DEGRADATION OF RESIDUAL DYES IN TEXTILE WASTEWATER BY OZONE: EFFECT OF HYDRODYNAMICS AND CAVITATION

Downstream dyeing facilities, a noticeable amount of dyes may remain in the wastewater giving anaesthetic colouration. Conventional biological treatment alone cannot guarantee decolouration and tertiary treatments have to be considered: two oxidation routes by ozone were considered in this work. A bubble column reactor (benchmark, also at industrial scale) and a recycle well-mixed reactor were compared to reach a complete decolouration. In addition, hydrodynamic and ultrasonic cavitation were considered in the recycled well-mixed reactor to intensify its performance. Ozone treatment was protracted to obtain different decolouration degrees on wastewater from wool dyeing. The resulting water was tested as recycled fluid to generate dyeing liquors, the definition of minimal quality specification being the goal of this procedure