Enhancing the removal of contaminants of emerging concern from wastewater effluents using recharge-dependent soil aquifer treatment with reactive barriers

Soil-Aquifer Treatment (SAT) systems are a sustainable option for improving wastewater quality and addressing freshwater scarcity. This study assessed how recharge operation (continuous vs. pulsed) and reactive barriers of natural organic materials influence contaminants of emerging concern (CECs) removal from treated wastewater effluents. Our results demonstrate that continuous recharge enhances SAT system performance, achieving CECs removal efficiencies up to 58% in woodchip barriers and 35% in compost barriers, compared to 20-25 % under pulsed recharge. Reactive barriers promoted microbial activity by releasing labile DOC, generating redox gradients, and supporting both adsorption and biodegradation processes. Pulsed recharge led to temporary CECs release although further removal occurred along the aquifer. Low molecular weight, polar, aromatic and readily biodegradable CECs were efficiently removed, while nonpolar and chemically stable compounds showed lower removal or accumulation. Physicochemical factors such as pH (6.8-7.8), oxygen availability, and ionic composition strongly influenced treatment outcomes. The use of locally available, low-cost materials such as woodchips and vegetable compost as reactive barriers, combined with passive SAT operation, supports the system's cost-effectiveness.