Different Techniques Recently Used For the Treatment of Textile Dyeing Effluents: A Review

Industrial textile processing comprises the operation of pretreatment, dyeing printing and finishing. These production processes produce a substantial amount of chemical pollution. Textile finishing's wastewater, especially dye house effluent contain different classes of organic dyes, chemicals and auxiliaries. They are colored and have extreme pH, COD and BOD values, and contain different salts, surfactants, heavy metals and mineral oils. Therefore, dye bath effluents have to be treated before being discharge into the environment or municipal wastewater reservoir. This paper presents the review of different techniques currently used for the treatment of textile effluent, which are based on carbon adsorption, filtration, chemical precipitation, photo degradation, biodegradation and electrolytic chemical treatment. Membrane Technology has also been applied with the objective of recovering dyes and water. Biological processes could be adopted as a pretreatment decolorization step, combined with conventional treatment system (e.g. coagulation-flocculation, adsorption on activated carbon) to reduce the COD and BOD, an effective alternative for use by the textile dyeing industries. Electrochemical oxidation is an efficient process for the removal of colour and total organic carbon in reactive dyes textile wastewater. The ozonation is effective for decolorization of several dyes of different classes. Practical application of this process is feasible by treating industrial textile effluent after biological treatment. Processes using membranes technique, very interesting possibilities of separating hydrolyzed dyestuffs, dyeing auxiliaries and reuse treated wastewater in different finishing operation of textile industries.