Análise de risco aplicada à qualidade da água do sistema de abastecimento de Campina Grande (PB).

Abstract

Safety on the quality of water supply for human consumption is an always present concern of modern societies in order to avoid the harmful effects of pollution on human health. Control, exerted by the water supply service, and surveillance under the responsibility of the public health authority, are two complementary aspects of quality aiming the compliance with the water potability standard. This study aims evaluating the degradation of water quality of a supply system of médium size, through a risk analysis approach, applying the FMEA method. During monitoring period the indicators facultative heterotrophic bactéria (FHB), pH, turbidity, apparent color, free residual chlorine (FRC) and combined residual chlorine (CRC) were determined in sampling points of Block 1 (PO, AD500, AD700, AD800 and R-5), representative of the treated water mains and of Block 2 (P6, P8 and P12), representative of the distribution network of the supply system of Campina Grande City, Paraíba state, northeast Brazil. Each set of data, for each indicator, at each sampling point, consisted of 30 elements, each of which is the arithmetic mean of three replicates. Each of these data sets was subjected to descriptive statistical analysis being adopted the median as the measure of central tendency. FMEA methodology was, firstly, applied to ali indicators and, subsequently, to a selection consisting of FHB and the sentinel indicators turbidity and FRC. In the first analysis risk at sampling points of Block 1 were categorized as moderate and risk at points of Block 2 as high while in the second analysis, considering only FHB and sentinel indicators, points of Block 1 maintained their categorization of moderate risk with the exception of point AD800, which moved to low risk, and points of Block 2 had improved its category to moderate risk. The dangers most influential in the categorization of risk of sampling points of Block 1 were the high concentrations of FRC, in the first analysis, to which high turbidity values joined together in the second analysis. With the exception of P8, whose risk was more influenced by the absence of FRC, risk categorization of points of Block 2 was, in both analyzes, mainly influenced by the danger of high concentration of FRC. After risk classification, risk maps were drawn regarding the quality of water at each sampling point.