Indicadores de vigilância da qualidade da água de abastecimento da cidade de Areia (PB).

Abstract

Water used for human consumption must undergo a treatment process to make it potable by ensuring the attendance of legal standards. Disinfection is a fundamental unit operation commonly carried out at the water treatment plant in order to provide water free from pathogenic agents. However water can be contaminated as water flows throughout water network due to the existence of cracks and leaks in the pipes. The main objective of this work was to monitor the quality of drinking water distributed in the city of Areia (6°58'30,97"S and 35°41'50" W), Paraiba state, northeast Brazil, on the basis of both sentinel and microbiological indicators intending to get useful information for the formulation of a municipal plan of sampling for the surveillance of water quality. Monitoring, conducted from March to December 2009, was based on the determination of physicochemical (pH, residual chlorine, turbidity and temperature) and microbiological (total eoliforms, Escherichia coli and heterotrophic bacteria) indicators in grab samples collected, three times a day (7 and 11 a.m. and 5 p.m.), in five sampling points throughout the water network. Results showed the occurrence of a great number of violations of standards established in the Brazilian Ministry of Health Ordinance 518/2004, mainly related with free residual chlorine, turbidity and pH. In the last collection time of the day (5 p.m.) population received water more turbid, with a lesser concentration of free chlorine. Results of bacteriological indicators complied with standards as a result of the very high residual concentrations of hypochlorous acid caused by superchlorination at low levels of pH. Monitoring of sentinel indicators (free residual chlorine and turbidity) proved to be a reliable way to survey water quality and in small towns where resources (human and financial) are limited they can play an important role in monitoring the water supply system because they are easy to perform and relatively inexpensive compared with microbiological tests.