MECHANICALLY STIRRED AnSBBR APPLIED TO ORGANIC MATTER AND SULFATE REMOVAL: EFFECT OF FEED STRATEGY AND SULFATE LOAD

ABSTRACT: A mechanically stirred anaerobic sequencing batch reactor containing anaerobic biomass immobilized on polyurethane foam cubes (AnSBBR), treating low-strength synthetic wastewater (500 mgCOD.L-1), was operated at different operational conditions to assess the removal of organic matter and sulfate. These conditions were related to fill time, defined by the following feed strategies: batch mode of 10 min, fed-batch mode of 3 h and fed-batch mode of 6 h, and using COD/[SO42-] ratios of 1.34, 0.67 and 0.34 defined by sulfate concentrations of 373, 746 and 1493 mgSO42-.L-1 and organic matter concentration of 500 mgCOD.L-1 in the influent. The reactor operated with an agitation of 400 rpm with a total volume of 4.0 L and treated 2.0 L of synthetic wastewater in 8-h cycles at 30 ± 1°C. In general, the results showed that the 3-h fed-batch operation with a COD/[SO42-] ratio of 0.34 represented the best conditions for organic matter removal (89%). The best efficiency for sulfate removal (71%) was registered during the assay with a COD/[SO42-] ratio of 1.34 and a fill time of 6 h. It was also observed, that as fill time and sulfate concentration in the influent increased, the ratio between removed sulfate load and removed organic matter load also increased