Análise da Qualidade da Água do Rio Benfica (Benevides, Pará) com Ênfase na Concentração de Metais Pesados e Coliformes Fecais/Totais

Abstract

The sources of water contamination are directly associated with domestic and industrial waste and leachate, which contaminate the water tables and river courses with heavy metals and pathogenic microorganisms. The effects of this reality are felt in all urban equipment related to water resources, especially in cities where there is no urban planning. The present work characterizes the quality of the water of Benfica River, a very important ecosystem for the city of Benevides, Pará, regarding the concentration of heavy metals and fecal/total coliforms. To this end, the concentrations of heavy metals and total coliforms were analyzed in 4 water collection points in this river course and the results were compared to those established by the current legislation. The reading of heavy metals was done by Atomic Emission Spectrometer (ICP-AS), while the total coliform count was done by standard plate count method. The pH values were higher downstream of the urbanized area due to the discharge of industrial effluents. The point located in the direct influence zone of the brewery had the highest pH value, probably due to the discharge of organic waste from the industry, taking into account the inputs and raw materials used in the manufacturing process. As for the heavy metals, all the elements analyzed presented concentrations below those established by the resolution 357 of CONAMA. At the source of the Benfica River a small anomaly was detected in the concentration of lead (Pb), at a value higher than that allowed by the aforementioned resolution. Nearby agricultural activities may be using fertilizers or pesticides in cultivation, which may be reaching the spring. The concentrations of total coliforms show two points in disagreement with the concentrations established by the legislation in force, probably because they are located in a sector with low hydrodynamic energy, which would facilitate the proliferation of coliforms. The results showed that, in general, the water quality does not yet offer risks to public health, since the industrial pollution is recent (e.g. brewery effluents) and the organic load discharged into the water body is being purified.