JP6970698B2 - Disinfection method for ammonia-containing nitrogen-containing wastewater - Google Patents

Description

The present invention relates to a method for disinfecting ammonia nitrogen-containing wastewater, and in particular, sterilizes coliforms or coliform bacteria in wastewater containing ammonia nitrogen discharged from a sewage treatment plant, a pumping station, or a rainwater spout into a public water area. Regarding disinfection methods.

The sewage treatment plant is a facility for detoxifying sewage discharged from homes and factories and discharging it into public water areas. From the rainwater spout, sewage mixed with rainwater (hereinafter referred to as sewage in rainy weather) is discharged into public water areas in a few tens of seconds to a few minutes without being sufficiently treated. In this case, coarse suspended solids and SS (suspended substance) are discharged into public water areas, which may cause aesthetic problems, and also the discharge standard value (3000 CFU / mL) stipulated in the Water Pollution Control Law. Coliforms and coliforms that significantly exceed the following) may be detected.

Even in a sewage treatment plant, if the inflow sewage significantly exceeds the treatment capacity, some sewage in rainy weather may be simply treated and discharged. In this case, since bacterial sterilization is not sufficiently carried out, coliform bacteria and coliforms that greatly exceed the discharge standard value (3000 CFU / mL or less) stipulated in the Water Pollution Control Law may be detected. These are phenomena especially seen in the combined sewerage system, but even in the split-type sewerage system, soil coliform bacteria and coarse suspended matter flow in, so if they overflow and are discharged into public water areas, they will merge. There was a problem similar to that of the sewerage system.

According to "Sewerage Facility Planning / Design Guidelines and Explanations" (published by the Japan Sewerage Association, 2009 edition), disinfection at sewage treatment plants includes sodium hypochlorite, liquefied chlorine, chlorinated isocyanuric acid, and calcium hypochlorite. A method of disinfecting coliform bacteria by using chlorine agents such as the above and contacting them with sewage in a mixing pond for 15 minutes or longer has been shown. In addition, "Sewerage facility planning / design guidelines and explanations" also describes disinfection with ozone and ultraviolet rays. Furthermore, by storing temporarily wet-weather sewage is provided a pond tens of thousands m ^3, if the overflow has occurred by rainfall or more storage amount is a method of disinfection with chlorine disinfectant of the Proposed.

However, chlorine-based disinfectants do not exert their bactericidal action sufficiently because they have a short contact time with wastewater when they are discharged into public water areas in a short time due to their high rainfall intensity, such as sewage in rainy weather. In wastewater with a high content of sex nitrogen, chlorine and ammonia nitrogen easily react to form chloramine, which reduces the bactericidal action. Therefore, the number of Escherichia coli is reduced below the standard value specified by the Water Pollution Control Law. There is a problem that chloramine cannot be used, and that chloramine remains in public water as a binding chlorine for a long time and has an adverse effect on the environment. Therefore, for example, a disinfection method in which a solution of hypochlorous acid or hypochlorous acid formed by adding equimolar or more of sodium bromide to sodium hypochlorous acid is added to wastewater (Patent Document 1). (A) Sodium hypochlorous acid or 1,3-dichloro-5,5-dimethylhydantin, (B) Sodium bromide or potassium bromide, and (C) L-ascorbic acid, glycolic acid or glyoxylic acid (A) ) Hypochlorous acid: (B) bromide ion = 1: 1 to 1: 5 (molar ratio) and (A) hypochlorous acid: (C) = 1: 0.05 to 1: 1 (molar ratio) Disinfection method of adding disinfectant water containing a certain amount to wastewater (Patent Document 2), hypochlorous acid, bromide and 5,5-dimethylhydantoin 1: (0.2 to 3) :( 0.2 to 0. 9) Hypochlorous acid and N-monochromelo used in (molar ratio) and formed by mixing hypochlorous acid with a bromide corresponding to the hypochlorous acid remaining by the reaction of hypochlorous acid with 5,5-dimethylhydantoin. A method using hypochlorous acid such as a microbial killing agent (Patent Document 3), which is an aqueous solution containing -5,5-dimethylhydantin, has been proposed.

Japanese Unexamined Patent Publication No. 2003-12425 Japanese Patent No. 4398161 Japanese Unexamined Patent Publication No. 2009-226409

Even with the method using hypobromous acid that has been proposed in the past, the bactericidal effect of wastewater containing ammoniacal nitrogen is insufficient, and it cannot be treated to the release standard value of 3000 CFU / mL for coliform bacteria, and E. coli can be sufficiently treated. There were times when it could not be sterilized.

An object of the present invention is to provide a reliable, simple and economical method for sterilizing Escherichia coli and coliform bacteria in wastewater containing ammoniacal nitrogen.

Escherichia coli is Escherichia coli, and coliform bacteria are Citrobacter other than Esherichia coli.
Includes genera, Enterobacter, Klebsiella, etc. Coliform bacteria are an index of fecal contamination and are inspection items for confirming safety against intestinal pathogens (Typhus, Shigella, etc.). By combining two or more drugs that react to produce hypobromous acid and adjusting the amount of each drug added according to the concentration of ammoniacal nitrogen in the wastewater, the present inventors have developed a conventional coliform bacterium. It was confirmed that not only the bactericidal action using only as an index but also the bactericidal action using Escherichia coli as an index was exhibited, and the present invention was completed.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a method for disinfecting ammonia nitrogen-containing wastewater for sterilizing Escherichia coli and coliform bacteria in ammonia nitrogen-containing wastewater according to the following embodiment. The specific embodiment is as follows.
[1] In the wastewater containing ammoniacal nitrogen, a drug (A) that generates ^{hypochlorite ion (OCl −} ) in water and a drug (B) that generates ^{bromide ion (Br −) in water are added.} A method for disinfecting ammoniacal nitrogen-containing wastewater by adding and sterilizing coliforms and coliform bacteria in the wastewater, depending on the concentration of ammoniacal nitrogen in the wastewater, Cl in the agent (A) and the agent ( B) A method comprising adjusting the molar ratio with Br in medium to add the drug (A) and the drug (B) to the wastewater.
[2] When the ammoniacal nitrogen concentration in the wastewater is 30 mg / L or less, the molar ratio of Cl in the drug (A) to Br in the drug (B) is Br / Cl <1.0. The drug (A) and the drug (B) are added to the wastewater in such an amount, and when the ammoniacal nitrogen concentration in the wastewater exceeds 30 mg / L, Cl in the drug (A) and the drug (B) The method according to [1], wherein the drug (A) and the drug (B) are added to the wastewater in an amount such that the molar ratio with Br in Medium is Br / Cl ≧ 1.0. ..
[3] The agent (A) contains one or more selected from hypochlorite, dichloroisocyanuric acid or a salt thereof, trichloroisocyanuric acid or a salt thereof, and calcium hypochlorite (bleached powder). The method according to [1] or [2], wherein the agent (B) contains one or more selected from sodium bromide, potassium bromide, ammonium bromide, and calcium bromide.
[4] The method according to any one of [1] to [3], wherein the drug (A) and the drug (B) are not reacted before being added to the wastewater.
[5] The method according to any one of [1] to [4], wherein the drug (A) and the drug (B) are added to the wastewater as a solid.
[6] The method according to any one of [1] to [4], wherein the drug (A) and the drug (B) are added to the wastewater as separate solutions.
[7] The method according to any one of [1] to [3], which comprises adding the drug (A) and the drug (B) to the wastewater as a mixed solution.

According to the present invention, by utilizing the bactericidal action of E. coli and Escherichia coli by hypobromous acid, which is optimal according to the concentration of ammoniacal nitrogen in wastewater, the hypochlorite which has been conventionally proposed can be compared. Compared with disinfectants and bactericidal methods formed by adding equimolar or more odorants, and bactericidal agents and bactericidal methods adding a third component such as organic acid or hydridein, it is superior to Escherichia coli and Escherichia coli in a short time. Provided is a disinfection method for sterilizing Escherichia coli and Escherichia coli in ammonia nitrogen-containing wastewater, which can exert a bactericidal effect and is economical.

It is explanatory drawing which shows the treatment flow when the disinfection method of this invention is applied to a sewage treatment plant. It is explanatory drawing which shows the processing flow when the disinfection method of this invention is applied to a rainwater pump station. It is a graph which shows the relationship between the ammoniacal nitrogen concentration in wastewater and the molar ratio of Br in agent (B) to Cl in agent (A) regarding the bactericidal effect of coliform bacteria. It is a graph which shows the relationship between the ammoniacal nitrogen concentration in wastewater and the molar ratio of Br in agent (B) to Cl in agent (A) regarding the bactericidal effect of Escherichia coli.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
The present invention comprises a drug (A) that generates ^{hypochlorite ion (OCl −} ) in water and a drug (B) that generates ^{bromide ion (Br −} ) in water in wastewater containing ammoniacal nitrogen. To provide a disinfection method for sterilizing Escherichia coli or coliform bacteria in ammonia nitrogen-containing wastewater by adding

In the conventional method, a hypobromous acid solution formed by mixing 1 mol of a metal bromide salt with 1 mol of hypochlorite is added to the wastewater, but the present invention comprises ammonia in the wastewater. The molar ratio of Cl in the drug (A) that generates ^{hypochlorite ion (OCl −} ) in water and Br in the drug (B) that generates ^{bromide ion (Br −} ) in water according to the sex nitrogen concentration. It is characterized by preparing. Specifically, when the concentration of ammoniacal nitrogen in the wastewater is 30 mg / L or less, the molar ratio of Br / Cl in the drug (B) to Cl in the drug (A) is less than 1.0. When the drug (A) and the drug (B) are added to the ammoniacal nitrogen-containing wastewater in an amount preferably 0.5 or less and 0.2 or more, and the ammoniacal nitrogen concentration in the wastewater exceeds 30 mg / L. In the above-mentioned drug (A), the molar ratio Br / Cl of Br in the drug (B) to Cl in the drug (A) is 1.0 or more, preferably 1.5 or more and 2.0 or less. ) And the agent (B) are added to the ammoniacal nitrogen-containing wastewater. Optimal bactericidal action can be economically achieved by adjusting the addition ratio of the chemicals (A) and the chemicals (B) according to the concentration of ammoniacal nitrogen in the wastewater.

The agent (A) contains one or more selected from hypochlorite, dichloroisocyanuric acid or a salt thereof, trichloroisocyanuric acid or a salt thereof, and calcium hypochlorite (bleached powder), and the agent (B). ) Preferably contains one or more selected from sodium bromide, potassium bromide, ammonium bromide, and calcium bromide, and any combination of the drug (A) and the drug (B) can be used. As the salt of the drug (A), sodium hypochlorite, potassium hypochlorite, sodium dichloroisocyanurate, potassium dichloroisocyanurate, sodium trichloroisocyanurate, potassium trichloroisocyanurate and the like can be preferably used. The combination of the drug (A) and the drug (B) is sodium hypochlorite and sodium bromide, calcium hypochlorite (bleached powder) and sodium bromide, sodium dichloroisocyanurate and sodium bromide, sodium dichloroisocyanurate. And potassium bromide, sodium dichloroisocyanurate, calcium bromide and the like can be preferably used.

It is preferable that the agent (A) and the agent (B) do not react before being added to the wastewater. By adding the chemicals (A) and the chemicals (B) individually to the wastewater, it is easy to control the Br / Cl molar ratio according to the water quality of the wastewater. For this reason, it is a situation that changes over time, such as when rainfall that is not so large continues for a long period of time and the amount of rainwater increases and the sewage is diluted, or when the amount of rainfall decreases and the sewage stays for a long time. However, the addition amounts of the drug (A) and the drug (B) can be individually controlled and supplied in a suitable molar ratio.

On the other hand, when the fluctuation in water quality of the water to be treated is small and the concentration of ammoniacal nitrogen is stable, it is not necessary to change the mixing ratio of the chemicals (A) and the chemicals (B), and operation control at a constant ratio becomes possible. .. In this case, since it is not necessary to separately control the addition amounts of the drug (A) and the drug (B), they can be added after being mixed. By adding the drug (A) and the drug (B) after mixing them, the addition line to the water to be treated can be made into one system, and it becomes easy to control the operation and the injection amount.

The agent (A) and the agent (B) are preferably added to the wastewater as separate solids or mixed solids. When a solution prepared by mixing two kinds of chemicals in advance as disclosed in the prior art document is added to wastewater, the number of auxiliary devices such as a dissolution device, a solution storage tank, and a solution injection device increases, so that the entire equipment However, the equipment required to add the solution by directly adding the chemicals (A) and chemicals (B) to the wastewater as solids is required, although the size of the equipment becomes large, the equipment configuration becomes complicated, and the management cost increases. No cost is required.

Alternatively, the agent (A) and the agent (B) may be added to the wastewater as separately prepared solutions. In this case, the drug (A) and the drug (B) can be easily quantitatively supplied as separate solutions.

Alternatively, the drug (A) and the drug (B) may be added as a mixed solution prepared by mixing in advance. When the fluidity of the water to be treated is extremely low and the contact efficiency between the drug (A) and the drug (B) at the drug addition position is low, or when the solubility of the drug (A) and the drug (B) is low, The bactericidal effect can be enhanced by adding it as a mixed solution prepared by mixing in advance. FIG. 1 shows a treatment flow when the disinfection method of the present invention is applied to a sewage treatment plant. In the figure, "○" indicates a valve. In a normal sewage treatment plant, wastewater is treated by a first settling basin, an aeration tank, and a second settling basin, and then discharged into a river. When a large amount of rainwater flows in, it exceeds the treatment capacity of the aeration tank and the second settling basin, so after the treatment in the first settling basin, it is discharged into the river as simple effluent in rainy weather. In the disinfection method of the present invention, the chemicals (A) and the chemicals (B) are individually added to the simple discharged water in rainy weather, preferably in solid form. Amount of drug (A) and drug (B), depending on the ammonium nitrogen concentration detected by the ammoniacal provided discharge lines of rainy simple effluent nitrogen detector (NH 4 _-N sensor), Determined by the operator. Specifically, when the ammoniacal nitrogen concentration is 30 mg / L or less, the molar ratio of Cl in the drug (A) to Br in the drug (B): Br / Cl is less than 1.0, preferably Br / Cl. When the concentration is 0.5 or less and 0.2 or more and the ammoniacal nitrogen concentration exceeds 30 mg / L, the molar ratio of Cl in the drug (A) to Br in the drug (B): Br / Cl is 1.0. The above is preferably 2.0 or less. It is preferable to measure the residual halogen concentration of the simple discharged water in rainy weather before discharging to the river, and if the residual halogen concentration is high, reduce the total injection amount of the chemicals (A) and (B).

FIG. 2 shows a treatment flow when the disinfection method of the present invention is applied to a rainwater pump station. In the figure, "○" indicates a valve. In a normal stormwater pump station, stormwater is treated in sand basins and pump wells and then discharged into rivers. In the disinfection method of the present invention, the chemicals (A) and the chemicals (B) are individually added to the sand basin, preferably in solid form. Amount of drug (A) and drug (B), depending on the ammonium nitrogen concentration detected by the rainwater provided in the line for supplying the sand basin ammonia nitrogen detector (NH 4 _-N sensor), Determined by the operator. Specifically, when the ammoniacal nitrogen concentration is 30 mg / L or less, the molar ratio of Cl in the drug (A) to Br in the drug (B): Br / Cl is less than 1.0, preferably Br / Cl. When the concentration is 0.5 or less and 0.2 or more and the ammoniacal nitrogen concentration exceeds 30 mg / L, the molar ratio of Cl in the drug (A) to Br in the drug (B): Br / Cl is 1.0. The above is preferably 2.0 or less. It is preferable to measure the residual halogen concentration of the stormwater-treated effluent before discharge to the river, and if the residual halogen concentration is high, reduce the total injection amount of the chemicals (A) and (B).

In FIGS. 1 and 2, the injection amount of the drug (A) from the Cl feeder and (B) from the Br feeder is controlled by an operator. In addition to the ammonia nitrogen concentration in the wastewater, the operator receives signals from external factors such as rainfall amount, rainfall time, simple discharge start time in rainy weather or rainwater pump operation start time, and the agent (A) and ( It is preferable to control the total injection amount in addition to the molar ratio of B). The agents (A) and (B) are preferably added as solids, and can be added using, for example, the powder supply equipment disclosed in Japanese Patent Application Laid-Open No. 2004-18013. Further, the agents (A) and (B) may be supplied as separate solutions or as a solution mixed in advance.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.
As the test water, simple effluent during rainy weather was used when the rainfall was 7 mm / hour. The properties of the test water are shown in Table 1.

Collect 1 L of test water in a beaker, set it in a jar tester, stir at 120 rpm, add the agents (A) and (B) in the types and ratios shown in Table 2, and stop stirring after 3 minutes for the test. 100 ml of water was collected. Immediately after collection, a part of the test water was subjected to analysis of the free residual chlorine concentration and the total residual chlorine concentration, and a part of the test water was collected in a sterile bottle containing sodium thiosulfate. The number of coliforms (Chromoregar ECC medium, plate culture method) and coliform bacteria (desoxycholate medium, plate culture method) were measured using the test water collected in a sterilization bottle.

Further, a predetermined amount of ammonium chloride was added to the test water shown in Table 1 to adjust the concentration to the ammoniacal nitrogen shown in Table 2, and the same measurement was performed. The results are shown in Table 2.
The drugs used are as follows.
Drug (A)
・ Sodium neochlore dichloroisocyanurate ・ 60 (Shikoku Kasei, effective chlorine content 64.48%, white crystalline solid)
・ Bleach powder Advanced bleaching powder (Japan Soda Industry Association standard JSIA07-1-1998 type I, effective chlorine 70% or more)
・ Sodium hypochlorite sodium hypochlorite reagent (Wako Pure Chemical Industries, Ltd. reagent special grade effective chlorine 12%)
・ Trichloroisocyanuric acid neochlor 90 (manufactured by Shikoku Kasei, effective chlorine content 90%, white crystalline solid)
Drug (B)
・ Sodium bromide (Wako Pure Chemical Industries, Ltd. reagent special grade)
・ Ammonium bromide (Wako Pure Chemical Industries, Ltd. reagent special grade)
・ Calcium bromide (Wako Pure Chemical Industries, Ltd. reagent special grade)
・ Potassium bromide (Wako Pure Chemical Industries, Ltd. reagent special grade)

When the concentration of ammoniacal nitrogen in the wastewater is 30 mg / L or less, the number of coliforms and the number of coliform bacteria are reduced by setting the molar ratio of Br in the drug (B) to less than 1.0 with respect to Cl in the drug (A). However, if the molar ratio of Br in the drug (B) to Cl in the drug (A) is 1.0 or more, the number of coliform bacteria is the release standard value. It turns out that it does not meet.

On the other hand, when the concentration of ammoniacal nitrogen in the wastewater exceeds 30 mg / L, the molar ratio of Br in the drug (B) to Cl in the drug (A) is 1.0 or more, so that both the number of coliforms and the number of coliform bacteria are both. It is decreasing and meets the release standard value (3,000 CFU / mL or less), but if Br in the drug (B) is less than 1.0 in molar ratio to Cl in the drug (A), the number of coliform bacteria is released. It can be seen that the standard value is not met.

Further, in Comparative Examples 18 and 19 to which the conventional method 5,5-dimethylhydantin was added, when the ammoniacal nitrogen concentration was 30 mg / L or less, Br in the drug (B) was added to Cl in the drug (A). Even if the molar ratio is less than 1.0, if the ammoniacal nitrogen concentration in the wastewater exceeds 30 mg / L, even if the molar ratio of Br in the drug (B) to Cl in the drug (A) is 1.0 or more, the E. coli group The number does not meet the discharge standard value. The hypobromite and hypochlorite produced from the drug (A) and the drug (B) react with 5,5-dimethylhydantoin to produce chlorinated and brominated 5,5-dimethylhydantin. It is presumed that this is due to the weakening of the oxidative activity.

Next, to the test water shown in Table 1, a predetermined amount of ammonium chloride was added to prepare three types of test water having an ammoniacal nitrogen concentration of 5 mg / L, 25 mg / L and 40 mg / L, and hypochlorite. The molar ratios of sodium chlorite and potassium bromide were changed as shown in Table 3 and added separately as solids, and the disinfecting effects were compared. The results are shown in Table 3 and FIGS. 3-4.

Claims (6)

^{A chemical (A) that generates hypochlorite ion (OCl −} ) in water and a bromide ion (Br ⁻ ) are generated in water in the sewage in rainy weather containing ammoniacal nitrogen that flows into the sand pond of the rainwater pump station. Ammonia-nitrogen-containing sewage disinfection method for sterilizing Escherichia coli and sewage groups in the sewage in the rain by adding the chemical (B) to the sewage. Then, the molar ratio of Cl in the drug (A) to Br in the drug (B) was adjusted, and the drug (A) and the drug (B) were added to the sewage in rainy weather.
When the ammoniacal nitrogen concentration in the sewage in rainy weather is 30 mg / L or less, the molar ratio of Cl in the drug (A) to Br in the drug (B) is Br / Cl <1.0. A method comprising adding the agent (A) and the agent (B) in an amount to the sewage in rainy weather. The agent (A) contains one or more selected from hypochlorite, dichloroisocyanuric acid or a salt thereof, trichloroisocyanuric acid or a salt thereof, and calcium hypochlorite (bleached powder).
The method according to claim 1, wherein the agent (B) contains one or more selected from sodium bromide, potassium bromide, ammonium bromide, and calcium bromide. The method according to claim 1 or 2 , wherein the agent (A) and the agent (B) do not react before being added to the sewage in rainy weather. The method according to any one of claims 1 to 3 , wherein the agent (A) and the agent (B) are added to the sewage in rainy weather as a solid. The method according to any one of claims 1 to 3 , wherein the drug (A) and the drug (B) are added to the sewage in rainy weather as separate solutions. The method according to claim 1 or 2 , wherein the drug (A) and the drug (B) are added to the sewage in rainy weather as a mixed solution.

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