Optimization of Heavy Metal Removal by Sulfate Reducing Bacteria in a High Concentration Zn-fed Fixed Bed Bioreactor Using Plackett Burman Design Experiments

Abstract

This study evaluated the combined effect of six processing factors on Zn, Cd removal and sulfate reducing by sulfate reducing bacteria in a high concentration Zn-fed fixed bed bioreactor. Statistically valid Plackett Burman design of experiments was employed to carry out this study. The results obtained showed a high removal of Zn (99.63%), Cd (99.73%) at a maximum influent Zn concentration of 320 mg/L. Analysis of variance (ANOVA) of Zn and Cd removal revealed that the effect due to glycerol dosage and reflux ratio were highly significant (P value < 0.05). To establish the role of sulfate reducing bacteria (SRB) in the metal removal process, the characteristics of microbial community in fixed bed bioreactor was analyzed by High-throughput Sequencing during the steady operational process. The results obtained shows that the percentage of the dominant sulfate reducing bacteria in the sludge, such as Desulfovibrio, could reach 45.7%. Qualitative EDS analysis of the precipitate was performed. The results revealed that the precipitates as ZnS were confirmed by the EDS spectrum with strong peaks of zinc and sulfur.