Using granular activated carbon for enhanced phosphate removal by aerobic granular sludge development with propionate as carbon source

Abstract

Abstract Despite propionate being an important constituent of domestic wastewater, its effect on aerobic granular sludge (AGS) development and biological nutrient removal (BNR) pathways is not well studied. This study investigated the cultivation of AGS and establishment of BNR pathways using propionate as a sole carbon source in the bioreactors with and without granular activated carbon (GAC) particles. The presence of GAC particles reduced the start-up period for AGS formation and established of BNR pathways with propionate feeding. Aerobic granules were compact and had stable settling characteristics (≥ 1 mm, 6 g/L MLSS and 40 mL/g SVI). An increase in alginate-like exopolysaccharide (ALE) up to 400 mgALE/gSS corroborated with stable AGS formation. Stable and effective ammonium and total nitrogen removals were established by day 30. Ammonium was removed via simultaneous nitrification and denitrification as well as partial nitrification and denitritation pathways. Stable and efficient phosphorus removal was established from day 80. High phosphorus removals were corroborated with the abundance of polyphosphate accumulating organisms in the GAC biofilms. The GAC biofilms separated from the co-existing granules exhibited efficient phosphorus removal via enhanced bio-P removal. The high abundance of Thauera sp. in the GAC biofilms indicated its role in granulation and phosphorus removal under propionate feeding conditions.