KR102779189B1 - Sewage treatment system using active sludge transport of bioreactor - Google Patents

Abstract

The present invention relates to a sewage treatment device utilizing the return of activated sludge from a biological reactor, which treats sewage using a biological reaction and returns the activated sludge generated during the treatment process to a reaction zone of a biological reactor with a low concentration of activated sludge, thereby controlling the concentration of the activated sludge, thereby improving the treatment efficiency of the sewage.
The sewage treatment device utilizing the return of activated sludge of a biological reactor according to the present invention comprises a biological reactor (10) divided into a plurality of reaction zones through a plurality of partition walls formed between an inlet and a discharge zone; and a return device (100) installed in an activated sludge recovery zone (MLSS 6,000 to 8,000 mg/l) of a reaction zone closer to a discharge zone than to the inlet among the plurality of reaction zones of the biological reactor to return and mix activated sludge in the activated sludge recovery zone to the reaction zone on the inlet side to control concentration, and the return device receives a mixture of activated sludge and treated water in the activated sludge recovery zone, settles the activated sludge on the bottom, and then returns the mixture to the reaction zone on the inlet side, while draining the supernatant separated from the activated sludge to the reaction zone on the discharge side.

Description

Sewage treatment system using active sludge transport of bioreactor

The present invention relates to a sewage treatment device, and more specifically, to a sewage treatment device utilizing activated sludge return of a biological reactor, which treats sewage using a biological reaction and returns activated sludge generated during the treatment process to a reaction zone of a biological reactor with a low activated sludge concentration to thereby control the concentration, thereby improving the treatment efficiency of sewage.

This section only provides background information related to the subject matter of the present application and is not necessarily prior art.

In recent centuries, the temperature of seawater has increased due to global warming, and the discharge of nutrients such as nitrogen and phosphorus has increased rapidly due to industrialization and urbanization, causing eutrophication of coastal waters and lakes, resulting in red and green tides, seriously polluting the water environment.

Accordingly, in addition to regulatory measures such as the implementation of the total pollutant load system that continuously strengthens the effluent quality standards for sewage treatment plants and permits development on the premise of reducing pollutants, the effluent from sewage treatment plants is encouraged to be recycled as reclaimed water or river maintenance water, and in accordance with the strengthening of effluent quality standards for public sewage treatment plants (effective January 1, 2008) to prevent eutrophication of lakes and other bodies of water, newly installed public sewage treatment facilities are to be installed with a focus on nitrogen and phosphorus treatment, and existing facilities are to be installed with advanced treatment facilities.

However, despite the government's policy as mentioned above, most of the sewage treatment facilities currently in operation nationwide are operated by secondary treatment facilities based on the activated sludge method. These existing facilities using the activated sludge method are composed of an aeration tank and a sedimentation tank. In the aeration tank where oxygen is supplied, organic matter in the sewage is removed through the metabolic process of microorganisms, and then in the sedimentation tank, the treated water from which the microorganisms and organic matter have been removed is separated by gravity sedimentation. Some of the sludge that has settled in the sedimentation tank is returned and circulated internally to maintain the microbial concentration in the aeration tank, and the remaining sludge is discharged to the outside. These existing activated sludge facilities had the problem that they were not suitable for advanced treatment of nutrients such as nitrogen and phosphorus contained in sewage.

Meanwhile, advanced treatment methods such as A2O, A/O, MLE, and VIP are being used to remove nutrients such as nitrogen and phosphorus contained in sewage, but these methods require additional facilities such as aeration tanks and sedimentation tanks of the existing activated sludge process, as well as several reaction tanks such as anoxic tanks and anaerobic tanks, and pumps for internal circulation, for biological reactions such as nitrification, denitrification, and phosphorus uptake and release, which are essential for the removal of nitrogen and phosphorus.

Therefore, in the case of currently operating sewage treatment plants, only recently constructed treatment facilities are being installed with advanced treatment facilities capable of treating nitrogen and phosphorus, and in order for existing sewage treatment facilities to apply advanced treatment processes to the existing activated sludge method, anoxic and anaerobic tanks must be additionally installed in the existing activated sludge facility, and facilities for internal circulation to the anoxic tank must also be additionally installed. However, in the case of most sewage treatment facilities, additional land for installing such additional facilities is not secured, making it difficult to improve existing facilities.

Patent registration No. 10-2009674 only features the structure of a sedimentation tank, including a sedimentation tank, a flow adjustment tank, an initial sedimentation tank, a biological reaction tank, a final sedimentation tank, a filtration facility tank, a disinfection tank, and a sludge thickening tank, and does not include a technology for recovering activated sludge from the biological reaction tank and returning it to the reaction zone on the inflow side.

According to the prior art, it was designed and devised in a way that the appropriate activated sludge concentration is determined based on low concentration, high concentration, and temperature according to the concentration of a certain amount of activated sludge inflow, and since it is a customized sewage treatment method of a general concept, advanced treatment methods such as A2O and A/O were introduced by defining a stage-by-stage section in the existing activated treatment method, but this method may result in the operation of a high F/M (ratio food-to-microorganism ratio) and there is a problem that the discharged water quality may deteriorate due to pollutants according to the increase or decrease in the sludge volume in the final sedimentation tank solid-liquid separation stage.

In addition, when the activated sludge concentration of the biological reactor is operated at a high level (high F/M ratio) to increase treatment efficiency, there are problems such as water quality accidents and operational difficulties due to overflow phenomenon and discharge at the final sedimentation tank interface, and increased chemical costs leading to increased maintenance costs.

Registered Patent No. 10-2009674

The present invention is intended to solve the above-mentioned problems, and provides a sewage treatment device utilizing the return of activated sludge from a biological reactor, which treats sewage using a biological reaction and returns the activated sludge generated during the treatment process to a reaction zone of a biological reactor with a low concentration of activated sludge to thereby control the concentration of the activated sludge, thereby improving the treatment efficiency of the sewage.

The sewage treatment device utilizing the return of activated sludge of a biological reactor according to the present invention comprises: a biological reactor divided into a plurality of reaction zones through a plurality of partition walls formed between an inlet and a discharge port; and a return unit installed in an activated sludge recovery zone (MLSS 6,000 to 8,000) as a reaction zone closer to the discharge port than the inlet port among the plurality of reaction zones of the biological reactor to return the activated sludge in the activated sludge recovery zone to the reaction zone on the inlet side for mixing and thereby controlling the concentration; and the return unit is characterized in that it receives a mixture of activated sludge and treated water in the activated sludge recovery zone, settles the activated sludge on the bottom, and then returns the mixture to the reaction zone on the inlet side, while draining the supernatant separated from the activated sludge to the reaction zone on the discharge side.

The above activated sludge recovery zone is characterized by being partitioned through a partition wall formed in the above reaction zone.

It is characterized in that the mixture in the above activated sludge recovery zone is supplied to the above return device or bypassed to the next reaction zone.

According to the sewage treatment device utilizing the return of activated sludge of a biological reactor according to the present invention, the reaction zone at the optimal location among the multi-stage reaction zones of the biological reactor is set as the activated sludge recovery zone, and the activated sludge (microbial flocs) is recovered and returned to the reaction zone in front (toward the inlet) to control the concentration of the activated sludge, thereby improving the purification rate of the sewage, and by separating the activated sludge (MLSS 6,000 to 8,000 mg/l) and supernatant in the biological reactor and supplying the supernatant with a low concentration (designed SS concentration 2,000 mg/l) to the last reaction zone of the biological reactor and returning only the activated sludge to the reaction zone with a lower activated sludge concentration than this, the purification efficiency of the sewage can be further improved, and the sedimentation coagulation power of the activated sludge can be promoted in the final sedimentation tank, and the stabilization of the flocs can be advantageous in that the chemical cost and treatment efficiency can be increased.

In addition, the activated sludge (MLSS design concentration 6,000-8,000 mg/l) can be returned to the reaction zone of the biological reactor to maintain the concentration of the mixture at an appropriate level, thereby increasing the reaction speed of microorganisms with a low F/M ratio, and thus phosphorus release, excess adsorption, nitrification, and denitrification are superior to the existing advanced treatment method, so there is also an effect of shortening the retention time.

In addition, it has the effect of helping the operation of related facilities by reducing the burden of returning sludge from the final sedimentation tank.

In addition, since treated water can be quickly supplied to the next reaction zone during maintenance of the return machine or under conditions where sewage treatment is possible without returning the activated sludge, it has the effect of operating the sewage treatment facility without stopping.

Figure 1 is a plan view showing the installation location of a sewage treatment device using activated sludge return of a biological reactor according to the present invention.
Figure 2 is a plan view showing an example of an activated sludge recovery area being defined in a sewage treatment device using activated sludge return of a biological reactor according to the present invention.
Figure 3 is a configuration diagram of a return device applied to a sewage treatment device using activated sludge return of a bioreactor according to the present invention.
Figure 4 is a plan view showing the flow path of the activated sludge recovery zone and the fourth reaction zone to which the sewage treatment device using the return of activated sludge of the biological reactor according to the present invention is applied.

In the following description of the present invention, if it is judged that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. In addition, the terms described below are terms defined in consideration of the functions in the present invention, and these may vary depending on the intention or custom of the user or operator. Therefore, the definitions should be made based on the contents throughout this specification.

As shown in Fig. 1, the sewage treatment device utilizing the return of activated sludge from a biological reactor according to the present invention controls the concentration by installing a return device (100) in the concentration control reaction zone of a biological reactor (10) that treats influent water through a biological reaction through a multi-stage biological reaction and returning and supplying activated sludge to the reaction zone on the inflow side.

The bioreactor (10) to which the present invention is applied is formed, for example, such that the inlet (11) and the outlet (12) are formed so as to face each other on both sides, and a plurality of (three as an example) partition walls (13, 14, 15) are installed inside between the inlet (11) and the outlet (12) to divide the bioreactor into four reaction zones (16, 17, 18, 19), and when the total residence time for the inlet water to sequentially pass through the reaction zones (16, 17, 18, 19) through the inlet (11) and then be discharged to the outlet (12) is 100%, for example, the first reaction zone (16) is within 20%, the second reaction zone (17) is 21-40% (or 21-69%), the third reaction zone (18) is 41-80% (or 70-80%), and the fourth reaction zone (19) is It's 81~100%.

In the present invention, for example, a return device (100) is installed in the 3rd reaction zone (18) to return the activated sludge to the reaction zone (16, 17) on the inflow side, and the 3rd reaction zone (18) can be called a concentration control reaction zone (activated sludge recovery zone). In the above structure, the reason why the activated sludge is recovered and returned in the 3rd reaction zone (18) is because it is the optimal condition (MLSS 6,000 to 8,000) for concentration control of the activated sludge, and it is difficult to recover and control the concentration of the activated sludge at an appropriate concentration in the remaining reaction zones. That is, the standard for recovering and returning the activated sludge by the present invention is MLSS 6,000 to 8,000, and it is also possible that the location at this time is not the 3rd reaction zone.

The aforementioned bioreactor (10) is operated in a known advanced treatment facility, and parts not related to the present invention are omitted for description. For example, an aeration pipe for aerating air may be applied.

The first reaction zone (16), the second reaction zone (17), and the third reaction zone (18) deliver treated water through pipes (or overflows), etc., and preferably, the pipes are arranged in a zigzag shape.

The third reaction zone (18) and the fourth reaction zone (19) supply treated water through a return device (100).

As shown in Fig. 2, the return device (100) is installed in a location where the MLSS is 6,000 to 8,000, and usually, the location where the retention time of the treated water in the biological reactor is 70 to 80% satisfies the above concentration. Therefore, an activated sludge recovery zone (18-1) can be formed separately in the 3rd reaction zone (18) partitioned by the partition wall (14, 15). Of course, in the case where the retention time in the 3rd reaction zone (18) is 70 to 80%, the 3rd reaction zone (18) is the installation zone of the return device (100), i.e., the activated sludge recovery zone.

The activated sludge recovery zone (18-1) is a separate space partitioned by a partition wall (18-2) within the third reaction zone (18) and is located far from the discharge port of the second reaction zone (17). Hereinafter, an example of a return device (100) being installed within the activated sludge recovery zone (18-1) will be described. Of course, the activated sludge recovery zone (18-1) is not necessarily limited to being partitioned by a partition wall (18-2) and also includes a location that can be operated without a separate partition.

In addition, the partition wall (18-2) can be formed during the construction of the bioreactor (10), or can be additionally installed to fit the return device (100). In the latter case, any material and structure that separates the perimeter of the return device (100) from the third reaction zone (18) is possible, and for example, a metal plate (or box) or a circular (or square) top-bottom open-type tube structure is also possible.

When a partition wall (18-2) is applied, it is possible to configure the flow path connecting the 3rd reaction zone (18) and the activated sludge recovery zone (18-1) as an openable type, and thus, under conditions where recovery of activated sludge is difficult, it is possible to prevent the mixture from flowing into the activated sludge recovery zone (18-1) from the 3rd reaction zone (18).

As shown in FIG. 3, the return device (100) includes a tank (110) having a space inside and receiving a mixture inside an activated sludge recovery zone (18-1) through a supply pipe (111), a water level sensor (120) installed inside the tank (110) to detect the water level inside, a stirrer (130) for stirring the mixture (mixture of activated sludge and treated water) introduced into the tank (110), a screening net (140) installed transversely inside the tank (110) to separate the activated sludge and supernatant, a return unit (150) for returning the activated sludge separated inside the tank (110) to the first and second reaction zones (16, 17) located in the front, toward the inlet (11), and a supernatant discharge unit (160) for discharging the supernatant separated inside the tank (110) to the fourth reaction zone (19), which is the next reaction zone.

The tank (110) provides a space in which a mixture is introduced into it and separated into activated sludge and supernatant. Considering that the activated sludge settles to the bottom, a supply pipe (111) is formed upward from the bottom. The supply pipe (111) is formed to penetrate the inside and outside of the tank (110), and the discharge-side end is formed to be open toward the top, while the inlet-side end is positioned at a location where the mixture is introduced.

The tank (110) is composed of a tank body that opens toward the top for maintenance and a cover that opens and closes the top of the tank body, and is installed via legs or the like supported on the floor of the activated sludge recovery area (18-1).

The water level sensor (120) is installed inside the tank (110) to detect the water level, which is an example of a sensor used to check the amount of mixture contained inside the tank (110).

Additionally, an MLSS meter (121) that measures the concentration of suspended solids in the mixture (supernatant) in the tank (110) as another sensor may be installed.

The agitator (130) agitates the mixture supplied into the tank (110) to help separate the activated sludge and the supernatant, and includes a motor installed on the outside of the tank (110) and a agitator rod installed on the inside of the tank (110) and rotated by the motor.

A screening net (140) is installed transversely inside the tank (110) to divide the lower part into a sludge recovery part and the upper part into a supernatant recovery part, and prevents activated sludge from passing upward through a number of holes.

The return section (150) includes a main return pipe (151) that discharges activated sludge collected in the tank (110) to the outside, branch return pipes (152, 153) that branch from the main return pipe (151) and return activated sludge to the first reaction zone (16) and the second reaction zone (17), a pump (154) that pumps activated sludge inside the tank (110), and valves that open and close the main return pipe (151) and branch return pipes (152, 153).

The main return pipe (151) is installed so that one side penetrates the bottom from the outside of the tank (110) and passes through to the inside, and is piped along the first and second reaction zones (16, 17).

The branch return pipes (152, 153) are each branched from the main return pipe (151) and have discharge sections positioned inside the first and second reaction zones (16, 17) to return the activated sludge.

The operation of the pump (154) and the opening and closing of the main/branch return pipes (151, 152, 153) can be based on the MLSS concentration (or water quality) of the reaction zones (16, 17) on the inflow side. That is, a measuring device for measuring the activated sludge concentration (or water quality) is installed in each of these reaction zones (16, 17), and the controller compares the measured value of the measuring device with a reference value, and returns the activated sludge to the reaction zone (16, 17) below the reference value to control the concentration. In addition, the MLSS in the activated sludge recovery zone (18-1) is measured, and if the concentration is appropriate, the activated sludge is returned to the front reaction zone.

The supernatant discharge unit (160) is installed inside the tank (110) and includes a supernatant inlet box (161) into which supernatant is introduced, a supernatant discharge pipe (162) that is piped from the supernatant inlet box (161) to the fourth reaction zone (19) and discharges supernatant to the fourth reaction zone (19), and a valve that opens and closes the supernatant discharge pipe (162).

The supernatant inlet box (161) is a structure in which supernatant overflows and flows in or flows in through an inlet hole formed on the periphery, and can be configured to rise or fall in response to the flow rate (water level) of supernatant. For example, a buoyancy body is mounted on the periphery and connected to a supernatant discharge pipe (162) through a corrugated pipe, that is, it is always placed on the water surface by the buoyancy of the buoyancy body, and at this time, it rises or falls through the expansion and contraction of the corrugated pipe.

In addition, it includes a bypass-type feeder (200) for supplying the mixture to the feed pipe (111) of the return device (100).

The bypass-type feeder (200) includes a feed box (210) into which a mixture in an activated sludge recovery area (18-1) is introduced, a buoyancy body (220) for floating the feed box (210) at a certain location on the water surface through buoyancy, a delivery pipe (230) for delivering the mixture introduced into the feed box (210), a corrugated pipe (240) for connecting the feed box (210) and the delivery pipe (230) and for inducing the elevation of the feed box (210), a three-way valve (250) for supplying the mixture delivered through the delivery pipe (230) to the feed pipe (111) of the return device (100) or bypassing it to the fourth reaction zone (19), a bypass pipe (260) for bypassing the mixture bypassed through the three-way valve (250) to the fourth reaction zone (19), and may include a pump for forcibly supplying the mixture by pumping it.

The supply box (210) has an opening formed at the top or periphery to allow the mixture to flow in and be supplied to the corrugated pipe (240) at the bottom.

The three-way valve (250) connects the delivery pipe (230) to the supply pipe (111) to supply the mixture to the return device (100) or connects the delivery pipe (230) to the bypass pipe (260) to return the mixture to the fourth reaction zone (19).
The basis for this operation is the water quality of the treated water in the activated sludge recovery area (18-1), and for this purpose, a water quality sensor (such as an MLSS meter to measure the concentration of activated sludge or measure water quality) is installed in the activated sludge recovery area (18-1) to measure the water quality.
The controller stores a reference value and compares the measured value of the water quality sensor with the reference value. If the measured value satisfies the reference value, the mixture is guided to the fourth reaction zone (19). If the measured value does not satisfy the reference value, the mixture is supplied to the return device (100).

According to this bypass type feeder (200), unnecessary return of activated sludge by the returner (100) is reduced, and sewage can be treated even when the returner (100) is stopped for maintenance.

In addition, as shown in FIG. 4, it is also possible to supply the mixture in the 3rd reaction zone (18) to the activated sludge recovery zone (18-1) or to directly supply the mixture in the 4th reaction zone (19) by bypassing the activated sludge recovery zone (18-1). As a configuration for this, holes (18-3, 15-1) are formed in the partition walls (18-2, 15) respectively for supplying the mixture in the 3rd reaction zone (18) to the activated sludge recovery zone (18-1) or the 4th reaction zone (19), and gates (18-4) that open and close these holes (18-3, 15-1) in opposite directions are installed. At this time, the partition walls (18-2, 15) are formed to have a right angle to each other, and the holes (18-3, 15-1) are arranged to have a right angle, and their positions are the opening and closing paths of the gates (18-4).

The gate (18-4) is configured as a single gate to open and close the holes (18-3, 15-1) in opposite directions, that is, one end is rotatably installed between the holes (18-3, 15-1) and rotates by a motor or the like to open the hole (18-3) of the activated sludge recovery zone (18-1), close the hole (15-1) on the 4th reaction zone (19) side, or conversely, close the hole (18-3) of the activated sludge recovery zone (18-1), open the hole (15-1) on the 4th reaction zone (19) side.

The opening and closing operation of the gate (18-4) is based on the measurement values of the water quality sensor described above.

The above gate (18-4) and related configurations are optionally applied to perform the same function as the bypass type supply (200).

A sewage treatment device utilizing the return of activated sludge from a biological reactor according to the present invention can be constructed as a sewage treatment facility as follows.

A screen and a sedimentation tank for removing sediment or silt; a first sedimentation tank for storing sewage water passing through the screen and the sedimentation tank and retaining it for a predetermined period of time to sediment the sediment and separate it from the supernatant; a biological reactor (10) for storing the supernatant discharged from the first sedimentation tank in a space where microorganisms inhabit for a set period of time and supplying oxygen to emit carbon dioxide and consume nitrogen and phosphorus through a reaction with microorganisms; a sewage treatment device using the return of activated sludge of the biological reactor according to the present invention installed and operated in the biological reactor (10); a final sedimentation tank for storing treated water discharged from the biological reactor (10) for a set period of time to separate the activated sludge and the supernatant; a filtration filter and a total phosphorus treatment facility for removing nitrogen or phosphorus from the treated water discharged from the final sedimentation tank; and a sterilization unit for providing a disinfectant and ultraviolet rays to the treated water discharged from the filtration filter and the total phosphorus treatment facility to remove microorganisms.

Among the above configurations, configurations other than those of the present invention are known technologies, so a detailed description thereof will be omitted.

10: Bioreactor, 11: Inlet
12: Exhaust, 13,14,15,18-2: Bulkhead
16,17,18,19: Reaction zone, 18-1: Activated sludge recovery zone
100: Return, 110: Tank
120: Water level sensor, 121: MLSS meter
130: Mixer, 140: Screen
150: Return section, 160: High-grade discharge section
200: Bypass type feeder, 210: Feeder box
220: Buoyancy body, 230: Transmission tube
240: Corrugated pipe, 250: 3-way valve
260 : Bypass pipe,

Claims (5)

It is installed in a bioreactor divided into multi-stage reaction zones through multi-stage baffles installed at regular intervals along the flow direction of the treated water between the inlet and outlet.
Among the multi-stage reaction zones of the above biological reactor, a return device is installed in the activated sludge recovery zone of the reaction zone closer to the discharge zone than the inlet zone to control the concentration by returning and mixing the activated sludge in the activated sludge recovery zone to the reaction zone on the inlet side.
The above-mentioned return device receives a mixture of activated sludge and treated water from the above-mentioned activated sludge recovery area, settles the activated sludge on the bottom, and returns it to the reaction area on the inlet side, while discharging the supernatant separated from the activated sludge to the next reaction area.
The above activated sludge recovery zone is partitioned by a partition formed inside the above reaction zone,
A sewage treatment device utilizing activated sludge return of a biological reactor, characterized in that the mixture of a reaction zone having the activated sludge recovery zone is supplied to the activated sludge recovery zone or the next reaction zone, the holes being respectively formed in the partition walls dividing the activated sludge recovery zone and the partition walls dividing the next reaction zone, and the gates opening and closing the holes in opposite directions, wherein the holes of the activated sludge recovery zone and the holes of the next reaction zone are arranged at a right angle, and the gate has one end rotatably connected between the holes of the activated sludge recovery zone and the holes of the next reaction zone so that when the hole of the activated sludge recovery zone is opened, the hole of the next reaction zone is closed, and conversely, when the hole of the activated sludge recovery zone is closed, the hole of the next reaction zone is opened. A sewage treatment device utilizing the return of activated sludge from a biological reactor, characterized in that in claim 1, the activated sludge recovery zone has an MLSS of 6,000 to 8,000 mg/l. delete A sewage treatment device utilizing activated sludge return of a biological reactor according to claim 1 or claim 2, comprising: a bypass-type feeder which supplies a mixture in the activated sludge recovery zone to the return unit or bypasses the mixture to a reaction zone on the discharge side through a bypass pipe; a water quality sensor which is installed in the activated sludge recovery zone to measure water quality; and a controller which controls the bypass-type feeder by comparing a measurement value of the water quality sensor with a reference value, wherein the controller connects a delivery pipe to the bypass pipe through the bypass-type feeder to guide the mixture to the reaction zone if the measurement value of the water quality sensor satisfies the reference value, and connects the delivery pipe to the supply pipe to supply the mixture to the return unit if the measurement value does not satisfy the reference value.
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