Evaluation of Greenhouse Gas Emissions from a Continuous Activated Sludge Process under Power Saving Conditions

Abstract

Emissions of greenhouse gases were evaluated using a lab-scale continuous activated sludge reactor for the purpose of power saving at on-site domestic wastewater treatment facility. In addition, the behavior of N₂O production was investigated to figure out the factors reducing N₂O production. The experiments were performed under three power saving conditions. The relation between N₂O production and ammonia, nitrite, nitrate, and dissolved oxygen concentrations was clarified. As a result, it was found that suitable control of ammonia oxidization is an important factor to reduce N₂O production. Higher emission of greenhouse gases was observed in long-term power saving condition compared with the other conditions because of high N₂O emission. The emissions of greenhouse gases were almost the same for conventional condition and short-term power saving condition. However, in light of power shortages, short-term power saving condition has an advantage over conventional condition.