OPTIMIZATION OF SOIL CONDITIONS FOR BIOREMEDIATION IN CHEMICALLY PRETREATED SOILS: SITE CHARACTERIZATION Nora B. Sutton 1* Tim Grotenhuis 1 Huub Rijnaarts 1 1 Wageningen University, Department of Environmental Technology NL-6703 HD, The Netherlands * Corresponding Author: N.B. Sutton, PhD student, Wageningen University, Department of Environmental Technology, PO Box 8129 NL-6700 Wageningen, The Netherlands Nora.Sutton@wur.nl Tel: +31 317483339 Fax: +31 317482108 Abstract Recent focus of remediation of contaminated subsurface and groundwater with organic compounds has shifted towards in situ based strategies, such as in situ bioremediation and in situ chemical oxidation (ISCO). The coupling of these two techniques into an efficient and effective technology requires further investigation into the optimization of bioremediation in chemically pretreated soil. To this end, a sampling trip to Węgliniec, Poland, a site within the EU consortium Upsoil, was planned and executed, as described here. Sampling locations at the site were chosen by integrating previous site investigations with the experimental setup and scientific goals of this project. By taking into consideration the influence of the type of field material on the relevancy of the experimental results, sampling was performed to ensure that findings from this project will be general conclusions transferable to a variety of sites requiring remediation. Keywords: site characterization, sampling strategy, subsurface contamination, remediation, in situ chemical oxidation, bioremediation Introduction Subsurface and groundwater contamination of xenobiotic organic compounds has created a large international market for remediation of these polluted sites valued at US$ 50-60 billion [1]. Conventional ex situ and on site technologies are being replaced by in situ techniques, where degradation of contaminants is contained within the subsurface [2]. In situ bioremediation and, more recently, in situ chemical oxidation (ISCO) are arguably the most commonly used in situ treatments, which provide rapid and cost effective remediation under a variety of subsurface conditions in combination with various contaminant types. ISCO is a remediation technology designed to rapidly remove pure product within the source zone area of a polluted site [3, 4]. In the course of a treatment, oxidants such as hydrogen peroxide (Fenton’s Reagent), permanganate, persulfate or ozone, are pumped into the subsurface to chemically remove contaminants. Chemical oxidation of a variety of contaminants has been observed, including removal of petroleum derived hydrocarbons [5, 6], polyaromatic hydrocarbons (PAH) [7-9], and chlorinated hydrocarbons [10-12]. Although ISCO is a versatile technology, chemical oxidation is ill-suited for areas outside of the source area. In situations in which the pollutant is dispersed, oxidation of soil organic matter consumes a larger fraction of chemicals than when pure product is present. Rather, bioremediation, although a lengthier overall process, is more appropriate for the plume. As opposed to the source area, lower contaminant concentrations in the plume do not impede biodegradation [1]. Both natural attenuation as well as biostimulation with electron acceptors or nutrients are effective remediation strategies for a variety of contaminant types [13-18]. The combination of chemical oxidation with bioremediation could provide an effective cleanup strategy able to remediate both the source and plume areas of a contaminated site. Although the oxidative stress associated with ISCO treatments is initially detrimental to the microbial population [19-21], work indicates that bacterial populations do regenerate degradation ability [22-24]. In many cases, chemical pretreatment improves bioremediation through decreasing contaminant concentrations to less toxic levels [25] and increasing biodegradability