Treatment method and application of hydroxylamine-containing wastewater

Abstract

The present invention belongs to the technical field of wastewater treatment, and particularly relates to a method for treating hydroxylamine-containing wastewater and its application. The method for treating hydroxylamine-containing wastewater includes: adding a reaction substrate to the hydroxylamine-containing wastewater, and the reaction substrate includes calcium bicarbonate. The method of the present invention can improve the treatment efficiency of hydroxylamine.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a method for treating hydroxylamine-containing wastewater and its application. Background Art

[0002] Nitrogen-containing compounds play an important role in the life metabolism process of the biogeochemical cycle. The content and distribution of nitrogen elements in the ocean are closely related to the productivity of marine organisms. In recent years, a large amount of nitrogen fertilizer has been used in the agricultural production process, and the excessive release of nitrogen elements has caused varying degrees of nitrogen pollution to water bodies, destroying the ecological balance.

[0003] Biological denitrification can remove excessive inorganic nitrogen in water and is environmentally friendly. However, the presence of hydroxylamine will inhibit the cell growth activity and the denitrification ability of microorganisms, reducing the denitrification efficiency of biological treatment. Hydroxylamine is an inorganic nitrogen-containing substance and is often released into water bodies as a denitrification by-product of ammonia-oxidizing bacteria, ammonia-oxidizing archaea, and complete nitrifying bacteria. In addition, hydroxylamine sulfate and hydroxylamine hydrochloride, which are widely used in the medical, pesticide, and semiconductor industries, will also release a large amount of hydroxylamine in nature. Hydroxylamine salts are often used as an important component of reducing agents in photography and a solution for dissolving photoresist after lithography in the semiconductor industry. More seriously, in the production of nylon-6, the dosage 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%. However, research shows that the presence of a small amount of hydroxylamine will cause mutations in phages, viruses, bacteria, fungi, protozoa, fruit flies, and plants, and the presence of free hydroxylamine in wastewater will also significantly inhibit the simultaneous nitrification and denitrification ability of bacteria. Therefore, most microorganisms cannot effectively remove hydroxylamine, which may mainly be because their presence will damage the nucleic acid-related components of bacteria and cause DNA damage. In addition, the stability of hydroxylamine is poor. When the pH and temperature change continuously, hydroxylamine and its salts can decompose rapidly and release heat. However, the continuous heat release may lead to safety accidents such as explosions.

[0004] To effectively remove hydroxylamine in water, various methods for removing hydroxylamine have been tried. For example, adding sodium nitrite to hydroxylamine-containing wastewater to remove hydroxylamine; adding a large amount of sodium hypochlorite to convert hydroxylamine, using iron ions as a catalyst under the condition of pH 2–8, and adding hydrogen peroxide to convert hydroxylamine. However, when degrading hydroxylamine salts by the above methods, a large amount of acid may be released to corrode equipment.

[0005] Since the presence of hydroxylamine will disrupt the protein translation process involving ribosomes in denitrifying bacteria, resulting in bacteria being unable to grow and reproduce, there are currently few microorganisms that can remove hydroxylamine, and it is also difficult for these microorganisms to quickly remove hydroxylamine.

[0006] To solve the above technical problems, the inventor team tried to add sodium carbonate to the hydroxylamine waste liquid, and the hydroxylamine could be completely converted. However, the treatment efficiency of hydroxylamine was low. After 24 hours of reaction, the conversion efficiency of hydroxylamine was only about 1%. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a reaction substrate and its application in the treatment of nitrogen-containing wastewater.

[0008] To achieve the above purpose, the technical solution of the present invention is as follows:

[0009] The purpose of the present invention is to provide a method for treating wastewater containing hydroxylamine, and the method for treating wastewater containing hydroxylamine includes:

[0010] Adding a reaction substrate to the wastewater containing hydroxylamine, and the reaction substrate includes calcium bicarbonate.

[0011] Further, the reaction substrate further includes sodium carbonate.

[0012] Further, the mass ratio of calcium bicarbonate to sodium carbonate is 5.5:9.5 - 8.5:6.5.

[0013] Further, the method for treating wastewater containing hydroxylamine further includes:

[0014] Adjusting the carbon-nitrogen ratio of the wastewater containing hydroxylamine to 15 - 20:1, preferably 12 - 18:1.

[0015] Further, the method for treating wastewater containing hydroxylamine further includes:

[0016] Adjusting the dissolved oxygen content of the wastewater containing hydroxylamine to 7 - 7.6 mg / L.

[0017] The purpose of the present invention is also to provide the application of the above-mentioned method for treating wastewater containing hydroxylamine in the treatment of wastewater containing hydroxylamine.

[0018] The purpose of the present invention is also to provide the application of a reaction substrate containing calcium bicarbonate in the treatment of wastewater containing hydroxylamine.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The method of the present invention can improve the treatment efficiency of hydroxylamine.

[0021] (2) In the present invention, calcium bicarbonate and sodium carbonate are compounded and used in a specific ratio, which can further improve the treatment efficiency of hydroxylamine.

[0022] (3) The method of the present invention has the advantages of simple operation, short time consumption and no secondary pollution, etc., and is convenient for market promotion. Brief Description of the Drawings

[0023] Figure 1 Results of the influence of different reaction substrates on the conversion efficiency of hydroxylamine (the values are the average of three replicates ± SD (standard error));

[0024] Figure 2 Results of the influence of different pH values on the conversion rate of hydroxylamine (the values are the average of three replicates ± SD (standard error));

[0025] Figure 3 Results of the influence of calcium acetate, calcium chloride, sodium acetate, and sodium sulfate on the conversion rate of hydroxylamine (the values are the average of three replicates ± SD (standard error));

[0026] Figure 4 Results of the influence of different carbon-nitrogen ratios on the conversion rate of hydroxylamine (the values are the average of three replicates ± SD (standard error)), A is sodium carbonate, and B is calcium bicarbonate;

[0027] Figure 5 Results of the influence of different temperatures on the conversion rate of hydroxylamine (the values are the average of three replicates ± SD (standard error)), A is sodium carbonate, and B is calcium bicarbonate;

[0028] Figure 6 Results of the influence of different dissolved oxygen levels on the conversion rate of hydroxylamine (the values are the average of three replicates ± SD (standard error)), A is sodium carbonate, and B is calcium bicarbonate;

[0029] Figure 7 Results of the influence of the hydroxylamine conversion product (the values are the average of three replicates ± SD (standard error));

[0030] Figure 8 Results of the influence of the mixing ratio of calcium bicarbonate and sodium carbonate on the conversion rate of hydroxylamine (the values are the average of three replicates ± SD (standard error). Detailed implementation manners

[0031] The examples given are for better illustration of the content of the present invention, but the content of the present invention is not limited to the examples given. Therefore, those skilled in the art who make non-essential improvements and adjustments to the implementation manners based on the above-mentioned invention content still fall within the protection scope of the present invention.

[0032] Example 1

[0033] It should be noted that in this application, the concentration of nitrous oxide is obtained by subtracting the inorganic nitrogen content from the initial hydroxylamine content and then multiplying by the conversion rate of nitrous oxide in the gas sample. Excel, SPSS Statistics, MEGA7.0, and Origin2021 software are used for statistical processing and charting. All results are expressed as the mean ± standard deviation.

[0034] (1) Investigation of the optimal substrate of hydroxylamine and the effect of different pH on the conversion of hydroxylamine

[0035] Weigh 0.0992 g of hydroxylamine and dissolve it in a 250 ml conical flask pre-filled with 100 ml of deionized water. Then, add equal amounts (the mass of carbon element in calcium carbonate, calcium bicarbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate is the same) of calcium carbonate, calcium bicarbonate, sodium carbonate, sodium bicarbonate, or potassium carbonate to each conical flask to investigate the conversion rate of hydroxylamine. To further explore the effect of pH on the conversion of hydroxylamine, use hydrochloric acid and sodium hydroxide to adjust the initial pH to 5.5, 6.5, 7.5, 8.5, 9.5, 10.5, and 11.5 respectively. After reacting for 24 h, measure the contents of ammonium nitrogen, hydroxylamine, nitrate, and nitrite in the reaction solution. The testing methods are as follows: the concentrations of ammonium nitrogen, nitrite, and nitrate are determined by the indophenol blue method, N-(1-naphthyl)-ethylenediamine spectrophotometry, and ultraviolet spectrophotometry respectively (Zhang, X., Xia, Y., Wang, C., Li, J., Wu, P., Ma, L., Wang, Y., Wang, Y., Da, F., Liu, W., Xu, L., 2020. Enhancement of nitrite production via addition of hydroxylamine to partial denitrification (PD) biomass: Functional genes dynamics and enzymatic activities. Bioresource Technology, 318, 124274). The content of hydroxylamine is detected by the spectrophotometric method recommended by Frear and Burrell (Frear D S, B.R.C., 1955. Spectrophotometric Method for Determining Hydroxylamine Reductase Activity in Higher Plants. Analytical Chemistry, Vol. 27, 1664 - 1665). The results are as Figure 1 and Figure 2 shown.

[0036] As Figure 1As shown in the figure, after 24 hours of reaction, when hydroxylamine reacts with calcium carbonate, calcium bicarbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate, the conversion efficiencies are 5%, 82.69%, 99.9%, 1%, and 25% respectively. In addition, when calcium bicarbonate and sodium carbonate are used as reaction substrates, the conversion rates of hydroxylamine can reach 0.72 mg / L / h and 1.2 mg / L / h respectively, which are higher than those of Pseudomonas putida Y-9 (0.03 mg / L / h) (Huang, X., Xu, Y., He, T., Jia, H., Feng, M., Xiang, S., Wang, S., Ni, J., Xie, D., Li, Z., 2019; Ammonium transformed into nitrous oxide via nitric oxide by Pseudomonas putida Y-9 under aerobic conditions without hydroxylamine as intermediate. Bioresource Technology, 277, 87-93) and Acinetobacter calcoaceticus HNR (0.01 mg / L / h) (Zhao, B., He, Y.L., Hughes, J., Zhang, X.F., 2010. Heterotrophic nitrogen removal by a newly isolated Acinetobacter calcoaceticus HNR. Bioresource Technology, 101, 5194-520). Interestingly, when calcium bicarbonate or sodium carbonate is used as the reaction substrate, the pH values of the reaction solutions (10.23 and 10.39) are much higher than those of other groups, indicating that hydroxylamine is more stable in acidic solutions than in alkaline solutions.Meanwhile, when calcium bicarbonate or sodium carbonate was used as the reaction substrate, only a small amount of nitrate and nitrite were formed with the conversion of hydroxylamine. This finding was the same as the phenomenon that the oxidation products of hydroxylamine were usually nitrate and nitrite, while this result was not exactly the same as that of strain EM-H8, which did not convert to nitrite when removing hydroxylamine, and a large amount of nitrate was observed to be generated (11.33 ± 0.64 mg / L) (Chen, M.P., Ding, C.Y., He, T.X., Zhang, M.M., Wu, Q.F., 2022. Efficient hydroxylamine removal through heterotrophic nitrification by novel bacterium Glutamicibacter arilaitensis EM-H8. Chemosphere, 288, 132475). Compared with using sodium hypochlorite to remove hydroxylamine, using sodium carbonate or calcium bicarbonate to convert hydroxylamine produced less solid waste, and this method did not require adding a large amount of sulfuric acid to pre-adjust the pH value of hydroxylamine wastewater.

[0037] As Figure 2 shown, when calcium bicarbonate or sodium carbonate was used as the reaction substrate, the conversion rate of hydroxylamine was not only high, but also the corresponding pH values were as high as 10.23 and 10.39. To further study whether the change in pH value directly affected the conversion of hydroxylamine, the pH value of hydroxylamine waste liquid was adjusted with hydrochloric acid and sodium hydroxide solutions. According to previous studies, hydroxylamine exists in the form of NH2OH in alkaline and weakly acidic solutions and usually acts as a reducing agent, while it exists in the form of H3NO in strong acid solutions. However, when the pH value was lower than 6.5, the content of hydroxylamine did not change, which might be because the concentration of H+ was low, and hydroxylamine and protonated hydroxylamine were still in equilibrium under acidic conditions (as Figure 2)。In addition, when the pH increased from 6.5 to 9.5, the content of hydroxylamine remained unchanged, which was consistent with the previous theory that when only hydroxylamine was mixed with strong base, they would not react. In addition, when the pH was 10.5, only trace amounts of hydroxylamine were converted to nitrite (0.21 ± 0.02 mg / L) and ammonium nitrogen (1.04 ± 0.02 mg / L). This was quite different from the research of Chen (Chen, M.P., Ding, C.Y., He, T.X., Zhang, M.M., Wu, Q.F., 2022. Efficient hydroxylamine removal through heterotrophic nitrification by novel bacterium Glutamicibacter arilaitensis EM-H8. Chemosphere, 288, 132475), etc., which showed that when the pH increased from 6.5 to 7.2, the conversion efficiency of hydroxylamine increased accordingly, and when the pH value exceeded 8, the conversion efficiency of hydroxylamine by the strain Glutamicibacter arilaitensis EM-H8 reached the maximum value, about 62.18%. In conclusion, directly adding acid or base to the hydroxylamine waste liquid had no significant effect on the conversion rate of hydroxylamine.

[0038] (2) Explore the effects of sodium acetate, sodium sulfate, calcium acetate and calcium chloride on the conversion of hydroxylamine

[0039] To further clarify the important ions for the conversion of hydroxylamine by sodium carbonate / calcium bicarbonate, 0.0992 g of hydroxylamine was weighed and dissolved in a 250 ml conical flask pre-filled with 100 mL of deionized water. Then, sodium acetate and sodium sulfate with the same mass of carbon element as sodium carbonate, or calcium acetate or calcium chloride with the same mass of carbon element as calcium bicarbonate were added to the conical flask as reaction substrates. After the mixed solution was reacted at 25 °C and 150 rpm for 6 h, the contents of hydroxylamine, nitrite, ammonium nitrogen and nitrate were measured. The test method was the same as above, and the results were as Figure 3 shown.

[0040] As Figure 3 shown, when these four substances were used as reaction substrates respectively, hydroxylamine could not be converted. However, when calcium bicarbonate and sodium carbonate were used as single reaction substrates, the conversion rates of hydroxylamine could reach 3.5 mg / L / h and 3.49 mg / L / h respectively. Combining the reaction results of hydroxylamine with calcium carbonate, calcium carbonate, sodium bicarbonate and sodium bicarbonate with potassium carbonate, it can be speculated that only when sodium ions and carbonate ions combine to form sodium carbonate, and calcium ions and bicarbonate ions combine to form calcium bicarbonate, can hydroxylamine be efficiently converted.

[0041] (3) Explore the optimal conditions for the reaction of sodium carbonate / calcium bicarbonate with hydroxylamine

[0042] Using sodium carbonate / calcium bicarbonate as the reaction substrate, the effects of the content changes of these two reaction substrates, temperature, and dissolved oxygen concentration on the conversion of hydroxylamine were further investigated. Specifically: when using sodium carbonate or calcium bicarbonate as the reaction substrate, the nitrogen content of hydroxylamine in the reaction solution was fixed at 20 mg / L, and the addition amount of inorganic carbon in sodium carbonate or calcium bicarbonate was changed respectively, and the C / N ratios in the reaction solution were set to 10:1, 15:1, 20:1, 25:1, and 30:1 respectively; then under the condition of C / N being 15:1, the temperatures were set to 10 °C, 15 °C, 20 °C, 25 °C, and 30 °C respectively; when exploring the effect of dissolved oxygen on the conversion of hydroxylamine, under the conditions of C / N being 15:1 and temperature being 25 °C, the shaker speeds were set to 0, 50, 100, 150, and 200 rpm respectively, and the corresponding dissolved oxygen levels were 6.0, 6.6, 6.9, 7.4, and 7.6 mg / L respectively. After the reaction ended, the contents of ammonium nitrogen, hydroxylamine, nitrate, and nitrite in the reaction solution were measured, and the results were as Figure 4 (For easy identification, the carbon-nitrogen ratio is expressed as an integer. For example, a carbon-nitrogen ratio of 15 means the ratio of carbon element to nitrogen element is 15:1), Figure 5 and Figure 6 shown.

[0043] As Figure 4 shown, when the C / N ratio was 10:1, the conversion rates of hydroxylamine were 41.62% and 38.45% respectively. When the C / N increased to 15:1, the corresponding conversion rates of hydroxylamine increased significantly to 99.14% and 99.06% respectively, and the corresponding conversion rate of hydroxylamine could reach 0.87 mg / L / h, which was significantly higher than that of the biological method for removing hydroxylamine. When the C / N ratio increased from 15:1 to 30:1, the conversion rate of hydroxylamine did not change significantly. The above results indicate that when the carbon-nitrogen ratio is greater than or equal to 15:1, the content of inorganic carbon has no significant effect on the conversion efficiency of hydroxylamine. Considering the cost issue, the optimal C / N ratio for the reaction between sodium carbonate / calcium bicarbonate and hydroxylamine is 15:1. Compared with adding an excessive amount of ferric compounds to hydroxylamine wastewater, the cost required for adding sodium carbonate / calcium bicarbonate to hydroxylamine wastewater is lower.

[0044] As Figure 5As shown, hydroxylamine can be converted in the range of 10 - 30°C. When using a mixture of calcium bicarbonate and sodium carbonate as the reaction substrate, the conversion rate of hydroxylamine is the lowest at 10°C, which are 36.13% and 45.71% respectively. As the temperature rises to 15°C, the conversion rates of hydroxylamine increase to 59.95% and 63.43% respectively. When the temperature rises to 20°C, the conversion rates of hydroxylamine increase significantly to 99.27% and 99.57% respectively. In addition, when the temperature is 30°C, the conversion rates of hydroxylamine reach the maximum values, which are 99.75% and 98.62% respectively, and the corresponding conversion rates of hydroxylamine can be as high as 1.00 mg / L and 0.86 mg / L respectively, which are much higher than those of Pseudomonas Taiwanensis J488 (0.28 mg / L) (He, T.X., Xie, D.L., Ni, J.P., Li, Z.L., Li, Z., 2020. Nitrous oxide produced directly from ammonium, nitrate and nitrite during nitrification and denitrification. Journal of Hazardous Materials, 388, 122114) and Photobacterium sp. NNA4 (0.02 mg / L) (Liu, Y., Ai, G., Wu, M., Li, S., Miao, L., Liu, Z., 2019. Photobacterium sp. NNA4, an efficient hydroxylamine-transforming heterotrophic nitrifier / aerobic denitrifier. Journal of Bioscience and Bioengineering, 128, 64 - 71). Considering the economic cost and experimental operability, 25°C is taken as the optimal temperature for the reaction of hydroxylamine with sodium carbonate / calcium bicarbonate.Compared with the methods of Yu et al. (Yu, W., He, J., Hu, J., Huang, W., 2021. A method for treating waste liquid containing hydroxylamine and / or hydroxylamine salts) using sodium nitrite to convert hydroxylamine at a temperature of 30 - 50 °C, Pio et al. (Pio, G., Mocellin, P., Vianello, C., Salzano, E., 2021. A detailed kinetic model for the thermal decomposition of hydroxylamine. J Hazard Mater, 416, 125641) decomposing hydroxylamine at 143 °C, Iwata and Koseki (2003) decomposing hydroxylamine by adding iron ions at 80 °C, and Anderson (Anderson, J.H., 1964. The Copper-catalysed Oxidation of Hydroxylamine. The Analyst, Vol. 89, 357 - 362) promoting the oxidation of hydroxylamine by adding copper ions at 30 °C, etc., it is safer and more convenient to use sodium carbonate / calcium bicarbonate to convert hydroxylamine at 25 °C.

[0045] Such as Figure 6As shown, when sodium carbonate and calcium bicarbonate are used as reaction substrates, after 6 h of reaction, the conversion rate of hydroxylamine is the lowest at 0 rpm, which are 49.92% and 53.93% respectively. When the rotation speed is further increased to 100 rpm, the conversion rate of hydroxylamine increases significantly to 62.11% and 68.66%. These results are similar to a previous study in which higher dissolved oxygen can promote the conversion of hydroxylamine in Glutamicibacter arilaitensis EM-H8 and ammonia-oxidizing bacteria. When the rotation speed is increased to 150 rpm, the conversion rate of hydroxylamine reaches the maximum, which are 99.91% and 99.79% respectively. However, when the rotation speed is further increased (200 rpm), the conversion rate of hydroxylamine decreases to 98.67% and 98.56% respectively. Therefore, 150 rpm is the optimal rotation speed for the reaction of hydroxylamine with sodium carbonate / calcium bicarbonate. At the same time, the maximum conversion rate of hydroxylamine is as high as 3.5 mg / L / h and 3.49 mg / L / h, which is much higher than that of previously reported Pseudomonas taiwanensis EN-F2 (2.12 mg / L / h) (Zhang, M.M., He, T.X., Chen, M.P., Wu, Q.F., 2022. Ammonium and hydroxylamine can be preferentially removed during simultaneous nitrification and denitrification by Pseudomonas taiwanensis EN-F2. Bioresource Technology, 350, 126912) and wild-type bacteria (1.86 mg / L / h). From this result, it can also be seen that compared with substrate concentration and temperature, the effect of dissolved oxygen on the conversion rate of hydroxylamine is more significant.

[0046] (4) Explore the intermediate and final products of hydroxylamine conversion

[0047] Add sodium carbonate or calcium bicarbonate and hydroxylamine hydrochloride into a 250 mL bottle with a rubber seal. After reacting for 6 h under the conditions of C / N = 15:1, temperature of 25 °C, and rotation speed of 150 rpm, collect gas samples with an airtight syringe and use gas chromatography (Agilent 7890A, chromatographic conditions: high-purity N2, flow rate of 25 cm 3 min -1, the column oven temperature was 55 °C) to determine the concentration of nitrous oxide. At the same time, an experimental group without sodium carbonate / calcium bicarbonate was used as a control. At the same time, the concentrations of ammonium nitrogen, hydroxylamine, nitrite, and nitrate in the reaction solution were measured after 6 h. In addition, in order to study whether there was ammonium nitrogen in the transformation products of hydroxylamine, five treatment groups were designed, and the reagent contents of each treatment group are shown in Table 1. Moreover, the initial pH of all the above experimental groups was adjusted to 10.5, and then the reaction was carried out at 25 °C and 150 rpm for 6 h. Subsequently, samples were taken to measure the contents of various inorganic nitrogen in the reaction solution. The test methods were as follows: the concentrations of ammonium nitrogen, nitrite, and nitrate were determined by the indophenol blue method, N-(1-naphthyl)-ethylenediamine spectrophotometry, and ultraviolet spectrophotometry, respectively (Zhang, X., Xia, Y., Wang, C., Li, J., Wu, P., Ma, L., Wang, Y., Wang, Y., Da, F., Liu, W., Xu, L., 2020. Enhancement of nitrite production via addition of hydroxylamine to partial denitrification (PD) biomass: Functional genes dynamics and enzymatic activities. Bioresource Technology, 318, 124274). The content of hydroxylamine was detected by the spectrophotometric method recommended by Frear and Burrell (Frear D S, B.R.C., 1955. Spectrophotometric Method for Determining Hydroxylamine Reductase Activity in Higher Plants. Analytical Chemistry, Vol. 27, 1664-1665). The results are shown in Table 2.

[0048] Table 1 Contents of nitrogen and carbon added to different treatment groups

[0049]

[0050] Table 2 Hydroxylamine transformation products after 6 h of reaction

[0051]

[0052] After 6 h of reaction, it was observed that the reaction solution was colorless, transparent, without precipitation, and no pungent smell was detected. As shown in Table 2 and Figure 7It can be seen that when sodium carbonate is used as the reaction substrate, the conversion rate of hydroxylamine can reach 100%, and nitrite (6.7±0.03 mg / L) and nitrate (6.70±0.71 mg / L) are detected in the reaction solution and will accumulate. In addition, the production amount of nitrous oxide is 0.99±0.08 mg / L; when calcium bicarbonate is used as the reaction substrate, hydroxylamine can also be completely converted, and the accumulation amount of nitrite can reach 6.51±0.12 mg / L. However, the production amount of nitrate (7.56±0.28 mg / L) is higher than that when sodium carbonate is used as the reaction substrate, and the nitrous oxide is 1.21±0.04 mg / L. The phenomenon of hydroxylamine oxidation to produce nitrous oxide can also be observed in heterotrophic nitrifying bacteria. It is speculated that part of the reason for the production of nitrous oxide in this reaction may be due to the auto-oxidation reaction of hydroxylamine, and the deeper reason needs further exploration. It can also be seen from the above results that when sodium carbonate or calcium bicarbonate is used as the reaction substrate, the nitrogen loss efficiency in hydroxylamine exceeds 37%, which is much higher than that of Glutamicibacter arilaitensis EM-H8 (26.86%) (Chen, M.P., Ding, C.Y., He, T.X., Zhang, M.M., Wu, Q.F., 2022. Efficient hydroxylamine removal through heterotrophic nitrification by novel bacterium Glutamicibacter arilaitensis EM-H8. Chemosphere, 288, 132475) and strain Acinetobacter calcoaceticus HNR (9.5%) (Zhao, B., He, Y.L., Hughes, J., Zhang, X.F., 2010. Heterotrophic nitrogen removal by a newly isolated Acinetobacter calcoaceticus HNR. Bioresource Technology, 101, 5194-5200).

[0053] As a reducing substance, when hydroxylamine reacts with oxidizing substances, it is difficult to determine whether hydroxylamine provides one or two electrons as a donor, so the final oxidation product is also difficult to determine (Duan et al., 2021). In this study, after hydroxylamine reacts with sodium carbonate / calcium bicarbonate, only nitrogen-containing substances with increased valence, such as nitrite, nitrate, and nitrous oxide, are detected, and no other nitrogen-containing substances with decreased valence are detected. In past studies, the disproportionation reaction of hydroxylamine was mainly the production and consumption of hydrazine (A.NH4+ +NH2OH → N2H4 + H2O + HB. 2NH2OH + N2H4 + 2H+ → 2NH4 + + N2 + 2H2O) (Oshiki et al., 2022; Soler-Jofra et al., 2020), and this disproportionation reaction also often occurs in different anaerobic ammonium-oxidizing bacteria (Pacheco et al., 2011; Oshiki et al., 2016; van der Star et al., 2008). Since no oily liquid was observed during the reaction of hydroxylamine with sodium carbonate / calcium bicarbonate, it was suspected whether hydrazine had been converted into other substances. To further clarify whether the converted substance was ammonium, an ammonium nitrogen addition experiment was designed (as Figure 7 ). After 6 h of reaction, the ammonium nitrogen content of 5 mg / L in treatment group 1 did not decrease. Similarly, the contents of hydroxylamine and ammonium nitrogen in treatment group 3 remained unchanged. In addition, when sodium carbonate or calcium carbonate was added (treatment groups 4 and 5), the ammonium nitrogen content still did not decrease. Since no ammonium nitrogen was detected after the reaction of hydroxylamine with sodium carbonate / calcium bicarbonate, we can rule out the possibility of the generation and conversion of ammonium nitrogen during the reaction of hydroxylamine with sodium carbonate / calcium bicarbonate. The above experimental phenomena prove that the reaction of hydroxylamine with sodium carbonate / calcium bicarbonate does not produce ammonium nitrogen, and the reducing substances produced in this reaction need to be further explored.

[0054] (5) Explore the effect of the mixture of sodium carbonate and calcium bicarbonate in different ratios on the conversion of hydroxylamine

[0055] The nitrogen content in hydroxylamine remained unchanged. The mass ratio of carbon element to nitrogen element of sodium carbonate and calcium bicarbonate in the waste liquid was fixed at 15:1 (the fixed C / N of 15 here was the optimal C / N of 15:1 when using sodium carbonate or calcium bicarbonate as a single reaction substrate in the previous description). Then, the mass ratio of calcium bicarbonate:sodium carbonate was adjusted to 5.5:9.5, 6.5:8.5, 7.5:7.5, 8.5:6.5, and 9.5:5.5 respectively as the mixed reaction substrate, and then the reaction was carried out at 25 °C and 150 rpm. After the reaction ended, the contents of ammonium nitrogen, hydroxylamine, nitrate, and nitrite in the reaction solution were measured, and the results were as Figure 8 shown.

[0056] As Figure 8As shown, when the mass ratio of calcium bicarbonate to sodium carbonate is 5.5:9.5 - 8.5:6.5, after reacting for 3 h 30 min, the conversion efficiency of hydroxylamine is as high as 98.36%, and its conversion rate is as high as 6.19 mg / L / h, which is much higher than the conversion rate of hydroxylamine (3.49 mg / L / h) when sodium carbonate or calcium bicarbonate is used as a single reaction substrate. However, when the mass ratio of calcium bicarbonate to sodium carbonate is 9.5:5.5, the conversion rate of hydroxylamine is only 76.77%. This result shows that the addition of an appropriate amount of sodium carbonate can significantly increase the conversion rate of hydroxylamine.

[0057] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for treating hydroxylamine-containing wastewater, characterized in that the method for treating hydroxylamine-containing wastewater includes: Adding a reaction substrate to the hydroxylamine-containing wastewater, the reaction substrate includes calcium bicarbonate, and the reaction substrate also includes sodium carbonate.

2. The method for treating hydroxylamine-containing wastewater according to claim 1, characterized in that the mass ratio of calcium bicarbonate to sodium carbonate is 5.5:9.5 - 8.5:6.

5.

3. The method for treating hydroxylamine-containing wastewater according to claim 1, characterized in that the method for treating hydroxylamine-containing wastewater further includes: Adjusting the carbon-nitrogen ratio of the hydroxylamine-containing wastewater to 15 - 20:

1.

4. The method for treating hydroxylamine-containing wastewater according to claim 1, characterized in that the method for treating hydroxylamine-containing wastewater further includes: Adjusting the dissolved oxygen content of the hydroxylamine-containing wastewater to 7 - 7.6 mg / L.

5. Application of the method for treating hydroxylamine-containing wastewater according to any one of claims 1 - 4 in the treatment of hydroxylamine-containing wastewater.

6. Application of a reaction substrate containing calcium bicarbonate in the treatment of hydroxylamine-containing wastewater.

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