Recent studies reported the use of suspended TiO2 powder as photo catalyst in the degradation process of several organic and inorganic substances in water, like chlorinated hydrocarbons, alkyl- and alkanoloammines and ammonia. In order to evaluate the possibility of using this method for a further removal of ammonia from wastewater after a biological nitrification/denitrification treatment, a kinetic study of photo oxidation over TiO2 of NH3/NH4 in the high concentration range of 26 - 214 mg/I, has been carried out. Effects of pH, TiO2, ammonium and dissolved O2 concentration on the degradation efficiency and reaction products distribution (NO2-, NO3- e N2) were studied. The results have shown that, at a catalyst concentration of 0.012% (p/v), the photo catalytic oxidation of ammonia can be described with the Langumuir- Hinshelwood kinetic model, as reported by several authors.