The Behavior Of17α-Ethinyl Estradiol And4-n-Nonylphenol In Soil By Groundwater Recharge With Reclaimed Water

With water crisis, excessive extraction of groundwater and other problemsintensifying, groundwater recharge by recycled water will play a more and moreimportant part. Most pollutants in recycled water can be removed by the soilaquifer. However, the fate of endocrine disrupting chemicals (EDCs) that hasbeen frequently reported to have low toxicological threshold value and highhealth hazards, is still not clear. This paper selected two typicalEDCs-17α-Ethinyl Estradiol (EE2) and4-n-Nonylphenol (NP), studied theadsorption and desorption in the soil and minerals, biodegradation in the soil,migration and transformation process of them in the recycled water rechargingprocess by the soil column, focusing on two conditions of influentwith low andand high concentration of EDCs.Studies have shown adsorption and degradation were the main mechanismof EDCs’ reduction in groundwater recharge. The adsorption of EE2and NP inthe soil was mainly physical adsorption and the adsorption rate of NP was2.0~4.7times of EE2. The adsorption capacity of NP was generally higher than EE2.Evident positive correlation was found between saturated adsorption capacityand organic matter content in the soil. There were desorption hysteresises ofEE2and NP in several soils and minerals and the desorption hysteresis of NPwas more evident than EE2.The degradation of EE2and NP in soil were well fitted with the first orderkinetics, the the half-life of EE2and NP were0.19~7.56d and0.16~16.58d,respectively. Moisture content, the content of EDCs, carbon sources andnitrogen sources could significantly affect the biological degradation of EE2and NP in the soil, in order of content of EDCs> moisture content> carbonsources> nitrogen sources for EE2and nitrogen sources> the content of EDCs>carbon sources> moisture content foe NP. Applied carbon and nitrogen sourcescould promote the degradation of EE2and NP and inorganic nitrogen in form ofammonium nitrate may be the promoting factors, while lactamine may serve asinvalid nutriment during biodegradation of EE2and NP. Column study showed that,during the83d of recharging by recycled waterwithout spiked EDCs, the concentration of EE2in effluent of each column wasbelow0.2ng/L, and concentration of NPwas lower than3ng/L and E2equivalent was below6ng/L. After183dof recharge by recycled water with10μg/L EE2and NP, it was found that the EDCs began to migrate downward, inthe average rate of1.66~6.38cm/d and0.632~0.636cm/d for EE2and NP,respectively.in sterilized soil column treatments the EDCs migrated verticalmore significantly. The migration rate of EE2and NP in constructed soil columnwere lower than natural sand column, which showed lower migration velocitythan sterilized sand column, demonstrating the importance of biodegradation byvadose zone in removal of EDCs.This research analyzed the transport and transformation of EE2and NP inGroundwater recharge and may benefit the prevention of groundwaterpollutionby EDCs.