Characterization of perchloroethene contamination associated with dry cleaning facilities
Spexet, AnnMarie Heather
Master of Science
Ten dry cleaning sites were evaluated in the Houston area. At the dry cleaning sites studied, the contamination may be attributed to deficiencies in the separation equipment of the dry cleaning equipment, allowing free phase perchloroethene (PCE) to enter the sanitary sewer lines and escape by permeating through the pipe, or through defects in the pipe. Three sites with different geologic characteristics were chosen for intensive study to examine if there exists a pattern of transformation of PCE to the daughter product trichloroethene (TCE) in the sites. Transformation is compared by calculating the ratio of PCE to TCE for each well for a single sampling event, and by modeling at one of the sites. One site was modeled with the model RT3D, and the results from the model confirm the change in PCE to TCE ratio as being a result of a change in the reaction rate. A pattern was noticed in the site data which sites with sandier hydrologies, as measured by hydraulic conductivity, tended to have lower transformation rates than sites with tighter formations. It is suggested that this difference in apparent reaction rate may be due to enhanced reaction in the tighter formations due to lack of oxygen recharge, leading to an anaerobic region that is conducive to reductive dechlorination.
Hydrology; Geochemistry; Sanitary and municipal engineering; Environmental science