The toxicity of metal ions on activated sludge and the effect of EDTA addition on the toxicity

Abstract

Using the Warburg manometer, the author investigated the toxicity of metal ions on oxygen utilization of activated sludge and estimated TC₅₀ (the concentration of toxic substance required to obtain 50% inhibition of the oxygen utilization of unintoxicated sludge)
1) The toxicity of the ions to activated sludge showed the tendency of decrease in the following order: Cu⁺⁺, Ag⁺, Hg⁺⁺, Ni⁺⁺, Cd⁺⁺, Zn⁺⁺, Co⁺⁺, Cr⁺⁺⁺, Cr⁺⁶, and Pb⁺⁺.
2) Detoxication effect by EDTA salt was found in case of Cu⁺⁺, Ni⁺⁺, Zn⁺⁺, Pb⁺⁺, Cd⁺⁺ and Co⁺⁺. However in Hg⁺⁺, Ag⁺, Cr⁺⁺⁺, Cr⁺⁶, the effect was negligible.