Removal of micropollutants in domestic wastewater by expanded granular sludge bed membrane bioreactor

Abstract

Sewage treatment plants effluent is considered the primary source of many micropollutants in aquatic systems since their biological treatment is commonly unable to remove persistent micropollutants. However, its efficacy can be achieved with the aid of advanced treatment technologies, such as membrane processes. This work evaluated the removal efficiency of 7 pharmaceuticals (Ketoprofen, Prednisone, Fenofibrate, Fluconazole, Betamethasone, Loratadine and 17α-Ethinyl estradiol) in a hybrid system (EGSB-MBR) where an ultrafiltration membrane was submerged in an anaerobic expanded granular sludge bed (EGSB) reactor. This integrated system improved the removal efficiencies of pharmaceuticals (>84 %) and chemical oxygen demand (COD). The EGSB reactor alone showed COD reductions around 92 %, while the EGSB-MBR system achieved COD reductions above 98 %. Furthermore, the permeate showed lower concentrations of nutrients (P, N-NH4+) and volatile fatty acids (VFAs) than the effluent from the anaerobic reactor alone. Anaerobic biodegradability tests, together with bioreactor results, pointed out the mechanisms involved in the removal of each drug. The risk assessment showed that the permeate presented a low probability of risk to human health and that the UF membrane was able to reduce the risk of the final effluent.