Biological removal processes in aerobic granular sludge for treating synthetic hospital wastewater: Effect of temperature

Abstract

Four aerobic granular sludge reactors operated in sequential batch mode were implemented to understand the effect of low (7 °C) and high (26 °C) temperature in the removal of pharmaceuticals in the treated effluent. The chemical oxygen demand and nitrogen removal ratio were affected during the startup period in reactors feeding with drugs, but systems reached steady stability, achieving similar values in terms of biodegradation processes. Pharmaceuticals were progressively being removed from the effluent at high temperature, while at low temperature, oscillations in results were obtained. Naproxen was the most recalcitrant compound and trimethoprim accomplished the better removal ratios for both temperatures. The microbial community was completely dependent on operational temperature, although the proliferation of specific OTUs, Flavobacterium and Leadbetterella, was detected in reactors amendment with drugs. The metabolically active bacteria community showed lower diversity than total community. The statistical analyses corroborated that the effect of the temperature on the microbial community was more decisive than the treatment of pharmaceuticals.