Perspective for Emission and Control of Nitrous Gas in Biological Wastewater Treatment

. Being the third most significant anthropogenic greenhouse gas, nitrous gas (N 2 O) has 300-fold stronger effect than carbon dioxide (CO 2 ) and 4 ~ 30-fold stronger effect than methane (CH 4 ). In this study, the main sources and mechanisms of N 2 O emission from biological wastewater treatment were reviewed, and the possible mitigation strategies were discussed. Parameters including dissolved oxygen, temperature, pH, organic carbon, and nitrite concentration have influences on the emission of N 2 O. The possible mitigation strategies were put forward by controlling these parameters in biological wastewater treatment and inducing modified technologies such as simultaneous nitrification-denitrification, denitrifying phosphorus removal, and aerobic granular sludge. In order to obtain a near-zero N 2 O emission, applying typical catalysts in the nitrification or denitrification tank to decompose N 2 O into harmless gas is recommended. Moreover, a method of developing photochemical processes to transform N 2 O could also be suggested.