QUALIDADE DE ÁGUA PARA CONSUMO HUMANO EM RIACHO FRIO, PIAUÍ

Abstract

Brazil is a privileged country due to the wealth it has. Groundwater is essential for public supply in Brazil, many regions depend on groundwater sources, more than half of Brazilian municipalities (53%), however, the natural distribution of this resource is not balanced. The state of Piauí is inserted in this reality: it has suffered for years with a lack or insufficiency of water even for human consumption, in some regions, with underground sources of supply being the natural resources traditionally used to supply these regions. Even though subsurface waters are more protected from contamination, due to the difficulty of access, drilling wells with inadequate location puts their quality at risk, since it generates a connection between the shallower waters. The present work sought to evaluate the quality of subsurface water used in the human supply system in the city of Riacho Frio, State of Piauí. The municipality's water collection and distribution system consists of two tubular wells and a lifting station from which water distribution continues through the city's water supply system. Sampling campaigns were carried out in dry and rainy periods. For each sample collected, physical-chemical, biochemical and microbiological parameters of the water were analyzed and the framework continued with the standard defined by the resolutions of the CONAMA 357/2005 y 396/2008 and ordinance of MS 05/2017, as well as construction of the Water Quality Index (IQA) and isotopic marking with natural isotopes δ18O y δD, for monitoring contamination risks. At all points, in both collection periods, the IQA was classified as a “good” or “excellent” level, with water quality considered satisfactory. In the dry period data, all OD samples, 75% of the thermotolerant coliform samples, are not adequate according to the standard, while in the rainy season, 75% of the total nitrogen samples and 100% of the total phosphorus samples are in non-compliance with the standard determined by legislation. The isotopic marking showed that there is no difference between the sample values found and those expected, discarding the possibility of contamination by any recharge mechanism of the subsurface source.