Characterization and coagulation/flocculation treatment of coloured wastewater of institutional dyeing laboratory

Abstract

This study focuses on the quantitative and qualitative characterization of coloured wastewater of an institutional dyeing laboratory and its treatment via coagulation/flocculation (CF), where the cumulative volume of wastewater is large and generally discharged without any treatment. Primarily woven fabric pieces of cotton, wool, silk, nylon, acrylic, and polyester are dyed using standard dyeing procedure maintaining the liquor ratio of 50. Total 23 dyes from the different class of dyes viz., direct, reactive, acid, cationic, sulfur, vat, and disperse are used for dyeing of fabric samples. The generated colored wastewater is characterized for its volume, pH, total dissolved solids, turbidity, colour concentration, and biological and chemical oxygen demand. The qualitative characteristics of generated coloured wastewater influenced the preparation of two types of simulated coloured wastewaters which later subjected to CF using the coagulants (ferric chloride and a commercial polymeric coagulant). The pH of coagulation bath, coagulant dose and type influenced the color removal efficiency, where the polymeric coagulant performed better as compared to ferric chloride. Adaptable approaches and strategies have also comprehended in this study, which are adaptable to reduce the colored wastewater volume, thus leading to achieve the sustainability.