Occurrence and removal of plant sterols in pulp and paper mill effluents

Pulp and paper mill effluents (PPMEs) are believed to contain some naturally occurring endocrine disrupting chemicals (EDCs) such as phytosterols or plant sterols, which may be related to a variety of physiological and morphological abnormalities in fish inhabiting receiving waters. Analyses of effluent streams from two Canadian pulp mills confirmed the presence of five different phytosterols in PPMEs. Sterol contents of biologically treated as well as untreated effluents are presented. ββ-Sitosterol, ββ-sitostanol (or stigmastanol), and campesterol formed the major fraction of plant sterols in PPMEs, accounting for 70 % or more of the total phytosterol content measured. Sterols entering the activated sludge treatment systems were generally removed from the effluents with average removal efficiencies of 72 and 66% for the two mills surveyed. Sorption and biodegradation may be responsible for the observed removal of plant sterols across the biological wastewater treatment systems. Key words: ββ-sitosterol, stigmastanol, campesterol, removal and mass flow of phytosterols or plant sterols, hormone disruptors, pulp mill effluents, activated sludge, industrial wastewater treatment.