Aplicação de indicadores ambientais para o cálculo do IQA (Indice de Qualidade da Água) em zona urbana de Manaus

Abstract

The city of Manaus is quite developed, however its water resources have been degraded over the last decades, due to the urbanization process. The stretch of Igarapé Tarumã in study has its flow passing through this city, being that it receives the sewers of regions of urban dwellings and also of areas of forest with fauna and wild flora. This study aimed to apply the calculation to determine the water quality index (IQA) adapted by the Environmental Company of the State of São Paulo (CETESB), and to compare the quality parameters with those established by Resolution no. 357/2005 of the National Environmental Council (CONAMA). The work methodology consisted of three field collections along the Igarapé, including hydrological variations (one in the low water period corresponding to the month of November 2015 and September 2016, and another in the full flood period corresponding to the month of May 2016), and physical, chemical and biological analyzes were performed on the collected water samples. In the calculation of the Water Quality Index, the IQA prepared by the National Sanitation Foundation (NSF) and adapted by the Environmental Sanitation Technology Company of São Paulo (CETESB) were taken into account with the corresponding curves and water quality bands. In order to represent as a natural environment and better environmental quality, a point considered as a control was used as reference, located in Igararé da Cachoeira da Asframa, as well as four other points in the urban area of Igarapé Tarumã. The worst water quality indexes were found at these points because they suffered strong anthropic pressure characterized by values that were not allowed by Resolution No. 357/05 of CONAMA for quality class 2, and indicating the entry of untreated domestic effluent as the main Source of pollution, with high concentrations of organic matter, nutrients and fecal coliforms. The calculations and equations proposed by CETESB represented well the water quality of the igarapé studied in an urban area with Bad classification, however, it was not adequate for the control point, which showed a Regular classification. Therefore, it can be noted that some parameters need adjustments in their weights because the waters of this region have different characteristics in relation to other regions of the country.