The effect of the simultaneous use of ozone, UVA or visible light, and small quantities of Fe(II)/Fe(III) ions in solution on the degradation rate of the organic content of a bleaching Kraft mill effluent was investigated. The same treatment was applied to synthetic samples of polychlorinated phenolic compounds, because these are one of the main groups of compounds found in real bleaching Kraft mill effluents. In order to improve the treatment efficiency and to lower the cost of the process several other strategies were investigated. It was found that a previous irradiation of the wastewater or the synthetic sample in the absence of ozone significantly improves the rate of removal of organic pollutants during the subsequent ozonation step.