This paper deals with the development and application of two methods for the de-contamination of waste and underground water polluted by a variety of hazardous halogenated organic substances, namely polychlorinated biphenyls, chlorophenols, perchlorates and especially their decomposition products dichloroethanes and vinyl. chloride, and potentially also polybrominated diphenyl ethers. The decomposition of organic substances by active! radicals (Fenton reaction under the action of UV-irradiation) and by reductive dehalogenation (dehalogenation of organics on metallic Pd deposited on different supports at the presence of zero-valent iron-Pd/Fe) has been studied. To test the efficiency of both methods, water spiked with contaminants in the laboratory and real contaminated water samples collected from the field were treated. The results presented document the feasibility of both methods, even though their efficiencies differ from those reported in the literature. The weak point of both methods is 3. tendency to gradual blocking of catalyst and UV lamp surfaces by inorganic precipitates when treating waters originating from polluted industrial sites.