Research On Production Of Soluble Microbial Products And Its Effect On Denitrification

During the catabolism of contaminants in wastewater by microbes inbiological sewage treatment, many microbial products as by-products are producedincluding the soluble microbial products(SMP) dissolved in the water as COD,which cause the secondary pollution. This article focused on the generative processof SMP during the wastewater treatment in SBR and its influence factors. For theissue of the lack of carbon source for denitrification, the potential of SMP aseffective carbon source and the relationship between the utilization of SMP anddenitrification effeciency were investigated. All the researches were to furthersupport for the improving of nitrogen removal effeciency through the quantitiveregulation of SMP.Obvious effects of C/N and pH on the production of SMP were observed. Withthe increasing of C/N (from2.5to4), the productions of both SMP and extracelluarpolymeric substances(EPS) were decreased, however, the proportions ofpolysaccharides and proteins in SMP were raised. Relatively, more SMP weregenerated under either acid and alkaline condition. Moreover, the generation ofSMP was affected unconspicuously by aeration rate.Generally, SMP was producted during the catabolism by microbes when thesubstrates were suffcient, and consumed as carbon source again under faminecondition. For the both A/O/A and O/A conditions, the concentrations of SMP wereincreased rapidly and reached the peak values at the end of aerobic phase, thendecreased in anaerobic phase. Comprehensively, SMP could be transformed to EPSthrough the utilization by microbes in famine and aerobic condition. Moreover,EPS could be hydrolyzed and then dissolved in the water as SMP under famine andanaerobic condition.The denitrificans could be forced to utilized partial SMP as carbon source todenitrify under famine and anaerobic condition. However, a portion of SMP couldnot be consumed as carbon source for denitrification directly before hydrolysisacidification. When the SBR operated as A/O/A,77.38%of the TN removal wasobserved, by contrast, the TN removal was increased to84.81%under O/Acondition. In addition, the removal of TN by denitrification, achieved by SMP asthe efficient organic carbon, accounted for12.14%and15.8%of the total TNremoval rate respectively, which revealled the prominent contribution of SMP forthe total nitrogen removal.