process for the treatment of waste water containing cyanides and cyanates

摘要

A process for treating a cyanide and cyanate-containing aqueous influent such as a wastewater stream (61) is provided. A two-stage method is included for destroying a cyanide-containing influent which comprises: (a) introducing said cyanide-containing influent (61) into a first ozone-contacting zone (Reactor Number 1); (b) contacting said influent (61) in said first zone (Reactor Number 1) with a second ozone-containing gas (78) at least a portion of said second ozone-contaning gas comprising a first ozone-depleted gas (74) withdrawn from a second contact zone (Reactor Number 2) to form a first cyanide-depleted effluent (65) and a second ozone-depleted gas (66); (c) introducing said first cyanide-depleted effluent (65) into a second ozone-contacting zone (Reactor Number 2); (d) contacting said effluent (65) in said zone (Reactor Number 2) with a first ozone-containing gas (71) to form a second cyanide-depleted effluent (83) and a first ozone-depleted gas (74); (e) withdrawing said first ozone-depleted gas from said second contact zone (Reactor Number2); and (f) withdrawing said second cyanide-depleted effluent (83) from said second zone (Reactor Number 2). A single stage method is also provided in this invention. Both single stage and double stage embodiments employ a turbine-gas injector (64) in each ozone-contacting zone to accomplish a high mass transfer of the ozone-containing gas to the influent. In both the single stage and double stage method, the cyanide-depleted effluents may be recycled to the aqueous influent stream prior to its introduction to either the first or second ozone-contacting zone or to the contacting zones themselves to destroy cyanides and cyanates in these effluents. This destruction is accomplished by allowing residual ozone or other oxidising species in the recycled effluent to react with the cyanide/cyanate species and reducing influent concentrations by diluting the influent entering the contacting zones while it the same time obtaining lower ozone-containing gas to liquid (G/L) ratios.