Aplicação de gráficos de controle estatístico de processo para avaliação de desempenho de estações de tratamento de água

The research presents results from an evaluation of performance and stability of fifteen water treatment plants (WTP) through the statistical process control charts application considering the data from 2015 and 2016 of turbidity, apparent color, concentrations of residual chlorine and fluoride. The analyzes were performed considering raw water, treatment efficiency, the standards of potability and stability of WTPs, according to the size and treatment technologies. The results showed that, in general, conventional WTPs presented higher values of raw water turbidity and color compared to other, fact that reflected the efficiency of removal of these parameters, allowing to achieve higher levels of performance. In reference to compliance the potability standards, it was noticed that for turbidity, in 2015, only one station didnt meet the established standard. In 2016, however, only six stations were successful in meeting the most restrictive standard. Considering the parameters color, chlorine and fluorine, it was observed that all the stations reached 100% of attendance for the color and fluoride and, also, 100% of for chlorine, except for two WTPs. Stability evaluation of treatment plants grouped by size showed that the midsize stations were more stable, followed by small and large treatment plants. Considering the stability of the treatment technology, it was verified that in the conjuncture of the small treatment plants, the WTP of direct filtration achieved higher performance, followed by conventional technology and, finally, by double filtration. As for the group of large ETAs, greater stability was observed for the oxidation filtration and direct filtration, followed by the complete cycle with flotation. It was not possible to confirm the hypothesis that, due to the progressive goals established by Brazilian Ordinance 2914/2011, any changes made during the course of 2015 in the water treatment process would increase efficiency and improve performance in 2016