Evaluation of the Nitrous Oxide Emission Reduction Potential of an Aerobic Bioreactor Packed with Carbon Fibres for Swine Wastewater Treatment

Nitrous oxide (N 2 O) is a potent greenhouse gas that is emitted from wastewater treatment plants. To reduce emissions of N 2 O from swine wastewater treatment plants, we constructed an experimental aerobic bioreactor packed with carbon fibres (ca. 1 m 3 bioreactor) as an alternative to conventional activated sludge treatment. The N 2 O emission factor for the aerobic bioreactor packed with carbon fibres (CF) was 0.002 g N 2 O-N/g TN-load and the value for the typical activated sludge (AS) reactor was 0.013 g N 2 O-N/g TN-load. The CF treatment method achieved more than 80% reduction of N 2 O emissions, compared with the AS treatment method. The experimental introduction of a CF carrier into an actual wastewater treatment plant also resulted in a large reduction in N 2 O generation. Specifically, the N 2 O emission factors decreased from 0.040 to 0.005 g N 2 O-N/g TN-load following application of the carrier. This shows that it is possible to reduce N 2 O generation by more than 80% by using a CF carrier during the operation of an actual wastewater treatment plant. Some bacteria from the phylum Chloroflexi, which are capable of reducing N 2 O emissions, were detected at a higher frequency in the biofilm on the CF carrier than in the biofilm formed on the AS reactor.