Ozone / perphosphate-based oxidation pretreatment method and its application

Abstract

The application discloses an ozone / perphosphate-based oxidation pretreatment method and application thereof, and the method comprises the following steps: adding ozone and perphosphate into a drinking water source, the ozone dosage is 2.0-5.0 mg / L, the perphosphate dosage is 5.0-10.0 mg / L; reacting for 5-10 minutes; and removing the end product phosphate through a coagulation and sedimentation process. When the initial concentration of an odor substance in water is less than or equal to 100 ng / L, the method can reduce the odor substance to below the odor threshold, and has no influence on water quality parameters such as total organic carbon and color. In the application, the end product of ozone oxidation is oxygen, and the end product of perphosphate is phosphate, which can be effectively removed through a subsequent conventional water treatment process (coagulation and sedimentation). The application has the advantages of simple operation, low cost, environmental friendliness and the like, and is suitable for pretreatment of various drinking water sources such as surface water and underground water.

Description

Technical Field

[0001] This invention pertains to water treatment, specifically to an ozone / superphosphate-based oxidation pretreatment method and its application. Background Technology

[0002] Odor-causing substances (such as geosmin and 2-methylisoborneol) in drinking water sources mainly originate from algal metabolites, humic matter decomposition, and industrial pollution. Conventional water treatment processes (such as coagulation, sedimentation, and filtration) are insufficient in removing these substances, posing a challenge to drinking water safety. In recent years, advanced oxidation technologies (AOPs) have attracted much attention due to their high efficiency, but existing technologies have the following shortcomings: 1. Ozone oxidation alone: ​​It does not completely degrade large molecular odor-causing substances and requires high concentrations of ozone (>5.0 mg / L), resulting in high costs; 2. Ozone / catalyst systems: They require the addition of metal catalysts, which may introduce heavy metals or make catalyst recovery difficult; 3. Persulfate activation technology: It relies on ultraviolet light or transition metal activation, resulting in high energy consumption and easy sulfate pollution. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide an ozone / superphosphate-based oxidation pretreatment method for efficiently degrading odor substances; another purpose of this invention is to provide the application of this method in removing odor substances from drinking water sources.

[0004] Technical solution: The ozone / superphosphate-based oxidation pretreatment method of the present invention includes the following steps: simultaneously adding ozone and superphosphate to a drinking water source, wherein the ozone dosage is 2.0-5.0 mg / L and the superphosphate dosage is 5.0-10.0 mg / L; reacting for 5-10 minutes; and finally removing the reaction end product phosphate through coagulation and precipitation processes.

[0005] Ozone reacts with superphosphate in situ to generate phosphate radicals (·PO4). 2 -), working together with ozone to degrade odor substances; the final product of ozone is oxygen, and the final product of superphosphate is phosphate. During the coagulation stage, aluminum salt coagulant can form insoluble salts with phosphate, which are effectively removed by subsequent precipitation.

[0006] Preferably, the ratio of ozone to superphosphate is 1:1 to 1:3.

[0007] Preferably, the superphosphate is at least one of disodium hydrogen superphosphate (Na2HPO5) and sodium superphosphate (Na6P2O8).

[0008] Preferably, the pH value of the reaction system is 6.5 to 8.5.

[0009] Preferably, the drinking water source contains odor-causing substances.

[0010] Preferably, the odorant includes at least one of geosmin and 2-methylisoborneol.

[0011] Preferably, ozone is added via a gas-liquid contact device; superphosphate is added continuously via a metering pump.

[0012] More preferably, the gas-liquid contact device includes an aeration titanium plate or a bubble diffuser.

[0013] The present invention relates to the application of the ozone / superphosphate-based oxidation pretreatment method in removing odor substances from drinking water sources.

[0014] Preferably, the drinking water source includes surface water, groundwater, reservoir water, and lake water.

[0015] Preferably, the initial concentration of odor substances in the drinking water source is ≤100 ng / L. After degradation using this technology, the concentration of odor substances is stable at <10 ng / L, and there is no significant impact on water quality parameters (TOC, color, pH).

[0016] Reaction principle: Ozone (O3) reacts with superphosphate in water:

[0017] O3+PO5 3- → - O3PO5 3- →·O3 - +·PO5 3-

[0018] ·PO5 2- +O3→·PO4 2- +2O2

[0019] 2O3+P2O8 4- →2·O3PO4 2- →·PO4 2- +3O2

[0020] The generated phosphate radicals (·PO4) 2 -) Degradation of odor substances through electron transfer or hydrogen extraction principles.

[0021] This invention proposes an ozone / superphosphate advanced oxidation system, which utilizes ozone to activate superphosphate to generate phosphate radicals (·PO4). 2 -), which works in conjunction with ozone under catalyst-free conditions to achieve efficient degradation of odor substances, and the final products are safe and controllable.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] 1. Highly efficient degradation: When the concentration of odor substances in the water source is ≤100ng / L, after ozone / superphosphate treatment, the odor substances can be stably lower than their odor threshold (<10ng / L).

[0024] 2. Environmentally friendly: The final product of ozone is oxygen, and the final product of superphosphate is phosphate. Both can form insoluble precipitates with aluminum salt coagulants, which can be effectively removed by subsequent precipitation processes without secondary pollution.

[0025] 3. Economic efficiency: Compared with ultraviolet-based advanced oxidation technologies, ozone / superphosphate technology significantly reduces energy input and can be applied under neutral conditions without the need for additional pH adjustment. This technology can be formed by simply adding superphosphate to the existing ozone pre-oxidation process in water plants without process modification, which greatly saves water plant investment costs.

[0026] 4. Universality: Applicable to different water sources (surface water, groundwater, reservoir water, lake water), and has a good removal effect on odor substances, especially one or two of 2-MIB and GSM. Attached Figure Description

[0027] Figure 1 This invention proves that PO4 2 - The generated electron paramagnetic resonance spectrum;

[0028] Figure 2 This is a result diagram of Embodiment 5 of the present invention; Figure 2 a is a graph showing the change in 2-MIB removal efficiency with pH value; Figure 2 b is a graph showing the change in GSM removal efficiency with pH value. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Example 1:

[0031] An ozone / superphosphate-based oxidation pretreatment method and its application, the specific steps of which are as follows:

[0032] (1) A water source from a reservoir was used, and the initial concentrations of 2-MIB and GSM in the raw water were measured to be 46.1 ng / L and 28.5 ng / L, respectively. The pH was 7.2, the TOC was 4.3 mg / L, and the color was 13 degrees.

[0033] (2) Ozone was introduced into the raw water sample through a titanium plate aeration at a dosage of 2.0 mg / L; at the same time, disodium superphosphate was added to the raw water sample at a dosage of 6.0 mg / L.

[0034] (3) Set up a comparative experiment:

[0035] Comparative Example 1 (ozonation): Ozone was introduced into the raw water sample through a titanium plate aeration at a dosage of 2.0 mg / L.

[0036] Comparative Example 2 (Ozone / Hydrogen Peroxide System): Ozone was introduced into the raw water sample through a titanium plate aeration at a dosage of 2.0 mg / L, and hydrogen peroxide was simultaneously added to the raw water sample at a dosage of 1.0 mg / L.

[0037] Comparative Example 3 (UV / Sodium persulfate system): Sodium persulfate was added to the raw water sample, and UV lamps were turned on simultaneously. The UV dose was approximately 1600 mJ / cm². 3 ;

[0038] (4) After the reaction time is 10.0 minutes, samples are taken to determine the residual 2-MIB and GSM in the raw water after different system treatments;

[0039] (5) After the reaction, the raw water sample was subjected to coagulation and sedimentation process of water treatment by a six-unit stirrer. 20 mg / L of polyaluminum chloride was added, the coagulation stirring speed was 100 rpm, the coagulation time was 10 minutes, the settling time was 15 minutes, and the residual phosphate concentration was measured.

[0040] Results: After ozone / superphosphate treatment, the concentrations of 2-MIB and GSM decreased from 46.1 ng / L and 28.5 ng / L to 3.6 ng / L and 2.2 ng / L, respectively. The pH was 7.1, the TOC was 4.0 mg / L, the color was 13 degrees, and the phosphate concentration detected after simulated coagulation and precipitation was 0.08 mg / L.

[0041] In comparison, Comparative Example 1, ozone oxidation treatment reduced 2-MIB and GSM concentrations from 46.1 ng / L and 28.5 ng / L to 25.4 ng / L and 13.7 ng / L, respectively, with a pH of 7.1, TOC of 4.3 mg / L, and a color of 13 degrees. Comparative Example 2, ozone / hydrogen peroxide treatment reduced 2-MIB and GSM concentrations from 46.1 ng / L and 28.5 ng / L to 7.1 ng / L and 4.2 ng / L, respectively, with a pH of 7.1, TOC of 4.1 mg / L, and a color of 13 degrees. Comparative Example 3, UV / sodium persulfate treatment reduced 2-MIB and GSM concentrations from 46.1 ng / L and 28.5 ng / L to 27.3 ng / L and 19.1 ng / L, respectively, with a pH of 6.2, TOC of 4.1 mg / L, and a color of 13 degrees.

[0042] Example 2:

[0043] An ozone / superphosphate-based oxidation pretreatment method and its application, the specific steps of which are as follows:

[0044] (1) A lake was used as a water source. The initial concentrations of 2-MIB and GSM in the raw water were measured to be 63.6 ng / L and 28.3 ng / L, respectively. The pH was 7.4, the TOC was 3.9 mg / L, and the color was 15 degrees.

[0045] (2) Ozone was introduced into the raw water sample through a titanium plate aeration at a dosage of 5.0 mg / L; sodium superphosphate was added to the raw water sample at the same time at a dosage of 5.0 mg / L.

[0046] (3) After the reaction time is 5.0 minutes, a sample is taken to determine the residual 2-MIB and GSM in the raw water;

[0047] (4) After the reaction, the raw water sample was subjected to coagulation and sedimentation process of water treatment by a six-unit stirrer. 20 mg / L of polyaluminum chloride was added, the coagulation stirring speed was 100 rpm, the coagulation time was 10 minutes, the settling time was 15 minutes, and the residual phosphate concentration was measured.

[0048] Results: The concentrations of 2-MIB and GSM decreased from 63.6 ng / L and 28.3 ng / L to 2.4 ng / L and 1.1 ng / L, respectively. The pH was 7.3, the TOC was 3.6 mg / L, the color was 15 degrees, and phosphate was not detected after simulated coagulation and precipitation.

[0049] Example 3:

[0050] An ozone / superphosphate-based oxidation pretreatment method and its application, the specific steps of which are as follows:

[0051] (1) A water source from a reservoir was used, and the initial concentrations of 2-MIB and GSM in the raw water were measured to be 35.5 ng / L and 18.4 ng / L, respectively. The pH was 7.6, the TOC was 3.7 mg / L, and the color was 12 degrees.

[0052] (2) Ozone was introduced into the raw water sample through a titanium plate aeration at a dosage of 4.0 mg / L; at the same time, disodium superphosphate was added to the raw water sample at a dosage of 8.0 mg / L.

[0053] (3) After the reaction time is 8.0 minutes, a sample is taken to determine the residual 2-MIB and GSM in the raw water;

[0054] (4) After the reaction, the raw water sample was subjected to coagulation and sedimentation process of water treatment by a six-unit stirrer. 20 mg / L of polyaluminum chloride was added, the coagulation stirring speed was 100 rpm, the coagulation time was 10 minutes, the settling time was 15 minutes, and the residual phosphate concentration was measured.

[0055] Results: The concentrations of 2-MIB and GSM decreased from 35.5 ng / L and 18.4 ng / L to 2.7 ng / L and 1.8 ng / L, respectively. The pH was 7.5, the TOC was 3.5 mg / L, the color was 12 degrees, and the phosphate concentration detected after simulated coagulation and precipitation was 0.02 mg / L.

[0056] Example 4:

[0057] An ozone / superphosphate-based oxidation pretreatment method and its application, the specific steps of which are as follows:

[0058] (1) Ozone was introduced into pure water through a titanium plate aeration at a dosage of 2.0 mg / L; simultaneously, disodium superphosphate was added to the test water sample at a dosage of 4.0 mg / L, and 1 mmol / L of 5,5-dimethyl-1-pyrrolidone-N-oxide was added as ·PO4. 2- The capture agent was used, and the free radicals were immediately determined using an electron paramagnetic resonance spectrometer;

[0059] (2) The initial concentrations of 2-MIB and GSM were prepared using pure water at 30 ng / L and 30 ng / L respectively as test water samples, and the pH was adjusted to 7.0 using sulfuric acid and sodium hydroxide.

[0060] (3) Ozone was introduced into the test water sample through a titanium plate aeration at a dosage of 2.0 mg / L; at the same time, disodium superphosphate was added to the test water sample at a dosage of 4.0 mg / L;

[0061] (4) After reacting for 6.0 minutes, take a sample and determine the residual 2-MIB and GSM in the test water sample;

[0062] (5) After the reaction, the test water sample was subjected to coagulation and sedimentation process of water treatment by a six-unit stirrer. 20 mg / L of polyaluminum chloride was added, the coagulation stirring speed was 100 rpm, the coagulation time was 10 minutes, the settling time was 15 minutes, and the residual phosphate concentration was measured.

[0063] Result: As Figure 1 Electron paramagnetic resonance spectroscopy detected characteristic peaks of phosphate radicals, confirming that ·PO4 2- The formation of 2-MIB and GSM was achieved by reducing their concentrations from 30 ng / L and 30 ng / L to 3.9 ng / L and 4.6 ng / L, respectively, with a pH of 7.0. No phosphate was detected after simulated coagulation and precipitation.

[0064] Example 5:

[0065] An ozone / superphosphate-based oxidation pretreatment method and its application, the specific steps of which are as follows:

[0066] (1) The initial concentrations of 2-MIB and GSM were prepared using pure water at 30 ng / L and 30 ng / L respectively as test water samples. The pH was adjusted to 6.5, 7.0, 7.5, 8.0 and 8.5 respectively using sulfuric acid and sodium hydroxide.

[0067] (2) Ozone was introduced into test water samples with different pH values ​​through titanium plates at a dosage of 3.0 mg / L; sodium superphosphate was added to the test water samples at a dosage of 5.0 mg / L simultaneously.

[0068] (3) After the reaction time is 8.0 minutes, a sample is taken and the residual 2-MIB and GSM in the test water sample are measured;

[0069] (4) After the reaction, the test water sample was subjected to coagulation and sedimentation process of water treatment by a six-unit stirrer. 20 mg / L of polyaluminum chloride was added, the coagulation stirring speed was 100 rpm, the coagulation time was 10 minutes, the settling time was 15 minutes, and the residual phosphate concentration was measured.

[0070] Results: The removal efficiency of 2-MIB and GSM varies with pH value as follows: Figure 2 At different pH values, the levels of 2-MIB and GSM after treatment were both <10 ng / L, with the best removal efficiency observed at pH 7.5. Phosphate was undetectable after simulated coagulation and precipitation.

[0071] Example 6:

[0072] An ozone / superphosphate-based oxidation pretreatment method and its application, the specific steps of which are as follows:

[0073] (1) The initial concentrations of 2-MIB and GSM were prepared using pure water at 30 ng / L and 30 ng / L respectively as test water samples, and the pH was adjusted to 7.5 using sulfuric acid and sodium hydroxide.

[0074] (2) Ozone was introduced into the test water sample through a titanium plate aeration at a dosage of 2.0 mg / L; at the same time, disodium superphosphate was added to the test water sample at a dosage of 10.0 mg / L.

[0075] (3) After reacting for 10.0 minutes, take a sample and determine the residual 2-MIB and GSM in the test water sample;

[0076] (4) After the reaction, the test water sample was subjected to coagulation and sedimentation process of water treatment by a six-unit stirrer. 20 mg / L of polyaluminum chloride was added, the coagulation stirring speed was 100 rpm, the coagulation time was 10 minutes, the settling time was 15 minutes, and the residual phosphate concentration was measured.

[0077] Results: The concentrations of 2-MIB and GSM decreased from 30 ng / L and 30 ng / L to 5.9 ng / L and 7.4 ng / L, respectively, with a pH of 7.3. The phosphate concentration detected after simulated coagulation and precipitation was 0.09 mg / L.

Claims

1. An ozone / superphosphate-based oxidation pretreatment method, characterized in that, Includes the following steps: Ozone and superphosphate are simultaneously added to a drinking water source, with ozone dosage of 2.0 ~ 5.0 mg / L and superphosphate dosage of 5.0 ~ 10.0 mg / L. The drinking water source contains odorous substances. The reaction is carried out for 5 ~ 10 minutes. Finally, the phosphate, the final product of the reaction, is removed through coagulation and sedimentation processes.

2. The ozone / superphosphate-based oxidation pretreatment method according to claim 1, characterized in that, The ratio of ozone to superphosphate dosage is 1:1 to 1:

3.

3. The ozone / superphosphate-based oxidation pretreatment method according to claim 1, characterized in that, The superphosphate is at least one of disodium hydrogen superphosphate (Na2HPO5) and sodium superphosphate (Na6P2O8).

4. The ozone / superphosphate-based oxidation pretreatment method according to claim 1, characterized in that, The pH value of the reaction system is 6.5 ~ 8.

5.

5. The ozone / superphosphate-based oxidation pretreatment method according to claim 1, characterized in that, The odorant includes at least one of geosmin and 2-methylisoborneol.

6. The ozone / superphosphate-based oxidation pretreatment method according to claim 1, characterized in that, Ozone is added through a gas-liquid contact device; superphosphate is added continuously through a metering pump.

7. The application of the ozone / superphosphate-based oxidation pretreatment method of claim 1 in removing odor substances from drinking water sources.

8. The application according to claim 7, characterized in that, The drinking water sources include surface water, groundwater, reservoir water, and lake water.

9. The application according to claim 7, characterized in that, The initial concentration of odor substances in the drinking water source is ≤100 ng / L.

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