Bioaugmentation of cyanide-degrading microorganisms in a full-scale cokes wastewater treatment facility.

To enhance biological removal efficiency of total cyanides, bioaugmentation was applied to a full-scale cokes wastewaters treatment process. After a laboratorial-scale cultivation (up to 1.2 m(3)) of a cyanide-degrading yeast (Cryptococcus humicolus) and unidentified cyanide-degrading microorganisms, the microbial consortium was inoculated into a fluidized-bed type process (1280 m(3)), and then enriched for two months with a huge supply of glucose, KCN and other nutrients. Target wastewater was effluent of a biological pre-denitrification process for treating cokes wastewater, and contained about 14 mg/L of total cyanides in the form of ferric cyanide. This may be a first or rare report on the full-scale bioaugmentation of specialized-microorganisms. However, continuous operation of the full-scale cyanides-degrading bioprocess showed poor removal efficiency than expected owing to poor settling performance of microbial flocs, slow biodegradation rate of ferric cyanide and lack of organic carbon sources within the wastewater. Therefore, there is a need for further studies on how to solve these operating problems in full-scale bioaugmentation approach.