Treatment of copper wastewater by sulfate reducing bacteria in the presence of zero valent iron

Abstract

The present study was conducted to investigate sulfate-reducing bacteria (SRB) activity and copper removal utilizing SRB enhanced by zero valent iron (Fe0) with MgSO4·7H2O and Na2SO4 as sulfate source and sodium lactate as energy resource in three distinct systems: SRB system, Fe0 system and SRB+Fe0 system. The SRB activity and copper removal were tested in synthetic wastewater containing 1250mgL−1 sulfate, 600mgL−1chemical oxygen demand (COD), copper (0, 5, 10, 15, 20, and 25mgL−1) and pH 6.0. Sulfate reductions in the SRB system and SRB+Fe0 system were effective below 20 and 25mgL−1 of initial copper concentration, respectively. Copper concentrations higher than 20mgL−1 and 25mgL−1 were lethal to SRB in the SRB system and SRB+Fe0 system, respectively. The sulfate reduction rates in the SRB+Fe0 system were increased by 559% relative to SRB system with the copper concentrations of 15mgL−1. The results of sulfate reduction show that the addition of Fe0 enhanced the activity of SRB. In the copper removal experiment, the overall copper removal was around 99.5% after 40h in all three systems, whereas the SRB+Fe0 system exhibited a better performance of copper removal than the other systems with a reaction time of 120min. EDS (energy-dispersive spectroscopy) analysis showed that the precipitation of copper occurred in form of sulfide. The results of SRB activity and copper removal experiments demonstrated that the SRB+Fe0 system was more capable to treat acid copper wastewater than the SRB and Fe0 systems.