Simultaneous nitritation and denitritation in a multi-cycle SBR treating low-strength wastewater

Abstract

This study presents a novel control strategy to achieve simultaneous nitritation and denitritation in a multi-cycle sequencing batch reactor with integrated fixed-biofilm and activated sludge. 86.0% of total nitrogen was removed from synthetic wastewater with an average COD/N ratio of 3.3 at 15 °C–24 °C. Batch tests and high-throughput sequencing results showed that Nitrospira and Nitrosomonas genus mainly distributed in the biofilm, so some of the nitrite produced by Nitrosomonas could be simultaneously reduced by denitrifiers in the biofilm during aeration, leading to low nitrate accumulation. As such, nitrite could be removed by denitrifiers in both anoxic and oxic phases, and accordingly suspended Nitrospira was completely suppressed due to food shortage and easily washed out at a short solids retention time.