Toxicological evaluation of acid mine drainage waste water treatment options at Mt Lyell, Tasmania: Mount Lyell Acid Drainage Remediation Program,

Abstract

A primary aim of the development of an acid drainage treatment plant at Mt Lyell is the partial to complete rehabilitation of aquatic ecosystems in the lower King River (downstream of the junction with the Queen River) and upper Macquarie Harbour. A number of primary environmental remediation targets have been identified for this system. These include partial or complete recovery of macroinvertebrate and fish communities in the lower King River, partial or complete recovery of native fish recruitment into tributaries of the lower King River, no mortality or inhibition of growth of salmonids in aquacultural operations in northern Macquarie Harbour. A suite of toxicological tests were conducted to assess the relative success of three main treatment options for wastewaters from the proposed treatment plant at achieving the proposed remediation targets. Three 'test waters' were prepared from acid mine drainage (AMD) waters collected from the Mt Lyell lease. They were: pH 3.6 with sulphidisation (to simulate Cu removal by sulphide generating bacteria), pH 7.5 and pH 6.3. The latter two test waters were prepared by neutralisation of AMD with quicklime, followed by separation of supernatant from precipitates. The pH 3.6 test water was produced by partial neutralisation with limestone slurry, treatment of supernatant with sodium hydrogen sulphide and separation of supernatant.