Performance of suspended and attached growth bioreactors for the removal of cationic and anionic pharmaceuticals

Abstract

Removal of three pharmaceuticals, namely, atenolol, gemfibrozil and ciprofloxacin in three bioreactors namely, activated sludge process (ASP), submerged attached biofilter (SABF) and membrane bioreactor (MBR) was studied. Removal efficiencies at steady state for atenolol were found to be 93%, 82% and 95% in ASP, SABF and MBR, respectively. Removal efficiencies for gemfibrozil were 75%, 90% and 85%, while those for ciprofloxacin were 84%, 95% and 93% in ASP, SABF and MBR, respectively. Nearly 20% of the ciprofloxacin was found to be sorbed on the biomass in the reactors. Reduction in sludge residence time (SRT) decreased the removal of compounds in ASP and MBR, and reduction in hydraulic residence time (HRT) caused a negative impact on the performance of all the reactors. Considerable increase in easily available carbon source reduced the removal efficiency. Sorption coefficient (log Kd) of ciprofloxacin was found to be 3.86 and sorption was negligible in case of atenolol and gemfibrozil. Monod co-metabolic model could simulate biodegradation process satisfactorily. Inhibition concentrations (Ki) of atenolol, ciprofloxacin and gemfibrozil were found to be 2.8mg/L, 0.6mg/L and 0.89mg/L, respectively. Biokinetic parameters μmax, Ks and YX/S were 0.046h−1, 10mg/L and 0.36, respectively. Efficiency factor (ηc) was estimated to be 0.002, 0.0006 and 0.001mg compound/gCOD for atenolol, ciprofloxacin and gemfibrozil, respectively.