Low-temperature Aquifer Thermal Energy Storage combined with in situ bioremediation of chlorinated ethenes: Pilot-scale observations and model-based interpretation.

Microbial reductive dechlorination is a key process in aquifers contaminated with chlorinated ethenes and results in a net mass reduction of organic pollutants. Biodegradation rates in the subsurface are temperature-dependent and may be enhanced by increased groundwater temperatures. This study explores the potential of combining the temperature increase from low-temperature Aquifer Thermal Energy Storage with In Situ Bioremediation (ATES-ISB).

Managing the remediation strategy of contaminated megasites using field-scale calibration of geo-electrical imaging with chemical monitoring.

Groundwater contamination is a threat to drinking water resources and ecosystems. Remediation by injection of chemical reagents into the aquifer may be preferred to excavation to reduce cost and environmental footprint. Yet, successful remediation requires complete contact between contamination and reagents.

Assessment of chlorinated ethenes degradation after field scale injection of activated carbon and bioamendments: Application of isotopic and microbial analyses.

Over the last decade, activated carbon amendments have successfully been applied to retain chlorinated ethene subsurface contamination. The concept of this remediation technology is that activated carbon and bioamendments are injected into aquifer systems to enhance biodegradation. While the scientific basis of the technology is established, there is a need for methods to characterise and quantify the biodegradation at field scale.

Solubility and reactivity of surfactant-enhanced alkaline hydrolysis of organophosphorus pesticide DNAPL.

The study presented in this paper evaluated the effectiveness of surfactants in enhancing mass removal of organophosphorus pesticides (OPPs) from soil under highly alkaline conditions and potential for enhancing in situ alkaline hydrolysis for treatment of OPPs, particularly parathion (EP3) and methyl parathion (MP3). In control and surfactant experiments, hydrolysis products EP2 acid, MP2 acid, and PNP were formed in non-stoichiometric amounts indicating instability of these compounds. MP3 and malathion were found to have faster hydrolysis rates than EP3 under the conditions studied.

The influence of cosolvent and heat on the solubility and reactivity of organophosphorous pesticide DNAPL alkaline hydrolysis.

The presented research concerned the compatibility of cosolvents with in situ alkaline hydrolysis (ISAH) for treatment of organophosphorous (OPP) pesticide contaminated sites. In addition, the influence of moderate temperature heat increments was studied as a possible enhancement method. A complex dense non-aqueous phase liquid (DNAPL) of primarily parathion (~50 %) and methyl parathion (~15 %) obtained from the Danish Groyne 42 site was used as a contaminant source, and ethanol and propan-2-ol (0, 25, and 50 v/v%) was used as cosolvents in tap water and 0.

Development of a spectrophotometric method for on-site analysis of peroxygens during in-situ chemical oxidation applications.

Activated peroxygens are frequently used as active agents in in-situ chemical oxidation (ISCO) contaminated site remediation applications, and fast and simple quantitative analysis of these species on site is necessary. In this work, the use of a spectrophotometric method based on classic iodometric titration is studied for quantitative analysis of S2O8(2-) and H2O2. Instead of a back-titration step, the absorbance of the yellow iodide colour was measured at 352 nm in the presence of a bicarbonate buffer.

Influence of chloride and carbonates on the reactivity of activated persulfate.

Chloride and carbonates have the potential to impact pathway, kinetics, and efficiency of oxidation reactions, both as radical scavengers and as metal complexing agents. Traditionally, it is assumed that they have an overall negative impact on the activated persulfate performance. This study investigated the influence of carbonates and chloride on the reactivity of persulfate for three different activation techniques to produce reactive free sulfate radicals; heat, alkaline and iron activation.

Mobilization of metals during treatment of contaminated soils by modified Fenton's reagent using different chelating agents.

Changes in pH and redox conditions and the application of chelating agents when applying in situ chemical oxidation (ISCO) for remediation of contaminated sites can cause mobilization of metals to the groundwater above threshold limit values. The mechanisms causing the mobilization are not fully understood and have only been investigated in few studies. The present work investigated the mobilization of 9 metals from two very different contaminated soils in bench and pilot tests during treatment with modified Fenton's reagent (MFR) and found significant mobilization of Cu and Pb to the water in mg/l levels.