An integrated biological approach for treatment of cyanidation wastewater

The cyanidation process has been, and still remains, a profitable and highly efficient process for the recovery of precious metals from ores. However, this process has contributed to environmental deterioration and potable water reserve contamination due to the discharge of poorly treated, or untreated, cyanide containing wastewater. The process produces numerous cyanide complexes in addition to the gold cyanocomplex. Additionally, the discharge constituents also include hydrogen cyanide (HCN) - metallic complexes with iron, nickel, copper, zinc, cobalt and other metals; thiocyanate (SCN); and cyanate (CNO). The fate of these complexes in the environment dictates the degree to which these species pose a threat to living organisms. This paper reviews the impact that the cyanidation process has on the environment, the ecotoxicology of the cyanidation wastewater and the treatment methods that are currently utilised to treat cyanidation wastewater. Furthermore, this review proposes an integrated biological approach for the treatment of the cyanidation process wastewater using microbial consortia that is insensitive and able to degrade cyanide species, in all stages of the proposed process.