Technical Bulletin No. 0746: Development and Evaluation of a Method for the Determination of Phytosterols in Pulp and Paper Mill Effluents

<p align="justify">A method is reported which will measure phytosterols, specifically campesterol, stigmasterol, beta-sitosterol, and stigmastanol, in wastewater treatment plant influents and biologically-treated effluents from kraft, kraft/recycle, kraft/groundwood, thermomechanical/groundwood, and sulfite pulp and paper mills. The isolation technique involves liquid/liquid extraction with methyl-t-butyl ether as the solvent, followed by trimethylsilylation, clean-up (as required) using silica gel, and gas chromatography/flame ionization detector analysis. Confirmation using gas chromatography and mass spectrometry is also described. The method has a limit of detection of approximately 0.4 mcg/L, depending upon the sample matrix and target analyte. The method’s accuracy and precision have been assessed at the single laboratory level in treatment plant influents and biologically-treated effluents. A full description of the method and preliminary validation is presented. Information on the application of the developed method to estimate discharge levels of campesterol, stigmasterol, beta-sitosterol, and stigmastanol from 22 U.S. mills is included. The discharge rates of the different mills ranged from 0.2 to 25.2 g/T. Generally, beta-sitosterol discharge levels were the highest, but the observed range of discharge rates varied by more than one order of magnitude. Removal efficiencies were determined for nine U.S. mills utilizing biological treatment systems, including activated sludge systems and aerated stabilization basins. Data from activated sludge systems and aerated stabilization basins showed a decrease for campesterol, beta-sitosterol, and stigmastanol across the treatment systems for the majority of mill sites assessed. The only exception to these removal efficiencies was observed for stigmasterol.</p>