Field Testing Solar Photocatalytic Detoxification of TCE-Contaminated Groundwater

The Solar Detoxification Field Experiment was designed to investigate the photocatalytic decomposition of organic contaminants in groundwater at a Superfund site at Lawrence Livermore National Laboratory. The process uses ultraviolet (UV) energy available in sunlight in conjunction with a photocatalyst, titanium dioxide, to decompose organic chemicals into nontoxic compounds. The destruction mechanism, as in many other advanced oxidation processes, involves hydroxyl radicals. The field experiment was developed by three federal laboratories: the National Renewable Energy Laboratory, Sandia National Laboratory, and Lawrence Livermore National Laboratory. The United States Department of Energy funded the experiment. Groundwater at the test site was contaminated with trichloroethylene (TCE). A factorial test series examined four separate process variables: pH, catalyst loading, flow velocity, and solar intensity. Lowering the pH from pH 7 to pH 5 had the largest single effect, presumably by minimizing interference by bicarbonate. The catalyst was found to operate more efficiently at low, e.g. ambient sunlight, UV light levels. Information from these field tests suggest that treatment costs for the solar process would be similar to those for more conventional technologies.