Influence of feed time and sulfate load on the organic and sulfate removal in an ASBR

The removal of sulfate and organic matter was assessed in an ASBR, which treated wastewater containing 500 mg COD L−1 (3 g COD L−1 d−1) in 8 h-cycles at 30 °C. The wastewater was enriched with sulfate at [ COD / SO 4 2 - ] ratios of 1.34, 0.67 and 0.34 ( 8.8 , 4.5 and 2.2 gSO 4 2 - L - 1 d - 1 ). For each COD / [ SO 4 2 - ] ratio fill times used were: 10 min (batch), 3 and 6 h (fed-batch), achieving sulfate reduction of 30%, 72% and 72% ( COD / [ SO 4 2 - ] of 1.34); 25%, 58% and 55% ( COD / [ SO 4 2 - ] of 0.67) and 23%, 37% and 27% ( COD / [ SO 4 2 - ] of 0.34), respectively, and organic matter removal of 87%, 68% and 80% ( COD / [ SO 4 2 - ] of 1.34); 78%, 75% and 69% ( COD / [ SO 4 2 - ] of 0.67) and 85%, 84% and 83% ( COD / [ SO 4 2 - ] of 0.34), respectively. The results showed that fed-batch operation improved sulfate reduction, whereas organic matter removals were similar for batch and fed-batch operation. In addition, increase in sulfate loading in the fed-batch operation improved organic matter removal.