Verfahren zum Entfernen von Farben

Liq. effluent contg. dye(s) is treated as follows: (a) a reducing agent (I) is added at 50-100 ppm/1000 ADMI units of colour; (b) the effluent pH is reduced to 2-7; (c) a charge neutralisation mixt. comprising (i) 1 or more Al salts (II), and (ii) a cationic polymer (III) in wt. ratio 30-70:70-30 is added until the Zeta potential reaches +/-15 m volts; (d) the pH is adjusted to at least 5; and (e) the mixt. is flocculated by addn. of 1-5 ppm of a flocculant (IV). (II) is Al (poly)hydroxy-chloride, alum, AlCl3 and NaAlO2. (III) are (i) 1 or more H2O-soluble copolymer(s) of acrylamide with (meth)acryloylethyl tri-Me NH4 (X-) (X = Cl, Br, I, SO4, and MeSO4); (ii) cpds. of formula (III)(ii) below; and (iii) cpds. of formula (III)(iii) below. (IV) are (i) anionic acrylic acid/acrylamide copolymers of mol. wt. above 2,000,000, and/or (ii) nonionic polyacrylamides of mol. wt. above 2,000,000. H-[N+ (X-)(R1)(R2)-CH2CH(OH)CH2]m-H (III)(ii) R1, R2 = H or 1-8C opt. branched, opt. substd. alkyl; X- = Cl, Br, I, SO4, and MeSO4; m = 200-50,000; R3, R4 = 1-8C opt. branched alkyl.