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

Abstract

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.

This research was supported by the Spanish Research Agency (AEI) and Water-JPI (Project MARadentro, PCI2019-103603), European Union NextGenerationEU/PRTR through the program RyC2023 MICIU/ AEI/10.13039/501100011033 and project CONMIMO (TED2021- 131188B-C31), and the Generalitat of Catalonia (AGAUR-2021 SGR00753 and SGR00609). Authors are also grateful to Consorci d’Aigües Costa Brava Girona (CACBGi).

Peer Reviewed

Postprint (author's final draft)