Removal rates of antibiotics in four sewage treatment plants in South India.

The occurrence and removal of seven selected pharmaceutical compounds (PCs) in sewage treatment plants (STPs) in South India were investigated. The PCs selected for this study were sulfamethoxazole (SMX), trimethoprim (TMP), chloramphenicol (CAP), erythromycin (ERY), naproxen (NPX), bezafibrate (BZF), and ampicillin (AMP). Wastewater samples were collected from inlet and outlet of the STPs during pre-monsoon, monsoon, and post-monsoon seasons to investigate the seasonal influences in occurrence and removal rates. The analytical method was based on simultaneous extraction of all target compounds by solid phase extraction (SPE), using a hydrophilic-lipophilic-balanced (HLB) sorbent followed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The STP that catered exclusively to domestic wastewater had lesser concentrations of PCs compared to the STPs serving the combined hospital and domestic effluents. SMX was the dominant compound in all effluents with the highest concentration at 3.2 μg/L in the outlet of an STP. TMP and ERY were the other PCs present at higher concentrations in STP outlets (1 μg/L and 0-0.13 μg/L, respectively). Removal rates varied from 100 % for BZF to 60-100 % for SMX, CTX, and AMP.