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