Treatment of Acid Sulfate Soil Drainage By Direct Application of Alkaline Reagents

Abstract

Due to the episodic nature of rainfall and the high dissolved metal concentrations in the acid sulfate soil catchment of Clothiers Creek (NSW, Australia), active treatment was considered more appropriate than passive treatment. Alkaline reagents were added to oxidised shallow drains to remove acidities ranging from 438 to 1,837 mg/L CaCO 3 . A fine limestone slurry was produced from the pounding together of limestone rock fragments within a rotating drum and, on addition to drain waters, was found to remove acidity to varying degrees of effectiveness (from 12 to 100%). The efficiency decreased as the pH of the water approached neutrality due to calcite saturation and the slow reaction rate of limestone at high pH. Hydrated lime powder was also mixed with drain water in the rotating drum though most mixing occurred once the slurry entered the drain where efficiencies ranging from 67 to 89% were observed. A powdered mixture of MgCO 3 and CaCO 3 was only 11% effective in treatment of the drainage water due to the slow rate of reaction of MgCO 3 . Whilst R. Green

Acid neutralization by dissolution of alkaline paper mill wastes and implications for treatment of sulfide-mine drainage

“…The charge-balance error between the cations and anions of AMD samples was also calculated with PHREEQC to check the quality of the analysis, and it was within 5%; and within 10% after all simulations. These values are considered acceptable and within the range calculated in similar conditions (e.g., Green et al 2006;Rötting et al 2008b). In the experimental system used in this study, reactions only occur while the water is out of equilibrium.…”

Sulfur biogeochemical cycling and novel Fe–S mineralization pathways in a tidally re-flooded wetland

“…Remediation approaches have traditionally focused on treatment of existing soil and water acidity by amendment with neutralizing agents, such as lime (Tulau, 2002;Green et al, 2006;Å strö m et al, 2007). However, this approach typically requires ongoing financial inputs.…”

Contemporary pedogenesis of severely degraded tropical acid sulfate soils after introduction of regular tidal inundation

“…Many techniques focus on decreasing the severity of off-site water quality impacts via hydrological containment, neutralisation or dilution of aqueous acidic products (e.g. Blunden and Indraratna, 2000;Indraratna et al, 2002;Johnston et al, 2004b;Johnston et al, 2005;Green et al, 2006;Åström et al, 2007). However most of these techniques have been applied within a context of maintaining existing agricultural landuse.…”