Greenhouse gases emission from aerobic methanotrophic denitrification (AeOM-D) in sequencing batch reactor

Abstract

This study presents the effect of hydraulic retention time (HRT) on the characteristics of emission of three major greenhouse gases (GHGs) including CH4, CO2 and N2O during operation of a sequencing batch reactor for aerobic oxidation of methane with denitrification (AeOM-D SBR). Dissolved N2O concentration increased, leveled-off and slightly decreased as the HRT increased from 0.25 to 1d. Concentration of the dissolved N2O was higher at the shorter HRT, which was highly associated with the lowered C/N ratio. A longer HRT resulted in a higher C/N ratio with a sufficient carbon source produced by methanotrophs via methane oxidation, which provided a favorable condition for reducing N2O formation. With a less formation of the dissolved N2O, N2O emission rate was lower at a longer HRT condition due to the lower C/N ratio. Opposite to the N2O emission, emission rates of CH4 and CO2 were higher at a longer HRT. Longer HRT resulted in the greater total GHGs emission as CO2 equivalent which was doubled when the HRT increased from 0.5d to 1.0 d. Contribution of CH4 onto the total GHGs emission was most dominant accounting for 98-99% compared to that of N2O (< 2%).