An evaluation of the fate and behaviour of endocrine disrupting chemicals during anaerobic digestion of sewage sludge

Endocrine disrupting chemicals such as steroid estrogens and alkylphenol polyethoxylates entering the environment via regular domestic or industrial discharges have been demonstrated to cause feminization of aquatic organisms at trace levels. Despite these discharges, the solid-end product of wastewater treatment i.e. digested sludge, poses a potential source of these compounds in the environment when sewage sludge is recycled onto land. Greater concentrations of alkylphenolic metabolites such as alkylphenols and short-chained one to three ethoxy units, ethoxylates have been reported to occur in digested sludge than the parent compounds. This study investigates the fate and behaviour of these chemicals in mesophilic and thermophilic anaerobic digestion by using primary sludge and a mixture of primary and secondary sewage sludges. The analytical methodologies used for the determination of these endocrine disrupting compounds allowed accurate quantification at microgram per kilo of dry-sludge weight concentrations in the complex sludge matrices. Four mesophilic and two thermophilic semi-continuous lab-scale anaerobic digesters were examined. In addition, acclimated sludges were dosed with high nonylphenolic concentrations to observe the capacity of biomass to remove these compounds. Cont/d.