Avaliação da substituição do cloro gás pela produção eletrolítica de hipoclorito de sódio in loco em estação de tratamento de água de grande porte.

Abstract

The Bom Jardim Water Treatment Station (WTS) in Uberlandia-MG, with treatment capacity of up to 2 m³/s, currently uses as a water disinfection method the electrolytic process of active chlorine in loco (sodium hypochlorite production) instead of chlorine gas (Cl2). The main objective of this work was to verify the efficiency of sodium hypochlorite produced in loco as a disinfectant in the samples collected at the exit of the treatment and distribution network, comparing it with Cl2 in meeting drinking water standards for human consumption, established by ordinance Consolidation nº 05 (Annex XX) of the Ministry of Health of 09/28/2017, regarding the inactivation of total Coliforms and Escherichia coli, sodium amount (mg/L) and secondary disinfection products. It was also intended to carry out a more detailed analysis on cost/benefit and safety conditions and environmental quality. The data contained in this study are derived from the monitoring carried out, analyzed and collected in the WTS Bom Jardim treatment control reports. The delimitation of the investigated period corresponds to the period from January to December 2013 (use of chlorine gas) and from January to December 2016 (use of sodium hypochlorite produced in loco). The results showed that the solution investigated meets the established potability standards, being effective in disinfection, leaving residual chlorine in the network, with presence of sodium and disinfection secondary products well below the maximum allowed values. In addition, 0.65% aqueous sodium hypochlorite is generated in this electrolytic cell along with the hydrogen peroxide which gives this solution a greater disinfecting power. Other products such as sodium hydroxide also present in the generated solution, provided the alkalinizing reduction (in 36.17% on average) in the final stage of the water treatment (pH correction). In addition, it was concluded that the electrolytic production of sodium hypochlorite in loco is an option to replace the chlorine gas, in the disinfection of the water, because the sodium hypochlorite generated is an efficient disinfectant, that meets the determinations of the ordinance Consolidation nº 05 (Annex XX) of the Ministry of Health of 09/28/2017 both at the exit of the treatment and in the distribution network, with reduction of costs related to the maintenance and operation of the system, compared to the expenses with chlorine gas. The implanted system does not present environmental and operational risks, contributing to the maintenance of environmental quality, inside and outside the WTS.