Inovações tecnológicas para o tratamento de água para consumo humano

Abstract

Treatment of water for human consumption has as a great challenge the stability of water in the supply network, with a fundamental step being disinfection to control pathogenic microorganisms. Disinfection using chlorine gas can lead to the formation of disinfection byproducts (DBPs) that are harmful to health. Thus, new technologies for disinfection that do not form these by-products are being tested and one of them is electrochemically activated (ECA) water generated by direct electrolysis of sodium chloride (NaCl) solutions. Dirty (red/brown) water is a recurring phenomenon that causes several setbacks to the community and to sanitation companies and has as its causes the characteristics of raw water as well as structural, operational factors of the system and secondary reactions in the network. The objective of this work was to evaluate the technological innovations applied to improve the quality of water for human consumption in a case study, in the industrial plant using the two disinfection processes - chlorine gas and ECA water - for 36 months, covering periods of drought and rain with a total of 12960 laboratory analyses. The use of ortho-polyphosphate in the water supply to stabilize the water in the supply network, with 14 months of evaluation was also studied. The parameters iron, manganese, turbidity, residual chlorine, pH, total and thermotolerant coliforms were monitored, in addition to PSD - total haloacetic acids, bromate, chlorite, 2,4,6-trichlorophenol, total trihalomethanes. The data were submitted to statistical treatment by analysis of variance with significance level of 5%. No DBPs were formed in either system, residual chlorine using gas suffered a marked decay in both periods being more intense in the rainy season. On the other hand, ECA water kept the residual chlorine level until the tips of network (PR) without having significant variation between dry and rainy seasons. The cost of the two processes was compared and the electrolysis presented savings of 41.56%. For ortho-polyphosphate application, significant reduction of colour, turbidity, iron, manganese and pH and residual chlorine stability were observed. Thus, the techniques studied proved to be promising and sustainable as they present technical, economic and environmental advantages.