Environ. Sci. Technol. 1985, 19, 992-997
Organic Emissions from Shale Oil Wastewaters and Their Implications for Air Quality Steven B. Hawthorne,?Robert E. Slevers," and Robert M. Barkley Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309
rn The emission of organic compounds from shale oil wastewaters used to cool hot, retorted, spent oil shale and for codisposal with retorted shale was investigated. The major classes of compounds emitted are aromatic nitrogen-containing compounds, ketones, phenols, and nitriles, the same as those previously reported to be emitted from wastewaters exposed to air at room temperature. A gasstripping method was modified to allow the determination of several Henry's law constants simultaneously. Measured values of H for these solutes in the wastewaters (104-10-s atm m3mol-l) generally agreed with values determined for solutes in pure water, indicating that the wastewater matrix has little effect on H. Air samples collected in regions likely to be affected by atmospheric emissions from the shale oil industry had no detectable levels of the major organic species that are emitted from shale oil wastewaters, indicating that these species may be useful in tracing pollutant air masses resulting from shale oil production.
Introduction The retorting of oil shale to release oil produces several waste products, particularly spent shale, the material remaining after retorting, and shale oil process wastewaters, that will require control and disposal in an environmentally acceptable manner (1-6). Relatively little is known about the volatilization of organic compounds from shale oil wastewaters during storage, treatment, and disposal. The emission of atmospheric pollutants is of particular concern since the pristine mountain areas (including several wilderness areas protected by Federal Class I clean air status) downwind of the shale oil producing regions may be extremely sensitive to impacts from the emission of particulates, acid rain precursors, and organic species. We have previously reported the types and quantities of organic species that are volatilized from shale oil wastewaters exposed to large amounts of air at room temperature (7). Three process retort waters and three gas condensate waters all emitted similar proportions of the same classes of organic compounds, including aromatic nitrogen-containing species such as alkylpyridine isomers, phenols, ketones, and nitriles. Several of these species have noxious odors that also may degrade the air quality in the region. Although final plans for handling the wastewaters have not been made public, two major reuse and disposal options for shale oil wastewaters are for cooling hot spent shale as it leaves the retort and for codisposing,Le., mixing, with spent shale for ultimate disposal in open beds. As spent shale at 400-500 OC leaves a retort, it will be cooled to approximately 80 OC for final disposal. Although waste heat from a retort may be used to generate steam or to preheat incoming shale, it is likely that wastewaters will be used extensively to cool the spent shale. After being cooled, spent shale will be mixed with approximately 14-20% wastewater and disposed in open fields (8-10). Several environmentally significant consequences may t Present address: University of North Dakota Energy Research Center, Grand Forks,ND 58202.
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result from these reuse and disposal options. Chemical changes in the organic solutes may occur at the surface of hot spent shale, contact with hot surfaces may cause increased volatilization of organic solutes, and the spent shale surface may act as a sorbent or ion-exchange medium for organics, thus preventing some of the volatile organic species from being emitted. In the present investigation we have determined the types and quantities of organic compounds that are volatilized from and chemical changes which occur in untreated shale oil wastewaters that are exposed to high temperatures and potentially reactive surfaces. Thermodynamic properties such as the Henry's law constants (H) of volatile solutes are useful for determining their emission rates from water bodies open to the atmosphere (11-17 ) ,for designing the stripping apparatus used for water treatment (It?), and for calculating the solubility of a volatile species in a particular wastewater matrix (19). We have developed methodology to allow the simultaneous measurement of several Henry's law constants for volatile organic solutes found in shale oil wastewaters and to determine the effect that the wastewater matrix has on measured values of H. Previous work has shown that the major classes of organic compounds (particularly the nitrogen-containing organic species) that are released into the atmosphere from shale oil wastewaters are generally not detectable in urban air samples and are not reported to be emitted from gasoline- and diesel-powered vehicles (7,20,21). The unique sources of these organic species may make these compounds useful as tracer species for the assessment of the impact of oil shale retorting upon local air quality. This study reports the identities and concentrations of background organic species present in the air of the oil shale region and in air of nearby pristine areas before any major retorting operations begin.
Sample Description The collection and storage of gas-condensate and process retort water from test run 20 of the experimental 150-ton retort at the University of Wyoming Research Corp. (formerly Laramie Energy Technology Center) has been described previously (7). All of the necessary conventional precautions were taken to reduce losses of volatile constituents. The pH of the gas condensate and process retort waters were 9.1 and 8.8, respectively, and the dissolved organic carbon (DOC) concentrations were 600 and 2100 mg/L, respectively. A random sample of spent shale from the same retorting run was also collected. The spent shale was crushed to
