Treatment of Dyehouse Effluents with PERIFLOC Flocculants

Dyehouse wastewater, but also effluents from printing plants or laundries, are frequently tinted with residual dyes, water-soluble dyestuffs or colored pigments. Worldwide, the textile industry produces hundreds of millions of cubic meters of dyed wastewater, which, if not decolorized or treated, could reach surface water and pollute it.

Many finishing plants run on-site wastewater treatment facilities. For decolorization water-soluble dyestuff molecules in the wastewater can be precipitated with special flocculants. Usually, inorganic or synthetic organic flocculants and coagulants are used. First of all, the dyestuff molecules are precipitated with primary flocculants. Subsequently, the size and weight of the agglomerates should be increased with the help of so-called secondary flocculants in order to produce larger flocs. The mechanical mixing of the effluents with the flocculants has to be followed by a motionless sedimentation phase. Turbulence and shear forces could otherwise cause the relatively unstable agglomerates of flocculants and dyes to be disrupted again. Finally, the solid and liquid phases are separated by flotation or sedimentation and the sludge is disposed of accordingly. The decolorized wastewater can then be discharged into the sewer system for further wastewater treatment.