The fate and behaviour of steroid hormones in wastewater sludge anaerobic digestion at mesophilic and thermophilic temperatures

The disposal of biosolids to agricultural land is a major route for recycling municipal wastewater biosolids. However, there are concerns over the long-term build-up of endocrine disrupting chemicals (EDCs), a major constituent of biosolids in agricultural soils and their potential environmental effects. Hence, there is need to investigate the fate and behavior of EDCs in wastewater and sludge treatment processes. Thisstudy investigated the fate and behaviour of estrone (E1), 17ß-estradiol (E2) and 17α-ethynylestradiol (EE2) during anaerobic digestion of surplus activated sludge in a batch reactor at mesophilic and thermophilictemperatures. The results showed removal rates of 35%, 61% and 52% at mesophilic temperatures (35oC) and 24%, 63% and 79% at thermophilic temperatures (55oC) for E1, E2 and EE2 respectively. It was observed that E1 had a lower removal due to biotransformation of E2. Anaerobic digestion contributes to the overall reduction of EDCs in municipal biosolids, but EDCs remained persistent even under thermophilic digestion indicating the need for other treatments in order to achieve total removal.