Method for removing odor substances based on breakpoint chlorination

Abstract

The invention provides a method for removing smelly substances based on breakpoint chlorination, the method for removing smelly substances based on breakpoint chlorination is used for oxidative degradation of smelly substances, and the method comprises the following steps: S0, setting the initial concentration of smelly substances in a water body to be 10-100 ng / L; the method comprises the following steps: S1, adding ammonium sulfate into a water body containing odor substances; s2, free chlorine is added in the step S1 in a breakpoint chlorination mode, active species with oxidation capacity are generated in the breakpoint chlorination process, and the active species comprise hydroxyl free radicals, active chlorine free radicals and active nitrogen free radicals; and S3, fully stirring, uniformly mixing, reacting, and removing the odor substances through an oxidation-reduction reaction between the active species and the target pollutants, so that the odor substances, including geosmin and 2-methylisoborneol, in the water body can be rapidly degraded. The method for removing the odor substances based on breakpoint chlorination is efficient, economical and easy to operate, and has wide application prospects and remarkable social benefits.

Description

Technical Field

[0001] The present invention application relates to the technical field of odorant treatment, and specifically relates to a method for removing odorants based on breakpoint chlorination. Background Art

[0002] The abnormal odor of drinking water is the most directly perceived drinking water quality index by consumers. The improvement of living standards has also prompted people to put forward higher and higher requirements for the quality of drinking water, and the problem of drinking water odor has received extensive attention in the water treatment industry. The odorants in drinking water are characterized by wide sources and various types, and the odor thresholds of most odorants are very low, and the odor thresholds of many odorants are at the ng / L level. Geosmin (GSM) and 2-methylisoborneol (2-MIB) are the main substances causing earthy smell in drinking water. The new version of the Hygienic Standard for Drinking Water (GB 5749-2022) stipulates that the concentration limits of GSM and 2-MIB in the factory water are less than 10 ng / L. The odorants GSM and 2-MIB have the characteristics of low Henry's coefficient, strong antioxidant property, and steric hindrance in the chemical structure. Conventional drinking water treatment processes (coagulation sedimentation, filtration, and disinfection) are difficult to effectively remove GSM and 2-MIB. In addition, due to the relatively stable saturated cycloalcohol structures of both GSM and 2-MIB, the degradation ability of conventional oxidants (chlorine, chloramine, chlorine dioxide, potassium permanganate, etc.) for GSM and 2-MIB is also very limited. In related technologies, the advanced oxidation technology based on ultraviolet has high energy consumption and expensive equipment, and the use of persulfate will cause the sulfate in drinking water to exceed the standard and pose a potential risk to water quality. Therefore, it is urgent to solve the problem of simple, economical and efficient removal of odorants in water treatment. Summary of the Invention

[0003] The purpose of the present invention application is to provide a method for removing odorants based on breakpoint chlorination, which directly oxidizes and degrades odorants by generating reactive species through the reaction of free chlorine with common ammonia-nitrogen substances or externally added nitrogen sources in water.

[0004] To achieve the above purpose, the present invention application adopts the following technical solutions:

[0005] A method for removing odorants based on breakpoint chlorination, used for oxidizing and degrading odorants, includes the following steps:

[0006] Step S0: Set the initial concentration of odorants in the water body to 10-100 ng / L;

[0007] Step S1: Add ammonium sulfate to the water body containing odorants;

[0008] Step S2: Then, free chlorine is added in the way of breakpoint chlorination in Step S1. Active species with oxidation ability are generated during the breakpoint chlorination process, including hydroxyl radicals, active chlorine radicals and active nitrogen radicals;

[0009] Step S3: Stir thoroughly. After mixing evenly, the odor substances are removed through the redox reaction between the active species and the target pollutants, and the odor substances in the water body can be rapidly degraded, including geosmin and 2-methylisoborneol.

[0010] Preferably, in the said Step S1, the pH of the water body is adjusted to 6.0 - 9.0.

[0011] Preferably, the pH of the water body is adjusted to 6.8 - 8.0.

[0012] Preferably, in the said Step S1, the initial concentration of ammonium sulfate added is 0.1 - 1 mg-N / L.

[0013] Preferably, in the said Step S2, the concentration of free chlorine added to the water body is 0.9 - 10 mg-Cl 2 / L.

[0014] Preferably, in the said Step S3, the conditions for thorough stirring and uniform mixing are 100 - 300 revolutions per minute.

[0015] Preferably, in the said Step S3, the reaction time is 10 - 30 minutes.

[0016] Compared with the prior art, the present invention application has the following beneficial effects:

[0017] The present invention application adds free chlorine to the water body containing odor substances in the way of breakpoint chlorination, and precisely controls the Cl 2 / N mass ratio to be 9:1, and the present invention application realizes the efficient removal of odor substances in the water body.

[0018] The method of the present invention application can rapidly degrade stubborn odor substances such as geosmin and 2-methylisoborneol, and significantly improve the sensory quality of water quality.

[0019] The present invention application uses the common disinfectant free chlorine to react with the widely existing ammonia nitrogen. It is not only simple in operation, but also low in cost, and is easy to be popularized and applied in scenarios such as pre-chlorination treatment of source water, chlorine disinfection of drinking water and secondary chlorine addition in subsequent water supply pipe networks. It not only helps to ensure the safety and health of drinking water, but also can effectively reduce the water treatment cost and improve the water treatment efficiency.

[0020] This invention application ensures the optimization of reaction conditions by adjusting the pH value of the water body to an appropriate range and controlling the dosing concentrations of ammonium sulfate and free chlorine, further improving the removal effect of odor substances. The condition settings of sufficient stirring and uniform mixing also make the reaction more sufficient and uniform, thus ensuring the stability and reliability of the treatment effect.

[0021] In summary, this invention application provides an efficient, economical, and easy-to-operate method for removing odor substances based on breakpoint chlorination, which has broad application prospects and significant social benefits. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the principle of a method for removing odor substances based on breakpoint chlorination proposed by this invention application;

[0023] Figure 2 It is the effect diagram of breakpoint chlorination for degrading geosmin and 2-MIB under the condition of pH = 7.3 and the contribution of various reactive species in the degradation in Example 1 of a method for removing odor substances based on breakpoint chlorination proposed by this invention application.

[0024] Figure 3 It is the attenuation diagram of total chlorine and ammonia nitrogen when breakpoint chlorination degrades geosmin and 2-MIB under the condition of pH = 7.3 in Example 2 of a method for removing odor substances based on breakpoint chlorination proposed by this invention application.

[0025] Figure 4 It is the effect diagram of the influence of humic acid in water on the degradation of geosmin and 2-MIB by breakpoint chlorination under the condition of pH = 7.3 in Example 3 of a method for removing odor substances based on breakpoint chlorination proposed by this invention application.

[0026] Figure 5 It is the effect diagram of the influence of common anions in water on the degradation of geosmin and 2-MIB by breakpoint chlorination under the condition of pH = 7.3 in Example 4 of a method for removing odor substances based on breakpoint chlorination proposed by this invention application. Detailed Embodiments

[0027] Next, the technical solutions in the embodiments of this invention application will be clearly and completely described in conjunction with the drawings in the embodiments of this invention application. Obviously, the described embodiments are only a part of the embodiments of this invention application, rather than all of the embodiments.

[0028] As Figure 1 shown, a method for removing odor substances based on breakpoint chlorination provided in this embodiment for oxidative degradation of odor substances includes the following steps:

[0029] Step S0: Set the initial concentration of odor substances in the water body to 10 - 100 ng / L;

[0030] Step S1: Ammonium sulfate is added to the water body containing odorant substances, and the initial concentration of ammonium sulfate is 0.1 - 1 mg-N / L.

[0031] Then, the pH of the water body is adjusted to 6.0 - 9.0. Preferably, the pH of the water body is adjusted to 6.8 - 8.0.

[0032] Step S2: Then, free chlorine with a concentration of 0.9 - 10 mg-Cl 2 / L is added to the water body in step S1 by breakpoint chlorination. In the initial stage of the treatment in the water body, the Cl 2 / N mass ratio reaches 9:1. The breakpoint chlorination process generates active species with oxidation ability, including hydroxyl radicals, reactive chlorine radicals, reactive nitrogen radicals, etc.

[0033] Step S3: Stir thoroughly, and the condition for uniform mixing is 100 - 300 revolutions per minute. Then, the odorant substances are removed through the redox reaction between the active species and the target pollutants. The reaction time is 10 - 30 minutes, and the odorant substances in the water body can be rapidly degraded, including geosmin and 2-methylisoborneol (hereinafter referred to as 2-MIB).

[0034] The pH of the degradation reaction is adjusted to 6.0 - 9.0 by using an acid-base regulator, and the preferred pH condition is 6.8 - 8.0.

[0035] Example 1

[0036] 100 μL of 555 mg-N / L ammonium sulfate solution is added to 50 mL of water with a pH of 7.3 containing 5 mM phosphate buffer with an initial concentration of geosmin and 2-MIB of 100 ng / L. Then, 200 μL of 2.5 g-Cl 2 / L sodium hypochlorite solution is added. The reaction solution is placed on a magnetic stirrer and reacted for 30 minutes at 300 revolutions per minute. Samples are taken at regular intervals during the reaction to measure the concentrations of geosmin and 2-MIB. Control experiments with only monochloramine or only free chlorine treatment are carried out under the same reaction conditions. Using nitrobenzene as a probe, the exposure amount of hydroxyl radicals within 0 - 30 minutes of the reaction is calculated, so as to obtain the contribution of hydroxyl radicals in the degradation of odorant substances.

[0037] As Figure 2 shown, it is the effect diagram of breakpoint chlorination for degrading geosmin and 2-MIB and the contribution of various active species in the degradation under the condition of pH = 7.3 in Example 1 of a method for removing odorant substances based on breakpoint chlorination proposed in this example.

[0038] Among them, the abscissa represents the reaction time; the ordinate represents the ratio of the pollutant concentration to the initial concentration at the reaction time. Alone monochloramine or free chlorine can hardly oxidize geosmin and 2-MIB. During breakpoint chlorination, reactive substances (such as hydroxyl radicals, reactive chlorine species, and reactive nitrogen species) are generated, resulting in the rapid decay of geosmin and 2-MIB.

[0039] Example 2

[0040] Add 100 μL of 555 mg-N / L ammonium sulfate solution to 50 mL of water with a pH of 7.3 containing 5 mM phosphate buffer and an initial concentration of geosmin and 2-MIB of 100 ng / L, and then add 200 μL of 2.5 g-Cl 2 / L sodium hypochlorite solution. Place the reaction solution on a magnetic stirrer and react for 30 minutes at 300 revolutions per minute. At regular intervals during the reaction, take samples to measure the remaining concentrations of total chlorine and ammonia nitrogen.

[0041] As Figure 3 shown, it is the decay diagram of total chlorine and ammonia nitrogen during the degradation of geosmin and 2-MIB by breakpoint chlorination in Example 2 of a method for removing odor substances based on breakpoint chlorination proposed in this example under the condition of pH = 7.3.

[0042] Among them, the abscissa represents the reaction time; the left ordinate represents the remaining concentration of total chlorine at the reaction time, and the right ordinate represents the remaining concentration of ammonia nitrogen at the reaction time. Free chlorine and ammonia nitrogen decay very rapidly within the first 10 minutes and the decay is basically completed at 30 minutes. During breakpoint chlorination, reactive substances (such as hydroxyl radicals, reactive chlorine species, and reactive nitrogen species) are generated, which can not only degrade geosmin and 2-MIB, but also cause the rapid decay of total chlorine and ammonia nitrogen.

[0043] Example 3

[0044] Prepare a humic acid solution containing 2 mg-C / L in water with a pH of 7.3 containing 5 mM phosphate buffer. Add geosmin and 2-MIB to 50 mL of water containing humic acid to configure an initial concentration of 100 ng / L. Add 100 μL of 555 mg-N / L ammonium sulfate solution, and then add 200 μL of 2.5 g-Cl 2 / L sodium hypochlorite solution. Place the reaction solution on a magnetic stirrer and react for 30 minutes at 300 revolutions per minute. At regular intervals during the reaction, take samples to measure the concentrations of geosmin and 2-MIB. Conduct a control experiment without humic acid under the same reaction conditions.

[0045] As Figure 4As shown in the figure, in Example 3 of a method for removing odor substances based on breakpoint chlorination proposed in this embodiment, the effect diagram of the influence of humic acid in water on the degradation of geosmin and 2-MIB by breakpoint chlorination under the condition of pH = 7.3 is shown.

[0046] As shown in the figure, compared with the control group without humic acid, the experimental results of this Example 3 show that the effect of breakpoint chlorination on the degradation of odor substances is inhibited by humic acid, but the removal effect is still good.

[0047] Example 4

[0048] Solutions containing 5 mM of sodium chloride, 5 mM of sodium bicarbonate, and 5 mM of potassium nitrate were respectively prepared in water with pH = 7.3 containing 5 mM of phosphate buffer. Geosmin and 2-MIB were added to 50 mL of the solution containing different ions to configure an initial concentration of 100 ng / L. 100 μL of ammonium sulfate solution with a concentration of 555 mg-N / L was added, and then 200 μL of sodium hypochlorite solution with a concentration of 2.5 g-Cl 2 / L was added. The reaction solution was placed on a magnetic stirrer and reacted for 30 minutes at 300 revolutions per minute. Samples were taken at certain intervals during the reaction to measure the concentrations of geosmin and 2-MIB. A control experiment without ions was carried out under the same reaction conditions.

[0049] As Figure 5 shown in the figure, in Example 4 of a method for removing odor substances based on breakpoint chlorination proposed in this embodiment, the effect diagram of the influence of common anions in water on the degradation of geosmin and 2-MIB by breakpoint chlorination under the condition of pH = 7.3 is shown.

[0050] As shown in the figure, compared with the control group without common anions, the experimental results of Example 4 show that the effect of breakpoint chlorination on the degradation of geosmin is not affected by chloride ions and nitrate ions, while bicarbonate ions have an inhibitory effect, but the removal effect is still good. The effect of breakpoint chlorination on the degradation of 2-MIB is hardly affected by chloride ions, bicarbonate ions, and nitrate ions, and the removal effects are all good.

[0051] This embodiment uses the common disinfectant free chlorine and the widely existing ammonia nitrogen, and adopts the breakpoint chlorination method to remove odor substances. The treatment effect is excellent, the operation is simple, and the cost is low. It has a wide application prospect in the pre-chlorination treatment of source water, the chlorine disinfection of drinking water, and the secondary chlorination in the subsequent water supply pipe network.

[0052] In the description of the present invention application, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention application.

[0053] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention application, "a plurality of" means two or more, unless otherwise specifically defined.

[0054] As mentioned above, the above are only the preferred specific embodiments of the present invention application, but the protection scope of the present invention application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention application, according to the technical solution and inventive concept of the present invention application, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention application.

Claims

1. A method for removing odorous substances based on breakpoint chlorination, which is used for oxidative degradation of odorous substances, characterized in that: The steps include: Step S0: setting the initial concentration of odor substances in the water body to 10-100 ng / L; Step S1: adding ammonium sulfate to water containing odorous substances; Step S2: adding free chlorine to the water in step S1 by means of breakpoint chlorination so that the Cl2 / N mass ratio reaches 9:1, and the breakpoint chlorination process generates active species with oxidizing ability, including hydroxyl free radicals, active chlorine free radicals and active nitrogen free radicals; Step S3: Stir thoroughly, mix evenly, and remove odor substances through the redox reaction between active species and target pollutants, which can quickly degrade odor substances in water, including geosmin and 2-methylisoborneol.

2. A method for removing odorous substances based on inflection point chlorination according to claim 1, characterized in that: In the step S1, the pH of the water body is adjusted to 6.0-9.

0.

3. A method for removing odorous substances based on inflection point chlorination according to claim 2, characterized in that: The pH of the water body is adjusted to 6.8-8.

0.

4. A method for removing odorous substances based on inflection point chlorination according to claim 1, characterized in that: In the step S1, the initial concentration of ammonium sulfate added to the water body is 0.1-1 mg-N / L.

5. The method for removing odorous substances based on inflection point chlorination according to claim 1, characterized in that: In step S2, the concentration of free chlorine added to the water body is 0.9-10 mg-Cl2 / L.

6. The method for removing odorous substances based on inflection point chlorination according to claim 1, characterized in that: In step S3, the conditions for sufficient stirring and uniform mixing are 100-300 rpm.

7. The method for removing odorous substances based on inflection point chlorination according to claim 1, characterized in that: In step S3, the reaction time is 10 to 30 minutes.

Images