Variation of interception efficiency and transformation to natural glucocorticoids in three texture reclaimed water receiving riverbeds

Abstract

BackgroundThe efficacy of the interception and purification mechanism for low-dose toxic contaminants in riverbeds, which serve as a link between surface water and groundwater, is of paramount importance in ensuring groundwater safety, particularly considering the replenishment of reclaimed water. The specific objective of this work is to identify the variation of interception efficiency and transformation to natural glucocorticoids in three texture reclaimed water receiving riverbeds. MethodsHerein, an experimental percolation platform was set up to simulate hydrocortisone (HC) migration and biotransformation during the reclaimed water infiltration process through three typical types of riverbeds (silty clay (SC), loam (L) and sand (S)). Significant findingsThe attenuation of HC in time dimension and longitudinal direction was consistent with the two compartment first-order kinetic model, with decay rate constant greater than -0.031 m−1 and 2.71 d−1 in spatial and temporal distribution. The SC riverbed enhanced 36.36 % HC removal due to adsorption and microbial transformation. Furthermore, the major metabolic pathways of side chain oxidation and ring rupture were significantly enhanced due to the increasing diversity and relative abundance of the functional bacteria present in SC. The enrichment of functional genera, Stenotrophomonas and Sphingomonas contributed to the biotransformation enhancement. pH and TOC played the most significant role to the difference of migration and metabolism of HC. Moreover, pore volume was the primary factor leading to varying adsorption of three types of riverbeds for HC. The simulation results with HYDRUS showed that the ecological risk level of HC in L and S were 6.5 times higher than SC after 50 years infiltration. Therefore, future challenges and prospects concerning pollution control and enhancement measures should be pay attention to the physicochemical characteristics of various riverbeds.