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Analysis of octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane in wastewater, sludge and river samples by headspace gas chromatography/mass spectrometry




Zhang, Yu, author
Ömür-Özbek, Pinar, advisor
Carlson, Kenneth, committee member
Dooley, Gregory, committee member

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Siloxanes are commonly used in cosmetic and personal care products, healthcare products and many industrial applications. Because siloxanes are persistent, they end up in the wastewater and go untreated through the wastewater treatment units, which lead to contamination of the surface waters through effluent discharge. Siloxanes tend to be adsorbed onto or absorbed by the activated sludge in the wastewater treatment process. In the digesters, the siloxanes volatilize and accumulate in the biogas, which leads to mechanical problems due to scaling. The two most common siloxanes detected in wastewaters and sludge are: octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5). For this study, the D4 and D5 in wastewater and sludge samples were monitored using headspace gas chromatography/mass spectrometry. Samples were collected from the City of Loveland Wastewater Treatment Plant (WWTP), Loveland, CO and the Drake Wastewater Reclamation Facilities (WWRF), Fort Collins, CO. The levels of D4 were in the range of 0.7-11.3 ng•mL-1 in wastewater and 0.3-1.8 µg•g-1 dry solid in the sludge from Drake WWRF; 1.0-6.7 ng•mL-1 in wastewater and 0.3-1.7 µg•g-1 dry solid in the sludge from Loveland WWTP. D5 levels were determined in the range of 0.4-10.4 ng•mL-1 in wastewater and 3.2-31.4 µg•g-1 dry solid in the sludge from Drake WWRF; 0.5-14.0 ng•mL-1 in wastewater and 2.5-18.9 µg•g-1 dry solid in the sludge from Loveland WWTP. The concentrations of D4 and D5 were higher in this study compared to other researches in other countries and the concentrations in waste activated sludge were in a comparable range. The concentrations of D4 and D5 in the receiving water body near the discharging points were below the limit of detection. The average mass loadings in the influent were 53.1 and 159.9 g•d-1 of D4 and 155.3 and 225.3 g•d-1 of D5 respectively in two plants.


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