Managed aquifer recharge - a column study to disclose processes in reactive barriers

Managed aquifer recharge (MAR) holds the potential to be an attractive solution to ground- and drinking water deficits in many countries. Recently, reactive top layers such as mixtures with compost have been included in MAR infiltration areas. In order to get a better idea of the processes occurring in these reactive barriers, we simulated infiltration through sand-compost mixtures using laboratory columns. Our focus was on simultaneous removal of organic micropollutants and nitrogen species, with parallel monitoring of redox conditions and microbial community composition. A column setup with possibilities of depth specific sampling of water and sand-compost mixtures allowed for a detailed localisation of processes. During 17 weeks of operation, the columns were fed with synthetic wastewater. The development of microbial communities was monitored by Illumina amplicon sequencing of the 16S rRNA.