Keywords
drinking water
microbial indicators
chlorination
province of Valencia
How to Cite
Abstract
This study focuses on assessing the microbiological quality of drinking water and of water intended for drinking in the province of Valencia (Spain) between 2002 and 2010. Variation was found regarding space, time and source requirements in samples that did not meet the standards of quality established by Royal Decree 140/2003 for the following: total coliforms (TC); faecal coliforms (FC); Escherichia coli (EC); aerobic bacteria at 22 ºC (AB 22 ºC); faecal streptococci (FS); enterococci (EN); sulphite-reducing clostridia (SC); and Clostridium perfringens (CP). The samples were stratified by those meeting the standards (“Compliance”) and those that did not (“Non-Compliance”), as well as by their relationship with the degree of chlorination.
A total of 10057 water samples were examined from various sources: springs; surface waters; denitrifying plant waters; wells; and distribution networks. They were grouped into each of the 17 districts of the province of Valencia.
The total number of samples that failed to meet the standards of quality, for each criterion, were as follows: 34.0 % for TC; 16.0 % FS-EN; 13.0 % for FC-EC; 5.6 % for SC-CP; and 15.5 % for AB 22 ºC. Regarding spatial variation in samples, the highest percentages of samples in the “Non-Compliance” group were found in the interior part of the province. For time variation, the highest percentages of “Non-Compliance” were for the years: 2002 - 2004, 2008 and 2009. Regarding source variation, origin of the samples with “Non- compliance” was highest for surface waters, followed by springs and wells.
For all samples studied, 39.8 % were within the “Non-Compliance” group, of which 18.3 % came from sources that supply the population (distribution networks).
Of the samples within the “Compliance” group, 61 % were chlorinated, which confirms that chlorine is a powerful disinfectant and that chlorination is an effective water disinfection treatment.
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