Are Side-Stream Loads of Pharmaceutical Compounds Important for the Large-Scale Wastewater Treatment Plants?

Abstract

The presence of pharmaceutical compounds in the environment has become a serious global concern since they pose a direct or indirect threat for almost all aquatic species, animals and even people (Lee et al., 2019). Wastewater treatment plants (WWTPs) are considered as the one of the most important point sources with regard to the discharge of pharmaceutical compounds into receiving environments. Since most of the existing conventional WWTPs cannot completely remove pharmaceuticals (Tran et al., 2018), determining the individual and total pharmaceutical loads discharged from WWTPs into receiving environments is crucial for evaluating their potential adverse effects on all living creatures. Although there are numerous studies performed about occurrence, distribution and removal of pharmaceuticals in WWTPs found in different geographical regions, there are very few researches investigating the side-stream contribution of these compounds to total loads in WWTPs. In this study, the effect of side-streams of three pharmaceutical compounds belonging to different therapeutic groups on total loads were investigated in order to determine their behavior patterns both in sludge thickener and sludge dewatering units found in an advanced biological WWTP. Within this scope, diclofenac (DCF) from the group of nonsteroidal anti-inflammatory drugs, carbamazepine (CBZ) from the group of anticonvulsants and ciprofloxacin (CIP) from the group of antibiotics were investigated. Besides, the increase and decrease in the concentration values of the each investigated pharmaceutical compounds in the side streams returning to the beginning of the plant were evaluated based on the concentration values determined in the raw wastewater. Finally, within the scope of the findings, it was evaluated whether the side streams were a serious problem for a large-scale WWTP by calculating the extra pharmaceutical load percentages caused by the side-streams originating from both in sludge thickening and the sludge dewatering (decanter) units.