A method for strengthening wastewater desulfurization and denitrification based on C-S coupling

Abstract

This invention discloses a method for enhanced desulfurization and denitrification of wastewater based on C-S coupling, belonging to the field of industrial wastewater treatment technology. The method includes the following steps: (1) adding sulfur autotrophic denitrification sludge or sulfur autotrophic denitrification bacteria liquid into a reaction vessel, and then adding culture medium; (2) adding the wastewater to be treated into the above reaction vessel, and making the initial S / C / N ratio of the system in the reaction vessel range from 0.8 to 1.6: 0.25 to 0.75: 1, controlling the reaction vessel to be in an anaerobic or hypoxic environment, and continuously stirring to carry out denitrification reaction to achieve desulfurization and denitrification of wastewater; the method of this invention realizes the coupling of sulfur autotrophic denitrification and heterotrophic denitrification, greatly reducing the nitrate concentration in the effluent, improving the total nitrogen removal efficiency, reducing the toxic effect of sulfides on bacteria, and achieving high treatment efficiency and good effluent quality.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to a method for enhanced wastewater desulfurization and denitrification based on CS coupling. Background Technology

[0002] With the development of society, the discharge of urban domestic sewage and industrial and agricultural wastewater has increased. Wastewater treatment is not only related to environmental protection, but also affects the sustainable development of industries. Human activities such as agricultural fertilization, livestock wastewater discharge, and industrial wastewater discharge, as well as natural factors such as plants, organisms, and geology, can all lead to an increase in nitrate content in water bodies. Increased nitrate content in water bodies can lead to eutrophication, which has a serious impact on ecosystems and human health.

[0003] Therefore, the treatment of nitrate nitrogen pollution in aquatic environments has become increasingly critical and important. Biological denitrification technology has always been considered the most feasible denitrification technology due to its advantages of good economic practicality and good denitrification effect. It is mainly divided into two types: heterotrophic denitrification technology and autotrophic denitrification technology.

[0004] Heterotrophic denitrification technology refers to the process by which heterotrophic denitrifying bacteria carry out denitrification under anaerobic conditions, using organic matter to reduce nitrite or nitrate to nitrogen. The denitrification rate is fast, but it has the disadvantages of being cumbersome and requiring strict control of conditions. If there is insufficient bioavailable organic carbon source in the wastewater, additional organic carbon source often needs to be added when using this technology, which leads to an increase in wastewater treatment costs.

[0005] Sulfur autotrophic denitrification is a type of autotrophic denitrification technology, generally referring to the process by which sulfur-oxidizing bacteria (SOB) utilize sulfur in an anaerobic environment. 2- S0, S2O3 2- S4O6 2- or SO3 2- This process involves reducing inorganic sulfides acting as electron donors to reduce nitrite or nitrate ions to nitrogen gas, with sulfate and nitrogen gas as the final products. This technology can simultaneously remove nitrogen and sulfur and is suitable for groundwater and industrial wastewater treatment. However, in the sulfur autotrophic denitrification reaction, a large amount of OH-... - The consumption of these substances makes the reaction system acidic, affecting the activity of microorganisms; this process generates a large amount of sulfate, leading to secondary pollution of the water body; and the slow growth rate of autotrophic bacteria results in a long hydraulic retention time in engineering applications, thus affecting the denitrification efficiency.

[0006] Chinese patent document CN113735377A discloses a method for treating copper-ammonia complex wastewater by coupling copper removal and nitrogen removal using sulfur ions. This invention addresses the problem of the difficulty in effectively removing copper and nitrogen from copper-ammonia complex wastewater by sequentially subjecting the wastewater to precipitation and denitrification treatments. The denitrification treatment involves sequentially subjecting the effluent from the precipitation treatment to short-cut nitrification / denitrification, anaerobic ammonia oxidation, sulfur autotrophic short-cut denitrification, and sulfur autotrophic denitrification. This invention achieves synergistic removal of copper and nitrogen and also solves the problem of secondary pollution caused by sulfides during wastewater treatment.

[0007] Chinese patent document CN103373759A discloses a method for denitrification of wastewater from FCC catalyst production. This invention uses activated sludge from a wastewater treatment plant as a microbial carrier. Nitrifying bacteria are added when the activated sludge concentration is below 5000 mg / L. When nitrite nitrogen accounts for more than 50% of the total nitrification products in the system, denitrifying bacteria are added. By directly adding nitrifying bacteria and denitrifying bacteria, the optimal combination of microorganisms in the sludge is enhanced, and the population status of denitrifying microorganisms is changed. This method can achieve the removal of ammonia nitrogen, total nitrogen, and CODcr in the same reactor, resulting in good wastewater treatment effect.

[0008] However, the above methods involve a multi-step denitrification process or the use of multiple bacterial agents, which is quite cumbersome. Therefore, it is necessary to develop a process technology for wastewater desulfurization and denitrification based on CS coupling. Summary of the Invention

[0009] This invention provides a method for enhanced wastewater desulfurization and denitrification based on CS coupling. This method utilizes the autotrophic and heterotrophic denitrification of sulfur-autotrophic denitrifying bacteria to carry out biological denitrification and desulfurization. It can meet the needs of the heterotrophic denitrification process without adding a large amount of carbon source, and promotes the oxidation rate of sulfides to further enhance the autotrophic denitrification process, resulting in good wastewater treatment effect.

[0010] The specific technical solution adopted is as follows:

[0011] A method for enhanced wastewater desulfurization and denitrification based on CS coupling includes the following steps:

[0012] (1) Add sulfur autotrophic denitrifying sludge or sulfur autotrophic denitrifying bacteria liquid to the reaction vessel, and then add culture medium;

[0013] (2) Add the wastewater to be treated into the above reaction vessel, and make the initial S / C / N ratio of the system in the reaction vessel range from 0.8 to 1.6: 0.25 to 0.75: 1. Control the reaction vessel to be in an anaerobic or hypoxic environment, and continuously stir to carry out the denitrification reaction to achieve desulfurization and denitrification of the wastewater (the S / C / N ratio is the mass concentration ratio, where S is divalent sulfur, C is organic carbon, and N is nitrate nitrogen).

[0014] Preferably, the wastewater to be treated contains nitrate nitrogen, with a nitrate nitrogen concentration ≤50ppm and a pH value of 7-8.

[0015] Preferably, in step (2), the wastewater to be treated is added to the above-mentioned reaction vessel, and then sulfides and organic carbon sources are injected into the wastewater to be treated so that the initial S / C / N ratio of the system in the reaction vessel is 0.8-1.6:0.25-0.75:1.

[0016] More preferably, the sulfide is sodium sulfide nonahydrate, and the organic carbon source includes sodium acetate or glucose.

[0017] In this invention, sulfur-autotrophic denitrifying bacteria utilize sulfides as electron donors to denitrify and desulfurize wastewater. The elemental sulfur produced combines with sulfides to form polysulfides, thereby improving the bioavailability of sulfur. The addition of organic carbon sources further enhances this step. A coupled system of sulfur-autotrophic and heterotrophic denitrification is used to achieve simultaneous and efficient desulfurization and denitrification of wastewater. The specific reaction equations are as follows:

[0018]

[0019]

[0020] CH3COO - +4S₀ + 2H₂O → 2CO₂ + 4HS₂ - +3H +

[0021]

[0022] Preferably, in step (1), the culture medium includes phosphate, vitamins and minerals to ensure the normal growth of sulfur autotrophic denitrifying bacteria.

[0023] More preferably, the phosphate includes hydrogen phosphate and dihydrogen phosphate; the vitamin includes pyridoxine hydrochloride, biotin, riboflavin, folic acid, pantothenic acid, niacin, ammonium sulfate, para-aminobenzoic acid, lipoic acid, or vitamin B. 12 The minerals mentioned include magnesium sulfate, nitric acid, sodium chloride, manganese sulfate monohydrate, zinc chloride, calcium chloride dihydrate, cobalt chloride hexahydrate, ferrous sulfate heptahydrate, sodium tungstate dihydrate, sodium molybdate, nickel chloride hexahydrate, copper sulfate pentahydrate, alum, or boric acid.

[0024] Preferably, the ratio of the amount of sulfur autotrophic denitrifying sludge fed to the amount of wastewater treated is 15wt% to 25wt%; and the volume of the sulfur autotrophic denitrifying bacteria liquid accounts for 4% to 20% of the volume of the wastewater to be treated.

[0025] Preferably, the method for controlling the reaction vessel to be in an oxygen-free or oxygen-deficient environment is to purge with nitrogen to remove oxygen from the solution system.

[0026] Preferably, the stirring speed is maintained at 300-600 rpm during the stirring process, and the stirring is continued during the denitrification reaction to ensure that the sulfur autotrophic denitrifying sludge or sulfur autotrophic denitrifying bacteria are fully mixed with the wastewater.

[0027] Preferably, the duration of the denitrification reaction is 12–144 h.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The method of the present invention realizes the coupling of sulfur autotrophic denitrification and heterotrophic denitrification. The nitrate nitrogen or sulfur in the wastewater is removed by the autotrophic denitrification and heterotrophic denitrification of sulfur autotrophic denitrifying bacteria. The total nitrogen removal efficiency is higher than that of the single autotrophic denitrification method and the single heterotrophic denitrification method. It can greatly reduce the nitrate concentration of the effluent, with a technical effect of 1+1>2, and reduces the toxic effect of sulfides on bacteria.

[0030] (2) The method of the present invention achieves a 100% removal rate of sulfides and a 76%-100% removal rate of total nitrogen in wastewater, with high treatment efficiency and good effluent quality. Attached Figure Description

[0031] Figure 1 The graphs show the nitrogen removal effects of sulfur-autotrophic denitrifying bacteria in Comparative Examples 1-3 under different S / N ratios.

[0032] Figure 2 The graphs show the denitrification effects of sulfur-autotrophic denitrifying bacteria under different S / C / N ratios in Examples 1-3.

[0033] Figure 3 The graphs show the nitrogen removal effects of sulfur-autotrophic denitrifying bacteria in Comparative Examples 4-6 under different C / N ratios.

[0034] Figure 4 Comparative Examples 1-3: Influent and Effluent S of Sulfate Autotrophic Denitrifying Bacteria under Different S / N Ratios 2- and SO4 2- Concentration statistics results graph.

[0035] Figure 5 The influent and effluent S of sulfur autotrophic denitrifying bacteria under different S / C / N ratios in Examples 1-3 are... 2- and SO4 2- Concentration statistics results graph.

[0036] The blue dashed line is used to distinguish different S / N ratios, S / C / N ratios, or C / N ratios. Detailed Implementation

[0037] The present invention will be further illustrated below with reference to the embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] Cultivation of sulfur-autotrophic denitrifying bacteria: Sulfur-autotrophic denitrifying bacteria were enriched from anaerobic sludge. 2L of anaerobic sludge taken from the anaerobic biological filter of the Juhua Group wastewater treatment plant was inoculated into an 8L mixed flow reactor. Microbial nutrient solution was added. The solvent of the microbial culture solution was deionized water, and its composition included: sodium nitrate 1.2g / L, sodium sulfide nonahydrate 2.13g / L, sodium dihydrogen phosphate dihydrate 2.77g / L, disodium hydrogen phosphate dodecahydrate 11.63g / L, and vitamin solution 10mL / L (pyridoxine hydrochloride 10mg·L⁻¹). -1 Biotin 2 mg·L -1 Riboflavin 5 mg / L -1 folic acid 2 mg·L -1 Pantothenic acid 5 mg·L -1 Niacin 5 mg·L -1 Ammonium sulfate 5 mg·L -1 p-Aminobenzoic acid 5 mg·L -1 5 mg / L of lipoic acid -1 Vitamin B 12 0.1 mg·L -1 ) and mineral solution 25 mL / L (magnesium sulfate 3 mg·L) -1 1.5 mg·L⁻¹ of nitroglycerin -1 Sodium chloride 1 mg·L -1 0.5 mg·L⁻¹ manganese sulfate monohydrate -1 Zinc chloride 0.13 mg·L -1 0.1 mg·L⁻¹ calcium chloride dihydrate -1 0.1 mg·L⁻¹ cobalt chloride hexahydrate -1 Ferrous sulfate heptahydrate 0.1 mg·L -1 Sodium tungstate dihydrate 0.025 mg·L -1 Sodium molybdate 0.025 mg·L -1 Nickel chloride hexahydrate 0.024 mg·L -1 Copper sulfate pentahydrate 0.01 mg·L -1 Alum 0.01 mg·L -1 Boric acid 0.01 mg·L -1 Controlling NO3 in microbial nutrient solutions - -N was prepared at a concentration of 200 mg / L, and sulfide concentration was prepared according to S / N = 1.42. Changes in sulfide, nitrate nitrogen, and nitrite nitrogen were monitored daily. When detecting NO3... - When the NO3- concentration approaches 0 mg / L, replace the nutrient solution and reintroduce the feed, repeating this cycle. Wait until the system can stably remove NO3- from the solution.- -N indicates successful screening, domestication, and enrichment of sulfur-autotrophic denitrifying bacteria.

[0039] Example 1

[0040] In this embodiment, a mixed solution of sodium nitrate and sodium sulfide was used as the simulated wastewater to be treated, and sodium acetate was used as the organic carbon source. Domesticated sulfur autotrophic denitrifying bacteria were added to explore the desulfurization and denitrification effects of sulfur autotrophic denitrification and heterotrophic denitrification on wastewater.

[0041] (1) Centrifuge 700 mL of sulfur-autotrophic denitrifying bacteria solution, remove the supernatant and add it to the reaction vessel, then add culture medium to 3.5 L. In the culture medium, the concentration of sodium dihydrogen phosphate dihydrate is 2.77 g / L, the concentration of disodium hydrogen phosphate dodecahydrate is 11.63 g / L, and the vitamin solution is 10 mL / L (pyridoxine hydrochloride 10 mg·L). -1 Biotin 2 mg·L -1 Riboflavin 5 mg / L -1 folic acid 2 mg·L -1 Pantothenic acid 5 mg·L -1 Niacin 5 mg·L -1 Ammonium sulfate 5 mg·L -1 p-Aminobenzoic acid 5 mg·L -1 5 mg / L of lipoic acid -1 Vitamin B 12 0.1 mg·L -1 ), mineral solution 25 mL / L (magnesium sulfate 3 mg·L -1 1.5 mg·L⁻¹ of nitroglycerin -1 Sodium chloride 1 mg·L -1 0.5 mg·L⁻¹ manganese sulfate monohydrate -1 Zinc chloride 0.13 mg·L -1 0.1 mg·L⁻¹ calcium chloride dihydrate -1 0.1 mg·L⁻¹ cobalt chloride hexahydrate -1 Ferrous sulfate heptahydrate 0.1 mg·L -1 Sodium tungstate dihydrate 0.025 mg·L -1 Sodium molybdate 0.025 mg·L -1 Nickel chloride hexahydrate 0.024 mg·L -1 Copper sulfate pentahydrate 0.01 mg·L -1 Alum 0.01 mg·L -1 Boric acid 0.01 mg·L -1 ).

[0042] (2) Sodium nitrate and sodium sulfide nonahydrate were added to the above reaction vessel to simulate the wastewater to be treated. After adding sodium nitrate and sodium sulfide nonahydrate, the concentration of nitrate nitrogen in the reaction system was 50 ppm, the S / N ratio was 1.6:1, and the pH was about 7.3. Nitrogen gas was introduced into the reaction vessel to remove oxygen and control the reaction vessel to be in an anaerobic environment. Then, sodium acetate, an organic carbon source, was added. After adding sodium acetate, the S / C / N ratio ranged to 1.6:0.25:1. The vessel was sealed and placed in a constant temperature chamber at 27°C for denitrification reaction. The changes in sulfide, nitrate nitrogen, and nitrite nitrogen in the reactor were detected every 12 hours to investigate the desulfurization and denitrification effect of the method of the present invention.

[0043] Example 2

[0044] The only difference between this embodiment and the method in Example 1 is that, after adding sodium acetate, the S / C / N ratio ranges to 1.6:0.5:1.

[0045] Example 3

[0046] The only difference between this embodiment and the method in Example 1 is that, after adding sodium acetate, the S / C / N ratio ranges to 1.6:0.75:1.

[0047] Comparative Examples 1-3

[0048] The only difference between this embodiment and Example 1 is that, after adding sodium nitrate and sodium sulfide nonahydrate, the nitrate-nitrogen concentration in the reaction system is 50 ppm, and the S / N ratio is 0.8:1, 1.2:1, and 1.6:1. Furthermore, no organic carbon source, sodium acetate, is added. Under these conditions, the sulfur-autotrophic denitrifying bacteria only undergo the autotrophic denitrification process.

[0049] Comparative Examples 4-6

[0050] The only difference between this embodiment and the method in Example 1 is that sodium sulfide nonahydrate is not added, and after adding sodium acetate, the C / N ratio is maintained within the ranges of 0.25:1, 0.5:1, and 0.75:1. Under these conditions, the denitrifying bacteria only undergo heterotrophic denitrification.

[0051] Sample Analysis

[0052] Depend on Figure 1 It can be concluded that the total nitrogen removal rates of Comparative Examples 1-3 in the systems with S / N ratios of 0.8:1, 1.2:1 and 1.6:1 were 19.33±2.21%, 37.43±1.22% and 58.34±1.61%, respectively.

[0053] Depend on Figure 2It can be concluded that in the systems with S / C / N ratios of 1.6:0.25:1, 1.6:0.5:1, and 1.6:0.75:1, the total nitrogen removal rates in Examples 1-3 were 76.14±3.42%, 90.87±0.28%, and 100%, respectively.

[0054] Depend on Figure 3 It can be concluded that, in the systems with C / N ratios of 0.25:1, 0.5:1 and 0.75:1, the total nitrogen removal rates of Comparative Examples 4-6 were 7.35±1.98%, 10.95±3.13% and 23.24±3.10%, respectively.

[0055] Depend on Figure 1 , Figure 2 and Figure 3 It can be seen that, under the same conditions, the mixed culture system of autotrophic denitrification and heterotrophic denitrification of sulfur autotrophic denitrifying bacteria in Examples 1-3 has a better effect than comparative examples 1-6 because the C / S coupling effect enhances the total nitrogen removal rate and promotes the denitrification effect.

[0056] Depend on Figure 4 It can be concluded that in the system with an S / N ratio of 1.6, the sulfide oxidation rate is 61.3 mg / (L·d).

[0057] Depend on Figure 5 It can be concluded that in the systems with S / C / N ratios of 1.6:0.25:1, 1.6:0.5:1 and 1.6:0.75:1, the sulfide oxidation rates are 85.73 mg / (L·d), 111.4 mg / (L·d) and 133.8 mg / (L·d), respectively.

[0058] Depend on Figure 4 and Figure 5 It can be seen that gradually increasing the concentration of organic carbon source promotes the oxidation rate of sulfides and reduces the concentration of sulfate in the effluent, indicating that the increase of organic carbon source promotes the desulfurization effect during denitrification.

[0059] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for enhanced wastewater desulfurization and denitrification based on CS coupling, characterized in that, Includes the following steps: (1) Cultivation of sulfur-autotrophic denitrifying bacteria: Sulfur-autotrophic denitrifying bacteria were enriched from anaerobic sludge. Anaerobic sludge taken from the anaerobic biological filter of the sewage treatment plant was inoculated into a mixed flow reactor. Microbial nutrient solution was added. The solvent of the microbial nutrient solution was deionized water, and the composition included: sodium nitrate 1.2 g / L, sodium sulfide nonahydrate 2.13 g / L, sodium dihydrogen phosphate dihydrate 2.77 g / L, disodium hydrogen phosphate dodecahydrate 11.63 g / L, vitamin solution 10 mL / L and mineral solution 25 mL / L. The NO3 in the microbial nutrient solution was controlled. - -N was prepared at a concentration of 200 mg / L, and sulfide concentration was prepared at S / N = 1.

42. Changes in sulfide, nitrate nitrogen, and nitrite nitrogen were monitored daily. When detecting NO3... - When the NO3- concentration approaches 0 mg / L, replace the nutrient solution and start feeding again, repeating this cycle until the system can stably remove NO3- from the solution. - -N can be considered as successful screening, domestication and enrichment of sulfur autotrophic denitrifying bacteria; (2) Add the domesticated sulfur autotrophic denitrifying bacteria solution to the reaction vessel, and then add the culture medium, which includes phosphate, vitamins and minerals; (3) Add the wastewater to be treated into the above reaction vessel, and then continue to inject sulfide and organic carbon source into the wastewater. The sulfide is sodium sulfide nonahydrate, and the organic carbon source is sodium acetate or glucose, so that the initial S / C / N ratio of the system in the reaction vessel is 1.6:0.75:

1. Control the reaction vessel to be in an anaerobic or hypoxic environment, and continuously stir to carry out denitrification reaction to achieve desulfurization and denitrification of wastewater. The method to control the oxygen-free or oxygen-deficient environment inside the reaction vessel is to purge with nitrogen. Maintain a stirring speed of 300–600 rpm during the stirring process; The wastewater to be treated contains nitrate nitrogen, with a concentration ≤50 ppm and a pH value of 7-8.

2. The method for enhanced wastewater desulfurization and denitrification based on CS coupling according to claim 1, characterized in that, The culture medium contains phosphates including hydrogen phosphate and dihydrogen phosphate; vitamins including pyridoxine hydrochloride, biotin, riboflavin, folic acid, pantothenic acid, niacin, ammonium sulfate, para-aminobenzoic acid, lipoic acid, or vitamin B12; and minerals including magnesium sulfate, nitric acid, sodium chloride, manganese sulfate monohydrate, zinc chloride, calcium chloride dihydrate, cobalt chloride hexahydrate, ferrous sulfate heptahydrate, sodium tungstate dihydrate, sodium molybdate, nickel chloride hexahydrate, copper sulfate pentahydrate, alum, or boric acid.

3. The method for enhanced wastewater desulfurization and denitrification based on CS coupling according to claim 1, characterized in that, The volume of the sulfur-autotrophic denitrifying bacteria liquid accounts for 4% to 20% of the volume of the wastewater to be treated.

4. The method for enhanced wastewater desulfurization and denitrification based on CS coupling according to claim 1, characterized in that, The duration of the denitrification reaction is 12–144 h.

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