Physico-chemical treatment and biosorption of dyehouse effluents - possibility of water recycling

Abstract

Growing use of reactive dyeing in textile wet finishing processes causes unsustainable utilization increase of salts as essential auxiliary agent. Therefore, selection of wastewater treatment method and partial reuse of treated effluents, as well as quantification of electrolytes should be determined as non-negligible values of outmost importance, economically and environmentally significant. This paper approaches to these issues systematically from simulating dyeing processes under laboratory conditions to gathering synthetically obtained effluents, which are then treated using two methods; flocculation/coagulation and biosorption. Possibility of partial treated effluent reuse is based on continuous on-line water quality analysis (monitoring standardized water quality parameters: SAC, COD, BOD5 electrical conductivity) and application of mathematical dependency models between measured electrical conductivity and concentration of electrolytes. Depending on type of utilized dyeing process and effluent treatment method, a save of up to 10 % in electrolytes was obtained in a consecutive dyeing process. Regardless of dyestuffs‘ chemical constitution, high degree of discoloration is obtained for both applied methods. Relationship between usually measured biological parameters of wastewater BOD5 and COD indicates method of biosorption as more applicable (decrease in BODS a COD up to 75 %). Results confirm method of biosorption as more suitable for treating effluents, which are to be let out into the natural waterways, while greater salt concentrations are obtained in effluents treated by flocculation/coagulation. Biosorption results in 80 % electrolyte removal, referenced as highly efficient when compared to only 30 % of overall electrolytes removed by flocculation / coagulation.