Diagnostic of Groundwater Intended for Human Consumption in the Municipality of Abaetetuba, Pará - Brazil

The objectives of this research were to evaluate the quality and to determine the degree of vulnerability and accessibility of groundwater destined to the public supply of the municipality of Abaetetuba (State of Pará - Brazil), allowing to establish an environmental management program based on the national legislation. Analytical procedures for temperature, dissolved oxygen, pH, alkalinity, hardness, electrical conductivity, ionic concentration [Na+, K+, Ca2+, Mg2+, Cl-, Cl-did, SO42-, HCO3- and CO32-], TDS, BOD, total and fecal coliforms were applied in agreement with traditional standard methods in limnology and geochemistry. Collections were made between 2012 and 2016 in 20 wells located in priority areas such as schools, federal institutes of education, hospitals and clinics, water treatment plants, bus terminal and residences. The results obtained (in average) were: temp 23°C; DO 3 mg/L; O2 saturation 35.1%; pH 5.3; alk 25.8 and hard 38.4 mg/L; EC 128 µS/cm; ions Na+, K+, Ca2+, Mg2+, Cl-, Cl-dpd, SO42- and HCO3- plus CO32- were 14, 24, 42, 21, 19, 0.2, 1.3 and 29.5, respectively; TDS 91 mg/L;, BOD 2.4; total coliforms 279 MPN and fecal coliforms 20.4 MPN. The results indicate that, although from a physical-chemical point of view, the water meets the standards of supply and consumption presented in environmental legislation, in the biological aspect (BOD and coliforms) the samples presented different degrees of bacterial contamination. On the Water Quality Index of the groundwater, most of the samples indicated quality from acceptable to good to supply, with a certain degree of attention to possible sources of contamination, especially faecal coliforms. Cluster analysis indicated a strong association between the parameters [pH-Alk-Hard] and [BOD-tot coliforms-fecal coliforms]. Several factors have been identified as being responsible for contamination as from inadequate areas for good installation; lack of cleaning and maintenance; inadequate water storage; the presence of unauthorized personnel; and personnel unless proper training to handle the wells. Most of the wells in operation do not meet the minimum sanitary conditions to supply the population with quality drinking water.