Remediation of waters from a south-west Australian acid pit lake with oxic liming and an aerobic wetland

Clint McCullough (MiWER), Mark Lund (MiWER), David Bills (Griffin Coal)

Does treatment with oxic liming and an aerobic wetland remediate mine waters from a new acid pit lake?

A mine water treatment system was constructed at Griffin Coal Mining Company Limited in Collie Western Australia, to remediate acidified mine lake water from the nearby Chicken Creek pit lake (pH 3, containing approximately 8 million m3 of water) and make it suitable for cultivating plants or fish.

The first part of pit water treatment is a two-stage liming system utilising a fluidised bed of limestone. At each stage of liming there is a settling pond to remove particulate iron- and aluminium oxyhydroxides. From here the limed water gravity-feeds back to the lake though 5 ha constructed aerobic “polishing” wetland.

Photo: Fluidised liming of Chicken Creek pit lake water

Photo: Aerobic polishing of fluidised Chicken Creek pit lake water

This study is evaluating the way in which fluidised liming and aerobic wetland treatment can remediate pH and elevated metal concentrations in water from a typical recently groundwater-filled acid pit lake of Collie. Both water chemistry analyses and toxicity teas are being undertaken to evaluate water quality at each stage of treatment in order to better understand the processes taking place in this treatment system. The conclusions and recommendations of this project will enable better design of such systems for this mining region.

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