Findings of E. coli in more than one in 10 tests on private water supplies in Scotland is “unacceptable,” according to the body that regulates water quality.

A report from Scotland’s Drinking Water Quality Regulator (DWQR) found that in samples taken last year for E. coli from regulated private water supplies, 11.5 percent, or 260 samples, did not comply with drinking water standards.

DWQR said this indicates they are not receiving the necessary treatment to make water safe. The regulator added the figure has not changed for the past three years suggesting limited progress has been made.

Discussions with local authorities on private water supplies with E. coli failures for a number of years in succession identified fluctuating raw water quality, inadequate or inconsistent treatment processes and poor or no maintenance of treatment systems are common causes of failure.

Where there is a need for immediate action to safeguard health in the short term, users are advised to boil water or to use an alternative supply, including bottled water.

Coliform and metals

A total of 46,470 tests were taken from regulated private water supplies in 2017 and 95 percent met the required standard. The number of supplies sampled for at least one parameter was at its lowest level in the past five years.

DWQR found 22 percent of 2,256 samples were not compliant due to coliform bacteria. This means the disinfection process may not be operating effectively or water was contaminated after disinfection.

Many private water supplies did not comply with standards for metals. Iron (10.8 percent of samples failing), manganese (6.3 percent failed) and aluminum (2 percent failed) are mainly naturally occurring and many private water supplies have no treatment process capable of removing them.

Regulated private water supplies provide more than 10 cubic meters per day, serve more than 50 people or a commercial or public activity.

Around 3.6 percent of the Scottish population receive water from a private supply and not from Scottish Water. It is estimated that around 200,000 people rely on a private supply for drinking water, with thousands more using them occasionally, typically in holiday accommodation.

Sue Petch, from Drinking Water Quality Regulator, said a grant is available towards the cost of improvements.

“I am concerned with the poor quality of private water supplies, particularly the number that tested positive for E. coli and the health risks that its presence indicates. There is much that people responsible for a private water supply can do to protect water sources and ensure that there is an appropriate and robust treatment process in place together with a plan to ensure that this continues to be the case under all circumstances,” she said.

The rules governing the quality of regulated private water supplies came into force in October 2017 and an increase in formal enforcement action is expected.

Based on the report for public water supplies in 2017, there were 22 detections of coliforms at treatment works, representing an improvement on 2016’s performance but more than in 2015. One sample contained E. coli compared with two in 2016. Cryptosporidium was reported in 49 final water samples of which five were subject to ultra violet light treatment and inactivated. This figure is almost half that of the previous year.

Five samples from service reservoirs contained E. coli and 68 samples contained coliforms, compared with 53 in 2016.

Devolved powers after Brexit?

Meanwhile, Constitutional Relations Secretary Michael Russell has voiced concerns on EU withdrawal plans for food safety and standards.

Speaking at the Royal Environmental Health Institute of Scotland Food Update conference this week he said more power and resources must be transferred to the Scottish Parliament to guarantee food safety and standards after Brexit.

“Public health protection is a priority in Scotland and I am deeply concerned by any suggestion that Brexit could compromise food safety,” he said.

“Staying in the EU is the best way to protect Scotland’s high food standards but, if that is not possible, then all powers in devolved areas like food law must transfer directly to the Scottish Parliament. This must be matched by sufficient resources so we can continue to keep food safe – as well as our economy, jobs and living standards.”

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