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.r 1 Pegs 17 C media, slm0ar resuhs were obtained at air to liquid ratios <500. The goal of the studies was to reduce WAD cyanide to <10.0 mgil, which was achieved. Pressure drops of about 100mm water gauge were measured through the 3m of SOmm mass transfer media. ' Schematics for the layout of the full-scale Cyanisorb Process using either three complete mix reactors In series or two stripping towers are presented. In Figures 6 end 7. fused on a comparison of performance versus cost and ease of operation, the tise:of towers were selected es the preferted process configuration. The preferred configuration Invdves two single pass towers about 4.Om In diameter and tO.Om fn height operated in parallel, with a third tower as a stand-by unh. Testing continues to Identify any long-term mechanical or physical problems with the process. Fdlowing cyanide removal, the slurry pH will be readJusted to 9.5 to precipitate tree metals, prior to disposal of the slurry in the Impoundment. In conjunction wRh development and design of the Cyanisorb process, additional experiments and calculations were prepared to evaluate the Impact of the cyanide recovery circuh on cyanide and metals levels In the tailings Impoundment and associated leachates. The effect of cyanide recovery on cyanide concentrations at various points in the Golden Cross water management system are summarized In Table 10. These calculations were prepared by M.P.A. Williams and Associates, located In Melbourne, Victoria, Australia (9). The results of the analysis Indicated that total cyanide levels entering and exiting the tailings Impoundment were reduced from 186.0 to 30.0 mg/I and 42.0 to 9.0 mgJl, respectively. In addition, the total cyan'~de In the untreated feed to the wastewater treatment facility was reduced from 14.0 mg/I to about 5.0 mg/I. Prior to Incorporation of the cyanide recovery system Into the metallurgical process a tailings washing system was required, which was :subsequently eliminated at a substantial cost savings to the protect. TABLE t0 ESTIMATED CYANIDE CONCENTRATIONS W{TH AND WITHOUT CYANIDE RECOVERY AT THE GOLDEN CROSS MINE ~.. -a<- _ . . -., ... Cvanide Concentrationsr~~ Without Cyanide Recovery With Cyanide Recovery Soirrtiont't Total Cfr Total Cf~f WAD CN- Tailings slurry to Impoundment 186 30 10 Pumped decant from pond ~'t 42 - •• 9 - <.O4 Mine bacMill going underground - ~ t 1 3.7 Mine water pumped out -- ~ i.2 0.39 Influent to water treatment plant 14 4.7 0.06 t't Values taken from Goden Cross water management system model t~ All values In mg/~ unless otherwise stated. P1 A tirst order dewy rate was utilized In conJunction with dilution to catcutate cyanide values. The decay rate for total cyanide used prior to cyanide recovery was 0.0014/hr. The total cyanide va ues after cyanide recovery were calculated using dilution oNy, while a dewy rate of 0.006/hr was u:.ed for WAD cyanide. ~'~ The residence time In the pond before and after cyanide recovery was 14.7 and 56.4 days, respectively.