JP6849318B2 - Wastewater treatment system - Google Patents

Description

The present invention relates to a wastewater treatment system, and more particularly to a wastewater treatment system for treating wastewater containing a persistent substance.

Conventionally, a wastewater treatment system for treating wastewater containing a persistent substance is known (see, for example, Patent Document 1).

Patent Document 1 discloses a wastewater treatment system in which wastewater containing 1,4-dioxane (a persistent substance) is decomposed by accelerated oxidation treatment using ultraviolet rays and ozone. In this wastewater treatment system, two accelerated oxidation treatment tanks are provided in series.

Patent No. 4247712

However, in the wastewater treatment system as in Patent Document 1, when the accelerated oxidation treatment of wastewater is performed using hydrogen peroxide, it is considered that hydrogen peroxide is directly supplied to the accelerated oxidation treatment tank. Therefore, the wastewater in the tank and hydrogen peroxide may not be sufficiently mixed. As a result, there is a problem that it is difficult to efficiently decompose persistent substances in wastewater.

The present invention has been made to solve the above problems, and one object of the present invention is to provide a wastewater treatment system capable of efficiently decomposing persistent substances in wastewater. That is.

The wastewater treatment system according to one aspect of the present invention is provided in series and is provided, and supplies ozone to the accelerated oxidation treatment tank for treating wastewater containing persistent substances by the accelerated oxidation treatment and the accelerated oxidation treatment tank. Peroxidation that supplies hydrogen peroxide to the ozone supply unit and the pipe through which the waste water passes at least before it flows into the most upstream accelerated oxidation treatment tank among the plurality of accelerated oxidation treatment tanks connected in series. The most upstream of a plurality of accelerated oxidation treatment tanks provided with a hydrogen supply unit and connected in series is a parallel flow treatment in which both the direction in which ozone flows and the direction in which waste water flows are from bottom to top. A tank is provided, and the hydrogen peroxide supply unit is provided with a plurality of accelerated oxidations in the waste water before flowing into the parallel flow treatment tank, which is the most upstream accelerated oxidation treatment tank among the plurality of accelerated oxidation treatment tanks connected in series. It is configured to supply the entire amount of hydrogen peroxide supplied to the treatment tank.

In the wastewater treatment system according to one aspect of the present invention, as described above, hydrogen peroxide is mixed with the wastewater before flowing into at least the most upstream accelerated oxidation treatment tank among the plurality of accelerated oxidation treatment tanks connected in series. By providing a hydrogen peroxide supply unit that supplies hydrogen peroxide so as to allow the waste water and ozone to be sufficiently mixed before flowing into the accelerated oxidation treatment tank, hydrogen peroxide and ozone can be sufficiently mixed in the accelerated oxidation treatment tank. It is possible to increase the contact probability with. As a result, the hydroxyl radical (.OH) generated by the reaction of hydrogen peroxide and ozone can be efficiently reacted with the persistent substance in the accelerated oxidation treatment tank, so that the persistent substance in the wastewater can be efficiently decomposed. can do. As a result, it is possible to suppress an increase in the amount of ozone supplied, and thus it is possible to suppress an increase in the scale of the ozone generator.

In the wastewater treatment system according to the above one aspect, preferably, the persistent substance contains 1,4-dioxane, and the hydrogen peroxide supply unit is 5% with respect to the weight of ozone supplied by the ozone supply unit. It is configured to supply hydrogen peroxide having a weight of 50% or less. With this configuration, 1,4-dioxane contained in wastewater is oxidized and decomposed by ozone and hydrogen peroxide of 5% or more of ozone to decompose 1,4-dioxane in wastewater. It can be reduced efficiently. Further, by supplying hydrogen peroxide of 50% or less of ozone, it is possible to suppress an excessive supply of hydrogen peroxide, so that it is possible to suppress the residual hydrogen peroxide in the treated water treated with wastewater. Can be done. The weight of ozone supplied by the ozone supply unit is the total weight of ozone supplied to the plurality of accelerated oxidation treatment tanks. The weight of hydrogen peroxide supplied at a weight of 5% or more and 50% or less with respect to the weight of ozone is the total weight of hydrogen peroxide supplied to the plurality of accelerated oxidation treatment tanks.

The wastewater treatment system according to the aforementioned aspect, the plurality of advanced oxidation treatment tank connected in series, parallel flow treatment vessel in both directions of flow of the direction and the wastewater flowing ozone is the direction from bottom to top in the bath Is provided. As a result , both the concentration of the persistent substance and the concentration of ozone can be increased in the lower part of the parallel flow treatment tank, so that the contact probability between ozone and the persistent substance can be increased. As a result, the persistently decomposable substance can be decomposed more efficiently.

In the wastewater treatment system according to the above one aspect , a parallel flow treatment tank is provided in the uppermost stream among the plurality of accelerated oxidation treatment tanks connected in series. As a result , in the most upstream accelerated oxidation treatment tank, wastewater having the highest concentration of persistent substances is supplied to the lower part of the tank having a high ozone concentration. The probability can be effectively increased. As a result, the persistently decomposable substance can be decomposed more efficiently.

In the wastewater treatment system according to the above one aspect , preferably, the direction of ozone flow in the tank is from the bottom to the top, and the wastewater flows in the most downstream of the plurality of accelerated oxidation treatment tanks connected in series. A countercurrent treatment tank is provided in which the direction is from top to bottom. With this configuration, in the most downstream accelerated oxidation treatment tank, when a water seal tube is provided at the take-out portion of the treated water treated with wastewater, contact between the treated water and the gas in the upper part of the tank can be prevented. Therefore, it is possible to suppress the mixing of gaseous ozone into the treated water.

In the wastewater treatment system according to the above one aspect , a parallel flow treatment tank is preferably provided at the most downstream of the plurality of accelerated oxidation treatment tanks connected in series. With this configuration, a parallel flow treatment tank capable of efficiently decomposing persistent substances can be arranged at the most downstream, so that the concentration of persistent substances contained in the treated water treated with wastewater Can be reliably lowered.

The wastewater treatment system according to the aforementioned aspect, the hydrogen peroxide supply unit, the waste water prior to entering the advanced oxidation treatment tank at the most upstream among the plurality of advanced oxidation treatment tank connected in series, a plurality of advanced oxidation processes It is configured to supply hydrogen peroxide of the total amount of hydrogen peroxide supplied to the tank. As a result , in the most upstream accelerated oxidation treatment tank, the amount of hydrogen peroxide with respect to ozone can be increased, so that the contact probability between hydrogen peroxide and ozone can be increased. As a result, a large amount of hydroxyl radicals (.OH) due to the reaction between hydrogen peroxide and ozone can be generated in the most upstream accelerated oxidation treatment tank having a high concentration of persistent substances, so that hydroxyl radicals and persistent substances are persistent. The contact probability of substances can be effectively increased. As a result, the persistently decomposable substance can be decomposed more efficiently.

In the wastewater treatment system according to the above one aspect, preferably, the hydrogen peroxide supply unit is the hydrogen peroxide of the treated water flowing out from the most downstream accelerated oxidation treatment tank among the plurality of accelerated oxidation treatment tanks connected in series. The amount of hydrogen peroxide supplied so that the concentration is 0.5 mg / L or more and 10 mg / L or less is adjusted. In this way, by setting the concentration of hydrogen peroxide in the treated water flowing out from the most downstream accelerated oxidation treatment tank to 0.5 mg / L or more, even if the concentration of persistent substances in the wastewater fluctuates, it is excessive. Since hydrogen peroxide can be stably supplied so that hydrogen peroxide is not insufficient, the concentration of persistent substances contained in the treated water treated with wastewater can be surely lowered. By setting the concentration of hydrogen peroxide in the treated water flowing out from the most downstream accelerated oxidation treatment tank to 10 mg / L or less, it is possible to suppress excessive hydrogen peroxide remaining in the treated water. It is possible to suppress an increase in the burden of treating residual hydrogen peroxide in a process or the like. Moreover, since it is possible to suppress the excessive supply of hydrogen peroxide, it is possible to efficiently decompose the persistent substance.

According to the present invention, as described above, persistent substances in wastewater can be efficiently decomposed.

It is the schematic which showed the wastewater treatment system by 1st Embodiment of this invention. It is a figure for demonstrating the parallel flow treatment tank of the wastewater treatment system according to 1st Embodiment of this invention. It is a figure for demonstrating the countercurrent treatment tank of the wastewater treatment system according to 1st Embodiment of this invention. It is a table for demonstrating the reduction result of 1,4-dioxane of wastewater by Example A. It is a table for demonstrating the reduction result of 1,4-dioxane of wastewater by Example B. It is the schematic which showed the wastewater treatment system by 2nd Embodiment of this invention. It is the schematic which showed the wastewater treatment system by the 3rd Embodiment of this invention. It is the schematic which showed the wastewater treatment system by 4th Embodiment of this invention. It is a table for demonstrating the reduction result of 1,4-dioxane of wastewater by Example C. It is a table for demonstrating the concentration of residual hydrogen peroxide by Example D and the treatment result of 1,4-dioxane. It is the schematic which showed the wastewater treatment system by the modification of 1st Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
(Configuration of wastewater treatment system)
The configuration of the wastewater treatment system 100 according to the first embodiment of the present invention will be described with reference to FIG.

The wastewater treatment system 100 according to the first embodiment of the present invention is configured to treat 1,4-dioxane contained in wastewater (raw water) so as to have a predetermined concentration or less (for example, 0.5 mg / L or less). Has been done. As shown in FIG. 1, the wastewater treatment system 100 includes an accelerated oxidation treatment tank (AOP tank) 1, an ozone supply unit 2, a hydrogen peroxide supply unit 3, and a raw water supply unit 4. In addition, 1,4-dioxane is an example of the "persistent substance" of the present invention.

The accelerated oxidation treatment tank 1 includes a parallel flow treatment tank 11 and a countercurrent treatment tank 12. The parallel flow processing tank 11 has an inflow port 111, an outflow port 112, and an ozone supply port 113. The countercurrent processing tank 12 has an inflow port 121, an outflow port 122, and an ozone supply port 123.

The ozone supply unit 2 includes an ozone generator 21 and a pipe 22. The hydrogen peroxide supply unit 3 includes a pump 31 and a pipe 32. The raw water supply unit 4 includes a pump 41 and a pipe 42.

The accelerated oxidation treatment tank 1 is configured to oxidize the BOD source, COD source and 1,4-dioxane to reduce the concentrations of BOD, COD and 1,4-dioxane in the waste water (raw water). Specifically, in the accelerated oxidation treatment tank 1, hydrogen peroxide (H ₂ O ₂ ) and ozone (O ₃ ) are reacted to generate hydroxyl radicals (.OH) in the wastewater (raw water). It is configured to oxidize BOD sources, COD sources and 1,4-dioxane.

Two accelerated oxidation treatment tanks 1 are connected in series. Specifically, a parallel flow processing tank 11 is provided upstream, and a countercurrent processing tank 12 is provided in series downstream of the parallel flow processing tank 11. That is, the wastewater discharged from the outflow port 112 of the parallel flow treatment tank 11 flows into the inflow port 121 of the countercurrent treatment tank 12.

In the parallel flow treatment tank 11, both the direction in which ozone flows and the direction in which wastewater flows in the tank are from bottom to top. Specifically, the wastewater flows in from the inflow port 111 provided in the lower part (Z2 direction side portion) of the parallel flow treatment tank 11 and flows out from the outflow port 112 provided in the upper part (Z1 direction side portion). That is, ozone is supplied from the ozone supply port 113 provided near the bottom of the parallel flow treatment tank 11, and rises in the parallel flow treatment tank 11 by buoyancy. The unreacted ozone (excreted ozone) is discharged from the upper part of the parallel flow processing tank 11 and processed.

In the countercurrent treatment tank 12, the direction in which ozone flows in the tank is from bottom to top, and the direction in which wastewater flows is from top to bottom. Specifically, the wastewater flows in from the inflow port 121 provided in the upper part of the countercurrent treatment tank 12 and flows out from the outflow port 122 provided in the lower part. That is, ozone is supplied from the ozone supply port 123 provided near the bottom of the countercurrent treatment tank 12, and rises in the countercurrent treatment tank 12 by buoyancy. The unreacted ozone (excreted ozone) is discharged from the upper part of the countercurrent treatment tank 12 and processed. Further, the treated water flowing out from the outflow port 122 is discharged through the water sealing pipe.

The parallel flow treatment tank 11 is provided in the uppermost stream of the plurality of accelerated oxidation treatment tanks 1 connected in series. Further, the countercurrent treatment tank 12 is provided at the most downstream of the plurality of accelerated oxidation treatment tanks 1 connected in series.

The ozone supply unit 2 is configured to supply ozone to the accelerated oxidation treatment tank 1. Specifically, the ozone supplied from the ozone generator 21 is supplied to the parallel flow processing tank 11 from the ozone supply port 113 and to the countercurrent processing tank 12 from the ozone supply port 123 via the pipe 22. Will be done. Further, the amount of ozone supplied to the parallel flow processing tank 11 and the amount of ozone supplied to the countercurrent processing tank 12 are adjusted to be equal to each other. Specifically, the amount of ozone supplied to the parallel flow processing tank 11 and the countercurrent processing tank 12 is adjusted by a flow meter and a valve (not shown).

Here, in the first embodiment, the hydrogen peroxide supply unit 3 flows into at least the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11) among the plurality of accelerated oxidation treatment tanks 1 connected in series. It is configured to supply hydrogen peroxide to the previous wastewater to mix. That is, the hydrogen peroxide supply unit 3 supplies the wastewater before flowing into the parallel flow treatment tank 11 so as to mix the hydrogen peroxide. Further, the hydrogen peroxide supply unit 3 is configured to send a hydrogen peroxide solution (an aqueous solution containing hydrogen peroxide) by a pump 31 via a pipe 32. The pipe 32 is connected in the middle of the pipe 42 of the raw water supply unit 4. That is, the raw water (wastewater) and hydrogen peroxide are configured to merge and be mixed in the pipe 42.

Further, in the first embodiment, the hydrogen peroxide supply unit 3 supplies hydrogen peroxide having a weight of 5% or more and 50% or less with respect to the weight of ozone supplied by the ozone supply unit 2 (ozone generator 21). It is configured to supply. For example, the hydrogen peroxide supply unit 3 has a weight of 50% (half) of the total weight of ozone supplied to the accelerated oxidation treatment tank 1 (parallel flow treatment tank 11 and countercurrent treatment tank 12). It is configured to supply hydrogen peroxide.

Further, in the first embodiment, the hydrogen peroxide supply unit 3 is before flowing into the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11) among the plurality of accelerated oxidation treatment tanks 1 connected in series. The wastewater is configured to supply the entire amount (100%) of hydrogen peroxide to be supplied. That is, the hydrogen peroxide supply unit 3 supplies hydrogen peroxide to the wastewater before it flows into the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11), and also supplies hydrogen peroxide to the parallel flow treatment tank 11 and countercurrent treatment. Hydrogen peroxide is not supplied between the tanks 12. In other words, unreacted hydrogen peroxide in the parallel flow treatment tank 11 flows into the countercurrent treatment tank 12 in the subsequent stage (downstream).

Further, in the first embodiment, the hydrogen peroxide supply unit 3 is the treated water flowing out from the most downstream accelerated oxidation treatment tank 1 (counterflow treatment tank 12) among the plurality of accelerated oxidation treatment tanks 1 connected in series. The amount of hydrogen peroxide supplied is adjusted so that the concentration of hydrogen peroxide (residual hydrogen peroxide) is 0.5 mg / L or more and 10 mg / L or less. The amount of hydrogen peroxide supplied by the hydrogen peroxide supply unit 3 is adjusted so that the concentration of residual hydrogen peroxide is 10 mg / L or less, preferably 3 mg / L or less. The amount of hydrogen peroxide supplied by the hydrogen peroxide supply unit 3 is such that the concentration of residual hydrogen peroxide is 0.5 mg / L or more, preferably 1 mg / L or more, and more preferably 2 mg / L or more. It is adjusted to be.

The amount of hydrogen peroxide supplied by the hydrogen peroxide supply unit 3 is adjusted based on the concentration of hydrogen peroxide (residual hydrogen peroxide) flowing out from the most downstream accelerated oxidation treatment tank 1 (counterflow treatment tank 12). To. Specifically, the discharge rate of the pump 31 is adjusted to adjust the supply amount of hydrogen peroxide. When the concentration of residual hydrogen peroxide is less than the lower limit (for example, 0.5 mg / L), the amount of hydrogen peroxide supplied from the hydrogen peroxide supply unit 3 is increased. When the concentration of residual hydrogen peroxide is larger than the upper limit value (for example, 10 mg / L), the amount of hydrogen peroxide supplied from the hydrogen peroxide supply unit 3 is reduced. The amount of hydrogen peroxide supplied may be adjusted automatically or based on the user's operation.

The raw water supply unit 4 is configured to supply raw water (wastewater) to the accelerated oxidation treatment tank 1. Specifically, the raw water supply unit 4 is configured to send raw water by a pump 41 via a pipe 42. A pipe 32 is connected in the middle of the pipe 42. Further, the pipe 42 is connected to the inflow port 111 of the most upstream parallel flow treatment tank 11 of the accelerated oxidation treatment tank 1. Further, the pipe 42 is formed so as to pass through a position higher than the water surface of the parallel flow treatment tank 11 in front of the inflow port 111. As a result, even when the pump 41 is stopped, it is possible to prevent the wastewater in the parallel flow treatment tank 11 from flowing back to the pump 41 side.

(Explanation of parallel flow processing tank)
The features of the parallel flow processing tank 11 will be described with reference to FIG.

As shown in FIG. 2, the parallel flow treatment tank 11 has a high concentration of 1,4-dioxane, ozone, and hydrogen peroxide in the lower part (Z2 direction side portion) of the tank. Therefore, a wide area is formed in the lower part of the tank where the contact probability of 1,4-dioxane, ozone, and hydrogen peroxide is above a certain level. As a result, a wide region where the reaction efficiency is high is formed in the lower part of the tank. As a result, in the parallel flow processing tank 11, the treatment efficiency of 1,4-dioxane becomes higher in the entire tank. Note that FIG. 2 schematically shows an area where the contact probability of 1,4-dioxane, ozone, and hydrogen peroxide is above a certain level.

(Explanation of countercurrent processing tank)
The features of the countercurrent processing tank 12 will be described with reference to FIG.

As shown in FIG. 3, the countercurrent treatment tank 12 has a high concentration of 1,4-dioxane and hydrogen peroxide in the upper part (Z1 direction side portion) of the tank. In addition, the ozone concentration increases in the lower part of the tank (side in the Z2 direction). Therefore, it is considered that a region where the contact probability of 1,4-dioxane, ozone, and hydrogen peroxide is above a certain level is formed in the middle of the tank. Since the area where the contact probability of 1,4-dioxane, ozone and hydrogen peroxide of the countercurrent treatment tank 12 is above a certain level is narrower than that of the parallel flow treatment tank 11, the 1,4-dioxane in the entire tank The processing efficiency of the parallel flow processing tank 11 is higher than that of the countercurrent processing tank 12. Further, since the concentrations of 1,4-dioxane and hydrogen peroxide are high in the upper part of the tank (side in the Z1 direction), the probability of contact with the rising ozone is high, and the reaction is actively carried out. As a result, in the countercurrent treatment tank 12, unreacted ozone is less likely to be emitted from the upper part of the tank. Note that FIG. 3 schematically shows an area where the contact probability of 1,4-dioxane, ozone, and hydrogen peroxide is above a certain level.

(Effect of the first embodiment)
In the first embodiment, the following effects can be obtained.

In the first embodiment, as described above, hydrogen peroxide is added to the waste water before flowing into at least the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11) among the plurality of accelerated oxidation treatment tanks 1 connected in series. By providing the hydrogen peroxide supply unit 3 that supplies hydrogen so as to be mixed, the waste water and hydrogen peroxide can be sufficiently mixed before flowing into the accelerated oxidation treatment tank 1. Therefore, the accelerated oxidation treatment tank 1 It is possible to increase the contact probability between hydrogen peroxide and ozone. As a result, the hydroxyl radical (.OH) generated by the reaction of hydrogen peroxide and ozone can be efficiently reacted with 1,4-dioxane in the accelerated oxidation treatment tank 1, so that 1,4-dioxane in the wastewater can be efficiently reacted. It can be disassembled efficiently. As a result, it is possible to suppress an increase in the amount of ozone supplied, so that it is possible to suppress an increase in the scale of the ozone generator 21.

Further, in the first embodiment, as described above, the hydrogen peroxide supply unit 3 supplies hydrogen peroxide having a weight of 5% or more and 50% or less with respect to the weight of ozone supplied by the ozone supply unit 2. Configure to do. As a result, 1,4-dioxane contained in the wastewater is oxidized and decomposed by ozone and hydrogen peroxide of 5% or more of ozone, thereby efficiently reducing 1,4-dioxane in the wastewater. be able to. Further, by supplying hydrogen peroxide of 50% or less of ozone, it is possible to suppress an excessive supply of hydrogen peroxide, so that it is possible to suppress the residual hydrogen peroxide in the treated water treated with wastewater. Can be done.

Further, in the first embodiment, as described above, the parallel flow processing tank 11 is provided in the uppermost stream of the plurality of accelerated oxidation treatment tanks 1 connected in series. As a result, in the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11), wastewater having the highest concentration of 1,4-dioxane is supplied to the lower part of the tank having a high ozone concentration. The contact probability between ozone and 1,4-dioxane can be effectively increased. This makes it possible to more efficiently decompose 1,4-dioxane.

Further, in the first embodiment, as described above, the countercurrent treatment tank 12 is provided at the most downstream of the plurality of accelerated oxidation treatment tanks 1 connected in series. As a result, in the most downstream accelerated oxidation treatment tank 1 (counterflow treatment tank 12), by providing a water seal pipe at the take-out portion of the treated water treated with wastewater, the treated water comes into contact with the gas in the upper part of the tank. Therefore, it is possible to suppress the mixing of gaseous ozone into the treated water.

Further, in the first embodiment, as described above, the hydrogen peroxide supply unit 3 is connected to the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11) among the plurality of accelerated oxidation treatment tanks 1 connected in series. 50% or more of the total amount of hydrogen peroxide to be supplied is supplied to the wastewater before it flows into the wastewater. As a result, in the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11), the amount of hydrogen peroxide with respect to ozone can be increased, so that the contact probability between hydrogen peroxide and ozone can be increased. As a result, a large amount of hydroxyl radicals (.OH) due to the reaction between hydrogen peroxide and ozone can be generated in the most upstream accelerated oxidation treatment tank 1 (parallel flow treatment tank 11) having a high concentration of 1,4-dioxane. Therefore, the contact probability between the hydroxyl radical and 1,4-dioxane can be effectively increased. This makes it possible to decompose 1,4-dioxane more efficiently.

Further, in the first embodiment, the parallel flow treatment tank 11 is provided in the first stage, and the countercurrent treatment tank 12 is provided in the second stage, so that the parallel flow treatment tank 11 has a high performance of decomposing 1,4-dioxane. The wastewater can be treated by the countercurrent treatment tank 12, which is less likely to generate exhausted ozone and is easy to implement. As a result, while increasing the decomposition efficiency of 1,4-dioxane in wastewater, the generation of ozone exhaust can be suppressed, and the construction can be easily carried out.

Further, in the first embodiment, the hydrogen peroxide supply unit 3 is the treated water flowing out from the most downstream accelerated oxidation treatment tank 1 (counterflow treatment tank 12) among the plurality of accelerated oxidation treatment tanks 1 connected in series. The amount of hydrogen peroxide supplied is adjusted so that the concentration of hydrogen peroxide in the above is 0.5 mg / L or more and 10 mg / L or less. In this way, by adjusting the concentration of hydrogen peroxide (residual hydrogen peroxide) in the treated water flowing out from the most downstream accelerated oxidation treatment tank 1 (counterflow treatment tank 12) to 0.5 mg / L or more, the wastewater Even when the concentration of 1,4-dioxane in No. 1 fluctuates, hydrogen peroxide can be stably supplied so that hydrogen peroxide is not insufficient. Therefore, it is contained in the treated water obtained by treating wastewater. , 4-Dioxane concentration can be surely lowered. By reducing the concentration of hydrogen peroxide in the treated water flowing out from the most downstream accelerated oxidation treatment tank 1 (counterflow treatment tank 12) to 10 mg / L or less, it is possible to prevent excessive hydrogen peroxide from remaining in the treated water. Therefore, it is possible to suppress an increase in the burden of treating the residual hydrogen peroxide in the next step or the like. Moreover, since it is possible to suppress the excessive supply of hydrogen peroxide, 1,4-dioxane can be efficiently decomposed.

Further, by setting the concentration of residual hydrogen peroxide to 1 mg / L or more, hydrogen peroxide can be supplied more stably, so that the concentration of 1,4-dioxane contained in the treated water treated with wastewater can be adjusted. It can be lowered more reliably. By setting the concentration of residual hydrogen peroxide to 2 mg / L or more, hydrogen peroxide can be supplied more stably, so that the concentration of 1,4-dioxane contained in the treated water treated with wastewater is more reliable. Can be lowered to. Further, by setting the concentration of residual hydrogen peroxide to 3 mg / L or less, it is possible to further suppress an increase in the burden of treating the residual hydrogen peroxide.

(Example A)
Next, with reference to FIG. 4, the result of Example A in which water treatment was actually performed on the wastewater using the wastewater treatment system 100 according to the first embodiment shown in FIG. 1 (one embodiment of the present invention). Results of reduction of 1,4-dioxane) will be described.

In Example A, an example in which the injection ratio of hydrogen peroxide between the first-stage accelerated oxidation treatment tank 1 and the second-stage accelerated oxidation treatment tank 1 is changed will be described.

As shown in FIG. 4, in Example A1 of the present invention, the entire amount (100%) of hydrogen peroxide is injected into the first-stage (upstream) accelerated oxidation treatment tank 1 and the second-stage (downstream) accelerated oxidation treatment. Hydrogen peroxide is not injected into the tank 1. Further, in Example A1, hydrogen peroxide is supplied so as to be mixed with the wastewater before flowing into the first-stage accelerated oxidation treatment tank 1.

In Example A2, 75% of the total amount of hydrogen peroxide supplied is injected into the first-stage accelerated oxidation treatment tank 1, and 25 of the total amount of hydrogen peroxide supplied to the second-stage accelerated oxidation treatment tank 1. % Is infused. Further, in Example A2, in the first stage, hydrogen peroxide is supplied so as to be mixed with the wastewater before flowing into the accelerated oxidation treatment tank 1. Further, in the second stage, hydrogen peroxide is directly injected into the accelerated oxidation treatment tank 1 (AOP tank).

In Example A3, 50% of the total amount of hydrogen peroxide supplied is injected into the first-stage accelerated oxidation treatment tank 1, and 50% of the total amount of hydrogen peroxide supplied to the second-stage accelerated oxidation treatment tank 1. % Is infused. Further, in Example A3, in the first stage, hydrogen peroxide is supplied so as to be mixed with the wastewater before flowing into the accelerated oxidation treatment tank 1. Further, in the second stage, hydrogen peroxide is directly injected into the accelerated oxidation treatment tank 1 (AOP tank).

In Example A4, 25% of the total amount of hydrogen peroxide supplied is injected into the first-stage accelerated oxidation treatment tank 1, and 75 of the total amount of hydrogen peroxide supplied to the second-stage accelerated oxidation treatment tank 1. % Is infused. Further, in Example A4, in the first stage, hydrogen peroxide is supplied so as to be mixed with the wastewater before flowing into the accelerated oxidation treatment tank 1. Further, in the second stage, hydrogen peroxide is directly injected into the accelerated oxidation treatment tank 1 (AOP tank).

Further, in Examples A1 to A4, the total weight of hydrogen peroxide supplied to the first-stage and second-stage accelerated oxidation treatment tanks 1 is supplied to the first-stage and second-stage accelerated oxidation treatment tanks 1. It is 50% of the total weight of ozone.

As shown in FIG. 4, in Example A1, the residual rate of 1,4-dioxane (1,4-dioxane concentration at the outlet of the accelerated oxidation treatment tank 1 of the second stage / the inlet of the accelerated oxidation treatment tank 1 of the first stage). 1,4-dioxane concentration) is 1.2%. In Example A2, the residual rate of 1,4-dioxane is 1.6%. In Example A3, the residual rate of 1,4-dioxane is 1.4%. In Example A4, the residual rate of 1,4-dioxane is 3.0%. As a result, 50% or more of the total amount of hydrogen peroxide to be supplied is supplied to the wastewater before flowing into the most upstream accelerated oxidation treatment tank 1 among the plurality of accelerated oxidation treatment tanks 1 connected in series. By doing so, it can be seen that 1,4-dioxane in the wastewater can be decomposed more efficiently.

(Example B)
Next, with reference to FIG. 5, the result of Example B in which water treatment was actually performed on the wastewater using the wastewater treatment system 100 according to the first embodiment shown in FIG. 1 (one embodiment of the present invention). Results of reduction of 1,4-dioxane) will be described.

In Example B, the total weight of hydrogen peroxide supplied to the two-stage accelerated oxidation treatment tank 1 was changed with respect to the total weight of ozone supplied to the two-stage accelerated oxidation treatment tank 1. An example will be described.

As shown in FIG. 5, in Example B1 of the present invention, the total weight supplied to the two-stage accelerated oxidation treatment tank 1 is relative to the total weight of ozone supplied to the two-stage accelerated oxidation treatment tank 1. The weight of hydrogen peroxide is set to 5%.

In Example B2 of the present invention, the total weight of hydrogen peroxide supplied to the two-stage accelerated oxidation treatment tank 1 is 25 with respect to the total weight of ozone supplied to the two-stage accelerated oxidation treatment tank 1. %I have to.

In Example B3 of the present invention, the total weight of hydrogen peroxide supplied to the two-stage accelerated oxidation treatment tank 1 is 50 with respect to the total weight of ozone supplied to the two-stage accelerated oxidation treatment tank 1. %I have to.

Further, in Examples B1 to B3, the entire amount (100%) of hydrogen peroxide was injected into the first-stage (upstream) accelerated oxidation treatment tank 1 and the second-stage (downstream) accelerated oxidation treatment tank 1 was peroxidized. No hydrogen peroxide is injected.

As shown in FIG. 5, in Example B1, the residual rate of 1,4-dioxane (1,4-dioxane concentration at the outlet of the accelerated oxidation treatment tank 1 of the second stage / the inlet of the accelerated oxidation treatment tank 1 of the first stage). 1,4-dioxane concentration) is 10.2%. In Example B2, the residual rate of 1,4-dioxane is 1.3%. In Example B3, the residual rate of 1,4-dioxane is 1.2%. As a result, by making the total weight of hydrogen peroxide supplied to the accelerated oxidation treatment tank 1 5% or more of the total weight of ozone supplied to the accelerated oxidation treatment tank 1, 1 in the wastewater , 4-Dioxane can be decomposed efficiently. In particular, by making the total weight of hydrogen peroxide supplied to the accelerated oxidation treatment tank 1 25% or more of the total weight of ozone supplied to the accelerated oxidation treatment tank 1, 1, It can be seen that 4-dioxane can be decomposed more efficiently.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. In this second embodiment, unlike the first embodiment in which a parallel flow treatment tank is provided upstream and a countercurrent treatment tank is provided downstream, wastewater having a parallel flow treatment tank provided both upstream and downstream. An example of the processing system 200 will be described.

As shown in FIG. 6, the wastewater treatment system 200 includes an accelerated oxidation treatment tank (AOP tank) 5, an ozone supply unit 2, a hydrogen peroxide supply unit 3, and a raw water supply unit 4.

The accelerated oxidation treatment tank 5 includes a parallel flow treatment tank 51 and a parallel flow treatment tank 52. The parallel flow treatment tank 51 has an inflow port 511, an outflow port 512, and an ozone supply port 513. The parallel flow processing tank 52 has an inflow port 521, an outflow port 522, and an ozone supply port 523.

Two accelerated oxidation treatment tanks 5 are connected in series. Specifically, a parallel flow processing tank 51 is provided upstream, and a parallel flow processing tank 52 is provided in series downstream of the parallel flow processing tank 51. That is, the wastewater discharged from the outflow port 512 of the parallel flow treatment tank 51 flows into the inflow port 521 of the parallel flow treatment tank 52.

The inflow port 511, the outflow port 512, and the ozone supply port 513 of the parallel flow treatment tank 51 have the same configurations as the inflow port 111, the outflow port 112, and the ozone supply port 113 of the parallel flow treatment tank 11 of the first embodiment, respectively. Is. Further, the inflow port 521 and the ozone supply port 523 of the parallel flow treatment tank 52 have the same configurations as the inflow port 111 and the ozone supply port 113 of the parallel flow treatment tank 11 of the first embodiment, respectively.

The outlet 522 of the parallel flow treatment tank 52 has a gas-liquid separation portion so that ozone is not mixed in the treated water to be discharged. As a result, it is possible to prevent the gaseous ozone that has risen and accumulated in the upper part of the tank from being discharged from the outlet 522 together with the treated water.

The other configurations of the second embodiment are the same as those of the first embodiment.

(Effect of the second embodiment)
In the second embodiment, the following effects can be obtained.

As described above, in the second embodiment, as in the first embodiment, at least the most upstream accelerated oxidation treatment tank 5 (parallel flow treatment tank 51) among the plurality of accelerated oxidation treatment tanks 5 connected in series is used. By providing the hydrogen peroxide supply unit 3 that supplies hydrogen peroxide to the wastewater before it flows in so as to be mixed, it is possible to react the hydrogen peroxide sufficiently mixed with the wastewater with ozone in the accelerated oxidation treatment tank 5. .. As a result, 1,4-dioxane in wastewater can be efficiently decomposed.

Further, in the second embodiment, the parallel flow treatment tank 52 is provided at the most downstream of the plurality of accelerated oxidation treatment tanks 5 connected in series. As a result, the parallel flow treatment tank 52 capable of efficiently decomposing 1,4-dioxane can be arranged at the most downstream, so that the concentration of 1,4-dioxane contained in the treated water treated with wastewater can be adjusted. It can definitely be lowered.

Further, in the second embodiment, by providing the parallel flow treatment tanks 51 and 52 having a plurality of stages (two stages), wastewater is wastewater in two stages by the parallel flow treatment tanks 51 and 52 having high performance of decomposing 1,4-dioxane. Therefore, 1,4-dioxane in wastewater can be decomposed more efficiently.

The other effects of the second embodiment are the same as those of the first embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG. 7. In this third embodiment, unlike the first and second embodiments in which a parallel flow treatment tank is provided upstream, an example of a wastewater treatment system 300 having a configuration in which a countercurrent treatment tank is provided upstream will be described.

As shown in FIG. 7, the wastewater treatment system 300 includes an accelerated oxidation treatment tank (AOP tank) 6, an ozone supply unit 2, a hydrogen peroxide supply unit 3, and a raw water supply unit 4.

The accelerated oxidation treatment tank 6 includes a countercurrent treatment tank 61 and a countercurrent treatment tank 62. The countercurrent processing tank 61 has an inflow port 611, an outflow port 612, and an ozone supply port 613. The countercurrent processing tank 62 has an inflow port 621, an outflow port 622, and an ozone supply port 623.

Two accelerated oxidation treatment tanks 6 are connected in series. Specifically, a countercurrent processing tank 61 is provided upstream, and a countercurrent processing tank 62 is provided in series downstream of the countercurrent processing tank 61. That is, the wastewater discharged from the outflow port 612 of the countercurrent treatment tank 61 flows into the inflow port 621 of the countercurrent treatment tank 62.

The inflow port 611, the outflow port 612, and the ozone supply port 613 of the countercurrent treatment tank 61 have the same configurations as the inflow port 121, the outflow port 122, and the ozone supply port 123 of the countercurrent treatment tank 11 of the first embodiment, respectively. Is. Further, the inflow port 621, the outflow port 622, and the ozone supply port 623 of the countercurrent treatment tank 62 have the same configurations as the inflow port 121, the outflow port 122, and the ozone supply port 123 of the countercurrent treatment tank 12 of the first embodiment, respectively. Is.

The other configurations of the third embodiment are the same as those of the first embodiment.

(Effect of Third Embodiment)
In the third embodiment, the following effects can be obtained.

As described above, in the third embodiment, as in the first embodiment, at least the most upstream accelerated oxidation treatment tank 6 (counterflow treatment tank 61) among the plurality of accelerated oxidation treatment tanks 6 connected in series. By providing the hydrogen peroxide supply unit 3 that supplies hydrogen peroxide to the wastewater before it flows in so as to be mixed, it is possible to react the hydrogen peroxide sufficiently mixed with the wastewater with ozone in the accelerated oxidation treatment tank 6. .. As a result, 1,4-dioxane in wastewater can be efficiently decomposed.

Further, in the third embodiment, by making all the accelerated oxidation treatment tanks 6 into the countercurrent treatment tanks 61 and 62, it is possible to keep the wastewater in the tank at all times. Further, by providing the countercurrent treatment tanks 61 and 62 in which ozone exhaust is less likely to be emitted, the total amount of ozone exhaust can be reduced. Further, by adopting the countercurrent treatment tanks 61 and 62 in which the wastewater flows in from the upper part and is discharged from the lower part, the design and implementation can be easily performed.

The other effects of the third embodiment are the same as those of the first embodiment.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG. In this fourth embodiment, unlike the first embodiment in which a parallel flow treatment tank is provided upstream and a countercurrent treatment tank is provided downstream, a countercurrent treatment tank is provided upstream and a parallel flow treatment tank is provided downstream. An example of the wastewater treatment system 400 having the provided configuration will be described.

As shown in FIG. 8, the wastewater treatment system 400 includes an accelerated oxidation treatment tank (AOP tank) 7, an ozone supply unit 2, a hydrogen peroxide supply unit 3, and a raw water supply unit 4.

The accelerated oxidation treatment tank 7 includes a countercurrent treatment tank 71 and a parallel flow treatment tank 72. The countercurrent treatment tank 71 has an inflow port 711, an outflow port 712, and an ozone supply port 713. The parallel flow processing tank 72 has an inflow port 721, an outflow port 722, and an ozone supply port 723.

Two accelerated oxidation treatment tanks 7 are connected in series. Specifically, a countercurrent processing tank 71 is provided upstream, and a parallel flow processing tank 72 is provided in series downstream of the countercurrent processing tank 71. That is, the wastewater discharged from the outflow port 712 of the countercurrent treatment tank 71 flows into the inflow port 721 of the parallel flow treatment tank 72. Further, the outflow port 712 of the countercurrent treatment tank 71 is directly connected to the inflow port 721 of the parallel flow treatment tank 72 without passing through a water sealing pipe.

The inflow port 711, the outflow port 712, and the ozone supply port 713 of the countercurrent treatment tank 71 have the same configurations as the inflow port 121, the outflow port 122, and the ozone supply port 123 of the countercurrent treatment tank 12 of the first embodiment, respectively. Is. Further, the inflow port 721 and the ozone supply port 723 of the parallel flow treatment tank 72 have the same configurations as the inflow port 111 and the ozone supply port 113 of the parallel flow treatment tank 11 of the first embodiment, respectively.

The outlet 722 of the parallel flow treatment tank 72 has a gas-liquid separation portion so that ozone is not mixed in the treated water to be discharged. As a result, it is possible to prevent the gaseous ozone that has risen and accumulated in the upper part of the tank from being discharged from the outlet 722 together with the treated water.

The other configurations of the fourth embodiment are the same as those of the first embodiment.

(Effect of Fourth Embodiment)
In the fourth embodiment, the following effects can be obtained.

As described above, in the fourth embodiment, as in the first embodiment, at least the most upstream accelerated oxidation treatment tank 7 (counterflow treatment tank 71) among the plurality of accelerated oxidation treatment tanks 7 connected in series. By providing the hydrogen peroxide supply unit 3 that supplies hydrogen peroxide to the wastewater before it flows in so as to be mixed, it is possible to react the hydrogen peroxide sufficiently mixed with the wastewater with ozone in the accelerated oxidation treatment tank 7. .. As a result, 1,4-dioxane in wastewater can be efficiently decomposed.

Further, in the fourth embodiment, the countercurrent treatment tank 71 is provided in the first stage, and the parallel flow treatment tank 72 is provided in the second stage, so that the parallel flow treatment tank 72 having high performance of decomposing 1,4-dioxane is provided. And the wastewater can be treated by the countercurrent treatment tank 71 in which the exhaust ozone is hard to be generated. As a result, it is possible to suppress the generation of ozone exhaust while increasing the decomposition efficiency of 1,4-dioxane in wastewater.

The other effects of the fourth embodiment are the same as those of the first embodiment.

(Example C)
Next, with reference to FIG. 9, the wastewater treatment system 100 according to the first embodiment shown in FIG. 1, the wastewater treatment system 300 according to the third embodiment shown in FIG. 7, and the fourth embodiment shown in FIG. The result of Example C (result of reduction of 1,4-dioxane according to one example of the present invention) in which water treatment was actually performed on the wastewater using the wastewater treatment system 400 according to the embodiment will be described.

In Example C, examples in which the combination of the types of the first-stage accelerated oxidation treatment tank and the second-stage accelerated oxidation treatment tank are changed will be described.

As shown in FIG. 9, in the first stage (upstream), the parallel flow processing tank 11 is provided in the first stage (upstream), and the countercurrent processing tank 12 is provided in the second stage (downstream). Further, in Example C2, a countercurrent treatment tank 61 is provided in the first stage (upstream), and a countercurrent treatment tank 62 is provided in the second stage (downstream). In Example C3, a countercurrent processing tank 71 is provided in the first stage (upstream), and a parallel flow processing tank 72 is provided in the second stage (downstream).

As shown in FIG. 9, in Example C1, the residual rate of 1,4-dioxane (1,4-dioxane concentration at the outlet of the accelerated oxidation treatment tank 1 of the second stage / the inlet of the accelerated oxidation treatment tank 1 of the first stage). 1,4-dioxane concentration) is 0.70%. In Example C2, the residual rate of 1,4-dioxane is 1.23%. In Example C3, the residual rate of 1,4-dioxane is 0.91%. As a result, the results of Examples C1 and C3 provided with the parallel flow treatment tank decomposed more 1,4-dioxane in the wastewater than the results of Example C2 provided with only the countercurrent treatment tank. You can see that. That is, it can be seen that 1,4-dioxane in wastewater can be decomposed more efficiently by providing a parallel flow treatment tank.

(Example D)
Next, with reference to FIG. 10, the result of Example D in which water treatment was actually performed on the wastewater using the wastewater treatment system 100 according to the first embodiment shown in FIG. 1 (one embodiment of the present invention). The concentration of residual hydrogen peroxide and the treatment result of 1,4-dioxane) will be described.

In Example D, examples in which the concentrations of hydrogen peroxide (residual hydrogen peroxide) in the treated water flowing out from the most downstream accelerated oxidation treatment tank 1 are different from each other will be described.

In Example D, the entire amount (100%) of hydrogen peroxide is injected into the first-stage (upstream) accelerated oxidation treatment tank 1, and hydrogen peroxide is injected into the second-stage (downstream) accelerated oxidation treatment tank 1. Not. Further, in Example D, hydrogen peroxide is supplied so as to be mixed with the wastewater before flowing into the first-stage accelerated oxidation treatment tank 1.

Further, in Example D, the total weight of hydrogen peroxide supplied to the first-stage and second-stage accelerated oxidation treatment tanks 1 is that of ozone supplied to the first-stage and second-stage accelerated oxidation treatment tanks 1. It is adjusted based on about 30% of the total weight.

In Example D1, wastewater containing 3.96 mg / L of 1,4-dioxane in the wastewater before treatment was treated. Further, in Example D1, the concentration of residual hydrogen peroxide was 10 mg / L. In Example D2, wastewater containing 2.94 mg / L of 1,4-dioxane was treated in the wastewater before the treatment. Further, in Example D2, the concentration of residual hydrogen peroxide was 3 mg / L. In Example D3, wastewater containing 4.73 mg / L of 1,4-dioxane was treated in the wastewater before the treatment. Further, in Example D3, the concentration of residual hydrogen peroxide was 2 mg / L.

As shown in FIG. 10, in Example D1, the concentration of 1,4-dioxane in the treated water after the treatment was 0.039 mg / L, and the residual rate of 1,4-dioxane (second-stage accelerated oxidation treatment tank). The concentration of 1,4-dioxane at the outlet of 1 / the concentration of 1,4-dioxane at the inlet of the accelerated oxidation treatment tank of the first stage) is 1.0%. In Example D2, the concentration of 1,4-dioxane in the treated water after the treatment was 0.031 mg / L, and the residual rate of 1,4-dioxane (1,4- at the outlet of the second stage accelerated oxidation treatment tank 1). The dioxane concentration / 1,4-dioxane concentration at the inlet of the accelerated oxidation treatment tank 1 in the first stage) is 1.1%. In Example D3, the concentration of 1,4-dioxane in the treated water after the treatment was 0.117 mg / L, and the residual rate of 1,4-dioxane (1,4- at the outlet of the second stage accelerated oxidation treatment tank 1). The dioxane concentration / 1,4-dioxane concentration at the inlet of the accelerated oxidation treatment tank 1 in the first stage) is 2.5%.

In Examples D1 to D3, examples of residual hydrogen peroxide concentrations of 2 mg / L, 3 mg / L and 10 mg / L were shown, but when the residual hydrogen peroxide concentration was higher than 10 mg / L, It is considered that the residual rate of 1,4-dioxane does not change much because the decomposition efficiency approaches saturation. Further, since the concentration of residual hydrogen peroxide fluctuates and varies, it may be locally 0.5 mg / L. That is, if the concentration of residual hydrogen peroxide is 0.5 mg / L or more, the concentration of 1,4-dioxane can be decomposed to a specified value or less (for example, 0.5 mg / L or less). From Example D, by setting the concentration of hydrogen peroxide (residual hydrogen peroxide) in the treated water flowing out from the most downstream accelerated oxidation treatment tank 1 to 0.5 mg / L or more and 10 mg / L or less, 1,4 -It can be seen that dioxane can be decomposed efficiently and stably.

(Modification example)
It should be noted that the embodiments and examples disclosed this time are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the above-described embodiments and examples, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims.

For example, a biological treatment tank may be provided upstream of the accelerated oxidation treatment tank as in the first to fourth embodiments. For example, as in the modified example shown in FIG. 11, the wastewater treatment system 500 may include an ozone supply unit 2, a hydrogen peroxide supply unit 3, an accelerated oxidation treatment tank 8, and a biological treatment tank 9. .. The biological treatment tank 9 includes a first biological treatment tank 91, a second biological treatment tank 92, and a storage tank 93. The first biological treatment tank 91 is provided with an aerator 911 and a temperature control unit 912. The second biological treatment tank 92 is provided with aerators 921 and 922, a membrane 923, a temperature control unit 924, and a pipe 925.

As a general water treatment process of the wastewater treatment system 500, wastewater (raw water) is stored in the storage tank 93. The stored wastewater is transferred to the first biological treatment tank 91, and the first stage biological treatment (aeration treatment) is performed by activated sludge containing 1,4-dioxane-degrading bacteria. The primary treated water treated by the first biological treatment tank 91 is transferred to the second biological treatment tank 92 together with activated sludge containing 1,4-dioxane-degrading bacteria, and the second-stage biological treatment (MBR aeration treatment) is performed. Will be done. After that, the accelerated oxidation treatment is performed with hydrogen peroxide and ozone in the plurality of accelerated oxidation treatment tanks 8. In this way, wastewater (raw water) may be treated. The biological treatment tank may be provided in one tank or three or more tanks.

In the modified example shown in FIG. 11, the first biological treatment tank 91 is configured to perform biological treatment on wastewater (raw water) using activated sludge to mainly reduce BOD and COD in the wastewater. .. Further, the first biological treatment tank 91 is configured so that 1,4-dioxane-degrading bacteria in the activated sludge are acclimatized. The aerator 911 is configured to supply air to the wastewater of the first biological treatment tank 91. As a result, oxygen is supplied to the activated sludge in the first biological treatment tank 91, and the wastewater and the activated sludge are mixed.

The temperature adjusting unit 912 is provided so as to maintain the water temperature of the first biological treatment tank 91 (for example, 15 ° C. or higher and 40 ° C. or lower). Specifically, the temperature adjusting unit 912 is configured to allow water vapor to flow to raise the water temperature of the first biological treatment tank 91. As a result, the water temperature in the first biological treatment tank 91 is maintained at a temperature at which the activated sludge is activated, and at a temperature suitable for acclimatization of 1,4-dioxane-degrading bacteria.

The second biological treatment tank 92 is configured to perform biological treatment on the primary treated water using activated sludge containing 1,4-dioxane-degrading bacteria to mainly reduce 1,4-dioxane in the wastewater. ing. That is, in the second biological treatment tank 92, 1,4-dioxane in the primary treatment water is mainly decomposed by the 1,4-dioxane-degrading bacteria accustomed in the first biological treatment tank 91.

The aerators 921 and 922 are configured to supply air to the wastewater (primary treated water) of the second biological treatment tank 92. As a result, oxygen is supplied to the activated sludge in the second biological treatment tank 92, and the wastewater and the activated sludge are mixed. The membrane 923 is composed of a plurality of hollow fiber membranes. Further, the membrane 923 is configured to separate the activated sludge and the treated water. That is, the membrane 923 is configured to allow treated water to pass through, pass through the hollow interior, and remain in the second biological treatment tank 92 without passing through activated sludge.

The temperature adjusting unit 924 is provided so as to maintain the water temperature of the second biological treatment tank 92 (for example, 15 ° C. or higher and 40 ° C. or lower). Specifically, the temperature adjusting unit 924 is configured to allow water vapor to flow to raise the water temperature of the second biological treatment tank 92. As a result, the water temperature in the second biological treatment tank 92 is maintained at a temperature at which the 1,4-dioxane-degrading bacteria are activated.

The pipe 925 is provided to return the activated sludge. Specifically, the pipe 925 is configured to return the activated sludge from the downstream side of the second biological treatment tank 92 to the first biological treatment tank 91. Further, the pipe 925 is configured to return the activated sludge from the downstream side to the upstream side of the second biological treatment tank 92.

In this way, the concentration of 1,4-dioxane in the wastewater is lowered to some extent by the biological treatment tank 9, and then the concentration of 1,4-dioxane in the wastewater is lowered to a predetermined value or less by the accelerated oxidation treatment tank 8. You may. As a result, the concentration of 1,4-dioxane in the wastewater can be stably reduced by the decomposition treatment of both the biological treatment tank 9 and the accelerated oxidation treatment tank 8.

Further, in the first to fourth embodiments, an example of the configuration in which 1,4-dioxane is used as the persistent substance is shown, but the present invention is not limited to this. In the present invention, a substance other than 1,4-dioxane may be used as the persistent substance. Further, when a substance that decreases exponentially with respect to the amount of ozone injected is used as the persistent substance, it can be efficiently decomposed by the wastewater treatment system of the present invention.

Further, in the first to fourth embodiments, an example of a configuration in which two accelerated oxidation treatment tanks are provided in the wastewater treatment system is shown, but the present invention is not limited to this. In the present invention, the wastewater treatment system may be provided with three or more accelerated oxidation treatment tanks.

Further, in the first to fourth embodiments, an example of a configuration in which the accelerated oxidation treatment is performed using hydrogen peroxide and ozone in the accelerated oxidation treatment tank is shown, but the present invention is not limited to this. In the present invention, in the accelerated oxidation treatment tank, the accelerated oxidation treatment may be performed using ultraviolet rays in addition to hydrogen peroxide and ozone.

Further, in the first embodiment, the hydrogen peroxide supply unit has shown an example of a configuration in which 50% by weight of hydrogen peroxide is supplied with respect to the weight of ozone supplied by the ozone supply unit. The invention is not limited to this. In the present invention, the hydrogen peroxide supply unit may be configured to supply hydrogen peroxide having a weight of 5% or more and 50% or less with respect to the weight of ozone supplied by the ozone supply unit. The amount of hydrogen peroxide supplied may be adjusted according to the liquidity of the wastewater.

Further, a pH adjusting unit for adjusting the pH of wastewater may be provided. The pH regulator may supply, for example, sulfuric acid or sodium hydroxide to the wastewater. As a result, the pH of the wastewater can be adjusted to a pH suitable for accelerated oxidation, so that the persistently decomposable substance can be decomposed more efficiently. Further, the wastewater may be adjusted to be weakly basic (pH is about 8 to about 10) by the pH adjusting unit. As a result, hydroxide ions in the wastewater react with ozone to generate hydroxyl radicals, so that the generated hydroxyl radicals can more effectively decompose persistent substances. Further, a pH measuring device may be provided at each outlet of the plurality of accelerated oxidation treatment tanks, and the pH adjusting unit may automatically adjust the pH of the wastewater. Further, the pH adjusting unit may inject acid or alkali into a place including wastewater before treatment, outlets of each tank, pipes connecting each tank, and the like.

Further, in the first embodiment, the hydrogen peroxide supply unit supplies the hydrogen peroxide to the wastewater before flowing into the most upstream accelerated oxidation treatment tank among the plurality of accelerated oxidation treatment tanks connected in series. An example of a configuration in which the entire amount (100%) of hydrogen peroxide is supplied has been shown, but the present invention is not limited to this. In the present invention, the hydrogen peroxide supply unit is 50% or more of the total amount of hydrogen peroxide supplied to the wastewater before flowing into the most upstream accelerated oxidation treatment tank among the plurality of accelerated oxidation treatment tanks connected in series. It may be configured to supply less than 100% hydrogen peroxide. Further, hydrogen peroxide may be directly injected (supplied) into the second and subsequent stages of the accelerated oxidation treatment tank.

1, 5, 6, 7, 8 Accelerated oxidation treatment tank 2 Ozone supply unit 3 Hydrogen peroxide supply unit 11, 51, 52, 72 Parallel flow treatment tank (accelerated oxidation treatment tank)
12, 61, 62, 71 Stream processing tank (accelerated oxidation treatment tank)
100, 200, 300, 400, 500 Wastewater treatment system

Claims (5)

An accelerated oxidation treatment tank that is connected in series and is provided to treat wastewater containing persistent substances by accelerated oxidation treatment.
An ozone supply unit that supplies ozone to the accelerated oxidation treatment tank,
A hydrogen peroxide supply unit that supplies hydrogen peroxide to a pipe through which wastewater passes before flowing into at least the most upstream of the accelerated oxidation treatment tanks among a plurality of the accelerated oxidation treatment tanks connected in series. With and
The most upstream of the plurality of accelerated oxidation treatment tanks connected in series is provided with a parallel flow treatment tank in which both the ozone flow direction and the wastewater flow direction are from bottom to top.
The hydrogen peroxide supply unit provides a plurality of the accelerated oxidation to the wastewater before flowing into the parallel flow treatment tank, which is the most upstream of the accelerated oxidation treatment tanks, among the plurality of the accelerated oxidation treatment tanks connected in series. A wastewater treatment system configured to supply the entire amount of hydrogen peroxide supplied to the treatment tank. Persistent substances include 1,4-dioxane and
The first aspect of the present invention, wherein the hydrogen peroxide supply unit is configured to supply hydrogen peroxide having a weight of 5% or more and 50% or less with respect to the weight of ozone supplied by the ozone supply unit. Wastewater treatment system. In the most downstream of the plurality of accelerated oxidation treatment tanks connected in series, the direction in which ozone flows in the tank is from bottom to top, and the direction in which wastewater flows is from top to bottom. The wastewater treatment system according to claim 1 or 2, wherein a tank is provided. The wastewater treatment system according to claim 1 or 2, wherein the parallel flow treatment tank is provided at the most downstream of the plurality of the accelerated oxidation treatment tanks connected in series. In the hydrogen peroxide supply unit, the concentration of hydrogen peroxide in the treated water flowing out from the most downstream accelerated oxidation treatment tank among the plurality of the accelerated oxidation treatment tanks connected in series is 0.5 mg / L or more and 10 mg / L. The wastewater treatment system according to any one of claims 1 to 4, wherein the amount of hydrogen peroxide supplied so as to be L or less is adjusted.

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