INATIVAÇÃO DE MICRORGANISMOS INDICADORES POR SISTEMAS COMBINADOS DE DESINFECÇÃO

Abstract

This study evaluated the efficiency of individual disinfection methods using peracetic acid (PAA), hydrogen peroxide (H2O2) and UV radiation and the combined disinfection methods of PAA/UV and H2O2/UV for final effluent of municipal wastewater treatment plant. It was evaluated the performance of the disinfectants used according to the inactivation efficiency of the indicator microorganisms, E. coli, total coliforms, Clostridium perfringens and coliphages. To the experimental conditions adopted, the concentrations of PAA and H2O2 were 2,0 and 3,0 mg/L and contact time of 10 and 20 minutes, with mean exposure doses ranging from 30,62 to 206,65 mWs.cm² for UV radiation. The PAA/UV and H2O2/UV disinfection consisted of a combination of the times, concentrations and doses of disinfectants adopted in individual methods. The results obtained in the disinfection tests with peracetic acid and hydrogen peroxide did not promoted significant inactivations for any of the indicator microorganisms, under the experimental conditions employed. The UV radiation showed to be more effective in the reduction of all the indicator microorganisms, showing superior results compared to the other disinfectants. The disinfection processes PAA/UV and H2O2/UV showed near inactivations to those obtained by UV radiation method, reaching higher inactivation results for all the indicator microorganisms, these results occurred in isolation for the experimental conditions adopted. Clostridium perfringens was the microorganism that showed higher resistance to inactivation for all disinfectants used. The occurrence of synergism was observed for Escherichia coli, Clostridium perfringens and coliphages, only in the concentrations and times of superior contacts. There was a significant increase of 1 log of inactivation for C. perfringens compared to the results obtained by individual methods, when combined H2O2/UV disinfection method was used.