Effects of the physicochemical factors on autotrophic denitrification by Thiobacillus denitrificans.

A strain of Thiobacillus denitrificans(T.d.a) was isolated from anaerobic sludge of consecutive running UASB reactor.Based on culture media of Thiobacillus denitrificans,the effects of pH,temperature,NO3--N,NH4+-N,S2O32-,HCO3-,C6H12O6,P,Mg2+ and Fe2+ on the denitrification by T.d.a were studied in batch experiments using sodium thiosulphate as sulfur source.The nitrate removal velocities were high at pH 6.5～8.0 and temperature 20～35℃.The optimal conditions were pH 7.04 and 27.40℃.T.d.a exhibited a good adaptation when the concentration of NO3--N was below 416mg/L.At 554mg/L or above,however,the nitrate removal was markedly inhibited.The denitrification needed NH4+-N and its limiting concentration was 2.62mg/L.The effect of the concentration of S2O32-on the denitrificaion depended on different sulfur to nitrogen ratios.When NO3-was enough,the NO3--N removal efficiency was in similar direct proportion to the S2O32-added[0].Using HCO3-as sole carbon source,its limiting concentration was 29.05mg/L.The presence of glucose up to 2000mg/L didn't significantly affect the nitrate removal efficiency.The limiting concentrations of P and Mg2+ were 0.034mg/L and 0.059mg/L respectively.The limiting concentration of Fe2+ was below 0.058mg/L.