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Peracetic acid (PAA) is efficient for disinfection processes in environmental sanitation and in the presence of transition metals its oxidative performance is enhanced. Thus, the present study aim evaluated the influence of Fe3+ ions during the inactivation process of Escherichia coli and Total Coliforms (TC). The process PAA + Fe3+ ions were also evaluated in relation to the disinfection kinetics, the participation of H2O2 and the influence of the organic load of the treated water. The tests showed an inactivation efficient of 0.5 to 0.9 log in relation to E. coli and 1.3 to 1.5 logs for TC in the concentrations evaluated and complete inactivation of E. coli was achieved within 15 min for both PAA and PAA/Fe3+ There is no damage to the disinfection process in the presence of Fe3+ ions, however, the decomposition of PAA is favored. In this sense, the formation of radicals can justify the maintenance of disinfection efficiency. The decay constants were close both microorganisms: for E. coli with PAA and PAA/Fe3+were 0.0323 and 0.0476 and for TC were 0.0637 and 0.0667. The values of R2 were above 0.95. Computer simulations of peptidoglycans that make up the bacterial cell wall showed that radicals preferentially attacked the carbons from the rings that composes the cell wall peptidoglycan of gram-negative bacteria allowing to break the structure during the disinfection process. [ABSTRACT FROM AUTHOR]