Dn. Thompson et al., Sawdust-supported passive bioremediation of western United States acid rock drainage in engineered wetland systems, MIN MET PR, 17(2), 2000, pp. 96-104
Economical remediation of acid rock drainage (ARD) at secluded high-altitud
e western ore mines is difficult given the current treatment technology. Se
veral passive-engineered systems that are based on wetland technology were
tested in the laboratory with three western ore mine ARDs (Co, Cu and Fe mi
nes) and with a copper leachate effluent. These systems used well-weathered
lodgepole pine sawdust as the sole carbon source and mud from a pond at on
e of the mine sites as the source of sulfate-reducing bacteria (SRB). Simpl
e one pass flow-through systems removed 44% to 99% of the various heavy met
als from the Co and Cu mine ARDs and increased the pH from 3 to 7 after 28
days of SRB acclimation with a five-day residence time. Carbohydrate utiliz
ation rates were generally low: except for one 437-day run, which consumed
25%, 30% and 21 % of the cellulose, hemicellulose and lignin, respectively.
Initial pH, amounts of toxic heavy metals and the degree of predegradation
of the sawdust were found to significantly affect both remediation potenti
al and acclimation time. Engineered SRB systems, alone or in combination wi
th other passive technologies, offer promise for the economical remediation
of western US ore mine ARDs.