JP2022144774A - Wastewater treatment system - Google Patents

Abstract

To provide a wastewater treatment system that can perform a power saving operation, which is in demand since power consumption of an aeration device sometimes amounts to 40% of the entire power consumption of a wastewater treatment system.SOLUTION: The wastewater treatment system comprises a treatment tank to which water to be treated is fed, a post-treatment tank to which a treated liquid having been treated in the treatment tank is fed, a high oxygen concentration solution unit storing a solution of high oxygen concentration, an agitation device that agitates a liquid to be treated present in the treatment tank, and a controller. The treatment tank is provided with a DO meter. The high oxygen concentration solution unit is provided with a microbubble generator. The controller allows the high oxygen concentration solution to be fed to the treatment tank when a measured value measured by the DO meter is lower than a first threshold. The wastewater treatment system can be operated with a lower electric power than an electric power for operating the aeration device alone.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a system for treating wastewater using aerobic microorganisms, and more particularly to a wastewater treatment system that can save power for aeration using a blower compared to a conventional wastewater treatment system using an aeration tank. .

In conventional wastewater treatment systems, wastewater is guided to an aeration tank, and aerobic microorganisms in the aeration environment flocculate the waste into flocs called zooglare, and solid-liquid separation is performed by sedimentation or membranes to remove impurities in the wastewater. were separated.

One of the problems in such a wastewater treatment system is power saving of the entire wastewater system. In particular, the power consumption of blowers for aeration accounts for about 1/4 to 1/2 of the total power consumption. there is

For example, Patent Literature 1 proposes a power-saving system in which air bubbles generated by aeration are used as a driving force to raise water by a pump, and electricity is generated by head turbine hydroelectric power generation.

In addition, in Patent Document 2, when the raw water supply to the aeration tank is stopped due to the reduction of raw water in the raw water storage tank, the main aeration device is stopped and a small blower that only agitates the sewage in the aeration tank is used. Inventions have been proposed for saving power by switching.

JP 2014-144451 A JP-A-60-125296

In Patent Document 1, since the bubbles formed in the aeration device are first converted into the potential energy of water and then converted into electric power, there is a large amount of loss and the size of the equipment increases, resulting in a large initial investment. Further, in Patent Document 2, the main aeration device is operated intermittently, and the dissolved oxygen amount only decreases while the aeration device is stopped.

The present invention has been conceived in view of the above problems. A solution with a high dissolved oxygen content (high-oxygen liquid) is prepared in advance, and the high-oxygen liquid is supplied to the treatment tank instead of the aeration operation. By doing so, the amount of dissolved oxygen in the processing solution in the processing tank can be maintained at a predetermined value, thereby making it possible to significantly reduce power consumption.

More specifically, the wastewater treatment system according to the present invention is
a treatment tank into which treated water is introduced;
a post-treatment tank into which the treated liquid treated in the treatment tank is charged;
a high-oxygen liquid unit in which the high-oxygen liquid is stored;
a stirring device for stirring the processing solution in the processing tank;
A wastewater treatment system comprising a controller,
In the processing tank,
A DO meter is placed,
In the high oxygen liquid unit,
A microbubble generator is placed,
The control device is
The high-oxygen liquid is supplied to the processing tank when the measured value of the DO meter is lower than a first threshold value.

In the wastewater treatment system according to the present invention, instead of adjusting the amount of dissolved oxygen in the treatment tank and agitating the treated liquid, which were performed in the conventional aeration equipment, the high-oxygen liquid generated in the high-oxygen liquid unit is , and the amount of dissolved oxygen in the processing tank is adjusted to a predetermined value while stirring the processing liquid with an agitator, so the amount of dissolved oxygen in the processing tank is maintained at a predetermined value with less power than the power consumption of the aeration equipment. It is possible to reduce the power consumption of the wastewater treatment system.

It is a figure which shows the structure of the waste water treatment system which concerns on this invention, and shows the case where it drive|operates only with a stirring apparatus. 1 is a diagram showing the configuration of a waste water treatment system according to the present invention, showing a case of operation with a stirring device and a high-oxygen liquid unit; FIG. It is a figure which shows the principle of operation of a waste water treatment system. It is a flowchart which shows the process of the control apparatus of a waste water treatment system. FIG. 4 is a diagram showing changes in the amount of dissolved oxygen in the treatment tank when the wastewater treatment system is in operation. It is a figure showing the difference in power consumption between the case of aeration treatment and the wastewater treatment system according to the present invention.

A wastewater treatment system according to the present invention and its operation will be described below with reference to the drawings. The following description describes one embodiment of the invention, and the invention is not limited to the following description. That is, the following embodiments can be modified without departing from the gist of the present invention.

FIG. 1 shows the configuration of a wastewater treatment system according to the present invention. The wastewater treatment system 1 has a treatment tank 10 into which raw water V is introduced. A stirrer 14 and a DO meter 16 are provided in the processing bath 10 .

The agitating device 14 is for agitating the treatment liquid in the treatment bath 10, and a submersible mixer or an agitator having agitating blades at the tip of a motor can be preferably used. Here, the stirring device 14 is described as an underwater mixer 14 .

The wastewater treatment system 1 is also provided with a high-oxygen liquid unit 18 . The high-oxygen liquid unit 18 is a storage tank in which the microbubble generator 20 is built. A high-oxygen liquid unit 18 is connected to a liquid feed pipe 18c provided with a valve 18a and a pump 18b. A water jet nozzle 18d is connected to the tip of the liquid feed pipe 18c. Therefore, the high-oxygen liquid unit 18 is composed of at least a storage tank, a microbubble generator 20, a liquid feed pipe 18c and a valve 18a. A pump 18 b may be included in the high oxygen liquid unit 18 .

Further, the treatment tank 10 is provided with a drainage pipe 30 having a drainage pump 30a for discharging the treated liquid U. As shown in FIG. A post-treatment tank 32 is provided at the end of the drain pipe 30 . The post-treatment tank 32 is a tank for separating flocs formed in the treatment tank 10 . The post-treatment tank 32 may be, for example, a membrane separation tank or a sedimentation tank.

The supernatant of the post-treatment tank 32 is sent to the next treatment or discharged into nature as it is. Also, part of the supernatant of the post-treatment tank 32 is returned to the high-oxygen liquid unit 18 as recycled water R. A return pipe 34 provided with a feedback pump 34 a may be provided between the post-treatment tank 32 and the high-oxygen liquid unit 18 in order to return the recycled water R to the high-oxygen liquid unit 18 . A sand filter (not shown) may be provided between the post-treatment tank 32 and the high-oxygen liquid unit 18 .

Further, the high-oxygen liquid unit 18 may be supplied not only with the recycled water R but also with uncontaminated raw water V. FIG. This is because the raw water V may be normal water that is not polluted. Therefore, a water quality meter 11 for measuring the water quality of the raw water V and a branch channel 12 are provided in the route through which the raw water V is introduced into the treatment tank 10 . Further, the branch passage 12 may be provided with a raw water supply valve 12a.

The water quality meter 11 uses a measuring instrument for measuring water quality such as a dissolved oxygen meter (DO meter 16) and/or an SS meter. Here, the case where the water quality meter 11 is used as the DO meter 16 will be described.

The wastewater treatment system 1 also has a control device 22 . The control device 22 is electrically connected to at least the microbubble generator 20, the valve 12a, the valve 18a, the pump 18b, the water quality meter 11, the DO meter 16 and the underwater mixer . The control device 22 then sends signals to the microbubble generator 20, the pump 18b and the submersible mixer 14 to control starting and stopping.

The control device 22 can also send signals for controlling the opening and closing of the valves 12a and 18a. In addition, the controller 22 can receive the signal from the DO meter 16 as the current DO value in the treatment tank 10, and the signal from the water quality meter 11 as the DO value of the raw water V currently introduced into the treatment tank 10. can be received as a value.

Referring to FIG. 2, control device 22 controls valve 18a and pump 18b so that valve 18a is opened and pump 18b is operated so that the high oxygen liquid in high oxygen liquid unit 18 flows into treatment tank 10. is sent to Here, the high-oxygen liquid is the water (recycled water R, or mixed water of recycled water R and raw water V) stored in the high-oxygen liquid unit 18 may be mixed with microbubbles. It is a liquid containing microbubbles generated by the generator 20 .

The water in which the microbubbles are generated can increase the dissolved oxygen amount (DO amount) to near the maximum dissolved oxygen amount (approximately 10 mg/L) that can be dissolved in normal water. In addition, by adding microbubbles to water in which oxygen is dissolved to near the maximum dissolved oxygen amount, the oxygen retention amount per unit volume can be made equal to or greater than the dissolved oxygen amount of water. In addition, the high-oxygen liquid unit 18 may include a device such as a pressurization releasing device or a line mixer for crushing the generated microbubbles in order to increase the dissolved oxygen amount.

A spray nozzle 18d is provided at the tip of the liquid feed pipe 18c leading from the high-oxygen liquid unit 18 to the processing tank 10 . The fountain nozzle 18 d is arranged in the raw water V in the treatment tank 10 . Therefore, the water jet nozzle 18 d receives pressure from the pump 18 b and discharges the oxygen-rich liquid into the raw water V in the treatment tank 10 .

The controller 22 also controls the operation of the underwater mixer 14 . That is, the underwater mixer 14 can be operated or stopped. The underwater mixer 14 agitates the raw water V in the treatment tank 10 . The processing tank 10 can be filled with the high oxygen liquid by operating the underwater mixer 14 while discharging the high oxygen liquid from the water jet nozzle 18d in the processing tank 10 . The underwater mixer 14 may be operated all the time.

Next, the operating principle of the waste water treatment system 1 will be described with reference to FIG. The vertical axis indicates the DO value (mg/L) in the processing bath 10 measured by the DO meter 16. FIG. The waste water treatment system 1 starts supplying the oxygen-rich liquid when the DO value in the treatment tank 10 becomes lower than the first threshold value. High oxygen liquid ON state. Specifically, the valve 18a is opened and the pump 18b is operated. Therefore, the oxygen-rich liquid is released into the processing tank 10 . That is, the dissolved oxygen amount (DO value) in the processing tank 10 is increased by supplying the high-oxygen liquid.

In addition, hereinafter, "use of high-oxygen liquid", "ON of high-oxygen liquid", or "supply of high-oxygen liquid" means that the valve 18a is opened, the microbubble generator 20, the pump 18b and the underwater mixer 14 are operated, and the treatment is performed. It refers to filling the tank 10 with a high-oxygen liquid.

On the other hand, when the DO value in the processing tank 10 becomes higher than the second threshold value, the supply of the high oxygen liquid is stopped. Specifically, the valve 18a is closed and the pump 18b is stopped. In addition, the underwater mixer 14 is always operated. This is to increase the chance of contact between the aerobic microorganisms and the material to be treated. As is clear here, the second threshold is a larger value (higher DO value) than the first threshold.

The operation of the waste water treatment system 1 having the above configuration will be described. FIG. 4 shows the processing flow of the control device 22. As shown in FIG. 5 shows the transition of the DO value (dissolved oxygen content) in the treatment bath 10. As shown in FIG. In FIG. 5, the horizontal axis is the time, the left vertical axis is the DO value (mg/L) in the treatment tank 10, and the right vertical axis is the power consumption (W).

See FIGS. 4 and 5. FIG. When the processing flow is started (step S100), it is determined to end (step S102). A trigger for termination is not particularly limited. It may be a forced end operation by the user, or may be stopped after recognizing a preset time. When ending (Y branch of step S102), the waste water treatment system 1 is stopped (step S104). When continuing (N branch of step S102), the process is moved to the next step.

Next, it is determined whether or not the DO value in the processing tank 10 is lower than the first threshold value (denoted as "Th1" in FIG. 4) (step S106). When the DO value in the processing tank 10 is lower than the first threshold (Y branch of step S106), the high oxygen liquid is supplied to the processing tank 10 (turned ON). That is, the valve 18a is opened and the pump 18b is operated (step S108).

In FIG. 5, at time t1, the DO value in the processing tank 10 becomes lower than the first threshold value, and the supply of the high-oxygen liquid is started. Power W1 for operating the microbubble generator 20 and the pump 18b is consumed to supply the high-oxygen liquid. In addition, since the underwater mixer 14 (stirring device 14) is always continuously operated, the waste water treatment system 1 always consumes constant electric power W2.

The controller 22 determines whether or not the DO value in the processing tank 10 has become higher than the second threshold value (denoted as "Th2" in FIG. 4) (step S110). While the DO value in the processing tank 10 is not higher than the second threshold value (N branch of step S110), the process returns to step S108 to continue supplying the high-oxygen liquid. In FIG. 5, it is from time t1 to time t2.

The DO value in the processing bath 10 increases due to the supply of the high-oxygen liquid. Then, when the DO value in the processing tank 10 exceeds the second threshold (Y branch of step S110), the supply of the high oxygen liquid is stopped. Specifically, the valve 18a is closed to stop the microbubble generator 20 and the pump 18b (step S112). In FIG. 5, it is time t2.

The processing flow returns to end processing (step S102), and repeats step S106. After time t2, the DO value in the processing tank 10 is higher than the first threshold for a while. Therefore, in step 106, the N branch is selected, the process proceeds to step S112, and the state in which the supply of the high-oxygen liquid is stopped continues.

When the aerobic microorganisms decompose the material to be treated and use oxygen, the DO value of the treatment liquid in the treatment tank 10 gradually decreases. When the DO value of the treated water falls below the first threshold value at time t3, the Y branch is selected again in step S106, and the supply of the oxygen-rich liquid is started. This supply of the high-oxygen liquid continues until time t4 when the DO value in the processing tank 10 becomes higher than the second threshold.

The average power consumption Qw in such a drainage process is obtained by averaging the sum of power consumption W1T1 from time t1 to time t2 and power consumption W2T2 from time t2 to time t3. If written openly, it is expressed as in formula (1).

FIG. 6 shows the relationship between the waste water treatment system 1 of the present invention and the amount of power required for unit dissolved oxygen supply when a conventional aerator is used. The amount of power required to supply a unit of dissolved oxygen is the amount of power required to supply a unit of dissolved oxygen. The vertical axis indicates the amount of electric power (Wh), and the horizontal axis indicates the difference between the methods. The aerator requires a large amount of power Gar1 to supply unit dissolved oxygen. The power amount Gar1 is assumed to be W10 (Wh).

On the other hand, the waste water treatment system 1 according to the present invention does not require so much electric power to produce oxygen-rich liquid. Therefore, W11 (Wh) obtained by adding the power consumption Gar2 of the microbubble generator 20 and the power consumption Gh0 of the underwater mixer 14 is smaller than W10 (Wh) in the case of only the aerator. Therefore, the waste water treatment system 1 having the configuration of the present invention can be operated with lower power consumption than the conventional waste water treatment system.

In addition to the above process flow, the control device 22 may perform a process of supplying the high oxygen liquid unit 18 when DO in the raw water V is equal to or higher than a certain value and/or SS is equal to or lower than a certain value. . This is because normal water, which is not contaminated water, may flow as the raw water V, and is used effectively. The dissolved oxygen concentration in the raw water V is measured by the water quality meter 11 . Therefore, the water supplied to the high-oxygen liquid unit 18 may be recycled water R, raw water V, or raw water V+recycled water R.

As described above, by using the high-oxygen liquid produced by the microbubble generator 20, the power consumption of the aerator can be reduced.

INDUSTRIAL APPLICABILITY The present invention can be used as a wastewater treatment system capable of power-saving operation.

1 Waste water treatment system 10 Treatment tank 11 Water quality meter 12 Branch channel 14 Underwater mixer (stirring device)
16 DO meter 18 High oxygen liquid unit 12a, 18a Valve 18b Pump 18c Liquid feed pipe 18d Fountain nozzle 20 Microbubble generator 22 Control device 30 Drainage pipe 30a Drainage pump 32 Post-treatment tank 34 Return pipe 34a Return pump V Raw water U Treated Liquid R Recycled water

Claims (2)

a treatment tank into which treated water is introduced;
a post-treatment tank into which the treated liquid treated in the treatment tank is charged;
a high-oxygen liquid unit in which the high-oxygen liquid is stored;
a stirring device for stirring the processing solution in the processing tank;
A wastewater treatment system comprising a controller,
In the processing tank,
A DO meter is placed,
In the high oxygen liquid unit,
A microbubble generator is placed,
The control device is
A wastewater treatment system, wherein the high-oxygen liquid is supplied to the treatment tank when the measured value of the DO meter is lower than a first threshold value. The control device is
2. The wastewater treatment system according to claim 1, wherein the supply channel of the high-oxygen liquid is closed when the measured value of the DO meter is higher than a second threshold value.

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