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<br />r.... <br />en <br />1-" <br /> <br />, ., <br />-'. <br /> <br />1.3 Conclusions - ~odified In Situ Re~or~inq of Oil Shale <br />Two major water treatment and disposal problems present the~selve5 in the <br />modified in situ retorting of oil shale in the Pice~~ce Creek Basin of Colorado. <br />The first is L~e treatment of large quantities of brackish mine drainage water <br />6 . <br />of up to 16 x 10 gal/day (= 18,000 acre-ft/yr) for discharge to a surface <br />stream and for use in L,e plant. Associated with ~,is treatment is the disposal <br />of large quantities of concentrated waste equal to about IS percent of the <br />water to be treated. The second major problem is the treatment for internal <br />plant use cf large quantities of foul retort water generated in the process, <br />which are about equal in volume to the shale oil output of the plant. For a <br />6 <br />57,000 barrel/day plant, the retort water would amount to 2.4 x 10 gal/day or <br />2,700 acre-ft/yr. <br />The di:ficulties in assessing the treatment and disposal costs at this <br />time ste~ frcrn ~~e fact ~~at detailed information on ~~e quantity and, par~icularly <br />the quality, of the mine and retort waters is not known with any degree of <br />certainty. All estL~ates ~hich are given must therefore be used wit~ great <br />cauticn as ~~ey can only be considered educa~ed guesses in a number of instances. <br />This is e~phasized uJ ~~e fact that water balances and mine water flows differ <br />markedly between di::erent development plans. An illustrative plant water <br />balance, and mine and plant ~ater flow treatment sheets are prepared for <br />estimatir.g purposes. Illustrative mine and retort water qualities are suggested <br />on the basis of the most recent available data. The plant design, all flcw <br />rates and costs are based on the production of 57,000 barrels/day of shale oil <br />and 300 MW or byproduct electric power in ~~e central portion of the Piceance <br />Creek Basin of Colorado. A typical price for shale oil might be $lS(barrel, <br />6 <br />or $2.50/10 Btu. <br /> <br />a) Excess Mine Drainaqe Water <br /> <br />Quantity: <br /> <br />2,150-9,400 gpm (= 3460 - 15,130 acre-ft/yr) or even higher. <br /> <br />Very dependent on site. <br /> <br />900-1,350 mg/l total dissolved solids consisting principally <br /> <br />of bicarbonate, sodium and sulfate. High fluoride and <br /> <br />boron concentrations; taken to be 10-15 mg/1 and 2-4 mg/l, <br /> <br />respectively. Organic contamir.ation .unknown. <br /> <br />Trea~~ent by electrodialysis or reverse osmosis to potable <br /> <br />quality :or stream disc~arge. Se9arate removal of boron <br /> <br />by ion exchange. Disposal of concentrate from me~rane <br /> <br />process by :orcec evaporation in a va90r compression <br /> <br />Quali ty: <br /> <br />Disposal: <br /> <br />~J <br />