Treatment of domestic wastewater in step-feeding anoxic/oxic activated sludge–biofilm system at low temperature: Performance, removal characteristics, and community

Abstract

Domestic wastewater was treated with activated sludge system and activated sludge-biofilm system at low temperature (10°C), respectively. In both systems, step-feeding strategy were adopted while the aerobic and anoxic zones were designed. The performances of two different systems were compared. The microbial community in the activated sludge-biofilm system was studied deeply. As a result, the activated sludge-biofilm system achieved higher performance than the activated sludge system. In the activated sludge-biofilm system, the chemical oxygen demand (COD), NH4+-N and total nitrogen (TN) removal efficiencies reached 88%, 97% and 65%, respectively. However, in the activated sludge system, the COD, NH4+-N and TN removal efficiencies were 86%, 40% and 55%, respectively. Simultaneous nitrification and denitrification (SND) occurred in aerobic zones in activated sludge-biofilm hybrid system. The effluent TN concentration was 8.5 mg/L in average, which was mainly contributed by NO3–-N. The main microbial communities consisted of Proteobacteria, Bacteroidetes, Nitrospirae, Firmicutes, and Planctomycetes were at the phylum level, indicating the occurrence of nitrification, denitrification, and anammox.