University of Illinois at Urbana-Champaign. Water Resources Center
Abstract
The cleanup of ground-water resources which have been contaminated by anthropogenic organic compounds is difficult and expensive. Furthermore, most treatment methods merely transfer the contaminant to another phase, such as an adsorbant or the atmosphere. A treatment process which produces harmless by-products, could be set up on-site, and does not require the transport of hazardous materials is very desirable for such cleanup operations. Photolyticozonation, the combination of ozone treatment and ultraviolet irradiation, is an oxidative water treatment process which is capable of convert ing virtually any organic pollutant completely to carbon dioxide and water. Thus, it is potentially a very "clean" solution to many contamination problems. There has, however, been disagreement in the scientific literature concerning the effectiveness of the process, due largely to a lack of understanding of the chemistry which is involved. In this project, photolytic ozonation was studied at the laboratory scale, to better understand and, if possible, model the complex chemical reaction mechanism, so that the process can be more easily optimized from an economic stand point. It was shown that hydroxyl radical, the active species responsible for the destruction of organic pollutants, is not generated directly by ozone photolysisas has generally been speculated, but is produced by secondary reactions. A model has been developed which explains the behavior of the process under a variety of conditions and is useful for the prediction of process performance. The model includes parameters, the values of which may be inferred from the chemical structure of the organic pollutant. The reaction system is seen to be "versatile" in that it has alternate pathways by which pollutant destruction may proceed, depending on conditions in the water being treated.U.S. Department of the InteriorU.S. Geological Surve
