Microbial Community Dynamics during the Biochemical Treatment of Acid Mine Drainage under three different Hydraulic Retention Times

In the Zipaquira Mining District of Colombia, there are about 600 coal mines that generate 70,400 m3/month of acid mine drainage. A sustainable approach to remediate AMD is to use biochemical passive reactors. However, limited data is available on the dynamics (temporal and spatial) of microbial community and their activity under different hydraulic retention times, in the long-term operation of BPR. Seven 5L biochemical passive reactors (73 x 10 cm) were operated during 36 weeks, under three different hydraulic retention time (1, 2, and 4 days). The reactors were sacrificed on 8, 17 and 36 weeks, and the reactive mixture was sampled at the bottom, middle, and top layers. The microbial community of the post-treatment reactive mixtures was monitored by sequencing (Illumina MiSeq) and correlated with physicochemical parameters. The result showed that operation time, location and hydraulic retention time had significant effects on physicochemical changes of the reactive mixture and it is rather the combination of factors affect diversity during the AMD treatment. In addition, the microbial community analysis resulted in the identification of specialized groups related to cellulose degraders and fermentative bacteria that work in synergy for degrading substrate make the organic material available to sulfate-reducing bacteria. This microbial community analysis provides a base line for future studies in the BPR.