Effect of air flow rate on development of aerobic granules, biomass activity and nitrification efficiency for treating phenol, thiocyanate and ammonium

Abstract

The impact of air flow rate on aerobic granulation was evaluated for treating toxic multiple pollutants; phenol (400 mg L−1), thiocyanate (100 mg L−1) and ammonia nitrogen (100 mg L−1) by using three lab scale sequencing batch reactors (SBRs) (R1, R2 and R3). Larger granules (2938.67 ± 64.91 μm) with higher biomass concentration (volatile solids of 4.17 ± 0.09 g L−1), higher granule settling velocity (55.56 ± 1.36 m h−1) and lower sludge volume index (35.25 ± 1.71 mL gTSS−1) were observed at optimal air flow rate of 2.5 L min−1 (R2). Confocal laser scanning microscopic images illustrated the extended fluorescence for extracellular polymeric substances in R2. In R2, partial nitrification was achieved. Phenol was completely removed in all the reactors while partial removal of SCN− and no nitrification were observed with a decrease (1.5 L min−1) and an increase (3.5 L min−1) in air flow rates (R1 and R3, respectively). This study provides an experimental contribution to examine the effect of optimal combination of aeration and toxic multiple pollutants, governing characteristics and nitrification efficiency of granules along with SBR performance in an economic way in terms of optimal air supply.