Removal of Metals and Acidity from Acid Mine Drainage Using Liquid and Dried Digested Sewage Sludge and Cattle Slurry
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TECHNICAL ARTICLE
Removal of Metals and Acidity from Acid Mine Drainage Using Liquid and Dried Digested Sewage Sludge and Cattle Slurry Theresa A. Hughes • N. F. Gray • Olga Sa´nchez Guillamo´n
Received: 15 May 2012 / Accepted: 18 February 2013 / Published online: 6 March 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract The metal removal and neutralization capacities of digested sewage sludges from municipal wastewater treatment plants, cattle slurry (liquid manure), and Biofert granules (dried granular anaerobic sludge) were compared under batch conditions using synthetic AMD (pH 2.8) containing high concentrations of Al, Cu, Fe, Mn, Pb, and Zn (100, 15, 270, 15, 2, and 30 mg/L, respectively). The effects of contact time and solids concentration were examined. Metal removal was variable for all materials. Contact time had a significant effect, with total removal often increasing over the experimental time interval (i.e. 30 min to 24 h). Removal efficiency (%) was generally highest for Cu, Pb, and Al, while Mn and Zn were the least removed. Cattle slurry was the best material for metal removal, with the following maximum removals at a solids concentration of 12.9 g/L: Cu [98 %, Al [98 %, Fe [60 %, Mn [18 %, Pb [96 %, and Zn [60 %. Metal removal using digested sewage sludge reached 88 % for Al, 98 % for Cu, 94 % for Pb, and 30 % for Zn. Neutralization was complete within 30 min after AMD was mixed with digested sludges or cattle slurry, with the pH reaching a maximum of 5.5 with the slurry. In contrast, neutralization by the Biofert granules only reached equilibrium after 300 min, and pH remained \4.0 except at high solids concentrations. It appears that recycled waste-derived organic materials can neutralize AMD and remove
Electronic supplementary material The online version of this article (doi:10.1007/s10230-013-0217-9) contains supplementary material, which is available to authorized users. T. A. Hughes (&) N. F. Gray O. Sa´nchez Guillamo´n Water Technology Research Group, School of Natural Sciences, Centre for the Environment, Trinity College, Dublin 2, Ireland e-mail: [email protected]
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dissolved metals by adsorption and precipitation, creating a more treatable waste stream or one that could be discharged directly to surface water. Potential methods of safe disposal of metal-enriched organic materials are discussed. Keywords Adsorption Neutralization Organic wastes Precipitation Treatment
Introduction The key treatment processes required to remediate AMD are metal removal and acid neutralization (Skousen et al. 1998; Watzlaf et al. 2004). Organic waste materials can be used to remove dissolved metals from AMD by adsorption and precipitation, serving as effective low-cost substitutes for adsorbent materials such as activated carbon (Kurniawan et al. 2006). This approach provides an alternative to conventional active treatment processes (e.g. chemical precipitation, ion exchange, flotation, membrane filtration, reverse osmosis, or electro-deposition), and can reduce costs and eliminate th
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