Removal Of Heavy Metals From Wastewater By Biosorption Of ZVI-SRB

Removal of heavy metals by biosorption of ZVI-SRB is an innovative technology and its biosorption behavior of heavy metals was investigated.Some important factors that affect SRB reducing capacity including pH, COD/SO42- and NO37SO42- were determined. And the role of ZVI in sulfate reducing of SRB was also studied.The biosorption capacity of Cu, Cd, Zn and Ni by the mixed SRB population followed the order of Cu>Cd>Zn>Ni. Biosorption of heavy metal was a complex physiochemical process and followed the pseudo second order kinetics model. The concentration of heavy metal that inhibited activity of SRB was related to the toxicity of heavy metal and H2S. EPS also selectively biosorbed the heavy metals and followed the order of Cd2+>Cu2+>Zn2+. qm of Cd2+ was up to 2720.9mg/g EPS. The difference in absorption capacity of different heavy metals by EPS was due to the affinity between heavy metal and the groups of-OH and acyl of EPS. Biosorption isotherm of single heavy metal of mixed SRB population and their EPS could be represented well with Freundlich equation.The kinetics of SRB immobilized by calcium alginate followed the pseudo second order model and it involveed intraparticle diffusion and interlayer diffusion. The whole biosorption process could be divided into two obvious stages, i.e., physicochemical biosorption stage and bioprecipitation stage. ZVI-SRB particle had obvious advantage over SRB particle in removing heavy metals in water. The isothermal behavior of SRB immobilized by calcium alginate followed both Langmuir isotherm and Freundlich isotherm.ZVI-SRB reactor was creatively applied to remove toxic metals from wasterwater. It was obvious that the removal efficiency of SC42- and Ni2+ in the ZVI-SRB reactor was higher than that of SRB reactor.The synthetic wastewater containing 150mg/l Ni2+ was treated with ZVI-SRB biofilm filteradvantages over the former and has a potential to remediation of groundwater contaminated by heavy metals, AMD and other kinds of wastewater containing heavy metals.