Characterization of plant sterols from 22 US pulp and paper mills

Recent concerns regarding the possible biological effects of plant sterols, especially β-sitosterol and its metabolites, prompted the development of a method for the determination of campesterol, β-sitosterol, stigmastanol, and stigmasterol in pulp and paper industry wastewaters. The method utilizes a liquid/liquid extraction with methyl-t-butyl ether followed by trimethylsilylation derivatization with GC/FID analysis. The method has been applied to wastewater samples from biological treatment systems at 22 US mills. Estimated treatment system removal efficiencies and mass discharge rates are reported. Estimated treatment system removal efficiencies ranged from 64-79% for most analytes. However, the concentration of stigmasterol was observed to increase across aerated stabilization basins. The estimated mass discharge rates for total plant sterols ranged from a low of 0.2 g/T to a high of 25.2 g/T, depending on the specific mill sampled.