Evaluation of the microbiological quality of drinking water in the district of Braganca (Northwest Portugal) throughout a ten-year period (1996-2005), during the implementation of the 1998/83 EC directive.

The microbiological quality of drinking waters was evaluated in northwestern Portugal between 1996 and 2005, according to the guidelines of European Directives of 1980 and 1998. Out of the 21,630 microbiological analyses done, the percentage of treated and nontreated waters analyzed were similar, but the fraction of conforming samples were higher for treated (74.2%) than for nontreated (37.8%) water. The microbiological quality of potable water improved throughout the study period, particularly in the last 2 yr, when drinkable water reached 70%. The increase during the last 2 yr is a result of at least two different causes: an increase in the use of treated waters and the change in the legislation (1998/83 EC Directive). Although the number of treated waters has increased, the nonconforming treated water is still very high (25%) even when evaluated under the 1998/83 EC Directive.