The objective of this study was to evaluate the efficiency of dissolved ozone flotation (DOF) in comparison to dissolved air flotation (DAF) for treatment of milk industry wastewater (MW). In the first phase of the experiment, a synthetic milk wastewater (SMW) was used to evaluate DOF and DAF, with and without addition of hydrogen peroxide, at pH 4.0 and pH 11.4. In the DOF tests, the concentration of ozone was equal to 19 ( 0.5) mg L-1 and in the tests with addition of hydrogen peroxide, the H2O2/O3 ratios tested were 0.5, 1.0 and 1.5. In the second phase, tests were performed using three MW from three different industries to validate the results obtained and to determine the DOF system's ability to treat this type of effluent. The parameters tested during validation were turbidity, total suspended solids, oils and greases (O&G), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP). It was observed that the efficiency of the treatments was better at pH 4.0. The results showed a reduction of the efficiency with the use of DOF. The addition of H2O2 in DAF and DOF also resulted in reduced system efficiency. The results obtained with SMW only approximated those obtained with the MW from one of the industries that contained the largest traces of milk and cheese. ; The objective of this study was to evaluate the efficiency of dissolved ozone flotation (DOF) in comparison to dissolved air flotation (DAF) for treatment of milk industry wastewater (MW). In the first phase of the experiment, a synthetic milk wastewater (SMW) was used to evaluate DOF and DAF, with and without addition of hydrogen peroxide, at pH 4.0 and pH 11.4. In the DOF tests, the concentration of ozone was equal to 19 ( 0.5) mg L-1 and in the tests with addition of hydrogen peroxide, the H2O2/O3 ratios tested were 0.5, 1.0 and 1.5. In the second phase, tests were performed using three MW from three different industries to validate the results obtained and to determine the DOF system's ability to treat this type of effluent. The parameters tested during validation were turbidity, total suspended solids, oils and greases (O&G), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN) and total phosphorus (TP). It was observed that the efficiency of the treatments was better at pH 4.0. The results showed a reduction of the efficiency with the use of DOF. The addition of H2O2 in DAF and DOF also resulted in reduced system efficiency. The results obtained with SMW only approximated those obtained with the MW from one of the industries that contained the largest traces of milk and cheese. ; O objetivo deste estudo foi avaliar a eficincia da flotao por ar e oznio dissolvido (FAOD) em comparao flotao por ar dissolvido (FAD) no tratamento da gua residuria de laticnios (ARL). Na primeira fase do experimento foi utilizada gua residuria de laticnios sinttica (ARLS) para avaliar a FAD e a FAOD, com e sem a adio de perxido de hidrognio em dois valores de pH, 4,0 e 11,4. Nos testes de FAOD, a concentrao de oznio utilizada no ar foi igual a 19 ( 0,5) mg L-1 e nos testes com adio de perxido de hidrognio, as relaes H2O2/O3 testadas foram de 0,5, 1,0 e 1,5. Na segunda parte do experimento, foram realizados testes com trs ARL de trs diferentes laticnios para validar os resultados obtidos e determinar a capacidade do sistema FAOD para tratar esse tipo de efluente. Os parmetros testados durante a validao foram: turbidez, slidos totais suspensos, leos e graxas (O&G), demanda qumica de oxignio (DQO), demanda bioqumica de oxignio (DBO), nitrognio total (NT) e fsforo total (PT). Ao final do experimento, observou-se que a eficincia dos tratamentos foi melhor em pH 4. Os resultados mostraram uma reduo da eficincia com o uso da FAOD. A adio de H2O2 na FAD e FAOD tambm resultou em menor eficincia nos dois sistemas. Os resultados obtidos com ARLS aproximaram-se apenas dos obtidos com o ARL de uma das indstrias que continham os maiores traos de leite e queijo.