For the heterotrophic denitrification of low C/N ratio wastewater, it is necessary to feed external carbon source as an electron donor. Commonly used methanol is not economic in the wastewater treatment Process because of high value and low denitrification efficiency. More economic autotrophic denitrification process was introduced by sulfur oxidizing bacteria which can grow with sulfur compound as an electron donor and nitrate as an electron acceptor. Sulfur oxidizing bacteria were isolattd by selective enrichment media from activated sludge used in municipal wastewater treatment in this experiments. Three kinds of bacteria were isolated and designated as strain ST1, ST2 and ST3 after physiological, morphological and fatty acid analysis. For more exactly identification of those bacteria, each 16S rDNA was sequenced and analyzed through databases. In batch denitrification tests, strain ST1 and ST3 can reduce nitrate with both thiosulfate and elemental sulfur as an electron acceptor after finding of optimum autotrophic denitrification conditions. Because the tedious growth of microorganism was one of the main problems in autotrophic denitrification process, high-concentrated culture were investigated. In physiological test, strain ST1 and ST3 can assimilate glucose during heterotrohic denitrification. Glucose medium was used and then those microorganisms can grow in it as a sole source of carbon and electron acceptor. High concentrated strain ST1 and ST3 from glucose medium can perform autotrophic denitrification without lag time and nitrite accumulation, That means high-concentrated strain ST1 and ST3 from heterotrophic culture can do denitrification in autotrophic condition and that can be used for more efficient autotrophic denitrification process application.
