Since they often inhibit abundant bacteriological populations in municipal wastewater treatment plants, alternative treatment methods should be investigated - including advanced oxidation processes. This paper studies the degradation of three representatives of phenolic compounds using the Fenton system in the presence of chlorides and sulfates: phenol, 2-chlorophenol and 2-nitrophenol. The presence of anions influenced degradation rates of all studied compounds, which is attributed to the reduction in hydroxyl radical generation due to the formation of iron-complexes as well as the formation of much less reactive inorganic radicals. Differences between degradation rates of studied compounds and their degradation products in comparison to the rates observed for pure components show higher resistance of formed intermediates in comparison to phenol or 2-nitrophenol. Additionally, it was found that present anions influence further biodegradation of phenolic compounds but not similarly for all the compounds.