Solution for cotton textile industrial wastewater

Industry Status

Wastewater in the cotton textile industry mainly comes from the dyeing and finishing process, including desizing, scouring, bleaching, mercerizing, dyeing, printing and finishing. Desizing wastewater is alkaline organic wastewater, containing pollutants such as various sizing decompositions, fiber debris, acids and enzymes, and the wastewater is yellowish.

Scouring wastewater is large in volume and strongly alkaline, with an alkali concentration of about 0.3%. The wastewater is dark brown, and both BOD and COD are as high as several thousand milligrams per liter. In the cotton textile production process, each procedure indirectly generates wastewater, so solving the impact of wastewater on people's lives is particularly important.

According to the water quality characteristics of cotton printing and dyeing wastewater, the main targets of wastewater treatment are alkalinity, organic matter that is not easily biodegradable or degrades slowly, dye pigments and toxic substances.

Domestic cotton and cotton textile dyeing wastewater mostly adopts aerobic treatment as the main process. Biological treatment works well for pure cotton fabric dyeing wastewater, but has poor effects on cotton blended fabric dyeing wastewater and pure chemical fiber fabric dyeing wastewater. Knitted products have no desizing wastewater, so the biological treatment effect of their wastewater is better than that of woven product wastewater.

Considering various technical conditions, biological fluidized beds, contact oxidation and aerated grit chambers are preferred, and treatment plans can be selected according to the specific conditions of each factory. It is generally believed that: when the wastewater volume is small (less than 500 m³/d), contact oxidation-coagulation sedimentation is selected; when the wastewater volume is large (more than 500 m³/d), to save floor space, biological fluidized bed-coagulation sedimentation is recommended.

For the treatment of cotton printing and dyeing wastewater, in addition to the typical processes mentioned above, some special treatment technologies should be adopted according to the water quality characteristics of specific discharge objects, such as the removal of alkalinity, chroma and some toxic substances.