Treatment efficiency and greenhouse gas emissions of non-floating and floating bed activated sludge system with acclimatized sludge treating landfill leachate

Abstract

This research investigates the treatment efficiency and greenhouse gas (GHG) emissions of non-floating and floating bed AS systems with acclimatized sludge treating landfill leachate. The GHGs under study included carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The non-floating and floating bed AS systems were operated in parallel with identical landfill leachate influent under different hydraulic retention time (HRT) conditions (24, 18, and 12 h). The experimental results showed that the treatment efficiency of organic compounds under 24 h HRT of both systems (90 – 98%) were insignificantly different, while the nutrient removal efficiency of both systems were between 54 and 98 %. The treatment efficiency of the floating bed AS system, despite shorter HRT, remained relatively unchanged due to an abundance of effective bacteria residing in the floating media. The CO2 emissions were insignificantly different between both AS systems under all HRT conditions (22 – 26.3 μmol/cm2.min). The CO2 emissions were positively correlated with organic loading but inversely correlated with HRT. The CH4 emissions were positively correlated with HRT (26.3 μmol/cm2.min under 24 h HRT of the floating bed AS system). The N2O emissions were positively correlated with nitrogen loading, and the N2O emissions from the floating bed AS system were lower due to an abundance of N2O-reducing bacteria. The floating media enhanced the biological treatment efficiency while maintaining the bacterial community in the system. However, the floating media promoted CH4 production under anoxic conditions. The originality of this research lies in the use of floating media in the biological treatment system to mitigate GHG emissions, unlike existing research which focused primarily on enhancement of the treatment efficiency.