Occurrence and fate of emerging trace organic chemicals in wastewater plants in Chennai, India

The presence of pharmaceuticals, hormones, pesticides and industrial contaminants collectively termed as trace organic compounds (TOrCs) in wastewater has been well-documented in USA, Europe, China and other regions. However, data from India, the second most populous country in the world is severely lacking. This study investigated the occurrence and concentrations of twenty-two indicator TOrCs at three wastewater treatment plants (WWTPs) in South India serving diverse communities across three sampling campaigns. Samples were collected after each WWTP treatment unit and removal efficiencies for TOrCs were determined. Eleven TOrCs were detected in every sample from every location at all sites, while only five TOrCs were detected consistently in effluent samples. Caffeine was present at greatest concentration in the influent of all three plants with average concentrations ranging between 56 and 65 μg/L. In contrast, the x-ray contrast media pharmaceutical, iohexol, was the highest detected compound on average in the effluent at all three WWTPs (2.1-8.7 μg/L). TOrCs were not completely removed in the WWTPs with removal efficiencies being compound specific and most of the attenuation being attributed to the biological treatment processes. Caffeine and triclocarban were well removed (> 80%), while other compounds were poorly removed (acesulfame, sucralose, iohexol) or maybe even formed (carbamazepine) within the WWTPs. The effluent composition of the 22 TOrCs were similar within the three WWTPs but quite different to those seen in the US, indicating the importance of region-specific monitoring. Diurnal trends indicated that variability is compound specific but trended within certain classes of compounds (artificial sweeteners, and pharmaceuticals). The data collected on TOrCs from this study can be used as a baseline to identify potential remediation and regulatory strategies in this understudied region of India.