Behavior of nine selected emerging trace organic contaminants in an artificial recharge system supplemented with a reactive barrier

Abstract

Artificial recharge improves several water quality parameters, but has only minor effects on recalcitrant pollutants. To improve the removal of these pollutants, we added a reactive barrier at the bottom of an infiltration basin. This barrier contained aquifer sand, vegetable compost, and clay and was covered with iron oxide dust. The goal of the compost was to sorb neutral compounds and release dissolved organic carbon. The release of dissolved organic carbon should generate a broad range of redox conditions to promote the transformation of emerging trace organic contaminants (EOCs). Iron oxides and clay increase the range of sorption site types. In the present study, we examined the effectiveness of this barrier by analyzing the fate of nine EOCs. Water quality was monitored before and after constructing the reactive barrier. Installation of the reactive barrier led to nitrate-, iron-, and manganese-reducing conditions in the unsaturated zone below the basin and within the first few meters of the saturated zone. Thus, the behavior of most EOCs changed after installing the reactive barrier. The reactive barrier enhanced the removal of some EOCs, either markedly (sulfamethoxazole, caffeine, benzoylecgonine) or slightly (trimethoprim) and decreased the removal rates of compounds that are easily degradable under aerobic conditions (ibuprofen, paracetamol). The barrier had no remarkable effect on 1H-benzotriazole and tolyltriazole.

Tracer test modeling for characterizing heterogeneity and local-scale residence time distribution in an artificial recharge site

“…The barrier comprises vegetable compost and aquifer sand in equal volumetric proportions and a very small fraction of clay and iron oxides. The vegetable compost aimed to release dissolved organic carbon into the infiltrating water to favor a broad range of redox conditions below the basin, thus increasing the diversity of microbial metabolic paths to enhance removal of organic contaminants (Li et al, 2013;Alidina et al, 2014;Valhondo et al, 2014Valhondo et al, , 2015. Clay and iron oxide were added to provide sorption sites for cationic and anionic organic compounds, respectively.…”

“…Clay and iron oxide were added to provide sorption sites for cationic and anionic organic compounds, respectively. Details on the barrier are provided by Valhondo et al (2014Valhondo et al ( , 2015.…”

“…Water quality is enhanced during passage through soil (Bouwer, 2002;Greskowiak et al, 2005) because the passage causes reduction not only in turbidity and suspended matter, but also in the concentrations of dissolved organic matter (Vanderzalm et al, 2006), nutrients (Bekele et al, 2011), pathogens , and some trace organic contaminants Hoppe-Jones et al, 2010;Valhondo et al, 2014Valhondo et al, , 2015. The appropriate management of artificial recharge systems requires an understanding of the fate of the potential contaminants.…”

“…To the best of our knowledge, however, no test has been performed for site-scale characterization. To this end, we performed a pulse injection test at the Sant Vicenç site (Barcelona, Spain;Valhondo et al, 2014Valhondo et al, , 2015 to obtain the RTDs by monitoring breakthrough curves.…”

Microbial community changes induced by Managed Aquifer Recharge activities: Linking hydrogeological and biological processes

“…Previous studies demonstrated that the reactive barrier enhanced the removal of some emergent contaminants, such as sulfamethoxazole or caffeine (Valhondo et al, 2014). More information about the site and the performance of the reactive barrier can be found in Valhondo et al (2014).…”