Treatability of Contaminated Ground Water and Aquifer Solids at 'Town Gas" Sites, Using Photolytic Ozonation and Chemical In Situ Reclamation

The feasibility of cleaning up contaminated ground water and aquifer solids from so-called "town gas" sites using photolytic ozonation and chemical in situ aquifer reclamation (CISR) techniques was investigated in the laboratory. At the actual site, coal was thermally oxidized to produce methane for municipal distribution. The degradation left a coal tar which, if released into the ground,could contaminate ground water and aquifer solids with a number of organic substances, including aromatic hydrocarbons such as benzene, toluene, xylene (BTX) , and polynuclear aromatic hydrocarbons (PAHs) at environmentally significant concentrations. Photolytic ozonation was used to destroy BTX and PAHs in ground-water samples taken from the Taylorville "town gas" site, using a stirred- tank reactor in the laboratory. Ozonation was found to be as effective as ozone/UV for this treatment. This is often seen in natural waters, and it is thought to be due to the presence of natural "promoters" for the free-radical reactions that are largely responsible for the destruction of organic compounds during treatment. Estimated treatment costs were $4.05 per thousand gallons (Kgal) for destruction of BTX and PAHs by ozonation, and $2.57 per Kgal if the BTX was removed by air stripping prior to ozone treatment. A chemical in situ treatment method using persulfate as a source of free radicals destroyed organic contaminants that were adsorbed to the aquifer solids. PAHs were reduced by 34 percent after 12 days of treatment and by 52 percent after 40 days. Preliminary evidence suggests that mobilization of contaminants by· oxidation of the natural and/or adsorbed organic matter associated with the solids may be important.