Biological Sulphate Removal from Tannery Wastewater using Mixed Microbial Culture in a Sequencing Batch Reactor

Industrial wastewater, particularly form tanneries, often contains high sulphate and metal concentrations that represents environmental and health risks and are costly to treat with conventional methods. In this context, biological processes employing sulphate-reducing bacteria (SRB) offer a promising and sustainable alternative, as SRB reduce sulphate (SO42-) to sulphide (S2-) under anaerobic conditions. In this study, unsterile mixed microbial consortium was employed to treat sulphate-rich tannery wastewater in a 4.5 L anaerobic Sequencing Batch Reactor (SBR), fed with ethanol or molasses as electron donors. Up to 71% sulphate removal was achieved when ethanol combined with molasses were used at neutral pH, a temperature of 30° C, a COD/SO42ratio (g/g) of 0.52 and an F/M ratio (g COD/g VSS) of 0.47. Both substrates sustained SRB activity with different sulphate-reduction behaviors. Overall, the results demonstrate the feasibility of SBR with mixed biomass as a cost-effective strategy for sulphate removal, particularly when combined with low-cost electron donors such as molasses, promoting process intensification and supporting the scalability for industrial wastewater treatment.