Migration and biotransformation of three selected endocrine disrupting chemicals in different river-based aquifers media recharge with reclaimed water

When using reclaimed water for the river-based artificial groundwater recharge, endocrine disrupting chemicals (EDCs) pollution is believed to be a potential threat to the drinking water supplies in Beijing, China. Lab-scale column experiments simulating recharge were conducted to study the migration and transformation of three selected EDCs, namely ethinylestradiol (EE2), 4-n-Nonylphenol (NP) and bisphenol A (BPA). The filler media of the two columns mainly consisted of fine sand (FS) in the middle section and less-permeable silty clay (SC) in the southern section, all representative soil vadose zone media from Chaobai river in Beijing. The results showed that the attenuation effect of EDCs was in the order of NP > EE2 > BPA and all of them followed a first-order kinetics, while the migration capacity was in the reverse order. The residual EDCs in different depths of SC were much higher than those in FS, suggesting that the SC soil has a significantly higher adsorption capacity. The attenuation effect of NP and BPA by unit mass was better in FS than that in SC, indicating that the biodegradation was the main attenuation mechanism. The bacterial biomass and community diversity decreased with depth in SC, while the changes in FS were unobvious. According to the DGGE fingerprints, the bacterial community in the middle layer was more diverse than in the upper layer, which was related to the EDCs concentrations and transformation products in the water-soil system. The dominant group was found to be proteobacteria, including Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria, suggesting that these microbes might play an important role in EDC transformation. The described process provides a potential pathway for improving the removal of EDCs.