Post-treatment of effluents from the sulfate reduction process by anaerobic sequencing batch biofilm reactors

The main objective of this research was to evaluate the potential use of a bench-scale anaerobic sequencing batchbiofilm reactor (ASBBR) containing mineral coal as inert support for removal of sulfide and organic matter effluentsfrom an ASBBR (1.2 m3) utilized for treatment of sulfate-rich wastewater. The cycle time was 48 h, including thesteps of feeding (2 h), reaction with continuous liquid recirculation (44 h) and discharge (2 h). COD removalefficiency was up to 90% and the effluents total sulfide concentrations (H2S, HS−, S2−) remained in the range of 1.5to 7.5 mg.l−1 during the 50 days of operation (25 cycles). The un-ionized sulfide and ionized sulfides were convertedby biological process to elemental sulfur (S0) under oxygen limited conditions. The results obtained in the benchscalereactor were used to design an ASBBR in pilot scale for use in post-treatment to achieve the emission standards(sulfide and COD) for sulfate reduction. The pilot-scale reactor, with a total volume of 0.43 m3, the COD and totalsulfide removal achieved 88% and 57%, respectively, for a cycle time of 48 h (70 days of operation or 35 cycles).