Enhancement of biodegradation of dichlorodiethyl ether by pre-oxidation

Wastewater from chemical manufacturing plants often contains hazardous xenobiotic (man made) compounds whose discharge into municipal treatment systems is prohibited because these compounds can persist in biological treatment systems and pass through to the effluent or absorb to the biosolids without any transformation. Some of these compounds, can upset the biological process through toxicity. Dichlorodiethyl ether (DCDE) is such a compound. DCDE is widely used in the United States in the manufacture of pesticides and pharmaceuticals, as a solvent and cleaning fluid, as a constituent of paints and varnishes, and in the purification of oils and gasoline. DCDE is non-biodegradable in conventional biological treatment systems (Lewis, 1991). It is reactive, flammable, a mutagen and a probable carcinogen. Its inhalation can cause central nervous system depression (Agency for Toxic Substances and Disease Registry [ATSDR], 1989). Because of these properties, DCDE is present on the "Toxic Substances" list and the "Community Right to Know" list. The objective of this study was to examine the feasibility of enhancing biodegradability through the pre-oxidation. The oxidation processes applied in this study were ozonation. Biodegradability was examined at different oxidation levels of DCDE: 25, 50, 75 and 100 %. The amount of non-oxidized DCDE was confirmed by gas chromatography, while total organic carbon (TOC) was used as surrogate parameters for oxidation products and the remaining DCDE, Activated sludge cultures were grown in steady-state conditions in our laboratories as non-acclimated or acclimated to DCDE, and were used in our experiments to test the biodegradability of oxidized DCDE solutions. The results indicated that the biodegradability of pre-oxidized DCDE solutions improved very significantly compared to non-oxidized solutions. The best degradation rate was at 75% oxidation of DCDE. There was no statistical difference in the rate of biodegradation of oxidized products by either acclimated or non-acclimated bacteria. These results are the first to show that DCDE can be degraded by an integrated treatment scheme of sequential chemical and biological oxidation processes.