Engineering of managed aquifer recharge systems to optimize biotransformation of trace organic chemicals

Managed aquifer recharge (MAR) systems provide effective removal of many water contaminants including suspended solids, organic matter, pathogens, and numerous trace organic chemicals (TOrCs). TOrC removal is primarily driven by biotransformations performed by subsurface microbial communities. However, variable extents of TOrC biotransformation have been reported across MAR systems. This review discusses major parameters affecting the biotransformation of TOrCs and summarizes recent efforts to enhance its efficiency in MAR systems. Approaches to enhance biotransformation of TOrCs during MAR include optimization of environmental conditions (redox conditions, substrate availability), inoculation of specific TOrC degraders and stimulation of degrader activity by providing growth substrates or co-factors. While concepts to optimize environmental conditions have been tested at different scale, inoculation and biostimulation approaches were mostly tested as a means to remove contaminants in biologically active sand filters or for the remediation of contaminated groundwater. Their application in MAR systems needs further research.