Volatile methylsiloxanes (VMSs) in sewage effluent from different origins: A comprehensive seasonal analysis

Anthropogenic chemicals used in a wide range of products, volatile methylsiloxanes (VMSs) may reach sewage and potentially cause environmental pollution. So far, no studies were found on the sewage networks leading to WWTPs, key to assess possible sources and incoming trends. Seven cyclic and linear VMSs were analyzed in sewage from four streams of different origin before entering a municipal WWTP, in four year-round seasonal campaigns. VMSs were detected in all samples and the cyclic congeners prevailed. The total VMSs mean concentrations (µg L -1 ) were 2.1 (Stream 1; urban/rural), 20.2 (Stream 2; beach), 4.5 (Stream 3; industrial) and 6.4 (Stream 4; urban), and the respective mean mass flows were 18.8, 23.7, 0.7 and 101.8 g day -1 . A strong daily variability depending on the sewage type and a tendency to higher VMS levels on the warmer months were found. Considering a scenario of untreated discharges, Stream 2 presented a higher risk to the environment, with RQ≥1 in 54% of the samples. This suggests that tourist-impacted beaches may exceed other urban, rural or industrial areas as hotspots of VMSs. However, the VMSs load (and the potential risk) can vary tremendously with land use, urging VMS monitoring plans to include sewage networks.