Qualidade da água de abastecimento urbano do município de Marapanim, Região Nordeste do Pará

Abstract

The City of Marapanim has groundwater as its main source of supply for the consumption of the population. The objective of this work is to verify the quality of the urban water supply of the city of Marapanim, aiming at improving the quality of life of the local community. The water samples were collected in April 2004, rainy season, in ten points distributed between groundwater wells and tap water supplied by COSANPA. In the field, temperature, electrical conductivity and salinity were measured. In the laboratory, total alkalinity, c1oride, sulfate, phosphate, ammoniacal nitrogen, nitrate, iron, K, Na, Ca and Mg, dissolved oxygen, COD, D80, total and fecal coliforms were analyzed, according to Standard Methods (1998). The water temperature reflected the climatic conditions of the region. The pH presented values in the range of 3.9 to 6.69 in the erratic well waters, and in the tap waters, the values ranged from 4.42 to 5.83. These acidic characteristics show the presence of H' ions capable of altering the composition and balance of common ions constituting water, and are also related to the geological profile of the area. There was no salinity manifestation in the waters. Iron concentration was not detected in the waters, making them favorable for human consumption. At points MP-I (dug well covered) and MP-9 (dug well with no lining), total and fecal coliform indices were above the potability standards for human consumption established by the Health Ministry's Administrative Rule 518, which requires total absence of coliforms, indicators of pollution by domestic sewage. The concentration of ammoniacal nitrogen is in conformity with the standard of acceptance for human consumption established by the Ordinance 518 of the Ministry of Health. The low levels of dissolved oxygen in the waters are characteristic of the presence of organic matter in the environment. Point MP-9 obtained a maximum COD concentration of 90 mg/L of 02, probably due to the presence of vegetal organic matter, capable of producing humic acids that influence certain properties of these waters. The concentrations of the cations remained in the average proportion of: Ca > Na > K. Although the samples are still being processed, the water consumed by the population of Marapanim is compromised, possibly because of contamination sources related to the lack of basic sanitation and urban activities.