High-COD (Chemical Oxygen Demand) hydroxylamine wastewater treatment method

Abstract

The invention relates to a treatment method of a high-COD (Chemical Oxygen Demand) hydroxylamine wastewater solution, and belongs to a wastewater treatment technology. According to the method, a mild treatment mode is adopted, the safe discharge standard can be met through combined and coordinated treatment of sodium hypochlorite, sodium sulfite and activated carbon, microorganisms can reach biodegradability through the treated wastewater, the purpose of turning waste into wealth is achieved, and the method is easy to operate and low in cost. The method is high in safety and can be used for industrial treatment.

Description

Technical Field

[0001] The invention relates to a wastewater treatment technology, in particular to a treatment technology of hydroxylamine, a toxic substance in wastewater. Background Art

[0002] Hydroxylamine (HA) and its derivatives refer to a class of inorganic highly active compounds containing -NH-OH groups, which are obtained by replacing hydrogen on amine groups with hydroxyl groups. It is reported that ammonium nitrogen can be oxidized to hydroxylamine under the action of ammonia monooxygenase of ammonia-oxidizing bacteria, ammonia-oxidizing archaea and holistic nitrifying bacteria. In addition, hydroxylamine sulfate and hydroxylamine hydrochloride, which are widely used in the medical, pesticide and semiconductor industries, also release a large amount of hydroxylamine in nature. Hydroxylamine salts are often used as an important component of reducing agents in photography and solutions for dissolving photoresists after photolithography in the semiconductor industry. More seriously, in the production of nylon-6, the amount of hydroxylamine salts can reach 80%. Due to the large-scale production and use of hydroxylamine, the concentration of hydroxylamine in wastewater has reached as high as 2%.

[0003] Hydroxylamine is a potential mutagen, which has obvious toxic effects on humans and the environment. Hydroxylamine has poor stability and is prone to explosion when heated, which increases the difficulty of treating hydroxylamine wastewater. Studies have found that hydroxylamine can destroy the protein translation process involved in ribosomes in denitrifying bacteria, causing the bacteria to be unable to grow and reproduce, or even die. Even trace amounts of hydroxylamine can cause mutations in many bacteriophages, viruses, bacteria, fungi, protozoa, fruit flies and plants, and when the concentration of hydroxylamine exceeds 5ppm, the performance of biological sewage treatment plants will also be disturbed. Most of the microorganisms isolated so far, such as strains Zobellella taiwanensis DN-7. mendocina X49 and P. stutzeri Gep-01, cannot grow in the presence of hydroxylamine. In addition, in the process of biological denitrification, the presence of hydroxylamine will also seriously affect the biological denitrification products. For example, 5 mg / L hydroxylamine can inhibit the activity of nitrite oxidizing bacteria and turn complete digestion into partial digestion; Kindaichi et al. in 2018 observed that ammonium nitrogen was partially oxidized to toxic nitrite in the biofilm with hydroxylamine added, while ammonium nitrogen was completely oxidized to nitrate in the absence of hydroxylamine. Therefore, the presence of hydroxylamine is not conducive to the growth and reproduction of microorganisms and wastewater denitrification.

[0004] The treatment methods for high-concentration organic chemical wastewater currently mainly include physical processes, chemical processes and biological processes. Physical process treatment mainly includes centrifugal separation, physical adsorption and filtration flocculation. This method can only perform simple separation and cannot achieve complete discharge safety. The biological process is to degrade and metabolize the pollutants in the wastewater through microorganisms to maximize their conversion into nitrogen, water and carbon dioxide. Common methods include microbial remediation, anaerobic treatment, aerobic treatment and other technologies. Pollutants in wastewater can cause microbial poisoning, resulting in the inability to degrade pollutants, which hinders the application of this method. The chemical process mainly uses oxidants to oxidize organic matter in wastewater into carbon dioxide and water, thereby achieving the purpose of removal. The methods mainly include photocatalytic technology, supercritical water oxidation technology, wet catalytic oxidation, and Fenton oxidation. Wet catalytic oxidation method, this method has a good treatment effect, but the reaction system is high temperature and high pressure, and has high requirements for equipment. At the same time, it needs to use precious metal catalysts, and the overall treatment cost is high. Hydroxylamine has poor stability and is prone to explosion when heated, which increases the difficulty of treating hydroxylamine wastewater, which also makes its application not widespread.

[0005] Fenton oxidation method, Chinese patent CN108217901A introduces a method for degrading hydroxylamine and / or hydroxylamine salt in wastewater, which mainly uses a certain acidity to dissolve iron oxide and other compounds containing trivalent iron, and finally reduces the concentration of hydroxylamine through redox reaction. This method only treats high-concentration hydroxylamine wastewater into low-concentration hydroxylamine wastewater, and this low-concentration hydroxylamine wastewater is still highly toxic wastewater. In addition, due to the relatively weak oxidizing property of trivalent iron ions, iron ions need to be excessive, the dosage is relatively large, the cost is high, and a large amount of solid waste will be generated, causing secondary pollution. The presence of residual iron and hydroxylamine greatly reduces the biodegradability of sewage.

[0006] Chinese patent CN109205840A introduces a method for treating hydroxylamine wastewater, which mainly utilizes the strong oxidizing properties of hydrogen peroxide and trivalent iron ions to degrade hydroxylamine in wastewater. However, since a strong oxidant, hydrogen peroxide, is used in the treatment process, the degradation rate of hydroxylamine is too fast, the reaction is significantly exothermic, and there are certain safety hazards. In addition, hydrogen peroxide can convert some organic matter in the wastewater into peroxides, and subsequent treatment may have certain explosion risks.

[0007] Hydroxylamine has poor stability and is prone to explosion when heated, which increases the difficulty of treating hydroxylamine wastewater. In order to ensure the safety of recycling and treating waste liquid containing hydroxylamine and / or hydroxylamine salt, it is necessary to gently treat the waste liquid containing hydroxylamine and / or hydroxylamine salt. In industry, hydroxylamine wastewater is generally treated by adding sodium hypochlorite aqueous solution. This method is relatively low in cost, but usually there will be a small amount of hydroxylamine and hypochlorite, which are biologically toxic and will reduce the biodegradability of wastewater, thereby making it impossible for wastewater to enter the biochemical pool for degradation. Summary of the invention

[0008] Technical problem to be solved: In view of the problems caused by various treatment methods for hydroxylamine in wastewater in the prior art, such as the generation of a large amount of iron sludge and the use of hazardous materials such as peroxides during the degradation process, the present invention provides a method that can not only effectively remove hydroxylamine in wastewater, but also the solution obtained by the method is biodegradable.

[0009] Technical concept: In the process of treating hydroxylamine wastewater solution with sodium hypochlorite, some residual hydroxylamine and hypochlorite will be produced. However, both substances are biologically toxic. If they are directly discharged for microbial cultivation, it will cause severe damage. Based on this, we adopted a combination of physical and chemical methods and proposed a sodium hypochlorite-sodium sulfite-activated carbon method to treat high COD hydroxylamine wastewater. Sodium hypochlorite is used to remove the main hydroxylamine and effectively reduce COD, sodium sulfite is used to remove residual sodium hypochlorite, and activated carbon is used to adsorb residual hydroxylamine, hypochlorite and other toxic substances, finally achieving the biodegradability of high COD hydroxylamine wastewater.

[0010] The object of the present invention is to protect the treatment method of hydroxylamine in high COD wastewater solution, and the specific steps include: Step 1: add sodium hypochlorite solution to hydroxylamine wastewater, stir and filter after the addition; Step 2: Add sodium sulfite to the above filtrate and adjust the pH to 11 with sodium hydroxide; Step 3: Add activated carbon to the above mixed solution, stir, filter, and adjust the pH of the filtrate to neutral.

[0011] In the further step 1, the mass ratio of the sodium hypochlorite solution added to the hydroxylamine wastewater is 0.5-0.7:1; Further, in step 2, the mass ratio of the sodium sulfite added to the hydroxylamine wastewater is 20-40:1; In the further step 3, the mass ratio of the activated carbon added to the hydroxylamine wastewater is 4:1; In step 3, the filtrate is adjusted to neutrality by hydrochloric acid.

[0012] Technical effects: 1) The treatment technology of this solution can solve the problem of secondary pollution caused by a large amount of iron sludge solid waste in the prior art. At the same time, this solution is gentle and easy to operate, reducing the risk of using peroxides; 2) This technology not only reduces the hydroxylamine concentration in the wastewater solution to a dischargeable standard, but also meets the requirements of microbial biodegradability, which is a level never achieved in the prior art; 3) This solution is simple to operate, highly safe, and low-cost. It provides a feasible solution for turning industrial wastewater into treasure and can be applied in large-scale industries. DETAILED DESCRIPTION

[0014] As used herein, the term "chemical oxygen demand (COD)" refers to the oxygen equivalent consumed by the reduced inorganic and organic matter (generally organic matter) that needs to be oxidized in the water sample measured by chemical reactions. This indicator is also used as one of the comprehensive indicators of the relative content of organic matter in water. The detection method generally adopts the dichromate method: the environmental standard HJ 828-2017 "Dichromate Method for Determination of Chemical Oxygen Demand of Water Quality" shall prevail. The principle is: add a known amount of potassium dichromate solution to the water sample, and use silver salt as a catalyst in a strong acid medium, and use a masking agent to mask the interference of chloride ions in the water body. After boiling and reflux, use ferrous iron as an indicator and ammonium ferrous sulfate to titrate the unreduced potassium dichromate in the water sample, and calculate the mass concentration of consumed oxygen from the amount of potassium dichromate consumed.

[0015] As used herein, the term "biochemical oxygen demand (BOD)" refers to the amount of dissolved oxygen required for microorganisms to decompose organic matter contained in 1L of water under aerobic conditions. Microorganisms need to consume oxygen when decomposing organic compounds in water. If the dissolved oxygen in the water is not enough to supply the needs of microorganisms, the water body is in a polluted state. Therefore, BOD is an important indicator that indirectly indicates the degree of organic pollution in water bodies. Through the determination of BOD, we can understand the biodegradability of sewage and the self-purification ability of water bodies. BOD is tested according to the differential pressure measurement principle. Simulating the biodegradation process of organic matter in nature, in a sealed culture bottle, the oxygen in the air above the culture bottle continuously replenishes the dissolved oxygen consumed by the decomposition of organic matter in the sample. By removing the CO2 produced during the degradation of organic matter, the air pressure in the culture bottle changes, and by monitoring the change in air pressure in the culture bottle, the biochemical oxygen demand (BOD) value of the sample is calculated.

[0016] The hydroxylamine wastewater used in this experiment contained 0.3% hydroxylamine.

[0017] The detection method of hydroxylamine in the experiment is to perform quantitative analysis by ion chromatography after acidification. The specific detection method is as follows: Chromatographic conditions: Chromatographic column: CS16 cation analysis column 5X250MM; column temperature: 40℃; detector temperature: 30℃ Detector: electrochemical detector; eluent: 30mmol / L methanesulfonic acid solution; flow rate: 1mL / min.

[0018] Example 1 Sodium hypochlorite-sodium sulfite-activated carbon method: Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.6 kg of sodium hypochlorite solution (10%), and stir for 16 hours after the addition is complete. Filter with suction, and add 50 g of sodium sulfite to the filtrate. Add 30 g of sodium hydroxide to adjust the pH to 11. Add 5 g of activated carbon and stir for 1 hour. Filter with suction, and adjust the pH of the filtrate to neutral with hydrochloric acid.

[0019] After testing, hydroxylamine was not detected and the biodegradability (BOD5 / COD) was 0.41.

[0020] Example 2 Sodium hypochlorite-sodium sulfite-activated carbon method: Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.3 kg of sodium hypochlorite solution (10%), and stir for 16 hours after the addition is complete. Filter with suction, and add 50 g of sodium sulfite to the filtrate. Add 30 g of sodium hydroxide to adjust the pH to 11. Add 5 g of activated carbon and stir for 1 hour. Filter with suction, and adjust the pH of the filtrate to neutral with hydrochloric acid.

[0021] After testing, the hydroxylamine content was 0.1% and the biodegradability (BOD5 / COD) was 0. Example 3 Sodium hypochlorite-sodium sulfite-activated carbon method:

[0022] Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.9 kg of sodium hypochlorite solution (10%), and stir for 16 hours after the addition is complete. Filter with suction, and add 50 g of sodium sulfite to the filtrate. Add 30 g of sodium hydroxide to adjust the pH to 11. Add 5 g of activated carbon and stir for 1 hour. Filter with suction, and adjust the pH of the filtrate to neutral with hydrochloric acid.

[0023] After testing, hydroxylamine was not detected and the biodegradability (BOD5 / COD) was 0.44. Example 4 Sodium hypochlorite-sodium sulfite-activated carbon method:

[0024] Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.6 kg of sodium hypochlorite solution (10%), and stir for 16 hours after the addition is complete. Filter with suction, and add 25 g of sodium sulfite to the filtrate. Add 30 g of sodium hydroxide to adjust the pH to 11. Add 5 g of activated carbon and stir for 1 hour. Filter with suction, and adjust the pH of the filtrate to neutral with hydrochloric acid.

[0025] After testing, hydroxylamine was not detected and the biodegradability (BOD5 / COD) was 0.43.

[0026] Comparative Example 1 Sodium hypochlorite method: Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.6 kg of sodium hypochlorite solution (10%) dropwise, stir for 16 hours after the addition is complete, filter, and adjust the pH of the filtrate to neutral with hydrochloric acid.

[0027] After testing, the hydroxylamine concentration was 0.05% and the biodegradability (BOD5 / COD) was 0.

[0028] Comparative Example 2 Sodium hypochlorite-sodium sulfite method: Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.6 kg of sodium hypochlorite solution (10%) dropwise, stir for 16 hours after the addition is complete, filter, add 50 g of sodium sulfite to the filtrate, and then adjust the pH to neutral with hydrochloric acid.

[0029] After testing, the hydroxylamine concentration was 0.05% and the biodegradability (BOD5 / COD) was 0.

[0030] Comparative Example 3 Sodium hypochlorite-activated carbon method: Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.6 kg of sodium hypochlorite solution (10%), and stir for 16 hours after the addition is complete. Filter with suction, and add 30 g of sodium hydroxide to the filtrate to adjust the pH to 11. Add 5 g of activated carbon and stir for 1 hour. Filter with suction, and adjust the pH of the filtrate to neutral with hydrochloric acid.

[0031] After testing, hydroxylamine was not detected and the biodegradability (BOD5 / COD) was 0.

[0032] Comparative Example 4 Sodium hypochlorite-sodium sulfite-activated carbon method (without pH adjustment): Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, add 0.6 kg of sodium hypochlorite solution (10%), and stir for 16 hours after the addition is complete. Filter with suction, add 50 g of sodium sulfite to the filtrate. Add 5 g of activated carbon and stir for 1 hour. Filter with suction, and adjust the pH of the filtrate to neutral with hydrochloric acid.

[0033] After testing, the hydroxylamine content was 0.01% and the biodegradability (BOD5 / COD) was 0. Comparative Example 5 Fenton method:

[0034] Take 2 kg of 3% hydroxylamine solution, adjust pH to 2 with sulfuric acid, add 50 g of ferrous sulfate, stir for 0.5 h, slowly add 200 g of 30% hydrogen peroxide with a dropping funnel, pay attention to the temperature and bubble generation rate to prevent spraying. Stir for 2 h, heat to 95 ° C, stir for 2 hours, and cool to room temperature.

[0035] The residual hydroxylamine concentration is 0.27% and the biodegradability (BOD5 / COD) is 0.

[0036] Comparative Example 6 Sodium sulfite-activated carbon method: Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, then add 30 g of sodium hydroxide to adjust the pH to 11. Add 5 g of activated carbon and stir for 1 hour. Filter by suction, add 50 g of sodium sulfite to the filtrate, and adjust the pH to neutral with hydrochloric acid.

[0037] After testing, the hydroxylamine concentration was 0.3% and the biodegradability (BOD5 / COD) was 0.

[0038] Comparative Example 7 Sodium hypochlorite-sodium sulfite-silica gel method: Add 1.3 kg of hydroxylamine wastewater to a 4L three-necked flask, then add 30 g of sodium hydroxide to adjust the pH to 11. Add 5 g of silica gel and stir for 1 hour. Filter by suction, add 50 g of sodium sulfite to the filtrate, and adjust the pH to neutral with hydrochloric acid.

[0039] After testing, the hydroxylamine concentration was 0.02% and the biodegradability (BOD5 / COD) was 0. Biodegradability of treated wastewater

[0040] In order to evaluate whether the treated wastewater is suitable for the survival of microorganisms, we used the above-mentioned methods 1-5 to pre-treat the hydroxylamine wastewater solution to remove the main organic matter and toxic substances, and then finally enter the biochemical pool, and then use the microorganisms in the biochemical pool to verify the biodegradability of the wastewater. Usually, people use BOD5 / COD (i.e., B / C ratio) to reflect the proportion of biodegradable organic pollutants in the total amount of organic pollutants in the wastewater, so as to evaluate the microbial degradability of the wastewater under aerobic conditions. When BOD / COD is greater than 0.3, it is generally believed that the wastewater is biodegradable, and the larger the BOD5 / COD value, the better the biodegradability of the wastewater.

[0041]

Claims

1. A method for treating high COD hydroxylamine wastewater, characterized in that include Step 1: add sodium hypochlorite solution to hydroxylamine wastewater, stir and filter after the addition; Step 2: Add sodium sulfite to the above filtrate and adjust the pH to 11 with sodium hydroxide; Step 3: Add activated carbon to the above mixed solution, stir, filter, and adjust the pH of the filtrate to neutral.

2. The processing method according to claim 1, characterized in that The concentration of the hydroxylamine wastewater solution in step 1 is not higher than 0.3%.

3. The processing method according to claim 1, characterized in that In step 1, the mass ratio of the sodium hypochlorite solution added to the hydroxylamine wastewater is 0.5-0.7:

1.

4. The processing method according to claim 1, characterized in that In step 2, the mass ratio of the sodium sulfite added to the hydroxylamine wastewater is 20-40:

1.

5. The processing method according to claim 1, characterized in that In step 3, the mass ratio of the activated carbon added to the hydroxylamine wastewater is 4:

1.

6. The processing method according to claim 1, characterized in that Step 3: The filtrate is adjusted to neutrality by hydrochloric acid.

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