Sediment Conditioning with Organic and/or Inorganic Carbon Sources as a First Step in Alkalinity Generation of Acid Mine Pit Lake Water (pH 2−3)

Abstract

Laboratory scale microcosm studies were conducted to determine the efficacy of controlled in situ saprobization of lake sediments as one opportunity for deacidification of artificial shallow lakes resulting from open cast lignite mining located in southeast Germany. Under lasting anoxic conditions iron and sulfate were removed from the lake water as a result of microbial iron-and sulfate reduction together with a subsequent precipitation of insoluble sulfide minerals to the lake sediment. The 2 L closed system microcosms were made up of a model of the sediment/ water interface. They were filled with lake water and sediment and treated subsequently with different organic and/or inorganic carbon sources in combination with wheat straw. Just the water was characterized initially and finally 8 weeks later. The rise of pH together with acidity consumption was observed. In the microcosms treated with wheat straw and pyruvate, ethanol, Carbokalk, or Pfezi-granula the pH rose to 5.5 and 7.0, respectively, and iron-and sulfate reduction were observed. With wheat straw and ethanol or Pfezi-granula sulfate concentrations decreased from initial concentrations of 11.5-13.5 mmol L -1 to final concentrations of < 3 mmol L -1 . However, the iron concentration decreased significantly to a value of 0.01 mmol L -1 exclusively with Pfezi-granula and wheat straw. For the most reactive microcosms geochemical equilibrium calculations suggest precipitation of different sulfide minerals. The critical revision of the results obtained from this study indicate that ethanol or Carbokalk together with wheat straw are suitable for further upscaling in largerscale microcosms.

Field-scale demonstration of the potential for sewage to remediate acidic mine waters

“…Given the high pH achieved, most of the remaining metals are likely to have been precipitated as insoluble oxyhydroxides or as amorphous sulphur minerals (probably metal monosulphides (Suits and Wilkin 1998) in the upper and middle sediment strata. The middle strata contained moderate amounts of pyrite, which was probably derived from secondary mineralisation of the amorphous minerals (Frömmichen et al 2003;Praharaj and Fortin 2004). The presence of gypsum as the main sulphur mineral in the bottom strata may suggest that this stratum was laid down prior to the mine water addition, when the lower Fe concentrations in the water would have favoured gypsum rather than pyrite formation.…”

“…Most published studies into the feasibility of SRB treatment systems have focused on highly labile, yet potentially expensive carbon substrates such as ethanol (Martin et al 2003;Kolmert et al 2001), sugar (Frömmichen et al 2003(Frömmichen et al , 2004Pöhler et al 2002), and cow manure (Drury 1999(Drury , 2000. However, many authors have now reported that the viability of this approach requires an organic matter source that is effective, economical, and locally available (Castro and Moore 1997;McCullough et al 2006b).…”

Microcosm Testing of Municipal Sewage and Green Waste for Full-Scale Remediation of an Acid Coal Pit Lake, in Semi-Arid Tropical Australia

“…Secondly, the use of largely fresh green waste as opposed to refractory organic substrates such as straw (Frömmichen et al, 2003;Frömmichen et al, 2004), rye grass (Harris and Ragusa, 2000;Harris and Ragusa, 2001), etc., distinguishes this research from many others in the published literature. The greater labile fraction of organic material available in this fresher material may have contributed directly to electron donors for SO 4 -2 reduction.…”

“…Hard et al (2003) echoed this view noting that, "For a microbial process to be economically feasible, the carbon (C) and energy source should be cheap, widely available and highly effective." However, most experiments into the utility of SO 4 -2 reduction processes for ameliorating AMD have instead focused upon highly labile but expensive C substrates such as ethanol (Kolmert and Johnson, 2001;Martin et al, 2003;McNee et al, 2003), sugar (Frömmichen et al, 2003;Frömmichen et al, 2004;Geller et al, 2003;Pöhler et al, 2002;Wendt-Potthoff et al, 2002), cow manure (Drury, 1999;Drury, 2000), etc. For many remote mining locations, these materials are unviable for practical and economic reasons.…”

Sourcing Organic Materials for Pit Lake Bioremediation in Remote Mining Regions

“…Labile organic substrates with low molecular weights, such as acetate, lactate, ethanol, glucose, and treacle, have been evaluated for their efficiency in stimulating and promoting bacterial sulfate reduction for treatment of AMD (Frömmichen et al 2003(Frömmichen et al , 2004Meier et al 2004). However, it is impractical to use most of these labile compounds for field applications due to the high costs of purchasing, storing, and transporting the quantities required (Neculita et al 2007).…”