Heavy Metal Removal Using Sulfate-Reducing Biomass Obtained from a Lab-Scale Upflow Anaerobic-Packed Bed Reactor

Biological sulfate reduction is an alternative and emerging technique to treat metal containing sulfate-rich wastewater. In this study, the potential of anaerobic biomass from three different wastewater treating systems was evaluated for heavy metal removal under sulfate-reducing conditions. Among the three different biomass sources tested in the study, the biomass from a lab-scale upflow anaerobic-packed bed reactor (UFAR) showed maximum sulfate reduction (>90%) within 96 h with a maximum wastewater chemical oxygen demand (COD) removal of up to 92.8%. The heavy metal removal efficacy was in the order Cu>Fe>Ni>Pb>Cd>Zn. Metal removal by the biomass was further established due to its precipitation with sulfide formed by the sulfate-reducing bacteria. The field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX) of the metal-loaded biomass showed that the precipitates formed during the process consist of mainly the metal sulfides. The transmission electron microscopy (TEM) along with energy dispersive spectroscopy (EDS) confirmed that the metal precipitates were confined to the exterior and interior surface of the bacterial cells. The Fourier transmission infrared spectroscopy (FTIR) spectra of the biomass, obtained during its growth, clearly established the presence of sulfate ions.