Reuse of decolourised wastewater of azo dyes containing dichlorotriazinyl reactive groups using an advanced oxidation method

The possibility of reusing textile wastewater in dyeing processes is invest igated in this study. Wastewater was first decolourised by an advanced oxid ation method and was then reused in the dyeing of cotton fabric. It was fou nd that decomposition products of the azo dyes used in this study released hydrogen peroxide and sodium sulphate, which were found to be present in th e initial wastewater following decolourisation. Removal of this hydrogen pe roxide from the wastewater prior to subsequent dyeings produced a dyeing co lour strength of 98.4% as compared to that of the standard dyeing. A second reuse of this wastewater resulted in a slightly lower colour strength of 9 4.4% as compared to standard dyeing.