The Adsorption of Dyes on Activated Sludge

Effluents from the textile dyeing and printing processes usually contain dissolved or suspended dyes in small quantities. One of the treatments which may be applied to such effluent is passage through a biological treatment plant in which colour removal proceeds via absorption on activated sludge. An indication was sought as to the likely efficacy of such a plant in dealing with intermittent influxes of dyes at concentrations similar to those to be expected in practice. A simple test method is described which enables the tendency of a dye to be removed by removed by adsorption on activated sludge to be categorized. Application of the test to six classes of the dyes by some of the member firms of ETAD has indicated that the adsorption depends on the class of dye and to structural differences within the classes