沼气厌氧/微氧生物脱硫体系构建及功能微生物分子生态学解析

Biodesulfurization processes are gaining the wide popularity because they have many advantages such as their sole selectivity, low energy requirement, the absence of residual products requiring further treatment, element sulfur product for recycling resources, etc. However, the sensitivity of bacteria to high loads of hydrogen sulfide in biogas is the main technical barrier to the widespread application of this technology. In this project, two biological systems are proposed under anoxic and microaerophilic conditions using nitrate in wastewater and oxygen in air as electron acceptors for H2S in biogas, respectively. The capacity and stability of H2S removal was investigated under different operating conditions to understand the key affecting factors. The selectivity for producing elemental sulfur as the end-product of the biological oxidation of hydrogen sulfide is identified by analyzing the electrons balance between the reactants, sulfur species and distribution in reactors. Molecular bio-techniques are used to study the dynamics of microbial community and sulfide-oxidizing bacteria (SOB) population structures based on functional genes in the two systems under different operating conditions. The study will reveal the relationship between the microbial community structures and system performance, to explore the sulfide oxidation pathway and the removal mechanisms of high loads of H2S from biogas. The high active SOB species are isolated from the reactors with high capacity and stability of H2S removal from biogas, to supply functional bacteria species for biogas biodesulfurization process. This study will provide the theoretical guide for systems selectivity and process optimization of biogas biodesulfurization.

生物脱硫具有专一选择性、低能耗、无二次污染、可生成单质硫回收资源等优点而日益受到广泛关注。然而，微生物对沼气中高浓度H2S的敏感性是限制该技术广泛应用的主要障碍。本项目构建分别以废水中的NO3-和空气中的O2作为H2S电子受体的沼气厌氧/微氧生物脱硫体系，研究体系在不同运行条件下的高效性和稳定性，弄清该过程关键参数的影响规律；分析反应氧化还原电子平衡和硫氧化产物的种类及其分布，识别系统对单质硫型去除途径的选择性。利用分子生物学技术研究体系在不同运行条件下的微生物群落和基于功能基因硫氧化菌种群结构的动态演变，揭示沼气脱硫系统中的微生物群落结构与系统性能之间的关系，探索生物脱除沼气中高浓度H2S的氧化途径和机理。从高效、稳定的生物脱硫反应器中分离获得高活性H2S耐受菌株, 为开发高效沼气脱硫工艺提供功能菌株。该研究将为沼气生物脱硫系统的选择和工艺优化提供理论指导。

在沼气利用过程中，硫化氢(H2S)的脱除是必不可少的关键步骤。针对目前生物脱除沼气中高浓度H2S的敏感性，本项目构建了分别以废水中的NO3-和空气中的O2作为H2S电子受体的沼气厌氧/微氧生物脱硫体系。分别利用装填多孔载体的生物滴滤池和生物鼓泡塔在不同条件下（运行方式、氧硫比/氮硫比、空床停留时间，H2S进口浓度等）对沼气脱硫性能进行评价和研究体系的微生物群落和基于功能基因硫氧化菌种群结构的动态演变。结果显示，微氧生物滴滤池启动较快，在启动后就能将沼气中浓度约为2000-7800 ppmv的H2S完全去除，在不同运行条件下性能稳定，最高去除能力高达约416 g H2S/m3/h；而生物鼓泡塔的最高H2S去除能力约为268 g H2S/m3/h。以NO3-为H2S的电子受体时，生物鼓泡塔和生物滴滤池都能在启动后较快地实现同步沼气脱硫与废水脱氮过程。在同样运行条件下，生物滴滤池的H2S去除率均高于生物鼓泡塔，这可能是由于生物鼓泡塔中存在气相到液相的传质阻力。而且，高通量测序结果表明，生物滴滤池中微生物的多样性程度均高于生物鼓泡塔，揭示了沼气脱硫系统中的微生物群落结构与系统性能之间的关系。硫氧比/硫氮比是控制脱硫产物的关键影响因素，通过控制合适的条件，系统中单质硫的生成率高达88%，不仅可避免反应器床层酸化，还能消除二次污染并可回收硫资源。该研究结果为沼气生物脱硫系统的选择和工艺优化提供了理论指导，为实际工程应用提供了有益的参考。