Assessment of rapid initiators and long-lasting nutrients for developing biological permeable reactive barriers to treat mine-contaminated groundwater

Abstract

ABSTRACT The formation of mine-contaminated groundwater as a result of acidic mine drainage from the oxidation of sulfur-containing minerals entering the groundwater. Biological permeable reactive barrier (Bio-PRB) technology is excellent for the remediation of mine-contaminated groundwater. Usually, the organic substrates utilized in Bio-PRB are a combination of rapid initiators, which are readily bioavailable, and long-lasting nutrients, which are more difficult to degrade. Herein, we investigated the effectiveness of three rapid initiators and three long-lasting nutrients to remove sulfate from simulated mine-contaminated groundwater via simulated column experiments. The rapid initiators comprised crude glycerol, sodium acetate, and industrial syrup (IS), and the long-lasting nutrients included biodiesel emulsified oil, soybean oil emulsified oil, and high-carbon alcohol emulsified oil (HO). Microorganisms were stimulated using IS to create a sulfate reduction system owing to its high total organic carbon content (24.30 g L−1), achieving optimal sulfate removal rate (1.69 mmol dm−3 d−1). The fastest (2.93 mmol dm−3 d−1) and highest (88%) sulfate removal rates were achieved using HO, which is probably associated with the ability of HO to provide the most suitable C/N ratio (111.75) and induce the growth of sulfate-reducing bacteria (SRB) for substrate degradation. Conversely, a high concentration of sulfate reduction products inhibited SRB growth in the HO column. The addition of organic materials promoted SRB growth and various organic substrate–degrading bacteria. Furthermore, the competitive growth of methanogens (86.6%) may be responsible for the decrease in the relative abundance of SRB during the later stages of the experiment in the HO column.