Concentrations of cyclic volatile methylsiloxanes in biosolid amended soil, influent, effluent, receiving water, and sediment of wastewater treatment plants in Canada.

A comprehensive surveillance program was conducted to determine the occurrence of three cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in environmental compartments impacted by wastewater effluent discharges. Eleven wastewater treatment plants (WWTPs), representative of those found in Southern Ontario and Southern Quebec, Canada, were investigated to determine levels of cVMS in their influents and effluents. In addition, receiving water and sediment impacted by WWTP effluents, and biosolid-amended soil from agricultural fields were also analyzed for a preliminary evaluation of the environmental exposure of cVMS in media impacted by wastewater effluent and solids. A newly-developed large volume injection (septumless head adapter and cooled injection system) gas chromatography - mass spectrometry method was used to avoid contamination originating from instrumental analysis. Concentrations of D4, D5, and D6 in influents to the 11 WWTPs were in the range 0.282-6.69µgL(-1), 7.75-135µgL(-1), and 1.53-26.9µgL(-1), respectively. In general, wastewater treatment showed cVMS removal rates of greater than 92%, regardless of treatment type. The D4, D5, and D6 concentration ranges in effluent were <0.009-0.045µgL(-1), <0.027-1.56µgL(-1), and <0.022-0.093µgL(-1), respectively. The concentrations in receiving water influenced by effluent, were lower compared to those in effluent in most cases, with the ranges <0.009-0.023µgL(-1), <0.027-1.48µgL(-1), and <0.022-0.151µgL(-1) for D4, D5, and D6, respectively. Sediment concentrations ranged from <0.003-0.049µgg(-1)dw, 0.011-5.84µgg(-1)dw, and 0.004-0.371µgg(-1)dw for D4, D5, and D6, respectively. The concentrations in biosolid-amended soil, having values of <0.008-0.017µgg(-1)dw, <0.007-0.221µgg(-1)dw, and <0.009-0.711µgg(-1)dw for D4, D5, and D6, respectively, were lower than those in sediment impacted by wastewater effluent in most cases. In comparison with the no-observed-effected concentrations (NOEC) and IC50 (concentration that causes 50% inhibition of the response) values, the potential risks to aquatic, sediment-dwelling, and terrestrial organisms from these reported concentrations are low.

Determination of cyclic volatile methylsiloxanes in water, sediment, soil, biota, and biosolid using large-volume injection-gas chromatography-mass spectrometry.

Several methods were developed to detect the cyclic volatile methylsiloxanes (cVMSs) including octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in water, sediment, soil, biota, and biosolid samples. Analytical techniques employed to optimize measurement of this compound class in various matrices included membrane-assisted solvent extraction in water, liquid-solid extraction for sediment, soil, biota, and biosolid samples. A subsequent analysis of the extract was conducted by large-volume injection-gas chromatography-mass spectrometry (LVI-GC-MS). These methods employed no evaporative techniques to avoid potential losses and contamination of the volatile siloxanes. To compensate for the inability to improve detection limits by concentrating final sample extract volumes we used a LVI-GC-MS. Contamination during analysis was minimized by using a septumless GC configuration to avoid cVMS's associated with septum bleed. These methods performed well achieving good linearity, low limits of detection, good precision, recovery, and a wide dynamic range. In addition, stability of cVMS in water and sediment was assessed under various storage conditions. D4 and D5 in Type-I (Milli-Q) water stored at 4°C were stable within 29d; however, significant depletion of D6 (60-70%) occurred only after 3d. Whereas cVMS in sewage influent and effluent were stable at 4°C within 21d. cVMS in sediment sealed in amber glass jars at -20°C and in pentane extracts in vials at -15°C were stable during 1month under both storage conditions.