Liquid Discharge
Liquid waste streams generated during scouring, bleaching, dyeing, and finishing operations carry heavy loads of dissolved chemicals and unfixed dyes. This wet processing effluent must be monitored and treated before it is discharged into public waterways or municipal systems. Its volume and composition fluctuate based on the specific fibers and dye classes processed by the mill.
Chemical Composition
Sizing agents like polyvinyl alcohol and starches increase the chemical oxygen demand of the raw discharge. Auxiliaries such as salts, surfactants, and heavy metal complexing agents are used to ensure even dye distribution but remain in the wastewater afterwards. Alkaline chemicals from mercerization and chlorine residues from bleaching add to the chemical complexity of the flow.
Treatment Necessity
Factories install specialized treatment systems to neutralize the high pH and remove the intense coloration from the water. Successful purification requires both chemical precipitation of dye pigments and biological digestion of organic surfactants. By recycling treated water back into the washing baths, modern mills can lower their fresh water consumption.
Environmental Boundary
Strict local discharge limits dictate the permissible levels of chemical oxygen demand and heavy metals in the treated stream. Failing to meet these environmental standards results in immediate legal penalties and can stop factory operations.
