Micropollutants removal during high rate thermophilic and hyper-thermophilic anaerobic digestion of concentrated black water

Abstract

Source separated toilet water (black water; BW) is an important alternative nutrient source for agriculture. However, reuse and recovery of nutrients from BW is limited by the presence of pollutants, such as pathogens and micropollutants. In this study, the fate of micropollutants during thermophilic and hyper-thermophilic anaerobic digestion (AD) of concentrated vacuum collected BW is assessed. A total of eight pharmaceuticals were selected and spiked with two distinct loading rates to concentrated BW treated in an Upflow Anaerobic Sludge Blanket Reactors (UASB). The removal of these micropollutants was followed by measuring concentrations in the liquid phase. It was shown that the micropollutant loading rate did not affect the removal efficiency. Irbesartan, propanol, sulfamethoxazole and trimethoprim were almost completely removed under both conditions (>95% removal). Metoprolol had 74% removal under thermophilic conditions. Caffeine showed high desorption from BW solids, whereas carbamazepine is thought to be removed by sorption to the sludge in the UASB reactor. Diclofenac removal was < 30% during both temperature conditions, which may have been caused by the lack of sludge adaptation which limits the biodegradation. There were no differences in micropollutant removal efficiencies between thermophilic and hyper-thermophilic AD of concentrated BW. Therefore, it is concluded that thermophilic AD is sufficient for safe nutrient recovery in terms of micropollutants presence.