Dyeing and finishing, also known as textile printing and dyeing, refers to the chemical treatment processes applied to textile materials. The resulting effluent, commonly termed “printing and dyeing wastewater,” constitutes a critical pollution source within China’s industrial sector. This wastewater contains substantial quantities of recalcitrant organic compounds that are difficult to biodegrade, posing significant challenges for effective treatment. This article outlines essential knowledge required prior to implementing online water quality monitoring systems for dyeing and finishing wastewater. Specifically, we examine the primary sources and characteristic features of this effluent.

Primary Sources of Dyeing and Finishing Wastewater

1.Pretreatment Processes:Effluent generated during bleaching, scouring, singeing, and desizing operations;

2.Printing and Dyeing Operations:Wastewater produced during pattern application and color fixation stages;

3.Soaping/Rinsing Stages:Discharge arising from soap-based washing procedures;

4.Finishing Treatments:Residual wastewater expelled during final functional or aesthetic finishing processes.

Key Characteristics of Dyeing and Finishing Wastewater

1.High Volume and Intense Coloration:The discharge exhibits large volumetric flow rates accompanied by deep chromaticity and high color intensity;

2.Alkaline Nature and pH Fluctuations:Beyond high color load, the wastewater demonstrates pronounced alkalinity and significant pH variability. For instance, facilities often employ evaporation-concentration techniques to recover sodium hydroxide (NaOH). After multiple reuse cycles, the resultant effluent typically presents strongly alkaline properties;

3.Dynamic Water Quality Variability:The composition and concentration parameters of the wastewater fluctuate markedly over time;

4.High Organic Load and Toxicity:Elevated concentrations of organic pollutants contribute to the presence of toxic substances, increasing the ecological risk associated with untreated discharge.

A comprehensive understanding of these characteristics is prerequisite to developing targeted treatment strategies (“precision intervention”). This foundational knowledge facilitates the design and implementation of robust wastewater treatment protocols and online monitoring systems, ensuring that all regulatory discharge standards are met before environmental release.