Sensibilidade de Escherichia coli, Salmonella, Typhimurium, Staphylococcus aureus e Pseudomonas aeruginosa à desinfecção com luz natural e artificial: avaliação da capacidade de reativação bacteriana.

Abstract

The disinfection o f waters destined to human consumption requires the use of safe and efficient methods in the inactivation o f pathogenic microorganisms and in the generation o f by-products non harmful to the human health. The lack or inadequacy of drinkable water supply, especially in rural areas, and small towns or villages, has been aggravating the transmission of hydric vehicled diseases. Alternative disinfection methods, characterized by their low costs and easy handling, have been being applied. Within these stand out the SODIS (Solar Disinfection of Water) technology, investigated in this research. For such, transparent PET bottles were used, filled up to 3A of their capacity with water o f turbidity inferior to 30UNT, and polluted with bacteria indicative o f fecal contamination and selected enteropathogenic bacteria, exposed from 4 to 6 hours to natural solar light, to the light of solar lamps and to artificial UV radiation supplied by germicide lamps. For evaluation of the occurrence or not of the restoration of the damage provoked in the DNA o f the microorganisms (bacterial regrowth) by the solar radiation and the UV artificial radiation, studies o f bacterial regrowth were accomplished 24 and 48 hours after the disinfection. The results evidenced 100% of efficiency o f the natural solar light and of the solar lamps in the destruction/inactivation o f the populations of S. typhimurium (ATCC 3985), Salmonella spp, E. coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). The technique of SODIS appeared as a viable alternative technology of disinfection when the water presents initial concentration from 103 to 105 CFU/lOOml, turbidity inferior to 30UNT and is under climatic conditions that favor the synergic action between UV radiation and heat. Although the germicide lamps possess strong bactericidal effect, there was no inactivation o f the enteropathogenic bacteria present in the waters submitted to that disinfecting agent. It was observed that inexistence of residual effect from the UV radiation, as well as the great capacity of resistance of P. aeruginosa (ATCC 939) favored the bacterial regrowth.