Abstract An enzymatic cocktail was used for the decolorization of process wastewater, containing mainly three reactive azo dyes, from a textile dyeing and printing company.

Water sampled from different processing streams and combinations thereof was decolorized to different extents.

The decolorization was greatest for C.I. Reactive Black 5, followed by C.I. Reactive Red 158, whereas C.I. Reactive Yellow 27 was the least decolorized. As wastewater from the printing process was inhibitory, the 1 m^sup 3^ stirred tank type reactor prototype was installed near the outlet prior to the discharge of wastewater from the printing process. Temperature and pH control systems were installed to ensure optimal enzymatic decolorization, this being about 45°C and pH 6.4. The average temperature observed at the reactor was 42.1°C,
which indicated the need for improved temperature control. Laboratory scale tests were done to assess the reuseability of the biotreated wastewater for the washing of dyed cotton fabrics.

Key words bioreactor, oxidoreductases, process wastewater, reactive dyes

One of the more urgent problems facing the textile industry is the removal of color from dyebath effluent prior to discharge to local sewage treatment facilities The textile dyeing and printing sector has a specific water consumption as high as 400 m^sup 3^/ton of fabric [7]. This represents not only a major expense but is also an environmental issue of much consequence. Several industrial-scale decolorization systems are commercially available [18]. These include adsorption, filtration, precipitation, and activated sludge systems.

All of these technologies work by concentrating the dyestuffs and transferring them to a solid phase that subsequently needs disposal.