In situ excess sludge reduction in SBBR through uncoupling of metabolism induced by novel aeration modes

Abstract

To minimize sludge yield (Y_obs) in bench-scale sequencing batch biofilm reactors (SBBRs) during wastewater treatment, novel aeration modes were employed: triangular-wave aeration, square-wave aeration, sawtooth-wave aeration and continuous aeration. SBBR with square-wave aeration showed the lowest observed Y_obs about 304% lower than SBBR with continuous aeration. The ATP inhibition phenomenon and lower density of micro-faunas in SBBR with square-wave aeration confirmed that the metabolism uncoupling contributed to lower Y_obs instead of micro-fauna predation. No significantly different removal efficiencies of chemical oxygen demand (COD) were found in 4 SBBRs, but the highest total nitrogen (TN) removal efficiency of around 69% was achieved in SBBR with square-wave aeration. The feasibility of using oxidation reduction potential (ORP) as an indication for in situ sludge reduction was illustrated based on the interrelation between ORP in the bulk and within the biofilm.