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

• Published in: Water (Basel) 2014-11, Vol.6 (11), p.3478-3494
• Main Authors: Singh, Rajesh, Moon, Chungman, Veeravalli, Sathyanarayan S, Shanmugam, Saravanan R, Chaganti, Subba Rao, Lalman, Jerald A
• Format: Article
• Language: English
• Subjects: Bacteria; Competition; Fatty acids; Heavy metals; Hydraulics; Optimization techniques; Organic chemicals; Sulfide compounds; Taguchi methods
• ISSN: 2073-4441; 2073-4441
• DOI: 10.3390/w6113478

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.