Enrichment Of Anaerobic Ammonium Oxidation Bacteria And Their Metabolism With Acetate

In recent years, the nitrogen pollution problem has become increasingly acute, and posedhazardous effects on human health and ecological safety. Therefore, more and more countriesand regions have formulated strict limits and discharging standards, and a variety of newwastewater treatment technologies were developed. Anaerobic ammonium oxidation (Anammox)is a new promising nitrogen removal biotechnology, and it has attracted much attention both athome and abroad due to its high efficiency and low expenses. However, the long stat-up periodof the process due to extremely slow growth rate of Anammox bacteria and its susceptibility tothe organic matters strongly restricted its application. This study intended to obtain Anammoxbacteria enrichment cultures rapidly through optimizing the inoculum, reactor configuration andoperation conditions, and then studied their metabolic characteristics with acetate.The anaerobic reactor inoculated with mixture of Anammox sludge which has beenenriched for half a year and activated sludge, was operated at36±1℃, pH7.01~7.71. After280dcultivation, Anammox enrichment cultures were obtained successfully. In the process ofcultivation, we found that short HRT and low substrate concentration was easier to obtain highnitrogen removal rate than long HRT and high substrate concentration. At the HRT of0.5d, thetotal nitrogen removal rate was2.29kg/(m3·d) when NH4+-N and NO2--N was580mg/L and730mg/L respectively. While at the HRT of0.2d, the total nitrogen removal rate reached to3.59kg/(m3·d) at a even low substrate concentration (NH4+-N and NO2--N concentration was325mg/L and480mg/L respectively). What is more, when the concentration of NH4+-N and NO2--Nreached470mg/L and640mg/L, the total nitrogen removal rate arrived at5.16kg/(m3·d). Thenitrogen removal rate was not depleted by shortening the HRT, the nitrogen removalperformance was enhanced instead. When the HRT reduced from0.4d to0.2d, total nitrogenremoval rate increased from1.89kg/(m3·d) to3.74kg/(m3·d). Anammox bacteria in red granularsludge were mainly cocci with a crater-like structure in the sureface, which is the typicalcharacterisitic of Anammox bacteria. The specific activity of the Anammox sludge was0.45kgNH4+-N/(kg·d). Analysis of16S rDNA of the Anammox bacteria in red granules revealed that theAnammox bacreria belonged to genus "Candidatus Kuenenia".Research on the metabolism of the Anammox bacteria with the acetate, we found that theaddition of acetate affected the metabolism of Anammox bacteria and reaction stoichiometry.Little effects was observed on the metabolism of NH4+-N and NO2--N when acetate was1mmol/L, except that effluent concentration of NO3--N decreased. The average total nitrogenremoval efficiency increased from89.27%to more than95%, and the acetate concentration inthe effluent basicly exhausted. Synergistic nitrogen removal through Anammox anddenitrificaiton processes occurred in the presence of1mmol/L acetate. Inhibitive effects onAnammox bacteria arised when the concentration of acetate increased to3mmol/L and4mmol/L. The concentration of NH4+-N in the effluent increased from1.54mg/L to54.7mg/L, the total nitrogen removal rate and total nitrogen removal efficiency were both decreased. Afterthe inhibition of the acetate, the NO2--N/NH4+-N was higher than the control group, theNO3--N/NH4+-N was lower. The stoichiometry between NH4+-N, NO2--N and NO3--N wasstablized at1:1.50:0.07. The reaction stoichiometry between acetate and nitrogen compoundswas associated with the acetate concentration.