Scottish drinking water quality slides

The quality of Scotland's drinking water declined in 1997 for the second year running, according to a Scottish Office report. 1 Only 98.1% of samples complied with all regulatory requirements, compared with 98.6% in 1996 and 98.7% in 1995. Problem parameters where compliance levels are falling include colour, turbidity, iron and trihalomethane disinfection by-products.

Scotland has always lagged behind England and Wales on drinking water quality. Compliance with water quality standards has improved south of the border, reaching 99.75% in 1997 (ENDS Report 282, p 14 ). In Scotland, slower investment and the many small rural supplies has held back quality improvements.

The Scottish Office portrays the situation as one of "little improvement". Because the sampling regime tends to focus on areas of non-compliance, compliance rates from year to year are not strictly comparable. But water quality in England and Wales measured on the same basis has only once showed declining compliance - and that was reversed the following year.

In Scotland, investment appears to have been too slow to prevent a slide in compliance. An example is the Loch Lomond treatment plants which supply 0.5 million people in central Scotland. As early as 1992, the plants were identified as a priority for improvement because of failures to meet standards on trihalomethanes - but the works are not scheduled for completion until 1999.

In the meantime, the proportion of Scottish supply zones in breach of trihalomethane standards has increased from 23.9% to 41.9%.

Microbiological compliance in 1997 was the same as in 1996, with 97.7% of samples from customers' taps meeting quality standards. However, compliance with iron, manganese, colour and turbidity standards fell, while there was a slight improvement in compliance for lead.

A serious water supply incident affected each of Scotland's three water authorities in 1997. Supplies to 60,000 people were contaminated following a spill of diesel from a generator at West of Scotland Water's Burncrooks treatment works north of Glasgow in December. The authority was fined £15,000 for supplying water unfit for human consumption (ENDS Report 282, p 56 ).

An oil contamination incident also hit East of Scotland Water following a spillage which entered an aqueduct. And supplies on the Orkney island of Westray were disrupted by a bloom of blue-green algae in August, when North of Scotland Water had to ship in drinking water for the island's 700 inhabitants.

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