Kitchen waste composting leachate as a compensatory carbon source intensifies nitrogen removal in sewage treatment

Abstract

Composting leachate (CL) from kitchen waste composting presented a valuable carbon source for sewage treatment. This study explored the use of CL to enhance nitrogen removal in the sewage treatment process. A sequencing batch reactor (SBR) scenario was evaluated. The addition of raw or pH-adjusted CL into the influent resulted in an increase of 3.6–11.0% (S1) and 2.9–11.5% (S2) in ammonium removal, and 16.9–38.8% (S1) and 15.8–40.4% (S2) in total nitrogen removal. No significant differences were observed in total nitrogen and ammonium removal between raw and pH-adjusted CL groups, although alkalinity adjustment was essential for CL addition ratios exceeding 1.5% to meet the influent quality standards of sewage plants (pH 6.5–8.0). CL supplementation induced shifts in the microbial community structure of activated sludge, increasing the relative abundance of nitrogen metabolic pathways, particularly denitrification (M00529), alongside an observed increase in the genetic potential for dissimilatory nitrate reduction to ammonium (M00530). It also altered the microbial contribution to denitrification and dissimilatory nitrate reduction to ammonium functional genes, favoring genera like Micropruina and Propioniciclava while diminishing the role of Nitrospira in nitrification genes (amoABC). This research provides essential insights into the utilization of CL as a supplementary carbon source in activated sludge systems and offers a theoretical foundation for its engineered application in WWTPs.