Volatile Methylsiloxanes in Sewage Treatment Plants in Saitama, Japan: Mass Distribution and Emissions

Wastewater, aeration gas, dewatered sludge, and incineration ash and flue gas (from dewatered sludge) were collected from 9 sewage treatment plants (STPs) located in Saitama Prefecture, Japan, and analyzed for seven cyclic and linear volatile methylsiloxanes (VMSs) namely, D3, D4, D5, D6, L3, L4, and The mass loadings and distribution of VMSs in STPs were estimated based on measured concentrations in liquid, solid, and gaseous samples, including incinerated dewatered sludge. Mass loading of Sigma VMS varied widely from 21 kg y(-1) to 3740 kg y(-1), depending on the volume of wastewater treated in each STP. Mass % of Sigma VMS distributed in aeration gas was 15% and that in activated sludge was 78%. Approximately 6.6% of Sigma VMS remained in the final effluent. Overall, partitioning onto the activated sludge was the dominant removal mechanism for D4, D5, and D6, whereas volatilization was also an important removal mechanism for D4. Incineration was effective to degrade VMSs in dewatered sludge, with a reduction rate of >99%. Activated carbon treatment removed >99% of VMSs from the aeration gas. In Saitama Prefecture, total emission of Sigma VMS via STPs was estimated at 434 kg y(-1), 86 kg y(-1), and 0.065 kg y(-1), to aquatic, atmospheric, and terrestrial environments, respectively, which accounted for 83%, 17%, and 0.01% of the total environmental emissions. Our results indicate that majority of VMSs in dewatered sludge can be removed by incineration and emission of VMSs through incineration ash landfill is negligible. (C) 2019 Elsevier Ltd. All rights reserved.