Operational strategies and environmental conditions inducing aerobic denitritation in short-cut biological nitrogen removal at side-line treatment

Abstract

ABSTRACTFactors promoting aerobic denitritation in a pilot-scale short-cut biological nitrogen removal (SBNR) process were investigated. The study implemented optimization of nitrogen removal in the anaerobic reject water (ARW) having a low organic C:N ratio ARW was produced in a large-scale municipal wastewater treatment plant (WWTP). Aerobic denitritation occurred consistently during study of a specific period of sequential batch reactor (SBR) where nitrite removal under fully aerobic conditions was obtained with a switch from oxygen to nitrite respiration, creating an aerobic (high oxidation–reduction potential) condition. Specific factors inducing aerobic denitritation were found related to several parameters as ammonium concentration, temperature, feeding mode, duration of the oxic stage and substrate availability due to beta-oxidation of lipid matter. Microbial analyses indicated a higher increase in nitrite reducing than ammonium oxidizing activity, as an evidence for nitrifying denitrifier bacterial dominance in the biomass. The reaction induced a reduction in the inhibitory products of the process as volatile fatty acids (VFAs) and free nitrous oxide (FNA), produced bicarbonate and increased removal efficiency of ammonium and nitrite, thus, total nitrogen. The outcome presents potential ways for further saving on aeration and chemical need via operational means, while taking advantage of the slowly degrading organic matter on SBNR performance.