Assessment of the environmental fate of endocrine disrupting chemicals in rivers

Highlights: • Biotransformation rates of EDCs are faster under oxic than reduced oxygen conditions. • Oxygen presence greatly affects EDCs' degradation pathway in river environment. • EDCs are removed from water through sorption and biodegradation in oxygen presence. • Bisphenol A biodegraded faster than triclosan and nonylphenols under oxic conditions. Laboratory tests were conducted with five endocrine disruptors (bishenol A, triclosan. nonylphenol, nonylphenol monoethoxylate and nonylphenol diethoxylate) under different redox conditions (aerobic, anoxic, anaerobic and sulfate-reducing conditions) to assess abiotic and biotic degradation in a river water/sediment system. The river water sample was collected from Spercheios River while the sediment was collected from the banks of a tributary of the river at the point where the discharge point of a wastewater treatment plant is located. To describe quantitatively elimination kinetics of the target compounds, pseudo first-order kinetics were adopted. According to the results from the microcosms studies, it can be stated that the substances are eliminated from the aqueous phase with relatively high rates under aerobic conditions due to both sorption and biotransformation processes. However, when reduced oxygen conditions were established in the microcosms incubations, biotransformation decreased, indicating the almost complete cease of the EDCs microbial degradation, while substances' sorption onto sediments showed no significant differences. All compounds were found to be biodegradable under aerobic conditions, and the low to high order of the calculated dissipation rate constants was 0.064 ± 0.004 d⁻¹ (TCS) → 0.067 ± 0.006 d⁻¹ (NP) →0.076 ± 0.009 d⁻¹ (NP2EO) → 0.081 ± 0.007 d⁻¹ (NP1EO) → 0.103 ± 0.011 d⁻¹ (BPA). Finally, regarding the biotransformation experiments, the elimination of the compounds limited in the absence of oxygen as compared to aerobic.