Study Of Sulfide Biotransformation To Sulfur

The corrosive and negative effects of sulfide on the organism could influence naerobic digestion during wastewater treatment process. Desulfurization by biological method can not only reduce sulfide content in wastewater, but also obtain as resource utilization.A desulfurizing chemoautotroph strain was isolated and named TL-1 in the study. The observation of colony morphology, mycelia morphology, and flagellum were investigated, and gram stain and other physiological and biochemical indexes were also identified. Moreover a phylogenetic tree was constructed by comparing with the published 16S rDNA sequences of the relative bacteria species. As a result, this strain was identified to be the strain of Thiobacillus neapolitanus.The growth curve and the change of pH during cell growth were investigated. And the effect of different rotational speed, salinity, temperature, pH, metal ions and sulfide concentration on the strain was also studied in shake flask culture. The result showed that the strain reached the optimum desufurization effect at the condition of 170 r/min, 30℃, initial pH7.5. When sodium sulfide concentration in the water was above 240 mg/L, the strain was restrained.The desulfurizing efficiency and the characteristics of the sulfur particles were investigated in the airlift reactor using Oxidation Reduction Potential (ORP) as the control factor. When keeping ORP at -370 mv, influent sulfide concentration at 350 mg/L, hydraulic retention time(HRT) at 3 h, sulfide removal rate was over 95% and over 85%.Moreover, the sulfur particles size was enlarged with the increase of ORP. When keeping ORP at -420 mv and-370 mv, the sulfur particles at the range of 0.05～0.5 um and 2～11 um. When ORP was -320 mv the sulfur particles will be at the range of 2～13 um and 100～700 um. This resulte indicated that cell can secrete extracellular polymeric substances which beneficial to sulfur particles aggregation. In this biological desulfurization system the increase of ORP lead to change of extracellular polymeric substances composition that hydrophobic group increase which lead to hydrophobicity enhanced.