Role of Secondary Sludge in the Removal of Phytosterols during Secondary Wastewater Treatment

Abstract

Proper control of phytosterols in pulp mill effluents is necessary before disposal into receiving environments because they have been suspected to be hormonally active to aquatic life. This study provides an insight into the adsorptive behavior of sterols and the role of secondary sludge in their removal during secondary treatment. The kinetics of sterol adsorption, extent of sterol adsorption onto inactivated secondary solids, adsorptive capacity of secondary solids, and the relative contribution of the adsorption mechanism in the overall removal of sterols during secondary treatment have been investigated in this study. Isotherm modeling revealed two different adsorption regimes for each sterol. The results show that adsorption plays a major role in the secondary treatment of pulp mill effluents and that secondary sludge serves as an efficient adsorbent to remove phytosterols. The obtained information is important to improve system design and optimize the operation of pulp mill effluent treatment facilities.