Pollution by sewage in rivers carries microbial load with potential for contamination of primary contact recreation areas and consequent risk to health. Contamination of seawater and sand on Leblon beach (Rio de Janeiro / RJ), which occurs in event of heavy rainfall carrying sewage to the beach, occurs by the overflow of the rivers of the drainage basin of the Lagoa Rodrigo Freitas system (LRF), due to the opening of the Avenida Visconde de Albuquerque s channel s lock . In this context, it is of great importance to prevent Leblon beach water and sand from this bacterial load. Studies conducted in the present work aimed at rapidly disinfecting water bodies polluted by sewage using peracetic acid (CH3CO3H) and sodium hypochlorite (NaClO) in comparison, in order to analyze their effect on the coliform count, taking into account the current Brazilian environmental legislation, assuring that the applied disinfectant agent do not exceed the lethal concentration for aquatic species in the rivers that are object of treatment. The effects of different doses (2.5 mg/L, 5.0 mg/L and 10.0 mg/L) of the two types of sanitizers on the coliform count over time. Previously, the waters of selected rivers were characterized in their main quality parameters. The analyses were performed by the Most Probable Number method. The study concluded that with peracetic acid the inactivation of coliforms is faster at lower doses (average of 2 minutes at a concentration of 2.5 mg/L) when compared to sodium hypochlorite, which also proved to be effective, but at higher concentration and contact time.