Kinetics and microbial ecology of batch sulfidogenic bioreactors for co-treatment of municipal wastewater and acid mine drainage

[Display omitted] •Innovative technology for co-treatment of municipal wastewater and acid mine drainage.•Maximum COD oxidation rate can be reasonably achieved with the MWW/AMD mixtures.•Ferric iron at 60mg/L completely inhibit the sulfidogenic bioreactors.•COD oxidation was mostly facilitated by SRB with a small contribution from IRB.•COD oxidation had a strong positive correlation with SRB dsrA gene copies. The kinetics and microbial ecology in sulfidogenic bioreactors used in a novel two-stage process for co-treatment of acid mine drainage (AMD) and municipal wastewater (MWW) were investigated. Michaelis–Menten modeling of COD oxidation by sulfate reducing bacteria (SRB) (Vmax=0.33mgL−1min−1, Km=4.3mgL−1) suggested that the Vmax can be reasonably achieved given the typical COD values in MWW and anticipated mixing with AMD. Non-competitive inhibition modeling (Ki=6.55mgL−1) indicated that excessive iron level should be avoided to limit its effects on SRB. The COD oxidation rate was positively correlated to COD/sulfate ratio and SRB population, as evidenced by dsrA gene copies. Phylogenetic analysis revealed diverse microbial communities dominated by sulfate reducing delta-proteobacteria. Microbial community and relative quantities of SRB showed significant differences under different COD/sulfate ratios (0.2, 1 and 2), and the highest dsrA gene concentration and most complex microbial diversity were observed under COD/sulfate ratio 2. Major species were associated with Desulfovirga, Desulfobulbus, Desulfovibrio, and Syntrophus sp. The reported COD kinetics, SRB abundances and the phylogenetic profile provide insights into the co-treatment process and help identify the parameters of concerns for such technology development.