Introducing sequential managed aquifer recharge technology (SMART) – From laboratory to full-scale application

Abstract

Previous lab-scale studies demonstrated that stimulating the indigenous soil microbial community of groundwater recharge systems by manipulating the availability of biodegradable organic carbon (BDOC) and establishing sequential redox conditions in the subsurface resulted in enhanced removal of compounds with redox-dependent removal behavior such as trace organic chemicals. The aim of this study is to advance this concept from laboratory to full-scale application by introducing sequential managed aquifer recharge technology (SMART). To validate the concept of SMART, a full-scale managed aquifer recharge (MAR) facility in Colorado was studied for three years that featured the proposed sequential configuration: A short riverbank filtration passage followed by subsequent re-aeration and artificial recharge and recovery. Our findings demonstrate that sequential subsurface treatment zones characterized by carbon-rich (>3 mg/L BDOC) to carbon-depleted (≤1 mg/L BDOC) and predominant oxic redox conditions can be established at full-scale MAR facilities adopting the SMART concept. The sequential configuration resulted in substantially improved trace organic chemical removal (i.e. higher biodegradation rate coefficients) for moderately biodegradable compounds compared to conventional MAR systems with extended travel times in an anoxic aquifer. Furthermore, sorption batch experiments with clay materials dispersed in the subsurface implied that sorptive processes might also play a role in the attenuation and retardation of chlorinated flame retardants during MAR. Hence, understanding key factors controlling trace organic chemical removal performance during SMART allows for systems to be engineered for optimal efficiency, resulting in improved removal of constituents at shorter subsurface travel times and a potentially reduced physical footprint of MAR installations.

Advancing Sequential Managed Aquifer Recharge Technology (SMART) Using Different Intermediate Oxidation Processes

“…Wiese et al [32] confirmed degradation under oxic conditions for diclofenac of >90%, whereas Rauch-Williams et al [18] reported a faster removal under anoxic conditions. Our findings are in accordance to Regnery et al [20], who proposed no complete removal of diclofenac during a short riverbank filtration but a rapid transformation in the second filtration step after reaeration.…”

“…After re-aeration of the extracted water, carbon-depleted and oxic conditions can be maintained in the subsequent subsurface filtration system. This approach was successfully demonstrated at the full-scale MAR facility Prairie Waters Project (Aurora, CO, USA) showing enhanced biodegradation of various TOrCs (e.g., caffeine, diclofenac, dilantin, gemfibrozil, meprobamate, and naproxen) compared to single-stage conventional riverbank filtration [20].…”

“…Previous studies have revealed that degradation of TOrC is more favorable under oxic and carbon depleted conditions represented by a low biodegradable dissolved organic carbon (BDOC) content [14][15][16][17][18][19]. The coupling of two MAR systems with an intermediate aeration step, as established by the sequential managed aquifer recharge technology (SMART) [20], was designed to provide these favorable conditions in the second infiltration system. In the first infiltration step of SMART (mimicking conventional riverbank filtration systems), easily biodegradable DOC is quickly consumed, usually resulting in complete oxygen depletion and prevailing anoxic conditions.…”

Artifisial replenishment of the deep aquifers

“…It should be mentioned, that artificial recharge of aquifers of the insufficient quality of pumped water may lead to increase the mobilisation of different pollutants in the unsaturated zone and reduce groundwater quality [4,10].…”

“…The Italian project WARBO aims at facilitating the artificial recharge regulation in Italy by testing its application to mitigate the groundwater level drop in the Mereto site where the unused surplus surface water, which is usually lost during the winter-spring season, is utilized [2]. These area of research are very popular in different parts of the world, such as in Russia, Australia, Europe [2][3][4], Asia [1,[5][6][7][8], America [9,10] etc. [11,12].…”