ENVIRONMENTAL OCCURRENCE OF POLYDIMETHYLSILOXANE

An extensive monitoring program was conducted to determine the occurre nce of polydimethylsiloxane (PDMS) in environmental compartments impac ted by consumer waste disposal practices. Eight wastewater treatment p lants, representative of those found in North America, were monitored to determine PDMS removal during wastewater treatment. Surface waters, sediments, and sludge-amended soils impacted by wastewater treatment plant effluents and sludges were also monitored for a more complete as sessment of the environmental fate of PDMS. Newly developed GPC-ICP an d/or HPLC-ICP analytical techniques were used to provide insight into the environmental fate of PDMS and anticipated PDMS degradation produc ts. PDMS was found to be highly removed during wastewater treatment wi th effluent concentrations, in most cases, below the quantitation limi t of the analytical technique (<5 mu g/L). PDMS sludge concentrations ranged from 290 to 5155 mg/kg and varied as a function of influent con centration and sludge processing method. Sediment levels of <6 mg/kg w ere measured near the outfall of the wastewater treatment plants sampl ed. Measured sludge-amended agricultural soil concentrations ranged fr om <0.41 to 10.4 mg/kg and were lower than expected in most cases base d on calculated PDMS loadings via historical sludge application. The l ower than expected PDMS concentrations in sludge-amended soil combined with detection of dimethylsilane-1,1-diol, an expected PDMS breakdown product, suggest degradation of PDMS in the soil environment.