A method for synergistic control of H2S and CH4 emissions from wastewater by bacteria and iron

Abstract

This invention provides a method for the synergistic control of H2S and CH4 emissions from wastewater by microorganisms and iron. The method includes adding a microbial agent and a ferric iron source to the wastewater to be treated; the microorganisms in the microbial agent include one or both of Bacillus subtilis and Saccharomyces cerevisiae; the inoculation concentration of the microorganisms is (1-2) × 10⁻⁶. 7 CFU / mL, the concentration of the ferric iron source is 5-30 mg Fe·L⁻¹ ‑1 The method for controlling the emission of H2S and CH4 in wastewater through the synergistic effect of bacteria and iron provided by this invention achieves simultaneous and efficient source reduction of H2S and CH4 in wastewater by constructing a synergistic system of microbial agents and ferric iron. While ensuring excellent emission reduction effect, it also takes into account the economic efficiency and engineering operability, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the fields of environmental engineering and environmental biotechnology, and in particular to a method for the synergistic control of H2S and CH4 emissions from wastewater by bacteria and iron. Background Technology

[0002] H2S is toxic and corrosive, easily causing foul odor pollution and harming human health. CH4 is both a potent greenhouse gas and poses an explosive risk, posing a dual threat to the climate system and public safety. In sewage pipe networks, sewage treatment structures, and other engineering systems that are in anaerobic or anoxic conditions for extended periods, sulfide reduction and CH4 production occur simultaneously, often resulting in the synchronous formation of H2S and CH4.

[0003] Existing source control methods for H2S and CH4 mainly include chemical oxidation, iron salt addition, aeration regulation, and bioaugmentation. While chemical oxidation and iron salt addition can reduce H2S and CH4 concentrations in the short term, they typically require high dosages, resulting in high operating costs. In anaerobic systems, excessive iron salt addition can also lead to increased sludge production and pipeline sediment accumulation, further increasing the burden on subsequent treatment processes.

[0004] Bioaugmentation methods have attracted widespread attention in recent years due to their advantages such as low resource consumption and environmental friendliness. By adding specific microbial mixtures to anaerobic systems, sulfur and carbon metabolism processes can be regulated to some extent, thereby inhibiting the formation of H2S and CH4. However, in practical applications, problems often arise such as difficulty in colonization, easy competition and exclusion by native microbial communities, and difficulty in maintaining long-term effects. This is especially true in anaerobic systems where hydraulic disturbances, environmental fluctuations, or complex substrate compositions are common, significantly limiting the stability and sustained effectiveness of the microbial agents. Furthermore, relying solely on microbial agent addition usually requires a high frequency or dosage to maintain a certain inhibitory effect, thus weakening its cost-effectiveness advantage in engineering applications. How to reduce the cost of microbial agent addition and improve its retention time and stability in anaerobic systems while ensuring emission reduction effects remains a key technical bottleneck for bioaugmentation technology. In addition, relying solely on microbial agent addition usually requires a high frequency or dosage to maintain a certain inhibitory effect, thus weakening its cost-effectiveness advantage in engineering applications.

[0005] Therefore, there is an urgent need to develop a technical method that is applicable to a broad range of anaerobic systems, takes into account emission reduction efficiency, operational stability and cost-effectiveness, in order to achieve continuous control of H2S and CH4. Summary of the Invention

[0006] This invention provides a method for the synergistic control of H2S and CH4 emissions from wastewater using bacteria and iron. This method addresses the shortcomings of existing technologies, such as high cost and secondary pollution associated with chemical methods, poor stability and unsustainable effects of biological methods, and a general lack of efficient synergistic control of the two gases. The invention achieves simultaneous, efficient, and long-lasting synergistic inhibition of H2S and CH4 within the same system, significantly improving the stability and sustainability of the inhibition effect, and ultimately balancing operating costs and engineering feasibility.

[0007] This invention provides a method for the synergistic control of H2S and CH4 emissions from wastewater by bacteria and iron, comprising: adding microbial agents and a trivalent iron source to the wastewater to be treated; The microorganisms in the microbial agent include one or both of Bacillus subtilis and Saccharomyces cerevisiae; the inoculation concentration of the microorganisms is (1-2)×10⁻⁶. 7 CFU / mL, wherein the concentration of the trivalent iron source is 5-30 mg Fe·L⁻¹. -1 .

[0008] The method provided by this invention involves the combined addition of specific microbial agents (Bacillus subtilis and / or Saccharomyces cerevisiae) and a ferric iron source to wastewater, with the inoculation concentration of the microbial agents and the concentration of the ferric iron source limited within specific ranges. This constructs a synergistic microbial-iron system, achieving a synergistic inhibition of H2S and CH4. Furthermore, the inhibition effect produced by this combined addition is significantly better than that of adding the microbial agents or the iron source alone, solving the problems of low efficiency or inability to simultaneously treat two gases using traditional single methods. In addition, the selected Bacillus subtilis and Saccharomyces cerevisiae are commonly used strains that can be mass-produced, with mature industrial production processes and high biosafety, causing no secondary pollution to the environment. They are suitable for application in anaerobic systems, require no large-scale facilities, are easy to operate, and meet environmental protection requirements.

[0009] The concentration of the trivalent iron source added is 5-30 mg Fe·L⁻¹. -1 For example, it could be 5 mg Fe·L -1 8mg Fe·L -1 10mg Fe·L -1 12mg Fe·L -1 15mg Fe·L -1 18mg Fe·L -1 20mg Fe·L -1 22mg Fe·L -1 25mg Fe·L -1 28mg Fe·L -1 Or 30mg Fe·L -1"etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0010] According to the method for synergistic control of H2S and CH4 emissions from wastewater by bacteria and iron as described in this invention, the concentration of the trivalent iron source is 10-20 mg Fe·L⁻¹. -1 .

[0011] This invention, by comparing ferrous (Fe2+) and ferrous (Fe0+) iron, found that ferric (Fe3+) achieves a better synergistic inhibition effect with microbial agents. Further experiments revealed that within this concentration range, the synergistic effect of microbial agents and ferric (Fe3+) can achieve more efficient simultaneous inhibition of H2S and CH4, balancing gas reduction efficiency, operational economy, and system stability; when the concentration is below 10 mg Fe·L... -1 The synchronous inhibition effect was not significant when the concentration was higher than 20 mg Fe·L⁻¹. -1 When the rate of increase in the suppression effect slows down, it exhibits the characteristics of diminishing marginal returns and it is difficult to obtain additional emission reduction benefits.

[0012] According to the method for synergistic control of H2S and CH4 emission in wastewater by bacteria-iron according to the present invention, a bacteria-iron composite floc is prepared by combining microbial agents with a ferric iron source and then added to the wastewater.

[0013] The bacteria-iron composite floc structure prepared in this invention serves as both a highly efficient carrier and physical barrier for microorganisms, effectively immobilizing functional bacteria and significantly reducing their loss under the hydraulic scouring of wastewater, thereby extending the residence time and action period of the bacterial agent within the system. Furthermore, the microenvironment created within the flocs tightly binds the bacteria and iron, enhancing their synergistic effect and resulting in a more concentrated and efficient inhibition of H2S and CH4. Compared to simple separate or simultaneous addition, this method achieves lower and more stable pollutant dispersion, demonstrating excellent operational stability and long-term control capabilities.

[0014] According to the method for synergistic control of H2S and CH4 emission in wastewater by bacteria and iron according to the present invention, the preparation method of the bacteria-iron composite flocs includes: adjusting the pH value of a ferric iron source to 7.0-7.5 by adding alkali to form ferric hydroxide colloid; mixing the ferric hydroxide colloid with the microbial agent to obtain a mixed solution; and then pre-shaking the mixed solution at 25-35 ℃ and 100-200 rpm for 20-40 min.

[0015] The method for preparing the bacterial-iron composite flocs of this invention involves adjusting the pH value to 7.0-7.5, which induces the formation of ferric hydroxide colloids with a large specific surface area and strong adsorption capacity from the ferric source, providing an ideal framework for subsequent steps. Then, the microbial agent is mixed with it, utilizing the adsorption properties of the colloid to efficiently capture and immobilize microbial cells. Finally, pre-shaking at suitable temperature and speed promotes and stabilizes the bacterial-iron binding, ensuring that the flocs have formed a mature and compact structure before addition, thereby improving the retention rate of the microbial agent and the synergistic effect of the bacterial-iron mixture, achieving a more stable and lasting H2S and CH4 inhibition effect than in-situ mixing.

[0016] According to the method for controlling the emission of H2S and CH4 in wastewater by bacteria-iron synergy as described in this invention, microbial agents and trivalent iron sources are added to wastewater sequentially or simultaneously.

[0017] In this invention, the microbial agent and the trivalent iron source can be added sequentially or simultaneously, ensuring the robustness and practicality of the method. This allows for flexible adaptation to various complex engineering environments, ensuring the achievement of synergistic emission reduction effects. Simultaneous addition simplifies the complex synergistic process into a one-step operation, significantly reducing the difficulty and cost of on-site implementation and making it easy to integrate into existing wastewater treatment processes. Sequential addition allows for process optimization based on different water quality characteristics and reaction stages, enabling operators to explore the optimal synergistic inhibition effect by adjusting the addition order.

[0018] According to the method for synergistic control of H2S and CH4 emissions from wastewater by bacteria and iron according to the present invention, the ferric iron source is selected from one or more soluble inorganic ferric salts. The use of soluble inorganic salts in this invention ensures that ferric iron is fully and uniformly dispersed in the wastewater in ionic form, guaranteeing a highly efficient synergistic effect with the subsequent microbial agents.

[0019] Preferably, the trivalent iron source is selected from ferric chloride.

[0020] According to the method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to the present invention, the microbial agent is composed of a mixture of Bacillus subtilis bacterial solution and Saccharomyces cerevisiae bacterial solution; the effective viable count of Bacillus subtilis in the Bacillus subtilis bacterial solution is (1-2) × 10⁻⁶. 8 CFU / mL; the effective viable count of the brewer's yeast in the brewer's yeast culture is (1-2)×10⁻⁶. 8 CFU / mL; the volume percentage concentration of the brewer's yeast liquid is 15-30%, for example, it can be 15%, 20%, 25%, 30%, etc.

[0021] This invention selects two safe, readily available, and industrially producible microbial strains: Bacillus subtilis and Saccharomyces cerevisiae, ensuring the engineering practicality and economic efficiency of the invention. Limiting the volume ratio of Saccharomyces cerevisiae to the optimized range of 15-30% allows for better synergistic effects between the microbial agent and ferric salts, effectively balancing the inhibition effects on both gases, and thus simultaneously and efficiently inhibiting the production of H2S and CH4. This invention limits the initial effective viable cell count of the agent, ensuring that it can quickly establish an ecological advantage in complex wastewater environments after addition, guaranteeing rapid onset and stability of the inhibitory effect.

[0022] According to the method for controlling the emission of H2S and CH4 in wastewater by bacteria-iron synergy according to the present invention, the preparation method of the Bacillus subtilis bacterial solution is as follows: take Bacillus subtilis bacterial powder, add sucrose solution, and rehydrate and activate for 3-12 h; wherein, the weight-volume ratio of the Bacillus subtilis bacterial powder to the sucrose solution is (0.05-0.1):(80-120).

[0023] According to the method for controlling the emission of H2S and CH4 in wastewater by bacteria-iron synergy according to the present invention, the preparation method of the brewing yeast liquid is as follows: take brewing yeast powder, add sucrose solution, and rehydrate and activate for 3-12 h; wherein, the weight-volume ratio of the brewing yeast powder to the sucrose solution is (0.1-0.5):(80-120).

[0024] The above-mentioned method for preparing bacterial solutions can efficiently awaken bacteria from their dormant state, restore their optimal metabolic activity and high survival rate, and thus ensure that when the bacterial agent is added to the sewage system, it can immediately provide a high concentration of active microorganisms with immediate function, thereby achieving the goal of rapid effect and stable establishment of dominant bacterial communities.

[0025] According to the method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron as described in this invention, the concentration of the sucrose solution is 10-50 g / L, preferably 10-30 g / L.

[0026] According to the method for synergistic control of H2S and CH4 emission in wastewater by bacteria-iron according to the present invention, the dissolved oxygen concentration in the wastewater to be treated is less than 0.2 mg / L.

[0027] According to the method for synergistic control of H2S and CH4 emission in wastewater by bacteria-iron according to the present invention, the H2S and CH4 emission in the wastewater to be treated is... 2- Concentration ≤0.01 mg S / L, SO4 2- The concentration is 100-200 mg S / L, the COD concentration is 300-350 mg / L, the VFA concentration is 0.1-0.3 mmol / L, the ORP is -(300-350) mV, and the pH value is 6.5-8.

[0028] In some specific embodiments, the wastewater to be treated is formed by a mixture of sludge and wastewater, wherein the volume ratio of sludge to wastewater is 1:(5-10); wherein the density of the sludge is 1.3-1.5 g / cm³. 3 The moisture content is 93.5-94.3%, the TSS is 61.6-67.2%, and the VSS is 2.4-2.8%.

[0029] The wastewater parameters are as follows: COD concentration 321 ± 10 mg / L, VFA concentration 0.2 ± 0.05 mmol / L, NH4+ concentration... + -N concentration was 22.4 ± 1.1 mg N / L, S 2- The concentration was 0.008 ± 0.002 mg S / L, SO4 2- The concentration was 145.6 ± 22 mg S / L, the DO concentration was 0.15 ± 0.05 mg DO / L, the ORP concentration was -315 ± 15 mV, and the pH value was 7.2 ± 0.5.

[0030] The method for controlling the emission of H2S and CH4 in wastewater by synergistic control of bacteria and iron according to the present invention includes: adding microbial agents and trivalent iron sources to wastewater and treating it at a temperature of 20-30°C.

[0031] In this invention, the temperature range of 20-30℃ ensures that the added microbial agent is in a suitable metabolic activity range, enabling it to exert its biological functions efficiently.

[0032] The method for controlling the emission of H2S and CH4 in wastewater by synergistic microbial-iron treatment according to the present invention comprises: preparing microbial agents and trivalent iron sources into microbial-iron composite flocs, and then adding them to wastewater for treatment at a temperature of 20-30°C and a rotation speed of 100-150 r / min; wherein the dissolved oxygen concentration in the wastewater is less than 0.2 mg / L; The inoculum concentration of the microorganisms in the microbial agent is (1-2)×10⁻⁶. 7 The concentration of CFU / mL of the microbial agent includes two of Bacillus subtilis and Saccharomyces cerevisiae; the concentration of the ferric iron source is 10-20 mg Fe·L⁻¹. -1 The preparation method of the bacterial-iron composite flocs includes: adjusting the pH value of a ferric iron source to 7.0-7.5 with alkali to form ferric hydroxide colloid; mixing the ferric hydroxide colloid with the microbial agent to obtain a mixed solution; and then pre-shaking the mixed solution at 25-35 ℃ and 100-200 rpm for 20-40 min. The ferric iron source is selected from ferric chloride.

[0033] The microbial agent is composed of a mixture of Bacillus subtilis bacterial solution and Saccharomyces cerevisiae bacterial solution; the effective viable count of Bacillus subtilis in the Bacillus subtilis bacterial solution is (1-2)×10⁻⁶. 8 CFU / mL; the effective viable count of the brewer's yeast in the brewer's yeast culture is (1-2)×10⁻⁶. 8 CFU / mL; the volume percentage concentration of Saccharomyces cerevisiae in the microbial agent is 15-30%.

[0034] This invention provides a method for the synergistic control of H2S and CH4 emissions from wastewater by bacteria and iron. By constructing a synergistic system of microbial agents and ferric iron, it achieves simultaneous and efficient source reduction of H2S and CH4 in wastewater, and its synergistic effect far exceeds the simple superposition of single methods.

[0035] The present invention provides a method for the synergistic control of H2S and CH4 emissions in wastewater by bacteria and iron. By forming an innovative bacteria-iron floc structure, it effectively solves the technical bottleneck of easy loss of bacterial agents and short-lasting effect in traditional biological methods, and significantly improves the stability and sustainability of the inhibitory effect.

[0036] The present invention provides a method for the synergistic control of H2S and CH4 emissions in wastewater by bacteria and iron. While ensuring excellent emission reduction effect, it also takes into account the economic efficiency and engineering operability, and has broad application prospects. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 The diagram shows the effect of the combined addition of microbial mixed inoculant and iron agents of different valence states provided by the present invention on the emission rates of H2S and CH4 in an anaerobic wastewater system; wherein, (a) is the effect on the H2S emission rate; and (b) is the effect on the CH4 emission rate.

[0039] Figure 2 The diagrams show the effects of the combined addition of the microbial mixed agent and different forms of Fe(III) to the anaerobic wastewater system on the emission rates of H2S and CH4. Among them, (a) is the effect on the emission rate of H2S; and (b) is the effect on the emission rate of CH4.

[0040] Figure 3 Different Fe provided by the present invention 3+The effect of dosage concentration on the emission rates of H2S and CH4 in the anaerobic wastewater system is shown in the figure; (a) is the effect on the emission rate of H2S; (b) is the effect on the emission rate of CH4.

[0041] Figure 4 The diagrams show the effects of different dosing methods on the emission rates of H2S and CH4 in the anaerobic wastewater system provided by this invention; (a) is the effect on the emission rate of H2S; and (b) is the effect on the emission rate of CH4.

[0042] Figure 5 The graphs provided by this invention show the emission rates, inhibition rates, and cost-effectiveness ratios of H2S and CH4 in wastewater after the addition of compound microbial agents with different compound ratios; wherein, (a) is the emission rate graph of H2S; (b) is the emission rate graph of CH4; (c) is the inhibition rate graph of H2S and CH4; and (d) is the cost-effectiveness ratio graph.

[0043] Figure 6 The following are rate graphs of H2S and CH4 production in the wastewater pipeline reactor after dosing in different experimental groups provided in Example 5 of the present invention; wherein, (a) is the rate graph of H2S production; and (b) is the rate graph of CH4 production. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0045] The Bacillus subtilis and Saccharomyces cerevisiae used in this invention are both commercially available bacterial powders. For example, Bacillus subtilis was purchased from Henan Wobao Biotechnology Co., Ltd., and Saccharomyces cerevisiae was purchased from Shandong Hezhong Kangyuan Biotechnology Co., Ltd. The mixed microbial agent used in the examples can be prepared by the following method: Take 0.5 g of Bacillus subtilis powder, add 400 mL of sterile sucrose solution (concentration 30 g / L), rehydrate and activate for 12 h to obtain Bacillus subtilis bacterial solution; take 5 g of Saccharomyces cerevisiae powder, add 400 mL of sterile sucrose solution (concentration 30 g / L), rehydrate and activate for 12 h to obtain Saccharomyces cerevisiae bacterial solution. Mix the Bacillus subtilis bacterial solution and the Saccharomyces cerevisiae bacterial solution to obtain the mixed microbial agent; wherein, the volume percentage concentration of the Saccharomyces cerevisiae bacterial solution is 20-80%.

[0046] The parameters of the bottom sludge in sewage pipelines are shown in Table 1 below: Table 1 Sediment index numerical values unit density 1.4 ± 0.1 <![CDATA[g / cm 3 ]]> Moisture content 93.9 ± 0.4 % TSS 64.4 ± 2.8 % (wet weight) VSS 2.6 ± 0.2 % (wet weight) The indicators for artificially prepared wastewater are shown in Table 2 below: Table 2 Wastewater Indicators concentration COD 321 ± 10 mg / L VFA 0.2 ± 0.05 mmol / L <![CDATA[NH4 + -N]]> 72.4 ± 1.1 mg N / L <![CDATA[S 2- ]]> 0.008 ± 0.002 mg S / L <![CDATA[SO4 2- ]]> 145.6 ± 22 mg S / L ORP -315 ± 15 mV DO 0.15 ± 0.05 mg DO / L pH 7.2 ± 0.5 Example 1 This embodiment uses a shake-flask experiment to simulate an anaerobic environment and study the synergistic inhibitory effect of a mixed microbial agent and iron agents of different valence states on the generation of H2S and CH4 in an anaerobic wastewater system. The experimental setup uses a sealed glass shake flask with a threaded neck. A gas collection bag is connected to the headspace of the shake flask to collect the gas generated during the reaction. The threaded neck is sealed with PTFE tape to prevent gas leakage. A PTFE gasket is also installed at the neck to reduce adsorption loss of gas at the sealed interface, thereby reducing detection error.

[0047] Two g of real sewage pipe sediment and 200 mL of artificially prepared sewage were added to a shake flask to obtain mixed sewage. Before adding the mixed sewage to the shake flask, nitrogen gas was introduced to remove oxygen, so that the DO concentration was below 0.2 mg / L, which is consistent with the characteristics of actual domestic sewage. The system was pre-cultured at 25 ℃ and 120 r / min for 12 h to allow the system to fully recover to the anaerobic state and complete initial adaptation. At the end of the pre-culture, the initial yields of H2S and CH4 in the gas phase of the shake flask were measured, proving that the initial gas production states of each experimental group were similar. Then, in the above system, 50 mL of mixed microbial inoculum (Bacillus subtilis and Saccharomyces cerevisiae inoculum volume ratio of 4:1), iron (including ferrous, ferric, and ferrous iron), and a combination of mixed microbial inoculum and iron were added according to different implementation methods to explore the effects of different addition methods on H2S and CH4 generation. The experimental groups were divided into a microbial inoculum (Bio) group (inoculation concentration 10... 7 CFU / mL), iron supplement group (dosage concentration 20 mg Fe·L⁻¹) -1 ) and combined group (microbial mixed inoculant: 10 7 CFU / mL; Iron supplement: 20 mg Fe·L -1 The shake flasks were sealed and placed in a constant-temperature shaker at 25°C and 120 rpm for subsequent experiments, with three replicates per group. After 12 h, the changes in H2S and CH4 concentrations and gas production in the gas sampling bag were measured, and the inhibition rate was calculated based on the average emission rate.

[0048] like Figure 1 As shown, the addition of iron significantly enhanced the inhibitory effect of the mixed microbial inoculant on H2S and CH4, and the synergistic effect varied with the valence state of iron. Specifically, the addition of Fe alone... 2+ Fe 3+ and Fe 0 The treated H2S emission rates all showed a decreasing trend compared to the control, but the overall difference was not significant. However, the inhibitory effect was further enhanced after combined application with a mixed microbial agent, especially for Fe... 3+ with Fe0 Group 1 is the most prominent, among which Fe 3+ The group exhibited the highest H2S inhibition rate, reaching 75.8%. The CH4 emission trend was similar to that of H2S; both the addition of single microbial mixed inoculants and iron agents effectively reduced the CH4 generation rate, with the combined group showing a more significant inhibitory effect. Among these, Fe... 3+ The group had the lowest CH4 emission rate, dropping to 0.78 μg·L⁻¹. -1 ·h -1 The inhibition rate reached 89.2%, demonstrating the strongest synergistic effect. Overall, the combined application of iron and microbial mixed inoculants significantly enhanced the simultaneous inhibition of H2S and CH4, with Fe showing the strongest effect. 3+ The synergistic effect is most prominent in Fe. 0 Secondly, Fe 2+ Relatively weak.

[0049] Example 2 In the basic system described in Example 1, different forms of ferric iron sources were selected and added in combination with microbial mixed inoculants, including: (1) anhydrous FeCl3 group (inorganic high-soluble type); (2) polyferric chloride PFC group (polymeric slow-release type); and (3) Fe2O3 group (solid-phase insoluble type). A control group was also set up (only inoculant added, without Fe). 3+ Five treatments were conducted, including a control group (without the added microbial mixed inoculant and iron). 225 mL of mixed wastewater was added to each shake flask, followed by 25 mL of additive to bring the total working volume to 250 mL. The control group was supplemented with 25 mL of sterile water, and the microbial mixed inoculant control group was supplemented with sterile water containing the inoculant (inoculum concentration of 1.0 × 10⁻⁶). 7 CFU·mL -1 The combined group was supplemented with a mixed solution or suspension containing bacterial agent and different Fe(III) concentrations (the bacterial agent inoculation concentration was 1.0 × 10⁻⁶). 7 CFU·mL -1 The Fe(III) dosage was kept constant at 20 mg Fe·L⁻¹ -1 For the Fe2O3 group, Fe2O3 powder was first dispersed in sterile water at the target concentration and sonicated for 10 min to improve dispersion uniformity. All reaction flasks were sealed and placed in a constant-temperature shaker at 25 ℃ and 120 rpm for incubation, maintaining anaerobic and light-protected conditions. Three replicates were set up for each group. After 12 h, changes in H2S and CH4 concentrations and gas production in the gas sampling bags were measured, and the inhibition rate was calculated based on the average emission rate.

[0050] like Figure 2As shown, the blank control group had the highest average CH4 emission rate, at 0.99 µg / L·h. In contrast, the Bio group had an average CH4 emission rate of 0.42 µg / L·h, a decrease of approximately 57.5% compared to the blank control group, indicating that the addition of the microbial agent had a certain inhibitory effect on CH4 formation. The combined FeCl3 group showed the strongest inhibitory effect on CH4 emission rate, with an average emission rate of 0.13 µg / L·h, significantly lower than other groups, and an inhibition rate as high as 86.9%, indicating that the addition of FeCl3 can effectively inhibit CH4 formation. The Fe2O3 group had an average CH4 emission rate of 0.67 µg / L·h, lower than the blank control group but higher than other experimental groups, showing a relatively mild inhibitory effect, with an inhibition rate of approximately 32.8%. The PFC group had an average CH4 emission rate of 0.40 µg / L·h, similar to the Bio group, indicating that PFC had a relatively mild inhibitory effect on CH4, with an inhibition rate of 39.8%.

[0051] In summary, FeCl3 exhibited the most significant inhibitory effect on H2S and CH4 among all treatment groups, particularly demonstrating a high inhibition rate in reducing the generation of these two gases. The inhibition effect of the FeCl3 group was significantly higher than that of other Fe(III) form treatment groups, indicating that FeCl3 has good potential for application in anaerobic systems and can effectively slow down the emission of H2S and CH4.

[0052] Example 3 In the experimental system described in Example 1, based on the addition of a mixed microbial inoculant, different concentrations of ferric iron (FeCl3) were set, and the Fe... 3+ Dosage concentration of 0.5 mg Fe·L -1 10 mg Fe·L -1 15 mg Fe·L -1 20mg Fe·L -1 and 30 mg Fe·L -1 A blank control group was set up for comparison. 225 mL of mixed wastewater was added to each reaction system, and an additional 25 mL of additive was added to bring the total working volume to 250 mL. The blank control group was added with 25 mL of sterile water, while the experimental group was added with 25 mL of Fe-containing solution. 3+ A mixed solution of microbial inoculants was prepared. Each reaction flask was sealed and placed in a constant-temperature shaker at 25°C and 120 rpm, maintaining anaerobic and light-protected conditions. Three replicates were set up for each group. After 12 h, changes in H2S and CH4 concentrations and gas production in the gas sampling bag were measured, and the inhibition rate was calculated based on the average emission rate.

[0053] like Figure 3 As shown, different concentrations of Fe were further added to the mixture of microbial inoculants.3+ Subsequently, the cumulative concentrations and emission rates of H2S and CH4 in the system decreased significantly, and with the decrease of Fe... 3+ The concentration showed a continuous decreasing trend as it increased, indicating that iron salts have a significant synergistic inhibitory effect in the biofortification system.

[0054] The H2S emission rate of the single microbial mixed inoculant group was approximately 0.39 μg·L⁻¹. -1 ·h -1 And when Fe 3+ Concentration increased to 15 mg·L -1 At the above levels, the emission rate is below 0.14 μg·L⁻¹. -1 ·h -1 The decrease reached over 78%. CH4 concentrations varied across different Fe... 3+ The concentration also showed a decreasing trend. Adding Fe... 3+ Subsequently, the CH4 concentration decreased significantly. The CH4 emission rate showed the same trend, with the emission rate of the microbial mixed inoculant control group being approximately 0.49 μg·L⁻¹. -1 ·h -1 And when Fe 3+ Concentration increased to 15 mg·L -1 At the above levels, the emission rate is below 0.18 μg·L⁻¹. -1 ·h -1 The decline reached over 78%.

[0055] Based on the combined characteristics of H2S and CH4 formation and emission, it can be concluded that Fe 3+ It exhibits a certain concentration dependence in the microbial mixed inoculant system: low concentration of Fe 3+ (5-10 mg·L) -1 It can produce a synergistic effect with mixed microbial inoculants, while medium and high concentrations of Fe... 3+ (15 mg·L) -1 This further enhanced the synergistic reduction of H2S and CH4 (inhibition rate >70%). However, when Fe... 3+ Concentrations exceeding 15 mg·L -1 At this point, the further decrease in H2S and CH4 significantly slowed, exhibiting diminishing marginal returns, indicating that adding concentrations above this level would hardly yield additional emission reduction benefits. Considering gas reduction efficiency, operational economics, and system stability, 15 mg Fe was determined to be optimal. 3+ ·L -1 This is the optimal dosage concentration for this system.

[0056] Example 4 Under the basic system described in Example 1 and the preferred FeCl3 dosage concentration determined in Example 3, the effects of different mixed microbial inoculants and FeCl3 dosage methods on H2S and CH4 generation were compared. Seven treatment groups were set up: a blank control group (25 mL of sterile water was added), an inoculant control group (bacterial solution was added to make the final concentration of inoculant in the reaction system 1.0 × 10⁻⁶), and a control group (the inoculant was supplemented to make the final concentration of inoculant in the reaction system 1.0 × 10⁻⁶). 7 CFU·mL -1 ), iron supplementation control group (Fe supplemented) 3+ The solution achieves a concentration of 20 mg·L⁻¹ -1 ), synchronous addition group (one-time supplementation of bacterial agent and Fe), 3+ The final concentrations of the mixture were 1.0 × 10⁻⁶. 7 CFU·mL -1 and 20 mg Fe·L -1 Alternating dosing group I (Fe was first added to the shake flask) 3+ Solution, pre-shaken at 30 ℃ and 150 rpm for 30 min before adding bacterial solution), Alternating addition group II (bacterial solution added first, pre-shaken for 30 min before adding Fe) 3+ (solution) and bacterial-iron flocculent groups.

[0057] The bacterial-iron floc group used artificially constructed bacterial-iron bioflocs as the additive system. The construction method is as follows: 20 mg Fe·L⁻¹ was added to the bacterial-iron biofloc group. -1 Fe 3+ The mixture was prepared using 0.5 mol·L⁻¹ -1 The pH of the mixture was slowly adjusted to 7.0–7.5 using NaOH solution to induce Fe... 3+ Hydrolysis produces ferric hydroxide colloid, which is then added with bacterial agents to form a bacterial-iron composite flocculent. The mixture is pre-shaken at 30 ℃ and 150 rpm for 30 min to promote stable floc formation before being added to the reaction flask. Each reaction flask is sealed and incubated in a constant-temperature shaker at 25 ℃ and 120 rpm under anaerobic and light-protected conditions, with three replicates per group. After 12 h, changes in H2S and CH4 concentrations and gas production in the gas sampling bag are measured, and the inhibition rate is calculated based on the average emission rate.

[0058] like Figure 4 As shown, the average emission rates of H2S and CH4 in the blank control group were 1.1 μg·L⁻¹. -1 ·h -1 and 1.3 μg·L -1 ·h -1 The concentration of the bacterial agent alone decreased to 0.8 μg·L⁻¹. -1 ·h -1 and 0.6 μg·L -1 ·h -1Fe added separately 3+ The groups were 0.6 μg·L⁻¹. -1 ·h -1 and 0.9 μg·L -1 ·h -1 The emission rates of all four composite systems were significantly lower than those of the two groups mentioned above, with the bacterial-iron floc system showing the lowest rates, at 0.1 μg·L⁻¹ for H₂S and CH₄ respectively. -1 ·h -1 and 0.2 μg·L -1 ·h -1 The levels were reduced by approximately 89% and 86% respectively compared to the control.

[0059] Overall, the addition of mixed microbial agents and Fe alone... 3+ All methods can reduce the generation rates of H2S and CH4 to some extent, but the bacteria-iron composite system exhibits a more significant synergistic effect. The emission reduction effects of the combined addition method are better than those of the individual treatments. Among them, the bacteria-iron flocs formed by simultaneous compounding show the best performance, and the data distribution is more concentrated with smaller errors, indicating that the system has higher stability and sustainability throughout the reaction stage.

[0060] Experimental Example Using the same experimental setup and wastewater samples as in Example 1, the compounding ratio was optimized by mixing Bacillus subtilis and Saccharomyces cerevisiae in a volume ratio (K:N) of 4:1, 3:2, 1:1, 2:3 and 1:4.

[0061] like Figure 5 As shown, all experimental groups exhibited inhibitory effects on H2S and CH4 emissions, with the mixed-strain group generally outperforming the single-strain group. The H2S inhibition effect was significantly enhanced when the proportion of *Saccharomyces cerevisiae* in the mixed inoculum increased: the H2S emission rates for the K:N=3:2, 1:1, and 2:3 groups were 0.688 μg·L⁻¹, respectively. -1 ·h -1 0.671 μg·L -1 ·h -1 and 0.680 μg·L -1 ·h -1 The reduction was 37%-39%, while the average emission rate for the K:N=1:4 group was 0.551 μg·L⁻¹. -1 ·h -1 Compared to the control, H2S emissions were reduced by 49.5%, demonstrating the best H2S suppression effect. Regarding CH4 emissions, the average emission rate of the K:N=4:1 group was only 3.203 μg·L⁻¹. -1 ·h -1 The concentration was reduced by 63.9% compared to the control, significantly better than the experimental group treated with a single bacterial strain. The K:N=3:2 group showed a reduction to 4.346 μg·L⁻¹. -1·h -1 The concentration of H2S was reduced by 51.0% compared to the control, indicating that an excessively high proportion of Saccharomyces cerevisiae in the culture weakens the inhibitory effect of CH4. The inhibition rates of H2S and CH4 showed significantly different response patterns to the proportion of Saccharomyces cerevisiae in the culture. The inhibition rate of H2S increased approximately linearly with the proportion of Saccharomyces cerevisiae in the culture (R0). 2 =0.76), indicating that increasing the proportion of Saccharomyces cerevisiae in the culture is generally beneficial to the inhibition of H2S; while the CH4 inhibition rate shows a unimodal change (R = 0.76). 2 =0.94), reaching its maximum at an incorporation ratio of approximately 20% (i.e., K:N=4:1), and subsequently decreasing significantly and plateauing as the proportion of brewing yeast liquid continues to increase.

[0062] The above results indicate a trade-off between the inhibitory effects of H2S and CH4. Considering the inhibitory efficacy of H2S and CH4 as equally weighted and calculating the overall benefit, the cost-effectiveness is optimal when 20% of the *Saccharomyces cerevisiae* culture is incorporated (R0). 2 =0.80), and then decreased with increasing proportion of Saccharomyces cerevisiae inoculum. This result indicates that, considering the overall inhibition effect obtained per unit cost, 20% is the most economical proportion of Saccharomyces cerevisiae inoculum; beyond this threshold, although the H2S inhibition effect may continue to improve, the marginal benefit decreases significantly due to the decline in CH4 inhibition effect and the increase in cost with increasing inoculum proportion.

[0063] Different formulation strategies can be adopted under different application scenarios: If the goal is to achieve optimal overall inhibition with equal weights for H2S and CH4, a blending ratio of approximately 20% in the Saccharomyces cerevisiae liquid is recommended, which can achieve the highest cost-effectiveness while maintaining a high overall inhibition rate; if H2S is prioritized for control, the proportion of Saccharomyces cerevisiae liquid can be moderately increased (e.g., ≥60%), but the cost of decreased overall cost-effectiveness and weakened CH4 inhibition effect must be weighed; if CH4 is prioritized for control, a high proportion of Saccharomyces cerevisiae liquid should be avoided, with around 20% being the optimal range. Under a decision-making framework that balances cost and benefit and maintains equal weights for H2S and CH4, a formulation with 20% Saccharomyces cerevisiae liquid blending (K:N=4:1) is preferable.

[0064] Example 5 Long-term experiments were conducted using four identical laboratory-scale piped reactors. The reactors were cylindrical, 100 mm in diameter and 250 mm high. Made of polyvinyl chloride acrylic, the reactors were airtight and sealed with PTFE components to prevent gas adsorption. Three stainless steel supports were installed inside the reactors to hold the plastic carrier (circular, approximately 1 cm in diameter, with a surface area of ​​approximately 0.1 m²). 2The biofilm will adhere to the inner wall of the reactor and a plastic carrier. The plastic carrier can be removed for biofilm sample analysis. To replicate a real drainage network environment, the entire reactor is covered with black blackout cloth to prevent light and algae growth. The reactor is operated at room temperature (approximately 20±2℃). The mixed wastewater from Example 1 is injected into the reactor through an inlet on the side wall using a peristaltic pump, and the effluent is simultaneously discharged from an outlet on the other side using a pump. The peristaltic pump is turned on 6 times a day (once every 4 hours), with an influent flow rate of 50 mL / min, corresponding to a hydraulic retention time of approximately 19 hours. This hydraulic retention time is close to the hydraulic retention time (14.5~19.5 hours) in actual pressure pipelines in Edmonton, Canada. To avoid significant negative or overpressure in the reactor due to influent and effluent operations, the influent and effluent are operated synchronously using independent pumps, and their flow rates are kept consistent after calibration. A gas sampling bag is connected to the top of the reactor, and a separate sampling port is provided vertically on one side of the reactor for daily indicator testing and periodic experimental sampling. The reactor effluent was collected in a wastewater tank and discharged periodically. The four reactors were designated as a control group (R1), a microbial agent group (using the mixed microbial agent from Example 1: 10... 7 CFU / mL, R2), Fe 3+ Group (FeCl3, 15 mg Fe·L) -1 , R3) and combined group (bacterial-iron flocculent of Example 4, R4).

[0065] The experiment runs in two phases: Phase I: Before the experiment began, the simulated drainage pipeline reactors had been running stably for about 330 days, and the H2S and CH4 generation rates of the four reactors were similar.

[0066] Phase II: To investigate Fe 3+ To enhance the bioaugmentation effect on H2S and CH4 control, wastewater was first drained from each reactor, and then 1500 mL of fresh water was injected into each reactor via a peristaltic pump, along with 200 mL of the corresponding reagent: R1 (control group) was treated with PBS buffer (0.01 mol·L⁻¹). -1 R2(Fe) 3+ Group) Add Fe 3+ The solution was prepared to achieve a final concentration of 15 mg Fe·L⁻¹. -1 R3 (bacterial agent group) was added to the compound microbial inoculum to bring the final concentration of the system to 10. 7 CFU·mL -1 R4 (combined group) was supplemented with bacteria-iron flocs, bringing their final concentrations to 10. 7 CFU·mL -1 With 15 mg Fe·L -1Subsequently, normal operation was resumed, with peristaltic pumps injecting liquid in cyclic pulses six times daily (hydraulic residence time 19 h). Each injection consisted of 300 mL of prepared water and 50 mL of PBS into R1, and 300 mL of prepared water and 50 mL of the corresponding reagent solution into R2-R4 respectively. The emission rates of H2S and CH4 in the gas phase were continuously monitored. Steady state was considered reached when the emission rates of H2S and CH4 in any experimental group decreased by more than 50% compared to the control group, and the variation was less than 15% for three consecutive days. Continuous injection was then stopped, meaning no more reagent solution was added, and only normal injection conditions were maintained, thus entering the recovery phase. The recovery trend of H2S and CH4 emission levels in the gas phase was continuously monitored to characterize the attenuation of the inhibitory effect and system recovery behavior of different control systems after the termination of exogenous intervention. Phase II continued until the emission rates of all reactors became consistent, and the fluctuation range was less than 15% for three consecutive days, at which point the reactors were considered to have fully recovered.

[0067] like Figure 6 As shown, during the baseline phase, the H2S production rate in the four reactors was approximately 0.06–0.07 mg·L⁻¹. -1 ·d -1 The CH4 production rate is approximately 5.4-8.5 mg·L⁻¹. -1 ·d -1 This indicates that the system operated in a relatively consistent state before the addition of the reagent. After four consecutive days of reagent addition, the inhibitory effects of each treatment on H2S and CH4 gradually became apparent, with Fe showing the strongest inhibitory effect. 3+ Both the bacterial and fungal agent groups showed some inhibitory effect on the production of the two gases, but the inhibitory effect and stability were limited. In contrast, the bacterial-iron flocculent group showed a rapid decrease in H2S production rate to 0.02 mg·L⁻¹ after drug administration. -1 ·d -1 Below this, the CH4 production rate is close to 0.1 mg·L⁻¹. -1 ·d -1 The treatment showed the most significant inhibitory effect. Overall, the bacteria-iron floc treatment was significantly superior to the single application of Fe in terms of both the intensity and persistence of inhibition of H2S and CH4. 3+ Or fungicides. After entering the recovery phase, Fe 3+ In the control group and the bacterial agent group, the production rates of H2S and CH4 essentially returned to the control group levels after 8 and 13 days, respectively. However, in the bacterial-iron floc group, the H2S production rate only showed a rebound trend 13 days after the cessation of treatment, while the recovery process for CH4 was even more delayed. Its production rate remained at a low level for 14 days after the cessation of treatment, began to rebound significantly after about 15 days, and returned to the control group levels approximately 25 days after the cessation of treatment. Overall, compared with H2S, CH4 showed a longer lag in response to treatment interference, while the bacterial-iron floc treatment exhibited a faster onset of action and stronger inhibitory ability during the treatment phase.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron, characterized in that, include: Microbial agents and ferric iron sources are added to the wastewater to be treated. The microorganisms in the microbial agent include one or both of Bacillus subtilis and Saccharomyces cerevisiae; the inoculation concentration of the microorganisms is (1-2)×10⁻⁶. 7 CFU / mL, wherein the concentration of the trivalent iron source is 5-30 mg Fe·L⁻¹. -1 .

2. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to claim 1, characterized in that, The concentration of the trivalent iron source added is 10-20 mg Fe·L⁻¹. -1 .

3. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to claim 1 or 2, characterized in that, The microbial agent and the trivalent iron source were combined to prepare a microbial-iron composite floc, which was then added to the wastewater to be treated.

4. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to claim 3, characterized in that, The preparation method of the bacteria-iron composite flocs includes: adjusting the pH value of the trivalent iron source to 7.0-7.5 with alkali to form ferric hydroxide colloid; mixing the ferric hydroxide colloid with the microbial agent to obtain a mixed solution; and then pre-shaking the mixed solution at 25-35 ℃ and 100-200 rpm for 20-40 min.

5. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to claim 1, characterized in that, Microbial agents and trivalent iron sources are added to the wastewater to be treated in sequence or simultaneously.

6. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to any one of claims 1-5, characterized in that, The ferric source is selected from one or more soluble inorganic ferric salts; preferably, the ferric source is selected from ferric chloride.

7. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to any one of claims 1-6, characterized in that, The microbial agent is composed of a mixture of Bacillus subtilis bacterial solution and Saccharomyces cerevisiae bacterial solution; the effective viable count of Bacillus subtilis in the Bacillus subtilis bacterial solution is (1-2)×10⁻⁶. 8 CFU / mL; the effective viable count of the brewer's yeast in the brewer's yeast culture is (1-2)×10⁻⁶. 8 CFU / mL; the volume percentage concentration of the brewer's yeast culture is 15-30%.

8. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to claim 7, characterized in that, The preparation method of the Bacillus subtilis bacterial solution is as follows: take Bacillus subtilis bacterial powder, add sucrose solution, and rehydrate and activate for 3-12 hours; wherein, the weight-volume ratio of the Bacillus subtilis bacterial powder to the sucrose solution is (0.05-0.1):(80-120). And / or, the preparation method of the brewing yeast liquid is as follows: take brewing yeast powder, add sucrose solution, and rehydrate and activate for 3-12 h; wherein, the weight-volume ratio of the brewing yeast powder to the sucrose solution is (0.1-0.5):(80-120).

9. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to any one of claims 1-8, characterized in that, The dissolved oxygen concentration in the wastewater to be treated is less than 0.2 mg / L.

10. The method for synergistic control of H2S and CH4 emission from wastewater by bacteria and iron according to any one of claims 1-9, characterized in that, include: Microbial agents and trivalent iron sources are added to wastewater and treated at a temperature of 20-30℃.

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