Dyeing and Printing Waste Water Treatment

The textile dyeing and finishing industry is a major emitter of industrial wastewater, primarily containing impurities from textile fibers, oils, salts, as well as various sizing agents, dyes, surfactants, auxiliaries, acids, and alkalis added during the processing. However, the treatment of most dyeing and finishing wastewater is actually not very complex. Our company has extensive construction experience in wastewater treatment, and the treatment process has found that the biochemical properties of the wastewater are excellent after pretreatment. By combining conventional anaerobic and aerobic processes as the main components, we can meet national discharge standards, resulting in very clear effluent.

Wastewater characteristics include high organic matter concentration, complex composition, deep and variable color, significant pH fluctuations, and large variations in water volume and quality, making it difficult to treat. With the development of chemical fiber fabrics, the rise of artificial silk, and the increased requirements for post-dyeing and finishing, difficultly biodegradable organic substances such as PVA slurry, alkali-soluble substances of artificial silk, new dyes, and auxiliaries have been大量 introduced into textile dyeing and finishing wastewater. This poses a severe challenge to traditional wastewater treatment processes, with COD concentrations rising from the original hundreds of milligrams per liter to 3,000 to 5,000 mg/l.

Waste water from dyeing and sizing processes has high color concentration and COD levels, especially for the dyeing techniques like silk blue, silk black, extra deep blue, and extra deep black developed for the overseas market in recent years. These processes extensively use sulfur dyes and dyeing auxiliaries like sodium sulfide, resulting in high levels of sulfides in the wastewater. Such effluent requires chemical pretreatment before undergoing a series of treatments to ensure stable compliance with discharge standards. Bleaching and dyeing wastewater contains dyes, sizing agents, and surfactants, among other additives. This type of wastewater has a large volume but low concentration and color intensity. If only physical-chemical treatment is employed, the effluent concentration would be between 100 to 200 mg/l, and the color intensity would meet discharge requirements. However, the pollution load would significantly increase, and the cost of sludge treatment would be high, with a risk of secondary pollution. Under the current stringent environmental protection requirements, it is essential to consider biochemical treatment systems. Conventional enhanced biological treatment processes can meet the treatment needs.