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WWRC 90-08
Oil Shale Process Water Evaporation


The primary objectives of this research program were to study chemical, microclimatological, and interactive effects on the evaporation of low-quality oil shale process wastewaters to develop more applicable evaporation models and evaporation design criteria for the disposal of oil shale process waters and to analyze the processes associated with the release of potentially toxic emissions from these low-quality effluents. The research program incorporated field and laboratory studies analyzing microclimatic and chemical effects on the evaporation of oil shale process wastewaters.

Field studies at Laramie, Wyoming were designed to continuously monitor microclimatological conditions and the evaporation from three low-quality effluents using Class A evaporation pans. Fresh water evaporation was monitored as a control. Process waters were routinely monitored for concentrations of organic and inorganic constituents. Laboratory studies were designed to isolate and describe significant climatic, chemical, and interactive effects on evaporation rates. Results from the above studies were utilized to develop a regression model to predict evaporation from these low quality effluents. This model was then compared to commonly utilized models to estimate evaporation. A stochastic model was developed using a first order markov process to generate 1000 20-year climatological records. Mass balance techniques were then used to evaluate the new data sets for evaporation processes and determine critical design parameters for evaporation disposal ponds. Laboratory studies were conducted to determine significant effects on the Henry's Law Constant for eight organic compounds in two process waters. Henry's Law Constant is a necessary component to estimate or model the emission of organics from these low quality effluents.

Results of the research program indicate that oil shale process water evaporation is not significantly changed by oil shale water chemical composition or concentration from that of fresh water. However, the regression model developed specifically contains five climatic and six chemical variables which were significant in affecting the overall oil shale process water evaporation rate. Key impoundment design parameters were found to be the pond depth and the total allowable input of process water. Even using conservative estimates for a full scale oil shale operation, extremely large areas (1,000+ acres) will be required of industry for disposal of oil shale process waters by evaporation. The emissions research indicated that Henry's Law Constant values are extremely dependent upon temperature and the specific chemical composition of the oil shale process water and in. order for the emission rates of a given compound to be accurately estimated for an oil shale process water, the Henry's Law Constant must be determined for each specific water and at expected disposal water temperatures of the process water.

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