Assessing nitrate contamination in groundwater for public supply: A study in a small Brazilian town

Abstract

Monitoring groundwater quality is essential for drinking water, avoiding risks to human health, and making it possible to identify and prevent environmental contamination. In Tupã, west of São Paulo-Brazil, the drinking water supply is carried out exclusively by underground water through the public service or alternative solutions using private tubular wells. In this context, this study evaluated the quality of drinking water from 25 private tubular wells in all areas of Tupã. Of these wells evaluated, 12% were contaminated with E. coli and 44% with total coliforms, indicating that the sanitary quality of the water is inadequate and may be directly associated with waterborne diarrheal diseases. The results of the physical-chemical analyses referring to water potability parameters, such as apparent color, turbidity, total dissolved solids, hardness, iron, ammonia, nitrite, chloride, and fluorine, met the requirements of Brazilian legislation. However, all samples showed NO3− contamination, whose concentrations ranged from 1.9 to 23.2 mg L−1NO3−-N, where 32% of the wells exceeded the maximum allowable limit of 10 mg L−1NO3−-N. The consumption of water contaminated with high concentrations of NO3− can cause health risks, especially to children due to their low body weight, causing methemoglobinemia or blue baby syndrome. In the study of the evolution of urban growth, the city's central area exhibited the most significant NO3− contamination because it is an older area with leakage problems and insufficient sewage system maintenance. The non-carcinogenic health risk associated with NO3− contamination was assessed using the Environmental Protection Agency (USEPA) methodology applied to oral ingestion and dermal contact in children and adults. The results revealed negligible risks from dermal contact. However, the assessment highlighted the susceptibility of children to nitrate contamination through oral ingestion, mainly from water from wells in the city's central area. This study emphasizes the importance of monitoring groundwater in Tupã, identifies potential sources of contamination, and provides information to improve water resources management. Implementing appropriate measures based on these findings can mitigate waterborne diseases, safeguard consumer health, and protect the environment.