Biological absorption as main route for amoxicillin reduction and heterotrophic kinetic modeling in a “NIPHO” bioreactor

Abstract

This research analyzes the different amoxicillin (AMX) removal routes, i.e. biodegradation, biological absorption and adsorption, within a “NIPHO” activated sludge reactor treating urban wastewater. Moreover, the impact of different AMX concentrations (15−75 mg L−1) on the kinetic performance of the heterotrophic biomass was evaluated. The “NIPHO” bioreactor worked at 4.8 ± 0.7 h of hydraulic retention time, 20.9 ± 1.4 °C of temperature, and 2000 ± 120 mgTSS L−1 of mixed liquor total suspended solids. High Pressure Liquid Chromatography was used to evaluate AMX removal by the different pathways and a respirometric method was applied to model the heterotrophic kinetics in absence and presence of AMX. Additionally, a multivariable statistical analysis was carried out to determine the influence of the operation variables on the response of the system. The results showed that the removal of AMX was essentially carried out via biological absorption (11.06–87.13 %), and biomass concentration and sludge volume index were the most influential variables on it. Additionally, the study concluded that the heterotrophic biomass of the bioreactor was not significantly influenced by AMX, although the net heterotrophic biomass growth rate at 75 mg L−1 AMX concentration showed statistically significant differences with the rest of concentrations, and was reduced up to 8.84 mgVSS L−1 h−1.