Fundamental Studies On Degradation Of Siloxane, Hydrogen Sulfide And Methanthiol Using Biological Method

Biogas often contains trace amounts of siloxane resulted from the degradation of organic silicon compounds, and siloxane is transferred into Si O2 when burning, which leads to blocking the pipeline and seriously hindering the heat transfer of the engine. Energy gas is produced by microbial decomposition of the debris of animals and plants, which is accompanied by hydrogen sulfide and methanethiol. Sulfide is corrosive, and it is finally transferred to sulfuric acid after burning, which is great harm to the environment. So siloxane and sulfide need to be removed from the energy gas before using.First, using D4 as the sole carbon source, Phyllobacterium myrsinacearum was obtained on the solid medium containing D4 for the first time after separation and purification repeatedly. Targeting at degrading D4, Phyllobacterium myrsinacearum was inoculated in the biotrickling filter, the influences of D4 inlet concentration, the empty bed residence time, p H and the flowrate of the nutrient solution on the removal efficiency and the elimination capacity of D4 were studied. The experiment results show that, the removal efficiency of D4 could reach more than 58.2% and the elimination capacity could reach more than 116 mg·m-3·h-1 at the D4 inlet concentration of 50 mg·m-3, p H of 5.0 and the empty bed residence time of 15 min. The degradation mechanism and degradation paths of D4 are proposed and testified.That H2 S was degraded by Denitrification Thiobacillus under anoxic condition was studied, the influences of H2 S inlet concentration, the empty bed residence time, p H and the flowrate of the nutrient solution on the removal efficiency and the elimination capacity as well as the impact of initial H2S/NO3- on SO42-/S0 in the product were investigated. The key operating conditions for the oxidation of H2 S to element sulfur were obtained when H2 S inlet concentration was 100~1000 ppm. Based on the experiment, the dynamic model of removing H2 S in the biotrickling filter was established, and it is found that the experimental data are in good consistency with the calculated value.Then, the performance of the simultaneous removal of H2 S, methanethiol and D4 was studied in one biotrickling filter and two-series biotrickling filters. It is found that methanethiol improves the removal of H2 S, and H2 S is removed prior to methanethiol, the influence on the elimination capacity of H2 S from shortening the empty bed residence time is less than on the elimination capacity of methanethiol; Denitrification Thiobacillus could not degrade D4 and Phyllobacterium Myrsinacearum could not degrade sulfide.Finally, the technological process of recycling the sulfur from the wastewater including S2- was designed. S2- was transferred into elemental sulfur via oxidation by Denitrification Thiobacillus in the internal recycle-three phase biological fluidized bed reactor. After the element sulfur was separated from a three phase separation and an inclined plate sedimentation, sulfur powder was obtained via purification and drying. In the bioreactor, the best operating condition for the high removal efficiency of S2- in the wastewater was obtained, and the anti-interference ability of the bioreactor was investigated when the S2- concentration in the waste water was 2~5 g?L-1.