Title : Biological Renovation and Reuse of Spent Reactive

The objective of this project was to biologically renovate reactive dyebaths and reuse the high-salt containing mixture in the dyeing process. This approach accomplishes two goals: (a) elimination of the color from the plant effluent; and (b) reuse of the renovated process water and salts, thus leading to final wastewater volume reduction, and water, as well as salt conservation. Nine commercial reactive dyes (Black 5; Blue 4, 7, and 19; Red 2 and 120; Yellow 3, 15 and 17) were used in this study. Decolorization assays of simulated reactive dyebaths were conducted with an anaerobic, methanogenic culture at low salt concentrations as well as with a halotolerant culture maintained under microaerophilic conditions and at elevated salt concentrations. In addition, decolorization of a spent dyebath obtained from a package-dyeing plant was tested using the suspended growth, methanogenic culture. Overall, fast decolorization kinetics were observed, especially with the reactive azo dyes. A fixed-film bioreactor was developed with the halotolerant culture and used for the decolorization of Red 2 simulated dyebath solutions under microaerophilic conditions. Repetitive dyeing tests were conducted with the same Red 2 solution which was decolorized by the halotolerant culture under anoxic conditions and then the decolorized liquor was reused in a new dyeing test. The results of dyeing tests conducted with decolorized and recycled dye liquor when compared with those of standard reactive dyeings (i.e., dyeings conducted with fresh dye) resulted in very small and acceptable color differences. In conclusion, biological decolorization of spent reactive dyebaths is feasible under anoxic/microaerophilic conditions and reuse of the renovated process water in subsequent dyeings results in an acceptable fabric color.