Earth Systems has designed and installed a Permeable Reactive Barrier (PRB) to intercept and contain surface runoff and shallow groundwater containing elevated dissolved arsenic from a derelict mine site.
The PRB removes soluble arsenic by adsorbing it to the reactive minerals. A suitable PRB substrate was identified and subjected to a series of geochemical and mineralogical tests.
The typical untreated (inflow) water is acid (pH ~3.5) with elevated concentrations of dissolved arsenic (20-60 mg/L), as well as elevated copper, cadmium, zinc, antimony, aluminium, and lead. Indicative water chemistry monitoring shows arsenic removal efficiencies of greater than 98%, and significant removal of other contaminants.
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Earth Systems has developed a series of algorithms that convert mineralogical and geochemical data into information that can be used to model and predict key environmental outcomes. With the right data inputs our algorithms can reveal potential hazards posed by:
Earth Systems was engaged to devise and implement a treatment strategy for two pit lakes containing acid and metalliferous (AMD) water at a quarry in Tasmania. To resume activities at the quarry, contaminated water needed to be treated and safely discharged in a way that complies with the ANZECC water quality guidelines for the protection of more than 95 % of species.
A dosing method was designed to meet on-site conditions.
99% metal removal was achieved enabling safe discharge to the local river.
In the battle to manage ARD/AMD, significant technological breakthroughs are few and far between. At the 9th Australian AMD Workshop in Burnie (November, 2017), Earth Systems announced a major advance in the prevention of ARD / AMD (acid and metalliferous drainage) from underground mines. The technology is applied in a two-stage process. Stage 1 involves engineering works that do not affect mine water discharge rates or water levels, but provide a primary control on air-entry into mine voids. Lowering air resupply into mine voids to levels that are below sulfide oxidation rates results in decreases in pollution production. Every cubic metre of oxygen consumed by sulfide oxidation within a mine void is replaced by a cubic metre of air, which only contains ~21 volume % oxygen. Hence if Stage 1 works are comprehensive, mine void oxygen reduction and nitrogen enrichment is inevitable.
Kinetic testwork in the form of column leach and humidity cell testwork is widely used for mining approvals to assess the indicative chemistry of leachate from sulfidic mine wastes. Advanced kinetic testwork methods based on oxygen consumption measurements can also reveal, a) the likely duration of sulfide oxidation processes, b) an accurate assessment of lag times (time before the onset of acid conditions), and c) the likely pollution loads over time. Oxygen consumption measurement techniques permit the quantitative assessment of sulfide oxidation rates (i.e. pollution generation rates) as a function of key waste storage facility variables such as temperature, moisture content, particle size distribution, oxygen concentration, pore water pH, and bacterial activity. Covers for sulfide wastes, capping zones, thin-lift and compacted oxygen control (encapsulation) bands and oxygen consuming layers can be accurately tested in the laboratory and field to optimise installation configurations (e.g. composition, particle size distribution, thickness, compaction, etc.) for operations and closure.
