Using a Statistical Model to Examine the Effect of COD: SO42− Ratio, HRT and LA Concentration on Sulfate Reduction in an Anaerobic Sequencing Batch Reactor

Singh, Rajesh; Moon, Chungman; Veeravalli, Sathyanarayan S.; Shanmugam, Saravanan R.; Subba Rao, Ch. S. V. R.; Lalman, Jerald A.

Using a Statistical Model to Examine the Effect of COD: SO42− Ratio, HRT and LA Concentration on Sulfate Reduction in an Anaerobic Sequencing Batch Reactor

2014

Taguchi statistical design, an orthogonal array (OA) method, was used to study the impact of the COD/SO₄2− ratio, hydraulic retention time (HRT) and linoleic acid (LA) concentration on sulfate (SO₄2−) reduction in an anaerobic sequencing batch reactor using glucose as the electron donor. Based on the OA, optimum condition for maximum SO₄2− reduction was evaluated. Increasing the COD/SO₄2− ratio and HRT caused decreasing SO₄2− reduction while increased SO₄2− reduction was observed with increasing LA concentration (1 g L−1). In control (not fed LA) cultures, higher SO₄2− reduction (87% ± 3%) was observed at a low COD/SO₄2− ratio of 0.8. This indicates that increasing SO₄2− reduction was observed at increasing SO₄2− loading rates. In general, results from this study reveal that limiting the substrate concentration with high SO₄2− levels (low COD/SO₄2− ratio) favors high SO₄2− removal. Surface plots were used to evaluate the significant interactions between the experimental factors. Accuracy of the model was verified using an analysis of residuals. Optimum conditions for maximum SO₄2− reduction (97.61%) were observed at a COD/SO₄2− ratio of 0.8 (level 1), 12 h HRT (level 1) together with 1000 mg L−1 LA addition (level 3). In general, the Taguchi OA provided a useful approach for predicting the percent SO₄2− reduction in inhibited mixed anaerobic cultures within the factor levels investigated.

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