Removal of Toxic Materials From In Situ Tar Sand Process Water

Abstract

Process waters collected during a Department of Energy in situ tar sand extraction experiment near Vernal, Utah, were chacterized as having a high level of emulsified bitumen, exhibiting toxic prroperties and possessing low levels of inorganic constituents. Various coagulants were employed in an attempt to destabilize this emulsion. Ferric chloride was found to be most effective in that more than 98% of the emulsion was removed as total organic carbon (TOC) by this treatment and over 99% was removed as suspended solids. Increased toxicity levels were measured, however, in these treated effluents. Additional treatment by activated carbon adsorption removed these toxic components. Gas chromatography/mass spectrometry (GC/MS) analysis, using a modification of the U.S. Environmental Protection Agency (EPA) method 625, showed an estimated 2,000 compounds in the untreated process water. Coagulation reduced this to 72 identifiable components while activated carbon adsorption lowered this to six, including internal and recovery standards. GC/MS was unable, however, to identify a relatively significant series of materials shown to exist by TOC analysis which apparently had low vapor pressures and could not be analyzed by gas chromatography. The source or sources of the residual toxicity is assumed to be contained in these unidentified materials.