The Effect Of Heterotrophic Denitrification On Anaerobic Sulfide And Nitrate Removal Process

The main reaction of anaerobic sulfide and nitrate removal process was autotrophic denitrification with sulfide as electron donors.Activated sludge,dead cells and microorganism afford organic carbon material as heterotrophic denitrification electron donors in the reactor.The effect of heterotrophic denitrification in the reactor could not be ignored.The aims of this paper was to study heterotrophic denitrification in sulfide and nitrate removal process.Based on heterotrophic denitrification,we studied the effects of signal molecules,phosphate and thiosulfate on the removal of sulfide and nitrate,sulfide and nitrate removal was studied.The removal of sulfide and nitrate as well as the yield of elemental sulfur was improved through the regulation of heterotrophic denitrification.The major conclusions from this research are following:(1)When 1?mol/L signal molecules was added in the reactor,10% increase of sulfide removal was obtained in the low sulfide load conditions after 24 h.The sulfide removal rate increased by 40% in the high sulfide load conditions after 36 h.The signal molecules improved sulfide removal rate.(2)Heterotrophic denitrification was enhanced after the addition of signal molecules OHHL,40% and 10% increase of nitrate removal was obtained in the low sulfide load and high sulfide load conditions respectively.Meanwhile,40% increase of sulfide removal rate as well as 10% increase of elemental sulfur yield was achieved at this condition.(3)The inhibition of the heterotrophic denitrification caused by phosphate lead to 10% decreased of nitrate removal rate in the high sulfide load conditions.At the same time,the sulfide removal rate decreased by 20%.(4)Effluent sulfate concentration was decreased with the addition of phosphate.The effluent sulfate was reduced by 33mg/L and 20mg/L in the low sulfide load and high sulfide load conditions respectively.The phosphate could be bad for the formation of element sulfur.(5)Thiosulfate could be used by microorganism preferentially as electron donor when thiosulfate and sulfide co-exist.The yield of sulfur is increased by 16% with the addition of thiosulfate.(6)The concentration of thiosulfate was reduced through autotrophic denitrification of nitrate and thiosulfate reaction.The yield of thiosulfate decrease as N/S increases,especially in high concentration of nitrate conditions.