Comparison of the capacity of biological desulfurization of Thiobacillus ferrooxidans from different sulfur-containing substrates with or without additional ferrous iron

Thiobacillus ferrooxidans,abbreviated as T.ferrooxidans is one of the important microorganisms in the field of biological desulfurization.Effects of ferrous iron and sulfur-containing substrates on biological desulfurization of T.ferrooxidans were studied.Results show that in the absence of Fe^(2+),T.ferrooxidans can utilize three kinds of sulfur-containing substrates of Na_(2)S_(2)O_(3),elemental S and Na_(2)SO_(3) for growth and metabolism.For utilization complexity,Na_(2)S_(2)O_(3) was easiest to use,next was elemental S,and Na_(2)SO_(3) was the worst for use.During the utilization of ferrous iron and sulfur-containing substrates by T.ferrooxidans,the iron oxidation system was first started.With the decrease of the Fe^(2+)concentration,the sulfur oxidation system was started,and then the two systems synergistically acted.The presence of three sulfur-containing substrates had different effects on Fe^(2+)oxidation,and elemental S did not inhibit the oxidation of Fe^(2+),while Na_(2)S_(2)O_(3) and Na_(2)SO_(3) had some inhibition on the oxidation of Fe^(2+),especially the inhibition of Na_(2)SO_(3) was significant,and complete oxidation of ferrous iron needed more time.The isolated T.ferrooxidans is applied to the removal of H2S gas,aiming to provide a new technological approach for biological removal of H2S.

Effects of temperature,pH and O_(2) on the removal of hydrogen sulfide from biogas by external biological desulfurization in a full scale fixed-bed trickling bioreactor(FBTB)

Hydrogen sulfide(H_(2)S)is a critical component of biogas formed under anaerobic conditions by sulfur and sulfate reducing bacteria from animal manure and renewable energy crops.H_(2)S causes high corrosion in equipment,has a negative environmental impact,inhibits the biogas formation process and is furthermore odorous and toxic.Although several methods for internal and external desulfurization found their way into practice and had been explored at laboratory scale,no data were available on the performance of such methods in full scale practice,especially for an external fixed-bed trickling bioreactor(FBTB).The effects of temperature,pH and air ratio on H_(2)S removal efficiency(RE)were studied.The study was conducted at a research biogas plant with a given output of 96 m^(3) biogas per hour,and an H_(2)S concentration ranging between 500 ppm and 600 ppm(1 ppm=1 cm^(3)/m^(3))on average.The FBTB column has been designed to hold a packing volume of 2.21 m^(3) at a gas retention time of 84 seconds being loaded at an average of 32.88 g H_(2)S/(m^(3)·h).The highest H_(2)S RE of 98% was found at temperatures between 30℃ and 40℃.A major decline in RE to 21%-45%was observed at temperatures from 5℃ to 25℃.The results clearly showed a temperature optimum range for sulfate reducing bacteria.The results reveal that RE is little affected by different pH values and air ratios.During the experimental period,the practical suitability of the FBTB system could be proved while avoiding the disadvantages of internal biological desulfurization methods.

Tentative Study on a New Way of Simultaneous Desulfurization and Denitrification

Thiobacillus denitrificans, a kind of autotrophic facultative bacteria, can oxidize sulfide into elemental sulfur or sulfate when nitrate was adopted as its electron accepter and carbon dioxide as its carbon resource under anoxic or anaerobic environment. In this way, nitrate is converted into nitrogen. In addition, ThiobaciWus denitrificans can accumulate sulfur extracellularly. In this study, in a process of simultaneous desulfurization and denitrification, a strain of Thiobacillus denitriificans is employed as sulfur-producer in the treatment of wastewater containing sulfide and nitrate. The key factors affecting this process are investigated through batch tests. The experimental results indicate that the sulfide concentration and the ratio of sulfide to nitrate (S2-/NO3-) in the influent are the key factors, and their suitable values are suggested to be 5/3 and no more than 300mg·L-1, respectively, in order to achieve high conversion of sulfur.