Biodesulfurization - Effect of biomass concentration and sulfide loading rate on polysulfides

Removal of hydrogen sulfide (H2S) can be achieved using the sustainable biological desulfurization process, where H2S is converted to elemental sulfur using sulfide-oxidizing bacteria (SOB). A dual-bioreactor process was recently developed where an anaerobic (sulfidic) bioreactor was used between the absorber column and micro-oxic bioreactor. In the absorber column and sulfidic bioreactor, polysulfides (Sx2-) are formed due to the chemical equilibrium between H2S and sulfur (S8). Sx2- are thought to be the intermediate for SOB to produce sulfur from H2S oxidation. In this study, we quantify Sx2-, determine their chain length distribution under high H2S loading rates, and elucidate the relationship between biomass and the observed biological removal of sulfides under anaerobic conditions. A linear relationship was observed between Sx2- concentration and H2S loading rates at a constant biomass concentration. Increasing biomass concentrations resulted in a lower measured Sx2- concentration at similar H2S loading rates in the sulfidic bioreactor. Sx2- of chain length 6 (S62-) showed a substantial decrease at higher biomass concentrations. Identifying Sx2- concentrations and their chain lengths as a function of biomass concentration and sulfide loading rate is key in understanding and controlling sulfide uptake by the SOB. This knowledge will contribute to a better understanding of how to reach and maintain a high selectivity for S8 formation in the dual-reactor biological desulfurization process. Temporal changes of the microbial community was followed. For this, sequencing of 16S rRNA gene amplicons using primers 515F and 926R on Illumina Miseq (190 and 200 bp for forward and reverse reads) was performed. The resulting raw sequence data have been deposited in this project.

采用可持续生物脱硫工艺可脱除硫化氢（hydrogen sulfide, H₂S），该工艺利用硫化物氧化菌（sulfide-oxidizing bacteria, SOB）将H₂S转化为单质硫（sulfur, S₈）。近期开发的双生物反应器工艺中，吸收塔与微好氧生物反应器之间设置了厌氧（硫化型）生物反应器。在吸收塔与硫化型生物反应器内，硫化氢与单质硫（S₈）间的化学平衡会生成多硫化物（polysulfides, Sₓ²⁻）。学界普遍认为，Sₓ²⁻是硫化物氧化菌通过H₂S氧化生成单质硫过程中的中间产物。本研究对Sₓ²⁻进行定量分析，测定其在高H₂S负荷率下的链长分布，并阐明厌氧条件下生物量与实测硫化物生物脱除率之间的关联机制。在生物量浓度恒定的条件下，Sₓ²⁻浓度与H₂S负荷率呈线性相关关系。在硫化型生物反应器中，当H₂S负荷率相近时，生物量浓度越高，实测的Sₓ²⁻浓度越低。链长为6的多硫化物（S₆²⁻）在生物量浓度升高时出现显著降低。明确作为生物量浓度与硫化物负荷率函数的Sₓ²⁻浓度及其链长分布，是理解并调控硫化物氧化菌对硫化物摄取过程的关键。该研究结果将有助于更深入地理解如何实现并维持双反应器生物脱硫工艺中单质硫生成的高选择性。本研究对微生物群落的时间动态变化进行了追踪监测。为此，本研究采用引物（primers）515F与926R对16S rRNA基因扩增子（16S rRNA gene amplicons）进行测序，测序平台为Illumina MiSeq（正向读长190 bp，反向读长200 bp）。所得原始测序数据已提交至本项目进行存档。