Abstract
Greenhouse gas emission from Johkasou may fluctuate daily within a day because of the time variation in the influent volume of domestic wastewater. Two Johkasou systems were operated in a temperature-controlled room, and the effects of anaerobic-aerobic circulation were investigated. Whole-day monitoring of CH4 and N2O revealed the time variation in the emissions of these greenhouse gases, which was due to the inflow of wastewater. Therefore, the time variation in the emissions of greenhouse gases should be considered for accurate emission reporting. Anaerobic-aerobic circulation operation reduced CH4 emission by 72% and N2O emission by 54%, although CH4 and N2O emissions transiently increased with the inflow of wastewater. This means a 68% reduction in CO2eq. In conclusion, anaerobic-aerobic circulation operation for nitrogen removal significantly contributes to greenhouse gas reduction in Johkasou.
