REMOVAL OF COLOUR FROM EFFLUENTS OF ANODIZING PLANTS.

Water-soluble organic dyestuffs used for dyeing the anodic coatings of aluminium cause hardly any damage to the biocenosis of the water into which the effluents of anodizing are released, as ecological laboratory investigations and years of practical experience have shown. However, the extremely high tinctorial strength of such dyes, even after being heavily diluted (less than 0. 1 ppm) causes conspicuous and unsightly discoloration of the water into which the effluent is released. The author explains how the adsorption with activated carbon can provide an especially economical and flexible solution to this problem of decoloration. The process can be carried out both in a stationary manner by the suspension principle, as well as by the percolation principle.