Drinking Water Quality: 1991-2011
Percentage of samples at consumers' taps containing coliform bacteria
The coliform group of bacteria is present in large numbers in the gut of all warm-blooded animals and is also widely distributed in the environment. Their presence in tap water indicates a breach in the integrity of the water supply system.
Scottish Water is required to analyse samples taken from water treatment works, service reservoirs and consumers' taps. The Water Supply (Water Quality) (Scotland) Regulations 2001 set strict standards for compliance for a wide range of parameters. The major centres of population in Scotland are served by modern water treatment works, which are generally well equipped to achieve the standards set. In recent years improvements have been made to some of the small, rural treatment works, many of which were previously unable to consistently treat water to the standard required by the Regulations.
Between 1991 and 2011, the percentage of samples from consumer taps containing coliform bacteria fell from 6.95% to 0.42% and the percentage containing E. coli fell from 2.99% to 0.01%. Samples containing coliform bacteria fail to meet the water quality standards. Between 2010 and 2011 the failure rate for E. coli remained the same while the failure rate for total coliforms decreased by 0.06 percentage points.
Email: Sandy McPhee
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