Effect of magnetic powder on nitrous oxide emissions from a sequencing batch reactor for treating domestic wastewater at low temperatures.

Abstract Low temperatures can lead to an increase of N2O generation and emission from the nitrogen removal process in wastewater treatment plants. This study investigated the effect of the addition of magnetic powder on N2O generation and emission from a sequencing batch reactor treating domestic sewage at low temperatures. The results showed that the magnetic powder simultaneously inhibited N2O generation and emission and improved the removal of NH4+, total nitrogen (TN), and chemical oxygen demand at low temperatures. Furthermore, the conversion rate of N2O (N2O generation to TN removal) was reduced. The efficacy of the magnetic powder depended on its concentration, which could be ordered as 1 mg/L > 2 mg/L > 4 mg/L. With the addition of magnetic powder, especially at the 1 mg/L level, the activities of nitrification and denitrification enzymes in activated sludge were significantly improved and the growth of ammonium and nitrite oxidizing bacteria was also promoted.