A method for intensifying the production of sulfides by sulfur disproportionation in wastewater

Abstract

The application discloses a method for enhancing sulfide production by sulfur disproportionation in wastewater, comprising the following steps: introducing sulfur disproportionation bacteria, adding elemental sulfur as a disproportionation substrate, and adding glutamic acid compounds as a sulfur production promoter in a wastewater pool; under the condition of alkalinity of 0.25-5 g / L CaCO3 and anaerobic condition, the disproportionation substrate reacts to generate sulfide under the action of the sulfur disproportionation bacteria; wherein the concentration of glutamic acid in the wastewater pool is 0.2-5 mmol / L; and the salinity of the wastewater in the wastewater pool is 0 g / L-50 g / L in terms of NaCl equivalent. The application greatly improves the sulfur production efficiency of wastewater with salinity of 0 g / L-50 g / L, and the method can realize efficient treatment of industrial wastewater with high salinity and carbon deficiency.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and in particular to a method for enhancing sulfur disproportionation in wastewater to produce sulfides. Background Technology

[0002] Biological sulfur production is a low-cost, sustainable method for producing sulfur compounds (S). 2- The production method operates on the principle that sulfate-reducing bacteria or elemental sulfur-reducing bacteria utilize organic carbon sources as electron donors to reduce sulfate or elemental sulfur to sulfur. 2- In the water treatment process, due to S 2- Its reducing properties and high bioavailability make it a highly efficient electron donor for the reduction of oxidizing pollutants such as nitrates, nitrites, and perchlorates. It can also form metal sulfide precipitates with metal ions to remove metal ions from water.

[0003] However, such biological sulfur production methods rely on the addition of organic carbon, leading to increased process costs and carbon emissions, and also posing a risk of organic carbon spillage in the effluent. In certain carbon-deficient scenarios, such as industrial wastewater and secondary effluent from municipal sewage, the application of this method is limited. In contrast, elemental sulfur disproportionation mediated by autotrophic sulfur-disproportionating bacteria (SDB) avoids the aforementioned problems caused by the addition of additional carbon sources. This is because SDB can disproportionate elemental sulfur to produce sulfides without consuming organic carbon. Therefore, compared to sulfate reduction or elemental sulfur reduction processes, sulfur disproportionation sulfur production methods can further reduce wastewater treatment costs and carbon footprint.

[0004] However, the sulfur production rate of sulfur disproportionating bacteria (SDB) is lower than that of heterotrophic sulfate reduction or elemental sulfur reduction processes, requiring further improvement in its sulfur production rate to enhance the advantages and competitiveness of the sulfur disproportionation method. Furthermore, previous studies have found that when SDB is exposed to a high salinity environment of 10 g / L, the efficiency of sulfide production decreases by approximately 70%, further limiting the application of the sulfur disproportionation process in the treatment of saline wastewater. Summary of the Invention

[0005] To overcome the aforementioned shortcomings and deficiencies of the prior art, the present invention aims to provide a method for enhancing the production of sulfides through sulfur disproportionation in wastewater. This method involves adding 0.2–5 mmol / L of glutamic acid compounds to the wastewater pond to improve sulfide production efficiency. In wastewater with a salinity of 0 g / L, the addition of glutamic acid compounds enhances the metabolic activity of sulfur disproportionating bacteria, thereby increasing their efficiency in producing sulfides. In wastewater with higher salinity (2 g / L–50 g / L), the addition of glutamic acid compounds alleviates the inhibitory effect of salinity on the activity of sulfur disproportionating bacteria, thus improving their sulfur production capacity under salinity conditions.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a method for enhancing sulfur disproportionation in wastewater to produce sulfides, comprising the following steps:

[0008] In a wastewater pond, sulfur disproportionating bacteria were introduced, elemental sulfur was added as a disproportionation substrate, and glutamic acid compounds were added as sulfur production promoters. Under alkalinity conditions of 0.25–5 g / L CaCO3 and anaerobic conditions, the disproportionation substrate reacted with sulfur disproportionating bacteria to generate sulfides.

[0009] The concentration of glutamic acid compounds in the wastewater pond is 0.2–5 mmol / L; the salinity of the wastewater in the wastewater pond, expressed as NaCl equivalent, is 0 g / L–50 g / L.

[0010] In some embodiments of the present invention, the concentration of elemental sulfur in the wastewater pool is 0.1 g / L or higher.

[0011] In some embodiments of the present invention, the wastewater is saline wastewater with a salinity of 2 g / L to 50 g / L, calculated as NaCl equivalent.

[0012] In some embodiments of the present invention, the wastewater is carbon-deficient wastewater.

[0013] In some embodiments of the present invention, the concentration of glutamic acid compounds in the wastewater pool is 0.5–1 mmol / L.

[0014] In some embodiments of the present invention, the introduction of sulfur-dismutating bacteria specifically refers to:

[0015] After acclimating and cultivating the anaerobic sludge with elemental sulfur for 15-30 days, it was inoculated into the wastewater pond.

[0016] In some embodiments of the present invention, the sulfur-disproportionating bacteria include the genera *Dissulfurimicrobium*, *Desulfobulbus*, *Desulfofustis*, *Desulfurella*, *Desulfurivibrio*, and *Dissulfuribacter*.

[0017] In some embodiments of the present invention, the glutamic acid compound is at least one of glutamic acid and soluble salts of glutamic acid.

[0018] In some embodiments of the present invention, the soluble salt of the glutamic acid is at least one of sodium glutamate and potassium glutamate.

[0019] In some embodiments of the present invention, the wastewater is wastewater containing metal ions; the sulfide combines with the metal ions to form metal sulfides, or the sulfide reduces the metal ions from a high valence state to a low valence state to achieve detoxification or removal of the metal ions.

[0020] In some embodiments of the present invention, the wastewater is wastewater containing oxidizing pollutants, and the sulfide acts as an electron donor to reduce the oxidizing pollutants, thereby achieving the removal of oxidizing pollutants.

[0021] In some embodiments of the present invention, the glutamate compound is added before, during, or after the sulfur-disproportionating bacteria are subjected to salinity stress.

[0022] In some embodiments of the present invention, the anaerobic sludge is sourced from at least one of the following: wastewater treatment plants, estuarine sediments, marine sediments, and riverbed silt.

[0023] In some embodiments of the present invention, the temperature in the wastewater tank is 25–50°C; and the reaction time is greater than 48 hours.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] (1) The method of enhancing sulfur disproportionation to produce sulfides in wastewater according to the present invention adds glutamic acid compounds as sulfur production promoters to a wastewater pool with a salinity of 0 g / L, which greatly improves the sulfur production efficiency compared with the method without adding glutamic acid compounds.

[0026] (2) The method of enhancing sulfur disproportionation to produce sulfides in wastewater according to the present invention involves sulfur disproportionating bacteria absorbing salt ions from wastewater under salinity stress (2 g / L to 50 g / L) to maintain osmotic pressure balance inside and outside the cells, thereby maintaining cell permeability and cell volume, and preventing cell death due to excessive salinity. The present invention provides compatible solutes to sulfur disproportionating bacteria by adding glutamic acid compounds, increasing the accumulation of compatible solutes by the bacteria, maintaining osmotic pressure balance inside and outside the bacterial cells, alleviating the inhibitory effect of salinity on the activity of sulfur disproportionating bacteria, and thus improving the sulfur production capacity of sulfur disproportionating bacteria under salinity conditions.

[0027] (3) The method of enhancing sulfur disproportionation to produce sulfides in wastewater of the present invention breaks the application limitations of sulfur disproportionation sulfur production process. It can directly and efficiently produce sulfur in carbon-deficient, saline or non-saline industrial wastewater, and realize the removal of oxidizing pollutants, metal ions and other pollutants in wastewater. Attached Figure Description

[0028] Figure 1 This is a graph showing the change in the average concentration of sulfides produced in the reaction tanks of the first to fourth groups of experiments in Example 1 of the present invention over time.

[0029] Figure 2 The graph shows the change in the average concentration of sulfides produced in the reaction tanks of the first to fourth groups of experiments in Example 2 of the present invention over time.

[0030] Figure 3 This is a graph showing the change in sulfide yield increase rate over time in the reaction tanks of the second to fourth groups of experiments in Example 2 of the present invention. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0032] Example 1

[0033] Anaerobic sludge taken from a wastewater treatment plant was acclimated with elemental sulfur for 30 days before being inoculated into a reaction tank. The sludge was then washed three times with deoxygenated water to completely remove any residual dissolved sulfides. The reaction tank was set with an alkalinity of 1 g / L, a pH of 8.0 ± 0.1, an elemental sulfur concentration of 1 g / L, a temperature of 25 ± 2℃, and a dissolved oxygen concentration of <0.5 mg / L.

[0034] Four sets of experiments were conducted:

[0035] Group 1: The salinity in the reaction tank is 0 g / L, and no L-glutamic acid is added;

[0036] Group 2: The salinity in the reaction tank is 0 g / L, and 1 mmol / L of L-glutamic acid is added;

[0037] Group 3: The NaCl salinity in the reaction tank is 10 g / L, and no L-glutamic acid is added;

[0038] Group 4: The salinity of NaCl in the reaction tank is 10 g / L, and 1 mmol / L of L-glutamic acid is added.

[0039] Community analysis of the acclimatized anaerobic sludge in this embodiment revealed that the main sulfur-disproportionating bacteria include the genera Dissulfurimicrobium, Desulfobulbus, Desulfofustis, Desulfurella, Desulfurivibrio, and Dissulfuribacter.

[0040] The sulfur-disproportionating bacteria carry out the following reaction in the reaction tank: S 0 +H₂O→1 / 4SO₄ 2- +3 / 4HS - +5 / 4H + Elemental sulfur undergoes redox reactions to form sulfides (HS-H2O). -) and sulfate. During the reaction, samples were taken to determine the concentration of sulfides in the reaction tank. The detection method was the national standard (HJ 1226—2021) methylene blue spectrophotometric method. The results are as follows: Figure 1 As shown.

[0041] As shown in the figure, adding 1 mmol / L L-glutamic acid as a sulfur production promoter to the wastewater tank with a salinity of 0 g / L (second group experiment, corresponding to SDB+1 mmol / L L-glutamic acid in the figure) significantly increased the concentration of sulfides in the reaction tank compared to the method without adding L-glutamic acid (first group experiment, corresponding to SDB in the figure): in the first group experiment, the sulfur disproportionating bacteria sludge could produce 47.0 mg S / L of sulfides in 61 hours, while in the second group experiment with 1 mmol / L L-glutamic acid, 158.0 mg S / L of sulfides were produced in 61 hours, and the sulfur disproportionation rate was increased by 236%. In the third group of experiments (SDB + 10 g / L NaCl in the figure), the salinity of 10 g / L NaCl significantly inhibited the rate of sulfur disproportionation. After 61 hours of reaction, the sulfur disproportionation sludge produced only 14.8 mg S / L of sulfide. However, in the fourth group of experiments (SDB + 10 g / L NaCl + 1 mmol / L L-glutamic acid in the figure), due to the addition of 1 mmol / L L-glutamic acid, the amount of sulfide produced reached 92.5 mg S / L, indicating that 1 mmol / L glutamate significantly alleviated the inhibition of sulfur disproportionation bacteria by salinity.

[0042] Example 2

[0043] Anaerobic sludge taken from estuarine sediments was acclimated with elemental sulfur for 25 days before being inoculated into a reaction tank. The sludge was washed three times with deoxygenated water to completely remove residual dissolved sulfides. The reaction tank was set with an alkalinity of 1 g / L, a pH of 8.0 ± 0.1, an elemental sulfur concentration of 1 g / L, a temperature of 25 ± 2℃, a NaCl concentration of 10 g / L, and a dissolved oxygen concentration of <0.5 mg / L.

[0044] Four sets of experiments were conducted:

[0045] Group 1: No glutamic acid is added to the reaction tank;

[0046] Group 2: L-glutamic acid was added to the reaction tank at a concentration of 0.5 mmol / L;

[0047] Group 3: L-glutamic acid was added to the reaction tank at a concentration of 1 mmol / L;

[0048] Group 3: L-glutamic acid was added to the reaction tank at a concentration of 2 mmol / L;

[0049] Community analysis of the acclimatized anaerobic sludge in this embodiment revealed that the main sulfur-disproportionating bacteria include the genera Dissulfurimicrobium, Desulfobulbus, Desulfofustis, Desulfurella, Desulfurivibrio, and Dissulfuribacter.

[0050] The sulfur-disproportionating bacteria carry out the following reaction in the reaction tank: S 0 +H₂O→1 / 4SO₄ 2- +3 / 4HS - +5 / 4H + Elemental sulfur undergoes redox reactions to form sulfides (HS-H2O). - ) and sulfate. During the reaction, samples were taken to determine the concentration of sulfides in the reaction tank. The detection method was the methylene blue spectrophotometric method according to national standard (HJ 1226—2021). The results are as follows: Figure 2 As shown.

[0051] Depend on Figure 2 It was found that after 99 hours of reaction, the sulfide concentration in the reaction tank of the first group of experiments without L-glutamic acid was 24 mg S / L, while the sulfide concentrations in the presence of 0.5 mmol / L, 1 mmol / L, and 2 mmol / L L-glutamic acid reached 175 mg S / L, 157 mg S / L, and 129 mg S / L, respectively. Throughout the experiment, the sulfide formation rate in the reaction tank without L-glutamic acid was 0.25 mg S / (L·h), significantly lower than the sulfide formation rates in the groups with added 0.5 mmol / L, 1 mmol / L, and 2 mmol / L, which were 1.78 mg S / (L·h), 1.59 mg S / (L·h), and 1.31 mg S / (L·h), respectively.

[0052] Figure 3 This represents the increase in sulfide yield at the end of the reaction in groups two through four. Figure 3 It was found that the addition of L-glutamic acid increased sulfide production by more than four times. Specifically, at a concentration of 0.5 mmol / L L-glutamate, sulfide production increased by 6.2 times compared to the level without L-glutamic acid.

[0053] As shown above, the addition of L-glutamic acid significantly accelerated the rate of sulfide production through sulfur dismutation, indicating that glutamic acid compounds can enhance the metabolic activity of sulfur-dismutating bacteria. Furthermore, in salinity-stressed environments, the addition of L-glutamic acid effectively alleviated the inhibitory effect of salinity on the metabolic activity of sulfur-dismutating bacteria, effectively improving their tolerance to salinity. The effect of alleviating salinity inhibition was even better when the concentration of L-glutamic acid was between 0.5 and 1 mmol / L, indicating that adding an appropriate amount of L-glutamic acid is beneficial for enhancing the metabolic activity of sulfur-dismutating bacteria in high-salt environments and increasing the reaction rate of elemental sulfur dismutation. The increased rate of sulfide production in high-salt wastewater environments will help promote the development and application of sulfur dismutation technology in the field of saline wastewater treatment.

[0054] The method of this invention breaks through the application limitations of sulfur disproportionation sulfur production process, and can directly and efficiently produce sulfur in carbon-deficient, saline or non-saline industrial wastewater, realizing the efficient generation of sulfides by sulfur disproportionation and the removal of oxidizing pollutants, metal ions and other pollutants in wastewater.

[0055] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for enhancing the production of sulfides from the disproportionation of sulfur in wastewater, characterized in that, Includes the following steps: In a wastewater pond, sulfur disproportionating bacteria were introduced, elemental sulfur was added as a disproportionation substrate, and glutamic acid compounds were added as sulfur production promoters. Under alkalinity conditions of 0.25~5 g / L CaCO3 and anaerobic conditions, the disproportionation substrate reacted with sulfur disproportionating bacteria to generate sulfides. The concentration of glutamic acid compounds in the wastewater pond is 0.2~5 mmol / L; the salinity of the wastewater in the wastewater pond is 0 g / L~50 g / L, calculated as NaCl equivalent.

2. The method of enhancing sulfide production from sulfur disproportionation in wastewater according to claim 1, characterized by, The concentration of elemental sulfur in the wastewater pool is above 0.1 g / L.

3. The method of enhancing sulfide production from sulfur disproportionation in wastewater according to claim 1, characterized by, The wastewater is saline wastewater, with a salinity of 2 g / L to 50 g / L as NaCl equivalent.

4. The method of enhancing sulfide production from sulfur disproportionation in wastewater of claim 1, wherein, The wastewater is carbon-deficient wastewater.

5. The method of enhancing sulfide production from sulfur disproportionation in wastewater of claim 1, wherein, The concentration of glutamic acid compounds in the wastewater pond is 0.5~1 mmol / L.

6. The method of enhancing sulfide production from sulfur disproportionation in wastewater of claim 1, wherein, The introduction of sulfur-dismutating bacteria specifically refers to: After acclimating and cultivating the anaerobic sludge with elemental sulfur for 15-30 days, it was inoculated into the wastewater pond.

7. The method of enhancing sulfide production from sulfur disproportionation in wastewater according to claim 1 or 6, characterized in that, The sulfur-disproportionating bacteria include the genera *Dissulfurimicrobium*, *Desulfobulbus*, *Desulfofustis*, *Desulfurella*, *Desulfurivibrio*, and *Dissulfuribacter*.

8. The method of enhancing sulfide production from sulfur disproportionation in wastewater of claim 1, wherein, The glutamic acid compounds are at least one of glutamic acid and soluble salts of glutamic acid.

9. The method of enhancing sulfide production from sulfur disproportionation in wastewater of claim 1, wherein, The wastewater contains metal ions; the sulfide combines with the metal ions to form metal sulfides, or the sulfide reduces the metal ions from a high valence state to a low valence state to achieve detoxification or removal of the metal ions.

10. The method of enhancing sulfide production from sulfur disproportionation in wastewater of claim 1, wherein, The wastewater contains oxidizing pollutants, and the sulfide acts as an electron donor to reduce the oxidizing pollutants, thereby achieving the removal of oxidizing pollutants.

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