Toxic effect of metal ions on biochemical oxygen demand

Toxic effect of metal ions like Al, Co, Ni, Cu, Zn, Pb and Hg on the Biochemical Oxygen Demand (BOD) exertion has been studied at various concentrations of the metal ions. Presence of these metal ions in the effluent samples significantly affects the observed BOD values. The magnitude of their dependence varies with the nature and concentration of the metals working as a toxicant. The detrimental effect of metal ions on the observed BOD is a resultant of the biological as well as chemical processes taking place in the sample. Addition of metal ions like Al, Zn, Cu and Pb results in the inhibition as well as increase in BOD. Mechanism for the effect of metal ion on BOD has been proposed and is correlated with their electrochemical potentials.