Coagulation–flocculation–decantation of dye house effluents: concentrated effluents

• Published in: Journal of hazardous materials 2004-12, Vol.116 (1), p.57-64
• Main Authors: Allegre, C., Maisseu, M., Charbit, F., Moulin, P.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical and Process Engineering; Coagulation–flocculation–decantation; Coloring Agents - chemistry; Coloring Agents - isolation & purification; Conservation of Natural Resources; Dye-house effluents; Engineering Sciences; Exact sciences and technology; Flocculation; High concentration; Industrial Waste; Industrial wastewaters; Pollution; Reactive dye; Treatment; Waste Disposal, Fluid - methods; Wastewaters; Water Movements; Water Pollutants, Chemical - isolation & purification; Water Purification - methods; Water treatment and pollution
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2004.07.005

The treatment and valorization (recycling of water and mineral salts) of dyeing effluents constitutes a major economic and environmental issue. Cotton dyeing using reactive dyes is actually the most polluting in terms of discharge. In order to treat and valorize the effluent from a dyeing process using reactive dyes, the firm Clariant and the LPPE have developed and patented a process allowing the recovery of most of the water and salts present in the effluent and also of a concentrate containing the hydrolyzed reactive dyes and the highly concentrated auxiliaries. This paper describes the coagulation–flocculation–decantation process used to optimize water recovery from the concentrate. Coagulants and flocculants are used in the industry for the treatment of effluents produced by the synthesis of dyes in general (acid, disperse, reactive). Although the settling velocity is relatively low, the results show that it is possible to recycle a great volume of water using a small decanter area, since the concentrate flow rate is low. These effluents are substantially discolored, it possible to envisage recycling them.