Effect of copper and tri- and hexavalent chromium on the work of an activated sludge.

The effect of metals (Cu2+, Cr3+, Cr6+) on the work of an activated sludge grown in crude oil refining or synthetic wastes was examined. The activated sludge method was found to be applicable for the purification of wastes carrying up to 0.8 mgCu2+/1,15mgCr3+/1, or 20mgCr6+/1. Higher concentrations of these metals inhibited the work of the activated sludge which was evident in inferior purification and reduced intensity of respiration of the activated sludge microorganisms.