Biological treatment of cyanide containing wastewater

Soluble cyanide leaches from the spent ore heaps of many gold mines in the United States and Canada. The leachate must be recovered and treated to protect the receiving water from potentially harmful cyanide. A sequencing batch biofilm reactor (SBBR) was tested as a mobile, closed system capable of treating these dilute cyanide waste streams. The cyanide degrading microbes were enriched from the Fairbanks, Alaska municipal wastewater treatment plant. With a 48-h cycle time, the SBBR was capable of removing 20 mg/l of cyanide from a waste stream provided 156 mg/l of glucose substrate. On average, the 1900-l pilot system was able to treat 0.5 mg cyanide/l-h. The SBBR is a practical system for treating spent heap leachate in cold regions where a mobile, compact unit with minimal power requirements is needed.