Owners of textile printing and dyeing plants and wastewater operation & maintenance personnel all know that printing and dyeing wastewater ranks among the most intractable types of industrial wastewater. Characterized by dark color, high organic content and strong alkalinity, it contains residual dyes, sizing agents, auxiliaries and fiber flocs. The wastewater appears black and turbid, featuring poor decolorization and sedimentation performance, while environmental supervision standards remain extremely stringent. Complicated treatment processes are unnecessary; selecting the proper polyacrylamide (PAM) can resolve most wastewater treatment challenges for printing and dyeing facilities. Prioritizing domestically manufactured polyacrylamide from China can further boost operational efficiency.
Unlike mine and sand washing wastewater, printing and dyeing wastewater boasts an extremely complex composition, consisting of residual dyestuffs, textile sizing agents, surfactants and microfiber suspended solids. These contaminants feature low molecular weight and complex surface charges, making natural sedimentation ineffective. Consequently, the effluent suffers from excessive chroma and elevated COD values, and unauthorized discharge will easily result in environmental penalties. Polyacrylamide serves as a high-efficiency water purification agent specifically developed for such complex wastewater streams.
A common pitfall for numerous manufacturers is indiscriminate dosing without matching PAM models. To put it plainly, two application scenarios apply to printing and dyeing wastewater:
Anionic polyacrylamide is the preferred choice for decolorization and front-end coagulation sedimentation;
Cationic polyacrylamide is mandatory for clarifying biologically treated effluent and sludge dewatering.
Incorrect model selection leads to persistent turbid water and unsatisfactory decolorization regardless of dosing volume, unnecessarily driving up chemical consumption costs.
Its working mechanism relies on adsorption and agglomeration. Dye particles, microfibers and colloidal contaminants in printing and dyeing wastewater are highly dispersed and remain suspended stably. Upon dosing fully dissolved polyacrylamide, the polymer molecular chains rapidly capture these micro-impurities and bind them together to form large, dense flocs. The heavier flocs settle rapidly, enabling immediate stratification and clarification of originally dark, colorful and turbid wastewater with visible improvements in decolorization and turbidity reduction.
Standard operation procedures are straightforward. Dissolve PAM in clean water at a mass ratio of 0.1%–0.2% and stir until no agglomerates remain. Meter the prepared solution into the coagulation tank or the inlet of the sedimentation tank according to wastewater concentration. Combined use with polyaluminum chloride (PAC) delivers superior decolorization performance, forms firmer flocs and cuts down PAM consumption. The treated clean effluent can be recycled for workshop rinsing and floor washing, reducing the plant’s tap water expenditure.
Furthermore, excess sludge generated from biochemical tanks in printing and dyeing plants features high moisture content and light texture, resulting in difficult filter pressing and severe equipment adhesion. Conditioning sludge with cationic polyacrylamide produces well-formed sludge cakes that do not stick to filter cloths, allowing spiral dehydrators and belt filter presses to efficiently extrude dry sludge cakes for convenient off-site disposal, completely eliminating sludge treatment bottlenecks. In summary, proper selection of polyacrylamide models and optimized combined dosing for textile printing and dyeing wastewater treatment achieve stable performance in decolorization, COD reduction, solid-liquid separation and sludge dewatering, with low dosage and minimal operation & maintenance costs. Polyacrylamide is an indispensable environmental protection chemical for the printing and dyeing industry.