Fate of selected organic micropollutants during anaerobic sludge digestion

Abstract

Organic micropollutants are incompletely removed from wastewater in Water Resource Recovery Facilities using conventional methods and can therefore enter the anaerobic sludge treatment together with primary and secondary sludge. This review compiles literature data on the fate of selected micropollutants (Carbamazepine (CBZ), Diclofenac (DCF), Ibuprofen (IBP), Sulfamethoxazole (SMX) and Triclosan (TCS)) during anaerobic sludge treatment and how the fate is affected by chemical properties, phase distribution and operating conditions. CBZ was found to be persistent to anaerobic degradation in most studies, with some exceptions reporting a degradation efficiency of 60 %. Removal efficiencies for DCF, IBP and TCS varied widely (from no to (very) high removal). For SMX, most studies reported a removal above 80 %. A correlation was found between the fate during anaerobic digestion and physicochemical properties (hydrophobicity and molecular structure). Sorption to sludge, affected in some cases by pH changes during digestion, is suggested to reduce bioavailability. IBP and TCS were mainly present in the liquid phase or solid phase, respectively, CBZ and DCF were present in similar proportions in both phases, while statements were contradictory for SMX. Parameters such as temperature and sludge age did not significantly influence the fate of investigated micropollutants during anaerobic digestion.