DEVELOPMENT STUDIES FOR SUITABLE TECHNOLOGIES
FOR THE REMOVAL OF CYANIDE AND
HEAVY METALS FROM GOLD MILLING EFFLUENTS
J. W. Schmidt, Head
Physical/Chemical Processes Section
L. Simovic. Process Development Engineer
Wastewater Technology Centre
Environment Canada
Burlington, Ontario
Canada L7R 4A6
E. E. Shannon, Engineer
Canviro Consultants, Ltd.
Kitchener, Ontario
Canada N2H 5M5
Since 1973 Environment Canada has been involved in the development and demonstration of suitable technologies for the removal of toxic contaminants from gold mine effluents. Contaminants of concern are cyanide, zinc, copper, nickel, and arsenic. It is recognized that there are a number of alternative technologies such as alkaline chlorination,
ozonation, ion exchange, electrochemical and others which have potential for the treatment
of gold mill effluents. These have recently been reviewed by Ingles and Scott [ 1 ].
Initial technology development activities included a joint project between the Environmental Protection Service (EPS), and Giant Yellowknife Mines Ltd., a gold producer located
in Yellowknife, NWT. Pilot scale studies were conducted during 1976 and 1977 on a two
stage process for cyanide and metal removal from various waste streams [2]. The process
incorporated alkaline chlorination for cyanide removal and the addition of alkali and iron
salts for the removal of arsenic and heavy metals. Since this study was successful, a decision
was made to expand the data base by conducting alkaline chlorination studies on effluents
from other gold mills.
In addition, a decision was made to examine alternative treatment processes, one of
which was natural degradation. In early 1979, EPS commissioned IEC, International Environmental Consultants to undertake a literature review of the factors affecting the natural
degradation of free and metal-complexed cyanides from gold mill effluents [3]. It was
apparent that tailings ponds or separate liquid impoundment areas have a high potential for
cyanide removal from gold mill effluents and in fact, several mines in Canada used such systems. One of these mines was Dome Mines Limited located near Timmins, Ontario, which
had constructed a separate impoundment area in 1975 for one of their effluents, the barren
bleed [4[. Initially, they experienced some operational problems. During the 1978/79 operating season, however, the system functioned successfully. In August 1979 the Wastewater
Technology Centre (WTC/EPS) approached Dome Mines regarding a joint assessment program for the 1979/80 operating season. A cooperative study was agreed upon and initiated
in September.
This paper reports on two studies conducted on effluents from Dome Mines. One was a
bench scale study using the alkaline chlorination process, the other was a field scale study
of the two "natural degradation" treatment systems at the mine site.
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