Fate of Emerging Contaminants in an Integrated Fixed-Film Activated Sludge Plant

Abstract

Conventional sewage treatment techniques have shown low removal efficiency for emerging contaminants (ECs). Hence, more efficient treatment systems need to be investigated. The current study suggests that an Integrated Fixed-Film Activated Sludge Process (IFAS) could be one such alternative. The degradation of eight ECs in municipal sewage has been studied during the transition of a pilot IFAS plant to a steady state and compared with the removal of the eight ECs in a conventional sequencing batch reactor (SBR)–based sewage treatment plant at a steady state. In the six weeks before attaining a steady state, the outlet total biochemical oxygen demand, total chemical oxygen demand, and total suspended solids (TSS) decreased from 42 to 10 mg/L, 96 to 26 mg/L, and 38 to 10 mg/L, respectively. The suspended biomass concentration, hydraulic retention, and return sludge rate of the plant were 1,600 mg/L, 6.9 h, and 175% of inflow, respectively. During the transition to a steady state in the IFAS plant, the removal efficiency of Caffeine, Gemfibrozil, and Testosterone was found to increase by 41% (15%–56%), 26% (63%–89%), and 65% (19%–84%) respectively, due to enhanced biological degradation. The SBR was found to be more efficient in the removal of ECs, which could be due to the higher concentration of suspended biomass.