Biological Treatment Of Hydrogen Sulfide And Recovery Of Elemental Sulfur

Hydrogen sulfide which is the principal odorous component in energy gases, andother sulfide-containing systems are main causes of odor nuisance and corrosionproblems in equipment. The pollution treatment calls for high performance systemssuch as bio-trickling filter and biofilter in the strategy of sustainable development. Asa developing carrier-packed biological deodorization, bio-trickling filter is anestablished waste gas treatment technology that may provide a cost-effective solution.Hydrogen Sulfide is rapidly degraded in bio-trickling filter. Biofilter is considered asa mature wastewater treatment process without secondary pollution, which resultsfrom the high microbial activity brought by the full contact between microorganismsand liquid in the reactor.The strictly aerobic bacteria (Thiobacillus thioparus) and the facultativeanaerobic bacteria (Thiobacillus denitrificans) were cultured and enriched.Thiobacillus thioparus experienced apparent lag phase, logarithmic phase and stablephase. After140h, the growth curve showed a marked decline. The growth ofbacteria is determined by pH value. Observed rapid declines in bacterial numbers afterlogarithmic phase were interpreted as the result of no apparent stable period forThiobacillus denitrificans.Bio-trickling filters inoculated with Thiobacillus thioparus and Thiobacillusdenitrificans respectively were established to recover elemental sulfur. Theinoculation system could only reach a removal efficiency of32%when fed with400mg/m3H2S at an air flow of0.1m3/h, which issue from low nitrate concentration. Theinoculation system of aerobic bacteria could reach removal rate of90%with15dayscontinuous operation. The recovery rate could reach60%when fed with800mg/m3H2S with an air flow of0.08m3/h. A stable oxidation could be achieved in neutralaerobic biofilter at hydraulic retention time (HRT)=40min corresponding to adissolved oxygen (DO) of2~3mg/L and at inlet concentration of120mg/L. Valuesexceeding90%sulfide removal efficiency and50%sulfur generating rate could beobtained. For HRT of40min, The anaerobic biofilter was also operated at a neutralpH, keeping N/S at0.4when sulfide inlet concentration was120mg/L. The sulfideremoval efficiency could reach90%and the generating rate of sulfur was up to60%.The deposition ratio of sulfur can be as high as90%by adding8mL polyaluminium chloride (PAC) solution at a mass concentration of5%into1Lwastewater at104.74mg/L of elemental sulfur concentration when the pH wasoptimized at8. Tetrachlorethylene and carbon disulfide were used as leaching agent toextract elemental sulfur. An optimum leaching effect appeared under the condition of80°C, liquid-solid ratio of13:1and leaching time of100min by usingtetrachlorethylene as leaching agent, and with the method the purity of sulfur couldreach95%. The optimized parameter settled for experiment with carbon disulfideacting as agent was liquid-solid ratio of7:1,50min and40°C. In this situation thepurity of sulfur was up to93%.