Estudo da eficiência de desinfecção com permanganato de potássio, cloro gasoso e ozono na etapa de pré-oxidação da água na ETASábiè

Abstract

Drinking water is an essential resource for human health and socioeconomic development, but increasing demand and pollution of water sources make its treatment of great importance. The preoxidation step in treatment is a crucial challenge. The pre-oxidation step in water treatment plays a key role in removing pathogenic microorganisms and improving water quality. The study compared the efficiency of three oxidants (potassium permanganate, chlorine gas and ozone) in the pre-oxidation step of water at the Sábiè Water Treatment Plant, located in the Corumana region, Maputo province. A total of 90 water samples were collected over 4 months (August 2023 to January 2024 excluding October and November), covering different microbiological load conditions. The samples were analyzed for the presence of total and fecal coliforms using the multiwell method, and the efficiency of the oxidants was calculated based on the decimal reduction and the percentage of microorganism removal. The statistical analysis for total coliforms revealed significant differences between the raw water results obtained for the different oxidants, as well as in the different months of treatment at a 95% confidence level. For fecal coliforms, there was a significant difference between oxidants; however, at the same confidence level, the raw water results obtained over the months under study were significantly equal. The results showed that ozone was the most effective oxidant, with an average efficiency of 97,28% in the removal of total coliforms, 87,44% for chlorine gas and 81,88% for potassium permanganate. Ozone is the most recommended oxidant for treatment plants that prioritize disinfection efficiency, although its cost and implementation complexity may be limiting. Chlorine gas, widely used due to its low cost and ease of application, remains a viable option, but requires rigorous monitoring to ensure its effectiveness. Potassium permanganate, although less effective in disinfection, can be used as a complement in treatment systems aimed at removing inorganic compounds.