Such phenomenon is a function of the
chemistry of the particular dye and of the microbial biomass
(Robinson et al., 2001): the most easily adsorbed dyes are direct,
basic and disperse dyes (activated sludge removes medium to high
portions of soluble basic and direct dyes, principally by adsorption),
while acid and reactive ones are poorly adsorbed (Delee et al.,1998;
Rozzi et al., 1998; Vandevivere et al., 1998).