Two remediation strategies have been considered to reduce the levels of
acidity and dissolved metals in acid mine drainage discharging from Sullivan
Mine, West Coast, New Zealand. The oxidising strategy involves adding alkalinity
and dissolved oxygen (DO) resulting in the precipitation of metallic oxides and
decreased acidity. The reducing strategy involves removing DO, resulting in the
precipitation of metallic sulfides, followed by addition of alkalinity to
decrease acidity. Field remediation trials indicate a reducing system may be
more effective for this site than an oxidising system. A residence time of
onlytwo hours in the limestone layer of a successive alkalinity producing
system (SAPS) is sufficient to reduce acidity by 100 per cent, iron by 71 per
cent, aluminium by 59 per cent, nickel by 38per centand manganese by
26 per cent. The proposed remediation plan will likely include a series of SAPS,
followed by an anoxic limestone drain, and settling ponds to capture any
remaining precipitates.