All over the world, the groundwater in many central urban areas is contaminated, mostly as a result of (former) industrial activities. Regulatory stipulations and/or new uses of the areas might require that this groundwater be treated. Application of photolysis using UV radiation is potentially an effective manner of transforming the contaminants into substances which are more easily biologically degradable. In addition, aquifer thermal energy storage (ATES) systems are increasingly being installed in areas of this type which contain contaminated groundwater. By applying a combination of ATES and UV as a treatment technique, it may be possible, on the one hand, to treat the contaminated groundwater and, on the other, to promote efficient energy use.
Organic contaminants in (ground) water can sometimes be transformed, by means of photolysis, for example, through the application of UV radiation. This project studies whether a closed UV system can be combined with an ATES installation. In this way, it could be possible to decontaminate the groundwater non-intrusively and, at the same time, generate energy.
A UV reactor is incorporated into an existing ATES system. This installation is used to analyse the transformation of chlorinated organic contaminants and the circumstances under which this transformation occurs optimally. In addition, a mobile UV installation is set up at several monitoring wells, where other types and concentrations of contaminants occur. A literature review is also carried out to permit predictions of the impact of treating groundwater with UV radiation on the degradation processes in the soil, and of the possible formation of (potentially harmful) by-products.
The idea was, while an ATES installation generated energy from contaminated groundwater, to decontaminate the water by breaking down and transforming the contaminants into harmless or more easily biodegradable substances through the use of photolysis. Unfortunately, the photolysis of the contaminants occurring at the test locations only resulted in the limited degradation of the substances. Apparently, this technology is not an efficient means of decontaminating groundwater with relatively small chlorinated hydrocarbons.