<Originals>The Toxicity of Metallic Ions on the Activated Sludge and the Detoxication Effect of EDTA

Using the Warburg manometer, the author investigated the effect of metallic ions on oxygen uptake of activated sludge and calculated the values of TC_(toxic concentration 50,the concentration of toxic substance required to obtain 50% inhibition of the oxygen uptake of unintoxicated sludge). The obtained results were as follows. 1) The toxicity was decreased with the following sequence in the unit of ppm. Cu^, Ag^+, Hg^, Ni^, Cd^, Zn^, Co^, Cr^. Cr^ and Pb^. 2) The detoxication effect by EDTA was observed with Cu^, Ni^, Zn^, pb^, Cd^ and Hg^. But for Ag^+ and Co^, it was small and for Cr^ and Cr^, the effect was negligible