Abstract
Domestic wastewater sludge can serve as a carbon source in the passive biotic treatment of acid mine drainage (AMD) in microbial bioreactors to create anaerobic conditions for the removal of sulphate, chemical oxygen demand (COD) and pH neutralization. A synthetic medium simulating domestic wastewater sludge was used in AMD treatment in a ratio of 1:1 AMD: synthetic domestic wastewater sludge (SDWWS). Sulphate and COD removal were determined at different incubation temperatures and with and without a biofilm in the bioreactors. Sulphate and COD were removed by 60.8% and 96% within 26 d, after which a plateau was reached. Bacterial community analyses using next generation sequencing showed that Chlorobium spp. dominated at a relative percentage of 36% followed by Magnetospirillum spp. and Ornithobacterium spp. The effect of a resident biofilm in the bioreactors showed dominance of Chlorobium spp. at a relative percentage of 62% and removal of sulphates and COD at 96% and 58%, respectively, after 26 d. Incubation at 17–19°C reduced sulphates by only 10% and COD by 12% after 17 d, after which a plateau was reached. Magnetospirillum spp. was the dominate organism at the end of this trial. Keywords : acid mine drainage, domestic wastewater sludge, sulphates, COD, bacterial community
Highlights
Acid mine drainage (AMD) refers to untreated wastewater from mining activities (Geremias et al, 2003) and poses a threat to human and environmental health (Keller et al, 2005; Lee et al, 2010)
The bioreactors showed an average removal of 674.3 mg-SO4-∙L−1 sulphate (96%) (Fig. 1) and 827 mg-chemical oxygen demand (COD)∙L−1 (60.8%) (Fig. 2), after which total removal was reached after 26 d for both
Treatment of AMD with synthetic domestic wastewater sludge, inoculated with sludge from an anaerobic digester, was successful in the removal of sulphates and COD in bioreactors incubated for 30 d at 25°C in a dimly-lit environment
Summary
Acid mine drainage (AMD) refers to untreated wastewater from mining activities (Geremias et al, 2003) and poses a threat to human and environmental health (Keller et al, 2005; Lee et al, 2010). Various remediation methods for AMD have been investigated since the 1900s (Barnes and Romberger, 1968; Olem and Unz, 1977) These methods involve abiotic and biotic methods, which can be divided into active and passive systems (Johnson and Hallberg, 2005). Passive biotic remediation methods rely on the use of microbial treatment systems by the once-off addition of one carbon source, such as domestic wastewater (Davison et al, 1989; Strosnider et al, 2011a and 2011b). This creates conditions that will select for specific microbial populations responsible for the removal of sulphates, organic matter content and heavy metals, as well as neutralize the pH of the AMD (Barton and Fauque, 2009). The main bacterial group responsible for sulphate removal during passive biotic treatment of AMD is sulphate-reducing
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