ABSTRACT
The traditional treatment approach for destruction of cyanide contained in metal finishing and gold milling wastewaters has been the alkaline chlorination process and automatic chlorine addition based on the measurement of effluent redox potential has been widely used for controlling the process. The bench scale tests also showed that the use of chlorine residual measurement would provide a superior feedback signal for process control and could result in a reduction in chlorine consumption. An alkaline chlorination pilot plant together with the process control system was assembled at the Wastewater Technology Center in a mobile trailer and later moved to the metal finishing plant located 100 km away. Based on concurrent sampling of the redox controlled full scale treatment plant and the residual chlorine controlled pilot plant treating a sidestream of the same wastewater, no significant difference in treated effluent quality was observed.
