Activity enhancement of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in activated sludge process: metabolite reduction and CO2 mitigation intensification process

The interaction of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) is of considerable importance in nitrification process. Ecophysiological interactions between the communities of AOB and NOB were investigated by monitoring NO2- as the intermediate compound in an organic carbon-depleted nitrifying activated sludge fed only NH4+ as a nitrogen source (40mg/L). The presence of boom and bust (feast and famine) cycle successfully indicates the activity cycles of AOB and NOB through cultivation-dependent method. The maximum growth rate and yield for AOB in nitritation-dominant period were (0.67day(-1), 0.17gVSSgN(-1)) and for NOB in nitratation-dominant period were (0.71day(-1), 0.072gVSSgN(-1)). Soluble microbial products (SMP) and extracellular polymeric substances (EPS) generated by AOB were 1.2 and 1.8mg/L, respectively, while NOB produced 0.6mg/L of SMP and 1mg/L of EPS. While NOB were low in utilization-associated products (UAP) (0.07mg/L) and biomass-associated products (BAP) (0.12mg/L), AOB were higher in UAP (0.15mg/L) and BAP (0.3mg/L). The continuation presence of zero C/N ratio, in either inlet ratio or net available ratio for the microbial community, can prolong and enhance nitratation process. NOB enrichment and nitratation intensification strategy through zero C/N ratio are able to reduce remarkably microbial metabolites 50% lower than conventional process and enhance nitrification efficiency in activated sludge-involved processes.