Study On The Biological Release And Sulfur Conversion Mechanism Of Hydrogen Sulfide In Water Treatment Process

The overall air quality in China is a cause for concern,with the issue of sulfur-containing malodorous gas pollution being particularly prominent and causing significant threats to human health and the ecological environment.Hydrogen sulfide（H₂S）is the main component of malodorous gas,and it is widely produced in various industrial production and water treatment processes.The high concentration of H₂S can be toxic to human health,and in severe cases,can even be a risk of death.Additionally,due to its acidic corrosion effects,H₂S may shorten the operation life of pipelines and equipments.Therefore,it is urgent to control the generation and release of H₂S during water treatment from the source,as well as to develop advanced reduction technologies for removing sulfur-containing malodorous pollutants in the water environment.This is of great significance for the treatment of water pollution,the prevention and control of air pollution,and the safety of human health.This paper focused on the sulfur conversion and fate during the biological release and removal of H₂S in water treatment processes.By changing water environmental impact factors to study the boundary conditions and laws of H₂S release,the blocking mechanism of H₂S was obtained to achieve source control of H₂S production and release.Furthermore,the biotrickling filter（BTF）was used to investigate the removal capability of H₂S,accumulation of desulfurization products,sulfur balance,microbial community,and pathways for sulfide oxidation at different O₂ concentrations.The effect of the empty bed retention time（EBRT）on H₂S removal mechanism in the acidic BTF was also explored,achieving long-term stable removal of high concentration H₂S under extremely acidic conditions.The main contents and innovative research results of this paper were as follows:（1）This study investigated the effects of substrate concentration,p H value,and DO concentration on the variation of gaseous G_H2S,dissolved D_H2S,SO₄^2-,SO₃^2-,S^2-,and p H value.The results showed that increasing the substrate SO₄^2-concentration promoted the activity and reduction efficiency of SRB,significantly enhancing the production and release of H₂S,with the highest G_H2S release concentration reaching 384.29 mg/m³ and an accumulated release of 0.28 g/L.Under acidic conditions,free sulfide was mainly in the form of H₂S,releasing a large amount of G_H2S with the highest release concentration of 666.01mg/m³ and an accumulated release of up to 0.46 g/L.Raising the p H value（alkaline environment）not only transformed free H₂S into sulfide ions(S^2-and HS^-),but also reduced the reduction efficiency of SO₄^2-,reducing or inhibiting the formation and release of H₂S.In addition,as the DO concentration increased,it gradually inhibited the activity of SRB,causing a decrease in SO₄^2-reduction efficienc and a significant reduction in the production and release of H₂S.Especially when the DO concentration was between 0.7-1.0 mg/L,H₂S was almost not released.Through 16S r RNA analysis,it was found that sulfate-reducing bacteria（SRB）,such as Desulfovibrio,Desulfomicrobium,and Desulfobulbus,which played a key role in the anaerobic process for the production of H₂S.The increase in DO value created the micro oxygen environment,also promoted the growth of some sulfur oxidizing bacteria（SOB）（Thiobacillus,Sulfuricurvum）,which oxidized sulfides(H₂S,HS^-,S^2-,etc.)into elemental sulfur or sulfate.The reaction pathway for the production and removal of H₂S in the anaerobic process was elucidated.The changes in SRB community and sulfur metabolism pathways were revealed.This study provided new insights into understanding the boundary conditions for sulfate reduction and H₂S release in the anaerobic process,and clarifying the blocking mechanism of sulfur-containing malodorous pollutants.（2）This study investigated the effects of different oxygen concentrations on the performance and microbial community of the BTF,elucidating the mechanisms and reaction pathways for H₂S removal.The results showed that with increasing O₂ concentration,the removal efficiency（RE）of H₂S increased from 94.1%to 100.0%.Under 1%O₂ condition,the elimination capacity（EC）of H₂S was 5.72±0.33 g/（m³·h）,and the proportion of S⁰-S desulfurization product was about 78.13%.As the O₂ concentration increased to 10%,the EC was 6.00±0.35 g/（m³·h）,and the main product was SO₄^2--S,accounting for 80.39%.In addition,the ratio of sulfur-containing compounds(S⁰-S,SO₄^2--S,and SO₃^2--S)was calculated according to law of conservation of mass,and the sulfur balance was verified.The 16S r RNA high-throughput sequencing analysis showed that Azoarcus and Thauera may be dominant genera producing S⁰ in the BTF,while Desulfovibrio and Desulfobulbus were SRB and important functional microbes in different desulfurization stages.Sulfuricurvum and Acidithiobacillus were high abundance sulfur-oxidizing bacteria（SOB）and played a major role in H₂S removal.Furthermore,possible reaction pathways for the conversion of H₂S to S⁰and SO₄^2-were proposed.The main product was S⁰ under limited oxygen route.When the oxygen content increases,the full oxygen route further oxidizes S⁰ to SO₄^2-and SO₃^2-.By exploring the mechanism of H₂S removal at different O₂concentrations,this study provided theoretical references to deepen the understanding of SOB desulfurization process.（3）The study investigated the H₂S removal capacity,accumulation of desulfurization products,sulfur balance,microbial community,and the biodegradation kinetics of the BTF under extremely acidic conditions for high concentration H₂S.The results showed that when the empty bed residence time（EBRT）reduced from 180 s to 60 s,the removal efficiency of H₂S decreased from 100%to 95.4%,and increased the EC from 18.0±1.3 to 51.5±3.2g/（m³·h）.Additionally,with increasing EBRT,the proportion of SO₄^2--S in the biological desulfurization products gradually decreased from 74.83%to 38.71%,while S⁰-S increased from 16.04%to 53.30%.The 16S r RNA high-throughput sequencing analysis showed that acidophilic SOB,such as Acidithiobacillus,Thiobacillus,Sulfuricurvum,and Sulfobacillus,were enriched in the BTF and accounted for over 68.00%of the total abundance,playing a crucial role in maintaining a high and stable H₂S removal efficiency under extremely acidic conditions.Moreover,extracellular polymeric substances（EPS）not only promoted the formation,structure,and stability of the biofilm,but also regulated the exchange of intercellular substances and energy.Based on the Michaelis-Menten equation and Lineweaver-Burk linear equation analysis,it was shown that the shorter the retention time of H₂S,the more significant the decrease in the elimination capacity of BTF.Acidic BTF could quickly adapt and maintain a high H₂S removal efficiency after shock loads and starvation periods,achieving long-term stable operation under extremely acidic conditions.This study provided a good technical method and theoretical research foundation for preventing the production of hydrogen sulfide and improving the efficient removal of the biotrickling filter.