Biodegradation of Wastewater Containing High Concentration of Sulfamethoxazole by Antibiotic Adopted Biofilm in Attached Growth Bioreactor

Pharmaceutical wastewater treatment is a complicated process due to the presence of various kinds of toxic chemicals and antibiotics that are harmful to any living organisms. In this study we employed a pilot-scale net-like rotating biological contactor (NRBC) with three compartments and total volume of 78.75 L to eliminate high concentrations of sulfamethoxazole (SMX) from a synthetic wastewater. In this system, 16 plastic discs in each compartment were fixed on a horizontal shaft, rotating with constant speed (4 rpm). Activated sludge collected from a local hospital wastewater treatment plant was used as inoculum and the system was working in batch condition in order to develop adapted living organisms as biofilm on the rotation discs. Then the NRBC was successfully operated at continuous mode for 10 months at various organic loading rates (OLR) (0 to 21.3 gCOD/L.d), hydraulic retention times (HRT) (12 to 72 h), and concentrations of sulfamethoxazole (5 to 120 mg/L). It was found that by increasing in OLR and HRT, SMX removal efficiency was increased. Also, the obtained results indicated that increasing COD concentration had a positive impact on SMX removal efficiency, which was most probably due to the utilization of SMX as a nitrogen source. Finally, it was revealed that most SMX and organic matter removal occurred in the first compartment of the NRBC, and antibiotic concentration was negligible in the outlet stream.