Molecular Biological Assessment Techniques on Acid Mine Drainage Treatment Processes

Microbial metabolism plays an important role in the weathering of sulfidic rocks and minerals, causing acid mine drainage(AMD). Even when AMD has been properly treated, unknown residuals can result in detrimental effects on the receiving water bodies. The aim of this work is to study the possibility of assessment of the heavy metals treatment system of AMD using molecular biological methods along with water quality analysis. The AMD treatment systems and a control site were chosen for the investigation. Water samples were taken from two sites in terms of influent, effluent and within treatment system, downstream with sediment and a control. To understand the roles of microorganisms in the wetland and surrounding ecosystems, the population diversity of microorganisms in different samples was evaluated by 16S rRNA sequencing. Among the total microbial population, moderately acidophilic iron-oxidizing bacteria(IOB) were found to be the dominant species in the AMD and sulfur-oxidizing bacteria (SOB), sulfate-reducing bacteria(SRB) and iron reducing bacteria(IRB) emerged as the second-dominant group. Finally, quantitative real-time PCR was conducted on specific genes of the observed microbes(i.e. IOB, SOB, SRB and IRB) and total bacteria genes(16S) to determine quantitative variation of the bacteria. Water quality parameters were concurrently analyzed, which was compared with the quantification of genes. From the investigation, it was observed that the ratio of genes for principal bacteria to those for total microorganisms were high in influent but decreased in the effluent of the wetland and was even less in the downstream water having almost same properties with that of the control. In addition, the copy numbers of principal bacteria genes correlated positively with sulfate and iron concentrations. As demonstrated in the study, based on the analysis of principal gene quantification and water quality, it was concluded that the ecosystem in the downstream will be eventually recovered bio-physicochemically.