Comparative Study of Nickel Removal from Synthetic Wastewater by a SulfateReducing Bacteria Filter and a Zero Valent Iron-Sulfate-Reducing Bacteria Filter

Nickel removal from wastewater by a zero valent iron sulfate-reducing bacteria (ZVI-SRB) filter and a sulfate-reducing bacteria (SRB) filter were investigated in this study on the basis of the assumption that integrating SRB with the ZVI system should enhance the removal efficiency of heavy metals from solution. The variation in oxidation-reduction potential (ORP) and pH in the effluent indicated that ZVI provided favorable anaerobic conditions for SRB growth. Measurement of sulfate concentrations confirmed that ZVI promoted sulfate-reducing activity of SRB. When the nickel concentration of influent was 150 mg/l with a HRT of 19h, the nickel-removal efficiency was > 98% for the ZVI-SRB filter and 94.3-96.5% for the SRB filter; with a hydraulic retention time (HRT) of 12h, the nickel-removal efficiency was 95.3-97.0% for the ZVI-SRB filter and 84.3-88.2% for the SRB filter, with a HRT of 6h, the nickel-removal efficiency was 94.2-96.5% for the ZVI-filter and 78.2-81.4% for the SRB filter. This result demonstrated that the ZVI-SRB filter had apparent advantages over the SRB filter, especially when filters were run with a shorter HRT. The scanning electron microscope-energy dispersive X-ray analysis (SEM-EDXA) analysis showed that nickel in the ZVI-SRB filter was mainly removed as nickel sulfide and zero valent nickel. This study demonstrated that a ZVI-SRB filter could be a promising technology for treating wastewater containing heavy metals and bioremediation of contaminated groundwater.