Water treatment design for site remediation at Casey Station, Antarctica: site characterisation and particle separation

Antarctica is commonly regarded as a pristine environment, but more than a century of human activity has left an extensive legacy of abandoned waste. The Australian Antarctic Division (AAD) has identified the Thala Valley Tip near Casey Station as a high priority site for remediation. However, there are difficulties with regards to contaminant dispersal by melt-water during extraction of wastes and contaminated sediments. Characterisation of contaminants and other site-specific conditions is crucial when designing appropriate water treatment technologies. Analysis of contaminants in Tip waters has found that heavy metals are predominantly associated with particles, although there are substantial concentrations of dissolved metals as well. The combined chemical and physical analyses indicate that the main heavy metals transport mechanism as adsorption to the surface of particles, which are then carried by surface and sub-surface runoff. ove heavy metals from contaminated water during the proposed clean-up of Thala Valley a multistage treatment process will be required. The first stage is one of particle removal. A plant has been designed that uses coagulation and flocculation chemicals to produce a fast settling, flocculated suspension. The flocculated particles will settle out in an inclined settler, producing a clarified effluent and a concentrated sludge. The clarified water will then be passed through a 1-μm filter to remove any residual particles prior to dissolved heavy metals removal either by ion exchange or distillation. Future research will focus on optimisation of the water treatment system, especially coagulation and flocculation processes and the impact of pH, turbidity, low temperature and water chemistry on flocculation efficiency.