Estudo da desinfecção por radiação ultravioleta em águas superficiais com diferentes valores de turbidez: uma análise crítica da portaria Nº 888/2021

Abstract

Drinking water is essential for human beings. Potable water is water that meets the drinking water standard established by Ordinance GM/MS No. 888, of May 4, 2021, and that does not pose any health risks. Water used for human consumption can present various health risks, which are associated with the presence of chemical, physical and microbiological contaminants. With regard to the microbiological standard, the Ordinance establishes that the maximum value allowed is the absence of total coliforms and Escherichia coli bacteria in 100mL of the sample analyzed and requires that all water for human consumption supplied collectively must undergo a disinfection process. One of the most commonly used techniques for disinfecting water is chlorination. However, some limitations have been associated with the use of chlorine and alternative methods, such as ozonation and the use of ultraviolet radiation, are already covered by GM/MS Ordinance No. 888/2021. The aim of this work was to study the process of ultraviolet (UV) disinfection, using batch and continuous flow reactors, in water samples collected from the Jaguaribe river, in João Pessoa (PB), after physical-chemical treatment. In addition, water samples collected at the point of consumption at the Federal University of Paraíba were also subjected to the ultraviolet radiation disinfection process. The influence of the remaining turbidity in the water and the radiation dose on the disinfection efficiency was evaluated, and the dose values obtained were compared with those established by Ordinance No. 888/2021. For batch disinfection, the results indicated that turbidity, although an important factor in the process, is not the only determining parameter. Inactivations of 1.19 log (94%) and 1.40 log (96%) were achieved for radiation doses of 138 and 140 mJ.cm-2 , respectively. However, for continuous flow disinfection, it was determined that turbidity is a limiting parameter in the process, since samples with higher values showed greater resistance to inactivation. A maximum inactivation of 1.24 log (94.3%) was achieved for a radiation dose of 128.4 mJ.cm-2 , for the sample with 0.69 uT. In addition, in view of the data obtained in this study and observed in the literature, it was noted that Ordinance GM/MS No. 888/2021 has minimum radiation dose values that do not certify efficient ultraviolet radiation disinfection under the established parameters