The textile dyeing industry consumes large quantities of water and produce large volumes of wastewater from different steps in the dyeing and finishing processes, it is often rich in color, containing residues of reactive dyes and chemicals, such as complex components, many aerosols, high chroma, high COD and BOD concentration as well as much hard-degradation materials.
Textile printing and dyeing processes include pre-treatment, dyeing and printing, fishing. The main pollutants are organic matters which come from the pre-treatment process of pulp, cotton gum, cellulose, hemicellulose and alkali, as well as additives and dyes using in dyeing and printing processes.
It will cause significant environmental problems if a textile mill discharges the wastewater into the local environment without treatment. It will has a serious impact on natural water bodies and land in the surrounding area.
Large amount of wastewater is discharged in the four printing and dyeing steps of cotton, hemp, chemical fiber and blended products. Other pretreatment processes including singeing, desizing, scouring, mercerizing also is accompanied by wastewater discharge. According to relative statistics, 100-200 tons of water is consumed for producing one ton of textile, among which 80?90% water become polluted water and should be treated. There are several technical problems to overcome, such as high TDS, high content of organic pollutant, deep color, wide pH variation range, dramatic water quality change, new additives.