Relationship between free residual chlorine concentration and the presence of microorganisms in well water intended for human consumption

Abstract

Water inequality in Brazil complicates access to potable water, especially in the Northeast region, where this disparity is more pronounced. Consequently, access to water for human consumption through artesian wells has become an alternative to supply communities in the interior of Brazil. This study aimed to evaluate the potability of water distributed by artesian wells in the villages of Pé do Veado, Roncador, Serra, and Terra Dura, located in the municipality of Itabaiana, in the Agreste region of Sergipe, through physicochemical parameters (free residual chlorine, temperature, hydrogen potential (pH), electrical conductivity, and salinity) and microbiological parameters (heterotrophic bacteria, thermotolerant and fecal coliforms - Escherichia coli). The quantitative determination of free residual chlorine was carried out using the colorimetric method N,N-diethyl-p-phenylenediamine (DPD), analyzed through UV-Vis molecular absorption spectrophotometry; heterotrophic bacteria were determined by the streak plate method; thermotolerant and fecal coliforms (Escherichia coli) were determined by the membrane filtration method. From the analyses conducted, considering the free residual chlorine and microbiological parameters, it was evident that all water samples from the analyzed artesian wells do not comply with GM/MS Ordinances No. 888, of May 4, 2021, and No. 2.914, of December 12, 2011, as well as Conama Resolution No. 357/2005 and Conama Resolution No. 396/2008, indicating the need for inspection, monitoring, and treatment of the analyzed waters. These results provide guidance for the implementation and/or improvement of environmental and public health management.