angle of 45 degrees. The treated water and activated sludge that have flowed out are activated by passing through the control cylinder 5 disposed close to the inclined surface of the frustoconical outer peripheral surface and the sludge concentrating part 5b formed by the inclined surface. Rapid forced sedimentation of sludge becomes possible. Moreover, separation of the purified treated water and activated sludge becomes easy, and the separated treated water is discharged from the treated water discharge port 11.
The activated sludge that has been rapidly forced to settle is concentrated and deposited between the inner surface of the outer tank and the outer peripheral surface of the inner tank. The accumulated activated sludge moves to the anaerobic microorganism treatment reaction section while mixing with the water to be treated and circulates in the microorganism reaction tank.
The wastewater treatment method of the present invention can easily absorb fluctuations in the load of raw water by circulating the inside of an anaerobic / aerobic tank at a circulation rate of 3 to 20 while the activated sludge is concentrated. Further, since the circulation rate is maintained within this range, the activated sludge is acclimatized and becomes an activated sludge that is optimal for wastewater treatment. Under such conditions, the pH in the aerobic treatment tank is in the range of 4.5 to 8.5, preferably 5.5 to 7.5.

In a microbial reaction tank, when the BOD load of raw water is small but the nitrogen concentration is high, denitrifying nutrients made of organic substances such as proton donors, such as methanol, are added to the anaerobic reaction treatment section. In this case, since the pH of the treated water is likely to increase, it is preferable to add a mineral acid such as hydrochloric acid.

The waste water treatment method of the present invention may use one microbial reaction tank or a plurality of tanks. In this case, the discharged water from the first tank is introduced into the raw water supply port of the second tank. For example, when two microbial reaction tanks are connected in series, the ratio of the volume of the nitrification reaction part and the volume of the denitrification reaction part in the second tank can be changed more effectively by changing the ratio in the first tank. Waste water treatment can be performed. Specifically, denitrification and dephosphorization can be performed by making the volume ratio smaller than that of the first tank.

By placing the microbial reaction tank in the wastewater treatment process, (1) the anaerobic and aerobic operation can be performed by suppressing the generation of harmful gases, so that the self-digestion ability of activated sludge cells is improved. As microbial cells capable of selectively degrading pollutants in raw water are acclimatized, it is possible to easily treat hardly decomposable substances.

The renovation method of the existing wastewater treatment facility of the present invention is a method of newly adding the above microbial reaction tank to the existing wastewater treatment facility. By adding a new microbial reaction tank and circulating the sludge through this microbial reaction tank, it is possible to reduce the odor of sludge generated by wastewater treatment in the combined sewer system, especially in urban areas. It becomes possible. Moreover, the sludge storage tank and the dehydration apparatus which occupied the important part with the existing waste water treatment equipment become unnecessary, and the installation area of a waste water treatment equipment can be made small.

Example 1
Inflow raw water of the combined sewer system was treated by the method shown in FIG. The microorganism reaction tank shown in FIG. 2 was used, and the sludge separator was operated as a centrifugal dehydrator by operating a shear press dehydrator at 2000 G to dehydrate sludge.
The quality of the influent raw water was BOD: 150 mg / L, COD: 89 mg / L, SS: 100 mg / L (evaporation residue: 34 mg / L), n-Hex: 9 mg / L, TN: 12 mg / L . The amount of treated water is 4000 m ³ / day.
The water quality of the discharged water obtained by this method was BOD: 9 mg / L, COD: 11 mg / L, SS: 15 mg / L, n-Hex: 0.2 mg / L, TN: 1 mg / L. . Moreover, the dewatered sludge obtained from the centrifugal dehydrator as surplus sludge had a water content of 65% by weight at 0.45 t / day. The obtained dehydrated cake had almost no foul odor and there was almost no fear of foul odor even if it was naturally dried in the atmosphere. The measurement result of the burning residue of this sludge was 75% by weight, and it was found that most of the sludge component was an inorganic component. The sludge concentration in the microorganism reaction tank used in the present invention was 6500 mg / L, and there was almost no change.

Comparative Example 1
After separating oil and SS by coagulation sedimentation using an inorganic flocculant in the sedimentation tank, the soluble organic content suitable for microbial treatment is sent to the aeration tank as the raw water for treatment, and the conventional wastewater treatment method is performed using activated sludge. The raw water of Example 1 was used. The amount of excess sludge withdrawn and the amount of sludge generated were 50 m ³ / day of sludge with an excess sludge concentration of 8000 mg / L, dehydrated with a dehydrator, and 2.6 t of dehydrated cake with a moisture content of 85% by weight. / Day occurred. Moreover, the generated sludge has a strong bad odor, requires deodorizing equipment, and is a factor of deteriorating the surrounding environment.

Since the method of the present invention is a wastewater treatment method in which a malodor is hardly generated in a dehydrated cake, it can be used for wastewater treatment of a combined sewer system installed in an urban area or its neighborhood.

DESCRIPTION OF SYMBOLS 1 Microbe reaction tank 2 Outer tank 3 Cylindrical inner tank 4 Circulation rate control apparatus 5 Control cylinder 6 Water quality measuring apparatus 7 Rotating shaft 8 Air blowing port 9 Support pillar 10 Raw water supply port 11 Treated water discharge port 12 Settling prevention prevention Device 13 Sludge outlet 14 Raw water aeration tank 15 Sludge separator

Claims

An activated sludge treatment method comprising a raw water aeration adjusting tank and a microbial reaction tank, and treating wastewater by a circulation system for circulating sludge-containing treated water generated in the microbial reaction tank to the raw water aeration adjusting tank,
Separating the sludge-containing treated water generated from the microbial reaction tank into the inorganic sludge and the treated raw water 2 by a sludge separation device provided between the microbial reaction tank and the raw water aeration control tank Supplying the treated raw water 2 to the raw water aeration tank,
The raw water mixed with the treated raw water 2 is aerated in the raw water aeration adjusting tank so that the oxidation-reduction potential becomes a positive value, and then the adjusted treated raw water 1 is supplied to the microorganism reaction tank. 3 and
And the step 4 of using discharged water from the microbial reaction tank as discharged water,
The microbial reaction tank includes an outer tank, a cylindrical inner tank disposed in the outer tank and having openings on the upper and lower sides, and a circulation rate of water to be treated provided in the upper part of the cylindrical inner tank. A circulation rate control device to control, a control cylinder provided on the upper outer periphery of the cylindrical inner tank to settle sludge, a water quality measuring apparatus to be treated provided on the outside and inside of the cylindrical inner tank, The raw water supply port provided in the circulation path of the water to be treated that circulates in the outer tank and the inner tank, and the treated water discharge port provided in the upper part of the outer tank,
The cylindrical inner tub is divided into a cylindrical upper part and a cylindrical lower part by a partition wall having a communication hole in a central part, and the cylindrical upper part has a truncated cone-shaped top part having an open top surface and a bottom surface. The inclination angle of the cross section in the height direction passing through the center is 40 to 60 degrees, and a plurality of air blowing ports are provided around the communication hole in the upper part of the cylinder and at the periphery of the partition wall, and are arranged in the outer tank. The aerobic microorganism treatment tank is disposed inside the outer tank with the partition walls supported by a plurality of support pillars, and the cylindrical lower part is an anaerobic microorganism treatment tank having an opening on the bottom surface,
A stirrer for stirring the aerobic microorganism treatment tank and the anaerobic microorganism treatment tank is provided,
Means for detecting at least one measurement value selected from the hydrogen ion concentration, redox potential, and dissolved oxygen content of the water to be treated measured by the water quality measuring device;
In accordance with the detected measurement value, the water level of the water to be treated provided in the circulation rate control device arranged at the upper part of the cylindrical inner tank is adjusted to be the lowest when the liquid level control valve is fully opened. Select from opening and closing of the liquid level control valve, vertical movement of the liquid level control plate that adjusts the level of water to be treated to the lowest level at the lowest level of the liquid level control plate, and the amount of air blown from the air inlet Means for controlling the in-tank circulation rate of the treated water to 3 to 20 by controlling at least one amount of
The raw water supplied from the raw water supply port circulates in the tank together with the activated sludge through the inside of the cylindrical inner tank, the outer peripheral surface of the cylindrical inner tank, and the activated sludge settled in the lower part of the outer tank. An activated sludge treatment method characterized in that anaerobic microbial treatment and aerobic microbial treatment are continuously performed.
The activated sludge treatment method according to claim 1, wherein the sludge separation device is a centrifugal dewatering device.
2. The activated sludge treatment method according to claim 1, wherein the microorganism reaction tank is provided with an anti-settling device for preventing the settling and fixing of the sludge inside and outside the outer tank and the inner layer.
4. The activated sludge treatment method according to claim 3, wherein the settling immobilization prevention device is a scraper provided on an inner wall of a lower part of the outer tank in which sludge settles.
4. The activated sludge treatment method according to claim 3, wherein the settling immobilization preventing device is a stirring flow generator for generating a stirring flow of sludge along the inner wall of the lower part of the outer tank.
A method of repairing an existing wastewater treatment facility that reduces the amount of sludge generated in a wastewater treatment facility from the amount of sludge generated in the existing wastewater treatment facility,
The refurbishing method includes a step of newly installing the microorganism reaction tank and the sludge separation apparatus according to claim 1;
A method for refurbishing existing wastewater treatment equipment, comprising the step of circulating the sludge-containing treated water by the method according to claim 1 through the newly installed microorganism reaction tank and sludge separation device.