2. Executive Summary
The drinking water quality results reported by Scottish Water for 2005 show that 345,761 tests were carried out on samples taken from water treatment works, service reservoirs and consumer taps. Of the 153,291 tests on samples taken from consumer taps, 99.56% met the required standard. This is an increase of 0.14% on compliance for 2004. A total of 669 tests gave results which did not meet the standard set out in the Water Supply (Water Quality) (Scotland) Regulations 2001. The largest number of fails were for the total coliform and trihalomethane parameters.
Compliance for the key microbiological parameters was slightly worse than in 2004. The 138 failures of the coliform standard at customers' taps in 2005, (0.97% of samples), compares unfavourably with 123 failures in 2004 and 135 in 2003. The number of faecal coliform ( E. coli) failures also increased slightly from 18 in 2004 to 21 in 2005. Although small this trend is disappointing. Undoubtedly, the number of water quality incidents reported in 2005 that involved failure of the disinfection process will have been a contributing factor. It is expected that the general improving trend in the microbiological quality of drinking water in Scotland will continue and DWQR is monitoring this situation very closely. Data going back to the year 1991 are shown in Figure 2.1, and these clearly show the 2005 results in the context of those of the previous 14 years.
Figure 2.1 Number of Microbiological Tests on Tap Samples Containing Coliforms and Faecal Coliforms
Extensive sampling of raw and final waters for Cryptosporidium was undertaken in 2005 in accordance with the Cryptosporidium (Scottish Water) Directions 2003. A total of 13,186 raw and final samples were taken from 296 water treatment works, of the final water samples, 728 contained Cryptosporidium oocysts.
DWQR receives details from Scottish Water of events which could affect drinking water quality. In 2005, 42 such events were considered sufficiently serious to be classified as incidents. Where appropriate, DWQR investigated the circumstances of these incidents and made recommendations. A summary of the findings may be found on the DWQR website, www.dwqr.org.uk