Using sewage sludge as a sealing layer to remediate sulphidic mine tailings: a pilot-scale experiment, northern Sweden

Abstract

At the Kristineberg mine, northern Sweden, sulphidic mine tailings were remediated in an 8-year pilotscale experiment using sewage sludge to evaluate its applicability as a sealing layer in a composite dry cover. Sediment, leachate water, and pore gas geochemistry were collected in the aim of determining if the sludge was an effective barrier material to mitigate acid rock drainage (ARD) formation. The sludge was an effective barrier to oxygen influx as it formed both a physical obstruction and functioned as an organic reactive barrier to prevent oxygen to the underlying tailings. Sulphide oxidation and consequential ARD formation did not occur. Sludge-borne trace elements accumulated in a reductive, alkaline environment in the underlying tailings, resulting in an effluent drainage geochemistry of Cd, Cu, Pb and Zn below 10 lg/L, high alkalinity (810 mg/L) and low sulphate (38 mg/L). In contrast, the uncovered reference tailings received a 0.35-m deep oxidation front and typical ARD, with dissolved concentrations of Cd, Zn and sulphate, 20.8 lg/L, 16,100 lg/L and 1,390 mg/L, respectively. Organic matter degradation in the sludge may be a limiting factor to the function of the sealing layer over time as 85 % loss of the organic fraction occurred over the 8-year experimental period due to aerobic and anaerobic degradation. Though the cover may function in the short to medium term (100 years), it is unlikely to meet the demands of a longterm remedial solution.

The possibilities and challenges of using industrial rest products on mine waste management in the Arctic

“…In recent years, studies have been focusing on the use of alternative materials such as industrial and municipal waste for mine waste remediation, which could solve two waste problems at the same time. The application of incineration ashes, waste from wood and paper industry and other industries, sewage sludge, steel slag and combinations of these materials for construction of sealing layers and for other applications in mine waste remediation have been investigated [8][9][10]. Using various types of materials as dry covers on mine waste has been successfully applied at many sites throughout the world [11,12].…”

“…The effectiveness of sewage sludge as a sealing layer over sulphide mine waste was evaluated. Data on tailings, leachate water and pore gas geochemistry during eight years from two experimental pilot-scale test cells revealed that the sludge was an effective barrier to oxygen influx [8]. The sulphide oxidation and ARD formation was prevented effectively.…”

Biodegradation of Biosolids Under Aerobic Conditions: Implications for Cover Materials for Sulfide Mine Tailings Remediation

“…The precision of the instrument was better than 2 % of the analyzed value according to the manufacturer. Aerobic degradation processes were calculated using an interpretation of data from Nason et al (2013), which showed a negative correlation between the concentrations of O 2 and CO 2 and no correlation between these gases and CH 4 , which indicated that solely aerobic degradation processes were occurring.…”

“…1) to the upper layer. The oxygen was transported to the sealing layer through the overlying protective layer, as it was more permeable (6 9 10 -7 m s -1 in the till; Höglund and Herberg 2004) than the sealing layer, which allowed oxygen to diffuse freely to the biosolids (Nason et al 2013). Figure 4b displays cumulative concentrations of all three gases.…”

Efficiency assessment of cascade aerator in a passive treatment system for Fe(II) oxidation in ferruginous mine drainage of net alkaline

“…2) (Dempsey et al 2012). Fe(III) reaches its minimum solubility at a pH of 8.0, and therefore, it can be said that a typical mine drainage treatment process creates a favorable environment for Fe oxides to precipitate (Hustwit et al 1992;Jia et al 2013;Nason et al 2013).…”