The role of microbial adaptation and biodegradable dissolved organic carbon on the attenuation of trace organic chemicals during groundwater recharge Christiane Hoppe-Jones, Eric R.V. Dickenson, Jörg E. Drewes ⁎ Advanced Water Technology Center (AQWATEC), Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401-1887, USA HIGHLIGHTS ► Attenuation of biodegradable trace organic chemicals (TOrC) requires biodegradable DOC and sufficient adaption. ► Adapted MAR systems that are fed with low BDOC levels performed better with respect to TOrC biotransformation. ► MAR facilities that are microbiologically active and are fed with highly treated water can still attenuate TOrC. abstract article info Article history: Received 17 March 2012 Received in revised form 1 August 2012 Accepted 2 August 2012 Available online xxxx Keywords: Adaptation Biodegradable dissolved organic carbon Managed aquifer recharge Pharmaceutical residues Pesticides Potable reuse It is widely recognized that efficient biological attenuation of bulk organic matter and trace organic chemicals (TOrC) can occur in managed aquifer recharge (MAR) systems receiving reclaimed water. The heterotrophic microbial activity in these subsurface systems is a function of the availability of biodegradable dissolved or- ganic carbon (BDOC) present in reclaimed water. This study examined the influence of environmental factors, such as BDOC-rich (>1.6 mg/L) and BDOC-starving (b 1 mg/L) conditions and microbial adaptation, on the attenuation of TOrC, including clofibric acid, dichlorprop, gemfibrozil, ibuprofen, ketoprofen, mecoprop, and naproxen, within soil-columns mimicking groundwater recharge. Under conditions that were character- ized by a lack of BDOC and a biocommunity that was not yet adapted to these conditions, attenuation of bio- degradable TOrC was less than 15%. After a three-month adaptation period, biotransformation increased to more than 80% for the biodegradable TOrC. This suggests that adaptation likely initiates enzyme expressions that eventually results in TOrC transformations even under seemingly less favorable conditions (i.e., lack of biodegradable carbon). For both non-adapted (stressed) and adapted conditions in the presence of higher concentrations of BDOC and travel times of 7 days, the degree of biotransformation was variable across com- pounds but generally exceeded 25%. This suggests that BDOC above a minimum level (>1.6 mg/L) can pro- vide favorable microbial conditions resulting in TOrC removal, even for non-adapted systems. However, it is noteworthy that adapted MAR systems that were fed with low BDOC levels performed similarly or better with respect to TOrC biotransformation than systems that received BDOC levels above 1.6 mg/L. These find- ings are important for field-scale applications. They suggest that MAR facilities that are microbiologically ac- tive and are fed with highly treated water with effluent concentrations of less than 1 mg/L (i.e., nanofiltration permeate) can still attenuate biodegradable TOrC. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Trace organic chemicals (TOrC), such as pharmaceutical residues, per- sonal care products, endocrine disrupting compounds, or emerging disinfection by-products, have been detected in wastewater effluents (Dickenson et al., 2011; Ternes, 1998; Tixier et al., 2003; Ying et al., 2009) and impaired surface water sources (Glassmeyer et al., 2005; Heberer et al., 1998; Tixier et al., 2003). Some of these compounds have been linked to potential adverse effects regarding human health and aquatic life (Lee et al., 1996; Mitch et al., 2003; Vajda et al., 2008). Managed aquifer recharge (MAR) systems, such as riverbank filtration (RBF) and soil-aquifer treatment (SAT), can provide attenuation of many of these TOrC (Drewes et al., 2003; Grünheid et al., 2005). MAR systems are characterized as multi-objective and low carbon-footprint treatment processes that could either substitute above-ground treat- ment systems or be employed in conjunction with engineered water treatment processes. However, the lack of process understanding and predictable performance of these systems is, besides other factors, hindering their widespread utilization as an alternative water treat- ment process. With respect to TOrC, previous research has identified that adsorption, biotransformation, and dilution are the most impor- tant attenuation mechanisms during subsurface treatment (Kühn and Müller, 2000; Rauch-Wiliams et al., 2010). However, the environmental Science of the Total Environment 437 (2012) 137–144 ⁎ Corresponding author. Tel.: +1 303 273 3401. E-mail address: jdrewes@mines.edu (J.E. Drewes). 0048-9697/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2012.08.009 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv