We evaluate the use of an industrial residue (copper slag) as catalyst in water treatment. ► The copper slag was effective to remove organic pollutants (phenol) from water. ► During experimentation, Cu and Fe leaching were not higher than the acceptable levels. ► Slag/H2O2/UV and slag/H2O2 treatments promoted biodegradability increment of the contaminated water. ► The control of the reaction time would minimize the environmental impact of the produced effluents in terms of acute toxicity.