Printing and dyeing wastewater is characterized by complex composition, high chromaticity, elevated organic content, and strong oxidation resistance. Additionally, it contains a wide variety of residual dyes, presenting significant challenges for treatment. This paper explores key methods for wastewater reuse in printing and dyeing factories.
The textile printing and dyeing industry is currently in a phase of high-capacity growth, yet it has long been plagued by issues of high water consumption and heavy pollution. The prevalent “pollute first, treat later” approach inherently increases treatment costs. To address this, factories should prioritize optimizing printing and dyeing processes to reduce wastewater-related challenges at the source, thereby achieving energy conservation and emission reduction goals. A critical component of this effort is wastewater reuse, which can be primarily accomplished through three technical approaches: physical methods, chemical methods, and biochemical methods.
1.Physical Methods
Physical treatment methods mainly include coagulation and membrane separation. Coagulation involves adding appropriate chemical agents to printing and dyeing wastewater to aggregate suspended solids or colloidal substances into large flocs, which are then removed via natural sedimentation.
2.Chemical Methods
Chemical treatment methods primarily encompass photocatalysis and electrochemical technology, with the latter being more commonly employed. In electrochemical technology, under the action of direct current, strong redox reactions occur at the anode and cathode. Pollutants are oxidized or reduced to low-toxicity or non-toxic substances, achieving decolorization and reducing pollutant concentrations.
3.Biochemical Methods
Biochemical methods include activated sludge processes, anaerobic hydrolysis, biological contact oxidation, and tower filter processes, among others. The working principle involves isolating microbial strains for industrial application; through the metabolism of these microorganisms, toxic substances are rendered harmless, and organic matter is mineralized (converted from organic to inorganic forms).
While the aforementioned methods enable wastewater reuse in printing and dyeing factories, online wastewater monitoring remains essential to prevent large-scale water pollution caused by the irrational discharge of sewage. After treating wastewater to meet relevant standards, discharge is only permitted after online monitoring confirms that all indicators are compliant. The scope of water quality monitoring is extensive, covering online domestic sewage monitoring, process water monitoring, online industrial water monitoring, and online medical wastewater monitoring, among others.
