JP2017104860A - Sewage treatment system and sewage treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewage treatment system and a sewage treatment method producing a hypobromous acid compound at a stable concentration, capable of swiftly and efficiently utilizing the disinfection effect of a hypobromous acid compound and capable of swiftly dealing with large quantity of sewage treatment upon large quantity rain fall as well.SOLUTION: Provided is a sewage treatment system comprising: a treatment passage 10 where sewage flows in-out; a reaction flow passage 20 in which the downflow edge 20b is connected to the treatment flow passage 10; a hypobromous acid feed apparatus 30 connected to the upstream edge 20a of the reaction flow passage 20 and feeding the aqueous solution of a hypobromous acid; and a bromide feed apparatus 40 feeding the aqueous solution of a bromine compound. The reaction flow passage 20 is the one reacting the aqueous solution of a hypobromous acid compound fed from the hypobromous acid feed apparatus 30 and the aqueous solution of a bromine compound fed from the bromide feed apparatus 40 while circulating the inside of the flow passage without being contacted with the air to produce a hypobromous acid compound.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sewage treatment system and a sewage treatment method.

In large cities, combined sewers are widely used, and various wastewater and rainwater flow into the sewage treatment plant through the sewers as sewage, and after purification and disinfection, Discharged as treated water.
However, in rainwater combined sewers, when there is rainfall that exceeds the treatment capacity of the sewage treatment plant, sufficient purification and disinfection cannot be performed, and the water is discharged without satisfying the water quality standards required for treated water. There is a problem that it may end up.
As a method of disinfection treatment, a method of adding a chemical is general, and a chlorine-based disinfectant, particularly, a sodium hypochlorite aqueous solution that is a hypochlorous acid compound is widely used. In order to increase the treatment efficiency, it is conceivable to use a high concentration of sodium hypochlorite as a disinfectant. However, if the concentration of the hypochlorous acid compound is increased, the effect of residual chloramine generated by the reaction with ammoniacal nitrogen in the sewage becomes a problem.

  Under such circumstances, in order to improve the treatment capacity of the sewage treatment plant, sewage using a hypobromite compound that has a high disinfection effect, can be disinfected in a shorter time, and does not produce residual by-products. A processing method has been proposed (Patent Documents 1 to 3).

  Compared to hypochlorous acid compounds, hypobromite compounds are known to have a higher disinfecting effect, but are generally unstable substances. Therefore, in the method for treating sewage with a hypobromite compound, a hypobromite compound is generated and used at the site where sewage is treated.

  In Patent Document 1, a bromide of a metal element is reacted with hypochlorous acid or a salt thereof to produce a hypobromite compound. However, since the reaction requires a certain time, a reaction vessel (hypobromite) is produced. The hypobromite disinfectant is generated in the acid generator, and then supplied to the sand basin into which the wastewater to be treated flows using the disinfectant supply pipe. In this embodiment, since the produced hypobromite compound is unstable, its decomposition cannot be controlled, and it is difficult to supply it to the wastewater at a stable concentration.

  Further, in order to cope with a sudden rain, it is necessary to quickly generate a disinfectant. Therefore, in Patent Document 2, in order to promote a reaction for generating hypobromite from a compound that generates hypochlorous acid and a compound that generates bromide ions, the reaction is performed in the presence of a specific organic acid. Is disclosed. However, when treating a large amount of sewage, the required amount of the hypobromite compound is increased, and the required amount of the organic acid is increased accordingly, which is disadvantageous in terms of cost.

  In Patent Document 3, sewage is disinfected using a disinfectant such as 1-bromo-3-chloro-5,5-dimethylhydantoin (hereinafter referred to as “BCDMH”) that can produce hypobromite. It has been proposed to do. BCDMH is an excellent disinfectant because it can be stored for a long time as a solid and the disinfecting effect is remarkable even when the contact time with sewage is short. However, the price is expensive and disadvantageous in terms of cost. Moreover, since it is solid, it is not easy to solve the problem when the supply device has a problem. Furthermore, 5,5-dimethylhydantoin produced by hydrolysis of BCDMH has a low solubility in water and has a problem that a large amount of undissolved 5,5-dimethylhydantoin is produced.

JP 2003-12425 A Japanese Patent No. 4398161 Japanese Patent No. 3668071

  An object of the present invention is to provide a sewage treatment system capable of quickly supplying a hypobromite compound to sewage at a stable concentration.

The present invention has the following configuration.
[1] A treatment flow path in which sewage flows from the upstream end and flows out from the downstream end;
A reaction channel having a downstream end connected to the processing channel;
A hypochlorous acid supply device for supplying an aqueous solution of a hypochlorous acid compound and a bromide supply device for supplying an aqueous solution of a bromine compound, connected to the upstream end of the reaction flow path,
The reaction channel circulates an aqueous solution of a hypochlorous acid compound supplied from the hypochlorous acid supply device and an aqueous solution of a bromine compound supplied from the bromide supply device without contacting the inside of the flow channel with air. A sewage treatment system, which is a flow path for generating a hypobromite compound by reacting with the reaction.
[2] The sewage treatment according to [1], wherein the length of the treatment channel from the upstream end to the downstream end of the treatment channel is at least one time the sewage flowing through the treatment channel travels per minute. system.
[3] The sewage treatment according to [2], wherein the length of the treatment channel from the upstream end to the downstream end of the treatment channel is 10 times or less the distance traveled by the sewage flowing through the treatment channel per minute. system.
[4] A control device is provided, and the control device allows a distance traveled by the aqueous solution flowing through the reaction channel per minute to be 1 / less than the reaction channel length from the upstream end to the downstream end of the reaction channel. The sewage treatment system according to any one of [1] to [3], which is controlled to 2 to 1/15 times.
[5] A control device is provided, and is controlled by the control device so that 0.4 to 8 mg of hypobromite compound in terms of effective chlorine amount is supplied to 1 L of sewage flowing through the treatment channel. The sewage treatment system according to any one of [1] to [4].
[6] The sewage treatment system according to any one of [1] to [5], wherein a mixing device that mixes the aqueous solution flowing through the reaction flow path without touching air is provided.
[7] A sewage treatment method in which an aqueous solution of a hypochlorous acid compound and an aqueous solution of a bromine compound are reacted while flowing through a flow path without being exposed to air, and the produced hypobromite compound is supplied to sewage.

  According to the sewage treatment system and the sewage treatment method of the present invention, an aqueous solution of a hypochlorous acid compound and an aqueous solution of a bromine compound that require a certain time for the reaction are allowed to flow without being exposed to air in the reaction channel. Because of the reaction, the hypobromite compound can be produced at a stable concentration. Further, since the sewage and the hypobromite compound can be brought into contact immediately after the hypobromite compound is produced, the disinfecting effect of the hypobromite compound can be used quickly and efficiently. Therefore, it is possible to respond quickly to a large amount of sewage treatment during heavy rainfall.

It is a mimetic diagram showing one mode of a sewage treatment system of the present invention.

  Hereinafter, the sewage treatment system and the sewage treatment method of the present invention will be described. The following embodiments are merely examples for explaining the present invention, and the present invention is not intended to be limited only to these embodiments. The present invention can be implemented in various forms without departing from the spirit of the present invention.

<Sewage treatment system>
FIG. 1 is a schematic view showing an embodiment of the sewage treatment system of the present invention. Hereinafter, the present invention will be described with reference to FIG. 1 showing an embodiment (hereinafter, also referred to as “this embodiment”).

  The sewage treatment system 1 includes a treatment channel 10 for treating sewage, a reaction channel 20 for producing a hypobromite compound, a hypochlorous acid supply device 30 and a bromide supply device 40.

(Processing channel)
The treatment channel 10 is a channel through which sewage flows from the upstream end 10a through the sewage inflow channel 60 (not included in the sewage treatment system of the present invention) and the treated sewage flows out from the downstream end 10b.
The downstream end 10b of the treatment channel 10 is connected to a public water area 70 (not included in the sewage treatment system of the present invention), and the sewage treated in the treatment channel 10 is a public water area including rivers and oceans. 70 is released.

The distance from the upstream end 10 a of the processing channel 10 to the downstream end 10 b of the processing channel 10 (hereinafter referred to as “processing channel length”) is the distance from the sewage flowing through the processing channel 10 to the public water area 70. It is necessary to have a sufficient distance for the processing to be performed.
The treatment channel length is preferably 1 or more times the distance traveled by the sewage flowing through the treatment channel 10 per minute, more preferably 2 or more, and even more preferably 3 or more. If the treatment channel length is equal to or longer than the lower limit value, sufficient time can be taken until the sewage comes into contact with the hypobromite compound supplied from the reaction channel 20 and is discharged into the public water area 70. .
When the treatment channel length is one time the sewage flowing through the treatment channel 10 travels per minute, the sewage and the hypobromite compound supplied from the reaction channel 20 come into contact with each other, and the public water area 70 It takes 1 minute to be released.

  Further, the length of the treatment channel is preferably 10 times or less, more preferably 8 times or less, and further preferably 5 times or less the distance traveled by the sewage flowing through the treatment channel 10 per minute. If the treatment channel length is equal to or shorter than the upper limit value, the space required for the sewage treatment system may be small.

  The treatment channel length is preferably 1 to 10 times the distance traveled by the sewage flowing through the treatment channel 10 per minute, more preferably 1 to 8 times, and more preferably 1 to 5 times. preferable.

In FIG. 1, the processing flow path 10 is a straight flow path, but may be bent in the middle or may be a curved flow path.
In addition, for example, sewage flowing from the sewage inflow channel 60 is supplied to the settling basin, and is transported to a storage pond or discharge beam through a pump or the like provided in the settling basin, and the treated sewage is discharged to the public water area 70. In some cases, the processing channel 10 may also serve as facilities such as a sand basin, a storage pond, and a discharge beam.
In this case, the hypobromite compound generated in the reaction channel 20 described later may be supplied to the sedimentation basin, or may be supplied to the storage pond and the discharge beam. In the facility, the supply point of the hypobromite compound from the reaction channel 20 is the upstream end 10 a of the processing channel 10.

(Reaction channel)
The reaction channel 20 is a channel whose downstream end 20 b is connected to the upstream end 10 a of the processing channel 10. A hypochlorous acid supply device 30 and a bromide supply device 40 which will be described later are connected to the upstream end 20a of the reaction channel 20. The reaction channel 20 causes the aqueous solution of the hypochlorous acid compound supplied from the hypochlorous acid supply device 30 and the aqueous solution of the bromine compound supplied from the bromide supply device 40 to come into contact with the air in the reaction channel. This is a flow path for generating a hypobromite compound by reacting while circulating. The hypobromite compound generated in the reaction channel 20 is supplied to the processing channel 10 from the downstream end 20b.

As described above, a certain time is required for the reaction of the hypochlorous acid compound and the bromine compound to form the hypobromite compound. Therefore, the distance from the upstream end 20a to the downstream end 20b of the reaction channel 20 (hereinafter referred to as “reaction channel length”) is sufficient for the reaction of the hypochlorous acid compound and the bromine compound to proceed sufficiently. It is necessary to have a certain distance.
The reaction channel length is preferably 2 to 15 times the distance traveled by the aqueous solution flowing through the reaction channel 20 per minute.
As a certain aspect, it is more preferable that it is 5 to 15 times, it is further more preferable that it is 5 to 12 times, and it is especially preferable that it is 5 to 10 times. If the reaction channel length is within the above range with respect to the distance that the aqueous solution flowing through the reaction channel 20 travels per minute, the hypobromite compound produced by the reaction of the hypochlorous acid compound and the bromine compound The amount of can be maximized.
Moreover, as another aspect, it is more preferable that it is 2 to 10 times, it is further more preferable that it is 2 to 8 times, and it is especially preferable that it is 2 to 5 times. If the reaction channel length is within the above range with respect to the distance that the aqueous solution flowing through the reaction channel 20 travels per minute, the reaction flow is sufficiently advanced while allowing the reaction between the hypochlorous acid compound and the bromine compound to proceed sufficiently. By shortening the road, the installation area can be reduced and the installation cost can be reduced.

Therefore, the distance that the aqueous solution flowing through the reaction channel 20 travels per minute is preferably 1/2 to 1/15 times the reaction channel length. As a certain aspect, it is more preferable that it is 1/5-1/15 times, 1/5-1/12 times are still more preferable, 1/5-1/10 times are especially preferable. Moreover, as another aspect, it is more preferable that it is 1/2 to 1/10 times, it is more preferable that it is 1/2 to 1/8 times, and it is that it is 1/2 to 1/5 times Particularly preferred.
The distance that the aqueous solution flowing through the reaction channel 20 travels per minute can be adjusted by, for example, controlling the flow rate of the aqueous solution flowing through the reaction channel 20, the tube diameter of the reaction channel 20, or the like.
When the distance traveled by the aqueous solution flowing through the reaction channel 20 per minute is 1/5 times the length of the reaction channel, the hypochlorous acid compound supplied as an aqueous solution from the hypochlorous acid supply device 30 and the bromide It takes 5 minutes for the bromine compound supplied as an aqueous solution from the supply device 40 to start the reaction and to be supplied to the treatment channel 10.

  In the present invention, the “aqueous solution flowing in the reaction channel” means an aqueous solution containing at least one of a hypochlorous acid compound, a bromine compound, and a hypobromite compound that flows in the reaction channel.

As shown in the test examples described later, since the hypobromite compound is rapidly decomposed by contact with air, in the present invention, the hypobromite compound is not brought into contact with air in the production of the hypobromite compound. For this reason, the reaction flow path 20 needs to be a closed space except for the upstream end and the downstream end. In addition, it is necessary to circulate the aqueous solution in a state where there is no air layer in the reaction channel 20.
As a method of circulating the aqueous solution in the absence of an air layer in the reaction channel, for example, the position of the downstream end 20b of the reaction channel 20 is higher than the position of the upstream end 20a of the reaction channel 20, A method of circulating an aqueous solution while extruding the air layer in the reaction channel 20 can be mentioned. Inevitable dissolved air may be contained in the aqueous solution.

The reaction channel 20 is used to promote the reaction between the hypochlorous acid compound supplied as an aqueous solution from the hypochlorous acid supply device 30 and the bromine compound supplied as an aqueous solution from the bromide supply device 40. You may provide the mixing apparatus 22 (not shown in FIG. 1) which mixes the flowing aqueous solution, without contacting air.
As the mixing device 22, a known stirring device such as a line mixer or a static mixer can be employed.
The mixing device 22 may be provided at any position in the reaction flow path 20, but the upstream end 20 a and the downstream end 20 b of the reaction flow path 20 are obtained in that the effect of promoting the reaction by stirring can be obtained at an earlier stage. It is preferable to be provided upstream of the intermediate point.

(Hypochlorous acid supply device)
The hypochlorous acid supply device 30 is a supply device that supplies an aqueous solution of a hypochlorous acid compound to the reaction flow path 20.

  Examples of the hypochlorous acid compound include sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, etc., from the point of reactivity with the bromine compound described below and the point that it can be obtained at low cost. Sodium hypochlorite is preferred.

The hypochlorous acid supply device 30 in the present embodiment includes a hypochlorous acid storage tank 32, a hypochlorous acid addition channel 36, and a hypochlorous acid addition pump provided in the hypochlorous acid addition channel 36. 34.
As the hypochlorous acid addition pump 34, it is preferable to use a pump having a quantitative property such as a diaphragm type or a snake type.

  If there is a sufficient difference between the liquid level of the hypochlorous acid storage tank 32 and the height of the upstream end 20a of the reaction channel 20, the flow rate can be controlled instead of the hypochlorous acid addition pump 34. A simple automatic valve can also be used.

  The effective chlorine concentration of the aqueous solution of hypochlorous acid compound may be lowered by long-term storage, and the effective chlorine concentration of the aqueous solution of hypochlorous acid compound stored in the hypochlorous acid storage tank 32 may vary. Therefore, the supply amount of the aqueous solution of the hypochlorous acid compound to the reaction flow path 20 can be controlled by interlocking the continuous measurement type effective chlorine concentration meter with the hypochlorous acid addition pump 34 or the above automatic valve. it can.

(Bromide feeder)
The bromide supply device 40 is a supply device that supplies an aqueous solution of a bromine compound to the reaction channel 20.

  Examples of bromine compounds include sodium bromide, alkali metal bromides including potassium bromide, magnesium bromide, alkaline earth metal bromides including calcium bromide, etc., and reactivity with hypochlorous acid compounds Sodium bromide is preferable because it can be obtained inexpensively.

The bromide supply device 40 in this embodiment includes a bromide reservoir 42, a bromide addition channel 46, and a bromide addition pump 44 provided in the bromide addition channel 46.
As the bromide addition pump 44, the same one as the hypochlorous acid addition pump 34 can be used.

  In the case where a sufficient difference is provided between the liquid level of the bromide reservoir 42 and the height of the upstream end 20a of the reaction channel 20, an automatic valve capable of controlling the flow rate is used instead of the bromide addition pump 44. You can also.

(Control device)
The sewage treatment system of the present invention may include a control device. The control device 50 can control the whole or a part of the sewage treatment system 1.
The control device 50 controls the distance that the aqueous solution flowing through the reaction flow path 20 travels per minute, so that the aqueous solution and bromide supply of the hypochlorous acid compound supplied from the hypochlorous acid supply device 30 to the reaction flow path 20 are supplied. The supply amount of the bromine compound aqueous solution supplied from the apparatus 40 to the reaction flow path 20 can be controlled.

The control device 50 also controls the molar ratio of the hypochlorous acid compound and the bromine compound supplied to the reaction channel 20 from the hypochlorous acid supply device 30 to the reaction channel 20. The supply amount of the aqueous solution of the chlorous acid compound and the aqueous solution of the bromine compound supplied from the bromide supply device 40 to the reaction flow path 20 are controlled.
The molar ratio of the bromine compound to the hypochlorous acid compound supplied to the reaction channel 20 is preferably controlled to 1 to 2, more preferably 1.2 to 1.8. More preferably, it is controlled to 4 to 1.6. If the molar ratio of the bromine compound to the hypochlorous acid compound supplied to the reaction channel 20 is equal to or higher than the lower limit value, almost the entire amount of the hypochlorous acid compound can be converted to the hypobromite compound. If the molar ratio of the bromine compound to the hypochlorous acid compound supplied to the reaction channel 20 is equal to or less than the upper limit, the use of excess bromine compound can be suppressed.

  The amount of sewage flowing into the processing channel 10 through the sewage inflow channel 60 may change according to the amount of rainfall in the upstream area of the sewage inflow channel 60. In particular, during heavy rainfall, a large amount of sewage flows into the sewage inflow channel 60, and as a result, a large amount of sewage flows into the treatment channel 10. The amount of the hypobromite compound supplied from the reaction channel 20 to the processing channel 10 is preferably controlled according to the amount of sewage flowing into the processing channel 10 through the sewage inflow channel 60.

The hypobromite compound supplied from the reaction channel 20 to the treatment channel 10 is preferably controlled to 0.4 to 8 mg in terms of effective chlorine amount with respect to 1 L of sewage flowing through the treatment channel 10. , More preferably 0.5 to 7 mg, and even more preferably 0.8 to 6 mg. A sufficient sewage treatment effect can be obtained if the hypobromite compound supplied from the reaction channel 20 to the treatment channel 10 is not less than the lower limit value with respect to 1 L of sewage flowing through the treatment channel 10. If the hypobromite compound supplied from the reaction channel 20 to the treatment channel 10 is less than or equal to the above upper limit value with respect to 1 L of sewage flowing through the treatment channel 10, excess hypochlorous acid compound and bromine The use of the compound can be suppressed.
Note that the sewage inflow passage 60 for supplying sewage to the treatment channel 10 is connected to a so-called sewage pipe, and it can be assumed that sewage flowing from the sewage pipe is supplied to the treatment channel 10. A large amount of sludge containing organic waste may remain on the pipe wall of the sewage pipe due to the increase or decrease of the sewage flow rate, that is, the water surface of the sewage goes up and down. In such a case, if there is a sudden increase in the sewage flow rate due to a large amount of rainfall, etc., the sludge remaining on the pipe wall of the sewage pipe will be washed away, causing the concentration of the disinfection target in the sewage to rise temporarily. There is. In that case, the amount of the hypobromite compound supplied from the reaction channel 20 to the processing channel 10 exceeds the above-mentioned amount, and may be controlled to, for example, 8 mg to 20 mg in terms of effective chlorine amount. However, if the concentration of the disinfecting object in the sewage returns to a steady state, such as after the sludge remaining on the pipe wall of the sewage pipe is washed away, the hypobromite compound supplied from the reaction channel 20 to the treatment channel 10 Is controlled to the aforementioned amount.
Further, the sewage flowing through the processing channel 10 is a combination of sewage flowing into the processing channel 10 from the sewage inflow channel 60 and an aqueous solution containing a hypobromite compound flowing into the processing channel 10 from the reaction channel 20. Means something.

  The amount of hypochlorous acid compound supplied from the reaction channel 20 to the treatment channel 10 in terms of the effective chlorine amount with respect to 1 L of sewage flowing through the treatment channel 10 is the hypochlorous acid compound supplied to the reaction channel 20. If the molar ratio of the bromine compound to the chloric acid compound is 1 or more, the hypochlorite compound in the mixture before the reaction of the hypochlorous acid compound and the bromine compound at the upstream end 20a of the reaction channel 20 starts. It is obtained from the effective chlorine concentration.

The amount of the hypobromite compound supplied from the reaction channel 20 to the treatment channel 10 is determined based on the amount of the hypochlorous acid compound aqueous solution and bromide supply device 40 supplied from the hypochlorous acid supply device 30 to the reaction channel 20. It can adjust by controlling the supply amount of the aqueous solution of the bromine compound supplied to the reaction flow path 20 from. However, when the amount of sewage flowing into the processing channel 10 through the sewage inflow channel 60 is small, the above supply is performed so that the amount of hypobromite compound supplied from the reaction channel 20 to the processing channel 10 is appropriate. If the amount is reduced, the distance that the aqueous solution flowing through the reaction flow path 20 travels per minute may not be adjusted to the above-described preferable range. In that case, in order to ensure the distance that the aqueous solution flowing through the reaction channel 20 travels per minute, the concentration of the hypobromite compound in the aqueous solution supplied from the reaction channel 20 to the treatment channel 10 is lowered. There must be.
As a method for reducing the concentration of the hypobromite compound in the aqueous solution supplied from the reaction channel 20 to the treatment channel 10, hypochlorous acid supplied from the hypochlorous acid supply device 30 to the reaction channel 20 is used. Although it is conceivable to dilute one or both of the aqueous solution of the compound and the aqueous solution of the bromine compound supplied from the bromide supply device 40 to the reaction flow path 20 before being supplied to the reaction flow path 20, Water may be supplied.
As the dilution water, clean water or sewage treated in the treatment channel 10 can be used. Moreover, the sewage which flows in from the sewage inflow path 60 as dilution water, or the sewage in which the process in the process flow path 10 is advancing can also be used.
When dilution water is supplied to the reaction channel 20, it is preferably supplied upstream from an intermediate point between the upstream end 20 a and the downstream end 20 b of the reaction channel 20, and is supplied from the upstream end 20 a of the reaction channel 20. Also good.
Further, one or both of an aqueous solution of a hypochlorous acid compound supplied from the hypochlorous acid supply device 30 to the reaction channel 20 and an aqueous solution of a bromine compound supplied from the bromide supply device 40 to the reaction channel 20 are reacted. When diluted before being supplied to the flow path 20, the dilution water may be supplied to one or both of the hypochlorous acid addition flow path 36 and the bromide addition flow path 46. In this case, the supply point of the dilution water may be upstream, downstream, or both of the hypochlorous acid addition pump 34 or the bromide addition pump 44.

<Action mechanism>
According to the sewage treatment system of the present invention, a hypochlorous acid compound and a bromine compound, which are supplied as an aqueous solution, are reacted while circulating in the reaction channel to generate a hypobromite compound, and immediately, the treatment channel Can supply.
Moreover, decomposition | disassembly of the produced | generated hypobromite compound can be suppressed by making a hypochlorous acid compound and a bromine compound react within a flow path avoiding a contact with air.
Further, by reacting the hypochlorous acid compound and the bromine compound while circulating in the reaction channel, the hypochlorous acid compound and the bromine compound that require a certain time for the reaction can be sufficiently reacted, and The produced hypobromite compound can be immediately supplied to the treatment channel. Therefore, the hypobromite compound can be supplied to the treatment channel at a stable concentration, and the disinfecting effect of the hypobromite compound can be used quickly and efficiently.

  According to the sewage treatment system of the present invention, when there is rainfall in the upstream area of the sewage treatment system, the amount of sewage flowing into the sewage treatment system is predicted in advance from the rain condition, and the sewage flows into the sewage inflow channel. The timing of supplying the hypobromite compound from the reaction channel to the processing channel and the hypobromite supplied from the reaction channel to the processing channel in accordance with the time to flow into the sewage treatment system of the present invention The amount of the acid compound can be controlled. Therefore, it is possible to respond quickly to a large amount of sewage treatment during heavy rainfall.

  Hereinafter, the present invention will be specifically described with reference to examples and reference examples, but the present invention is not limited to these examples.

Experimental Example A: Decomposition of Hypobromite Compound by Contact with Air [Example A1]
0.1 mL of a sodium hypochlorite aqueous solution having an effective chlorine concentration of 5% by mass is diluted with distilled water using a 100 mL volumetric flask, and approximately 50 ppm of a sodium hypochlorite aqueous solution (hereinafter referred to as “solution I”). .) Was obtained. 1.0-1.5 mL of solution I was added to the spectrophotometer cell.
Approximately 0.4 g of sodium bromide is dissolved in distilled water using a 100 mL volumetric flask, and 1 mL of this aqueous solution is diluted with distilled water using a 50 mL volumetric flask to obtain approximately 80 ppm of aqueous sodium bromide solution. (Hereinafter referred to as “II solution”). Solution II was added to a spectrophotometer cell containing 1.0 to 1.5 mL of Solution I to initiate the sodium hypobromite formation reaction.
The spectrophotometer cell was set in a spectrophotometer, and the absorbance until 30 minutes later was measured over time at a wavelength of 330 nm (maximum absorption wavelength of sodium hypobromite).
Table 1 shows changes with time in absorbance in the above test.

[Example A2]
Similarly to Example A1, the cell in which the liquid I and liquid II were mixed was set in a spectrophotometer, and the absorbance until the lapse of 15 minutes was measured over time at a wavelength of 330 nm. Then, after measuring the absorbance after 15 minutes, the solution was shaken for 1 minute using a vortex mixer to promote contact with air. After measuring the absorbance at 20 minutes, 26 minutes, and 32 minutes, the solution was shaken and mixed using a vortex mixer in the same manner as described above, and then the absorbance at 38 minutes was measured.
Table 1 shows changes with time in absorbance in the above test.

As described above, in Example A1, the absorbance at 330 nm gradually increased after mixing, and the formation of sodium hypobromite could be confirmed. The increase in absorbance at 330 nm reached approximately 80% of the maximum value (0.130 at 15 minutes) in 2 minutes, the increase was moderate in about 5 minutes, and gradually decreased after 15 minutes.
On the other hand, in Example A2, after prompting contact with air, the absorbance at 330 nm rapidly decreased compared to Example A1, and after 32 minutes, the absorbance immediately after mixing was lower. Thereby, it is considered that the generated sodium hypobromite was substantially decomposed in the third operation for promoting contact with air.

From the results of Example A1, the reaction for producing a hypobromite compound from a hypochlorous acid compound and a bromine compound was completed in about 5 minutes, and after 15 minutes, the decomposition of the hypobromite compound was dominant. It was thought to be. Moreover, the production | generation of the hypobromite compound by this reaction reached about 80% of the maximum value in 2 minutes, and it became clear that a hypobromite compound was fully produced | generated. That is, when using a hypobromite compound for sewage treatment, it has become clear that it is preferable to contact the sewage within 15 minutes after 2 minutes from the mixing of the hypochlorous acid compound and the bromine compound.
Considering that the above reaction proceeds to almost 100% of the maximum value, when using the hypobromite compound for sewage treatment, within 5 minutes and 15 minutes after mixing the hypochlorous acid compound and bromine compound It is considered preferable to contact the sewage. On the other hand, considering the use of a hypobromite compound in sewage treatment by balancing the reaction channel installation area constraints and cost viewpoints and allowing the above reaction to proceed about 80% or more of the maximum value In some cases, it is preferable to contact the sewage within 5 minutes after 2 minutes from the mixing of the hypochlorous acid compound and the bromine compound.
Further, from the results of Example A2, since the hypobromite compound is rapidly decomposed by contact with air, it is clear that it is necessary to avoid the contact with air when generating the hypobromite compound. became.

Experimental Example B: Effective chlorine concentration of sodium hypochlorite aqueous solution used as a raw material, reaction time of hypochlorous acid compound and bromine compound, and treatment time for E. coli solution against bactericidal action of hypobromite compound [Example B1]
4. Dissolve 4.95 mL of sodium hypochlorite aqueous solution with an effective chlorine concentration of 0.4 mg / L into a 15 mL centrifuge tube, and contain sodium bromide containing 1.5 times the molar sodium bromide sodium bromide 4.95 mL of aqueous solution was mixed. One minute after mixing, 0.1 mL of the E. coli solution was added.
The E. coli solution was prepared according to the following. E. coli was cultured overnight at 37 ° C. in Nutrient broth medium. The medium components were removed from the culture solution by centrifugation, and Escherichia coli was suspended in sterilized physiological saline to prepare an E. coli solution.
One minute after adding E. coli solution to the mixture of sodium hypochlorite aqueous solution and sodium bromide aqueous solution, 1 mL of 0.025 mg / L sodium thiosulfate aqueous solution was added to neutralize residual hypobromite.
The obtained mixture was diluted with sterilized physiological saline and applied to a nutrient broth medium at 100 μL. The cells were cultured overnight at 37 ° C., and the number of viable E. coli was calculated from the number of colonies formed. As a result, the viable count of E. coli was 2.8 × 10 ⁵ CFU / mL.

[Example B2 to Example B45]
Effective chlorine concentration (effective chlorine concentration A) of sodium hypochlorite aqueous solution, time from mixing sodium hypochlorite aqueous solution and sodium bromide aqueous solution to adding E. coli solution (reaction time B), and E. coli solution The number of viable Escherichia coli cells was calculated in the same manner as in Example 1 except that the time from the addition to the addition of the aqueous sodium thiosulfate solution (treatment time C) was changed as shown in Tables 2 to 4 below.
The results are shown in Tables 2-4.

[Reference Example B1]
4. Dissolve 4.95 mL of an aqueous sodium hypochlorite solution having an effective chlorine concentration of 1.0 mg / L into a 15 mL centrifuge tube, and contain sodium bromide containing 1.5 times the sodium bromide sodium bromide. 4.95 mL of aqueous solution was mixed. One minute after the start of mixing, 1 mL of 0.025 mg / L sodium thiosulfate aqueous solution was added to neutralize the produced hypobromite, and then 0.1 mL of E. coli solution was added. For the obtained mixture, the number of viable E. coli was calculated in the same manner as in Example B1. As a result, the viable count of E. coli was 3.9 × 10 ⁷ CFU / mL.

[Reference Example B2 to Reference Example B5]
The time from the mixing of the sodium hypochlorite aqueous solution and the sodium bromide aqueous solution to the addition of the sodium thiosulfate aqueous solution (reaction time D) was the same as in Reference Example B1, except that the time was changed as shown in Table 5 below. Thus, the viable count of E. coli was calculated.
The results are shown in Table 5.

In Reference Example B1 to Reference Example B5, E. coli is added after neutralization of hypobromite. Therefore, these show the viable count of E. coli before treatment. As a result, the viable count of E. coli before treatment was approximately 1 to 4 × 10 ⁷ CFU / mL (10,000,000 to 40,000,000 CFU / mL).

In Examples B1 to B15 using an aqueous sodium hypochlorite solution having an effective chlorine concentration of 0.4 mg / L, the viable cell count of E. coli was 1.4 × 10 ⁵ to 1 regardless of the reaction time B and the treatment time C. 5 × 10 ⁶ CFU / mL (140,000 to 1,500,000 CFU / mL), and no significant difference was observed in the viable count of E. coli after treatment.
In these examples, a sodium hypochlorite aqueous solution having an effective chlorine concentration of 0.4 mg / L is mixed with the same amount of sodium bromide aqueous solution, so that the hypochlorous acid compound in Examples B1 to B15 The effective chlorine concentration of hypochlorous acid in the mixture before the reaction with the bromine compound starts is 0.2 mg / L. In these examples, 4.95 mL of sodium hypochlorite aqueous solution, 4.95 mL of sodium bromide aqueous solution, and 0.1 mL of E. coli solution were mixed, so in 1 L of the mixture containing E. coli solution. The amount of the hypobromite compound (corresponding to the amount of the hypobromite compound in 1 L of sewage flowing through the treatment channel 10) is 0.198 mg in terms of the effective chlorine amount.

In Examples B16 to B30 using a sodium hypochlorite aqueous solution having an effective chlorine concentration of 1.0 mg / L, a higher bactericidal effect was recognized than the bactericidal effects observed in Examples B1 to B15.
In Examples B19 to B21 where the reaction time B was 5 minutes, a higher bactericidal effect was observed than in Examples B16 to B18 where the reaction time B was 1 minute. Thereby, it turned out that time of about 5 minutes is required from the reaction start of a hypochlorous acid compound and a bromine compound to contact with sewage.
The bactericidal effect in Example B19 to Example B21 is higher than Example B22 to Example B24 in which the reaction time B is 15 minutes, and it takes 15 minutes from the start of the reaction between the hypochlorous acid compound and the bromine compound to contact with sewage. It has been found that the sterilizing effect is reduced when it is required. This is considered due to the decomposition of the produced hypobromite compound.
In these examples, since the same amount of sodium bromide aqueous solution as the effective chlorine concentration of 1.0 mg / L was mixed with the sodium hypochlorite aqueous solution, the hypochlorous acid compound in Examples B16 to B30 The effective chlorine concentration of hypochlorous acid in the mixture before the reaction with the bromine compound starts is 0.5 mg / L. In these examples, 4.95 mL of sodium hypochlorite aqueous solution, 4.95 mL of sodium bromide aqueous solution, and 0.1 mL of E. coli solution were mixed, so in 1 L of the mixture containing E. coli solution. The amount of the hypobromite compound (corresponding to the amount of the hypobromite compound in 1 L of sewage flowing through the treatment channel 10) is 0.495 mg in terms of the effective chlorine amount.
From the results of the bactericidal effects in Examples B19 to B21 and the bactericidal effects in Examples B4 to B6, the amount of hypobromite compound in 1 L of the mixture including E. coli solution is 0.4 mg or more in terms of effective chlorine amount. I found out that it was necessary.

In Examples B31 to B45 using a sodium hypochlorite aqueous solution having an effective chlorine concentration of 2.0 mg / L, the sterilizing effect higher than the sterilizing effects observed in Examples B1 to B15 and Examples B16 to B30 Was recognized. Similar to Example B16 to Example B30, in Example B34 to Example B36 where the reaction time B is 5 minutes, Example B31 to Example B33 where the reaction time B is 1 minute or Example B37 to Example where the reaction time B is 15 minutes A higher bactericidal effect than B39 was observed.
In Example B34 to Example B36, a very high bactericidal effect was also observed in Example B34 in which the treatment time C was 1 minute.
In these examples, since the same amount of sodium bromide aqueous solution as the effective chlorine concentration of 2.0 mg / L is mixed with the sodium hypochlorite aqueous solution, the hypochlorous acid compound in Examples B31 to B45 and The effective chlorine concentration of hypochlorous acid in the mixture before the reaction with the bromine compound starts is 1.0 mg / L. In these examples, 4.95 mL of sodium hypochlorite aqueous solution, 4.95 mL of sodium bromide aqueous solution, and 0.1 mL of E. coli solution were mixed, so in 1 L of the mixture containing E. coli solution. The amount of the hypobromite compound (corresponding to the amount of the hypobromite compound in 1 L of sewage flowing through the treatment channel 10) is 0.99 mg in terms of the effective chlorine amount.

DESCRIPTION OF SYMBOLS 1 Sewage treatment system 10 Processing flow path 10a Processing flow path upstream end 10b Processing flow path downstream end 20 Reaction flow path 20a Reaction flow path upstream end 20b Reaction flow path downstream end 30 Hypochlorous acid supply device 32 Hypochlorous acid storage tank 34 Hypochlorous acid addition pump 36 Hypochlorous acid addition flow path 40 Bromide supply device 42 Bromide storage tank 44 Bromide addition pump 46 Bromide addition flow path 50 Control device 60 Sewage inflow passage 70 Public water area

Claims (7)

A treatment flow path where sewage flows from the upstream end and flows out from the downstream end;
A reaction channel having a downstream end connected to the processing channel;
A hypochlorous acid supply device for supplying an aqueous solution of a hypochlorous acid compound and a bromide supply device for supplying an aqueous solution of a bromine compound, connected to the upstream end of the reaction flow path,
The reaction channel circulates an aqueous solution of a hypochlorous acid compound supplied from the hypochlorous acid supply device and an aqueous solution of a bromine compound supplied from the bromide supply device without contacting the inside of the flow channel with air. A sewage treatment system, which is a flow path for generating a hypobromite compound by reacting with the reaction.   The sewage treatment system according to claim 1, wherein a length of the treatment channel from the upstream end to the downstream end of the treatment channel is one or more times a distance that sewage flowing through the treatment channel travels per minute.   The sewage treatment system according to claim 2, wherein a length of the treatment channel from the upstream end to the downstream end of the treatment channel is 10 times or less of a distance traveled by the sewage flowing through the treatment channel per minute.   Provided with a control device, and the control device allows a distance traveled by the aqueous solution flowing through the reaction channel per minute to be 1/2 to 1 with respect to the reaction channel length from the upstream end to the downstream end of the reaction channel. The sewage treatment system according to any one of claims 1 to 3, which is controlled to / 15 times.   A control device is provided, and the control device is controlled so that 0.4 to 8 mg of hypobromite compound in terms of effective chlorine amount is supplied to 1 L of sewage flowing through the treatment flow path. Item 5. A sewage treatment system according to any one of Items 1 to 4.   The sewage-treatment system as described in any one of Claims 1-5 provided with the mixing apparatus which mixes the aqueous solution which flows through the said reaction flow path without making air contact.   A sewage treatment method in which an aqueous solution of a hypochlorous acid compound and an aqueous solution of a bromine compound are reacted while flowing through a flow path without being exposed to air, and the produced hypobromite compound is supplied to sewage.

Images