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5. Drinking Water Quality by Region

5.1 Introduction

This section looks at drinking water quality in the five regions used by the Waterwatch Scotland panels. These areas mirror Scottish Water's current operational area structure, with the exception that the Western Isles, Orkney Islands and Shetland are considered separately from the rest of the North West area.

This section highlights a number of specific water quality issues, and it is worth summarising DWQR's approach to resolving these. Where one or more parameters are failing a regulatory standard and likely to continue to fail, DWQR will request that Scottish Water apply for an Authorised Departure which must include a commitment to make improvements to the supply concerned to ensure that it meets the relevant standards. Under certain circumstances, an Undertaking may be sought from Scottish Water, although for all intents and purposes this operates in the same way as an Authorised Departure.

Where a water quality issues is more urgent, or it is considered that the above approach has not delivered the required improvements, DWQR may take enforcement action against Scottish Water to ensure that it carries out a specified action by a certain date.

If large numbers of consumer complaints are received from one particular area, the DWQR will request that Scottish Water investigate the problem and take action to resolve it. DWQR may carry out an independent investigation with the assistance of local authorities and health boards and take action if appropriate.

Table 5.1 Regional Key Facts

Map 5.2c

5.2 Drinking Water Quality in the South West

5.2.1 Drinking Water Quality at Treatment Works in the South West

Table 5.2a Summary of Samples Taken from Water Treatment Works in the South West

Four out of the 20 failures for coliforms and two out of the six for E. coli in the South West were associated with the Craigmaddie outlet of Milngavie WTW.

Table 5.2b Summary of Samples Taken from Service Reservoirs in the South West

* 95% samples shall not contain coliforms

5.2.2 Drinking Water Quality in Distribution Systems in the South West

In the South West, 58 samples taken from service reservoirs contained coliforms, resulting in nine service reservoirs failing to meet the regulatory requirement of 95% compliance, the largest number of any region.

Table 5.2c OPI( TIM) in the South West

OPI( TIM) for the South West region was 99.12. Map 5c shows supply zones in the South West coloured according to OPI( TIM) score. Particularly low OPI( TIM) scores were found in the Castlehill and Camphill supply zones of North Ayrshire, where problems with manganese have caused a number of serious incidents in recent years. Throughout 2005 DWQR worked to obtain a commitment from Scottish Water to carry out improvement work at the treatment works supplying these zones.

5.2.3 Drinking Water Quality Incidents in the South West

In 2005 there were six water quality incidents in the South West region.

Table 5.2d Summary of Incidents in the South West

Figure 5.2e Consumer Complaints about Drinking Water Quality in the South West

Discolouration complaints make up by far the largest proportion of consumer complaints about water quality in the South West. Areas supplied by Castlehill, Camphill and Bradan experience a large number of complaints, largely due to the inability of the treatment process at these water treatment works to remove manganese, which occurs naturally in the source water. Discolouration complaints in the Greenock area tend to be as a result of a large amount of cast iron mains which are in poor condition. Scottish Water is aware of these problems, and DWQR will continue to monitor its efforts to resolve them.

The South West has the lowest rate of chlorine taste and odour complaints of any region, although Balmore C Water Supply Zone recorded a large number of complaints about both chlorine and metallic tastes and odours in 2005.

Complaints about Milky or Cloudy Water made up a lesser, but still significant, proportion of the total. The parts of Glasgow and East Renfrewshire supplied by South Moorhouse Treatment Works appear to have a particularly high incidence of this problem when compared with any other supply zone in Scottish Water.

Map 5.3c

5.3 Drinking Water Quality in the North West

5.3.1 Drinking Water Quality at Treatment Works in the North West

Table 5.3a Summary of Samples Taken from Water Treatment Works in the North West

Badentinan WTW was responsible for 26 of the 44 failures of the indicator standard for turbidity and Calder Hoy, serving the North coast, for five. The large number of microbiological exceedences in the North West can partly be explained by the many small works with only basic treatment. Scourie WTW is particularly notable for having five out of the 38 E. coli failures, although other sites also recorded more than one failure for this parameter during the year.

5.3.2 Drinking Water Quality in Distribution Systems in the North West

Table 5.3b Summary of Samples Taken from Service Reservoirs in the North West

* 95% samples shall not contain coliforms

Despite 41 samples containing coliforms in samples taken in the North West, only three service reservoirs failed to meet the requirement of 95% compliance. However, 17 samples contained E. coli, the largest number of any region.

Table 5.3c OPI( TIM) in the North West

Overall OPI( TIM) for the region appears excellent, however, this is due to the disproportionately large number of very small supply zones in the region, some of which achieved 100% compliance on the basis of very few samples. This disguises the fact that there are some supply zones in the region with a very low OPI( TIM) score. The map shows supply zones in the North West coloured according to OPI( TIM) score.

5.3.3 Drinking Water Quality Incidents in the North West

In 2005 there were 21 water quality incidents in the North West region.

Table 5.3d Summary of Incidents in the North West

5.3.4 Consumer Complaints About Drinking Water Quality in the North West

Figure 5.3e Consumer Complaints about Drinking Water Quality in the North West

Some of the supply zones in the North West reported exceptionally high rates of complaints about discoloured water, notably Laide, Savalbeg and Roybridge. Many of these sites have minimal treatment which does not remove natural colour and iron present in the source water. Work is currently underway to ensure the treatment works at Laide complies with the standard for both colour and iron, and the zone has been granted an Authorised Departure for both parameters until 2007. Roybridge treatment works has now been decommissioned and the area is fed from a new groundwater source.

Compared to other regions, with the exception of the Islands, the North West experiences a relatively large number of complaints about chlorine tastes and odours. This is probably, in part, due to the large number of very small treatment works with simple treatment processes which have difficulty in ensuring that chlorine doses keep pace with rapidly varying source water quality. The DWQR expects Scottish Water to work to improve control of chlorine dosing at such sites, and funding has been made available within the 2006-2010 investment period to undertake such work.

Mellon Udrigle and Sadell recorded an especially large number of chlorine complaints in 2005 (9 and 4 respectively) considering the small population of these zones, although some of these could be repeat complaints from the same consumer. DWQR will investigate the source of these complaints.

Map 5.4c

5.4 Drinking Water Quality in the North East

5.4.1 Drinking Water Quality at Treatment Works in the North East

Table 5.4a Summary of Samples Taken from Water Treatment Works in the North East

Out of the 21 coliform failures in the North East through 2005, Invercannie WTW serving Aberdeen was responsible for six of them. Glenfarg WTW recorded four of the turbidity failures.

5.4.2 Drinking Water Quality in Distribution Systems in the North East

Table 5.4b Summary of Samples Taken from Service Reservoirs in the North East

*95% samples shall not contain coliforms

Sixty eight samples contained coliforms, which was the greatest number of any region, although only two service reservoirs did not comply with the regulatory requirement of 95% of samples containing no coliforms.

Table 5.4c OPI( TIM) in the North East

Only four supply zones in the region fail to achieve a 100% OPI( TIM) score, resulting in a very high overall score for the region of 99.66%. Map 5.4c Shows supply zones in the North East coloured according to OPI( TIM)

5.4.3 Drinking Water Quality Incidents in the North East

In 2005 there were nine water quality incidents in the North East region.

Table 5.4d Summary of Incidents in the North East

5.4.4 Consumer Complaints About Drinking Water Quality in the North East

Figure 5.4e Consumer Complaints about Drinking Water Quality in the North East

In 2005 the North East experienced a slightly lower rate of complaints than the other regions. In common with all other areas, discoloured water represented the single largest category, with a rate of nearly 2.5 per 1,000 population.

Several supply zones in the North East had relatively high complaint rates for chlorine related tastes and odours. The three highest zones were Turret B, Whitehillocks and Glendevon A, with more than one complaint about chlorinous tastes for every thousand people during 2005 in Turret B and Whitehillocks.

Map 5.5c

5.5 Drinking Water Quality in the South East

5.5.1 Drinking Water Quality at Treatment Works in the South East

Table 5.5a Summary of Samples Taken from Water Treatment Works in the South East

Table 5.5a shows a summary of regulatory samples taken at water treatment works in the South East. Of the 25 samples which contained coliforms, 11 of these were taken from Alnwickhill WTW in Edinburgh. Both E. coli failures occurred at Fairmilehead WTW.

Marchbank WTW accounted for 11 of the failures of the indicator standard for turbidity, whilst Dodburn WTW near Hawick in the Borders recorded seven failures. This site is vulnerable to changes in raw water quality due to weather conditions.

5.5.2 Drinking Water Quality in Distribution Systems in the South East

Table 5.5b Summary of Samples Taken from Service Reservoirs in the South East

*95% samples shall not contain coliforms

All service reservoirs in the South East region complied with the regulatory requirement of 95% compliance for coliforms. E. coli was detected in samples from four sites.

Table 5.5c OPI( TIM) in the South East

The South East region had the lowest OPI( TIM) score of any region in Scotland during 2005. This was mainly due to zones in the Newton Stewart area of Dumfries and Galloway where the poor condition of cast iron mains combines with large amounts of iron and manganese not being removed by the treatment works. Map 5.5c shows supply zones in the South East coloured according to OPI( TIM) score.

5.5.4 Consumer Complaints About Drinking Water Quality in the South East

In 2005 there were 2 water quality incidents in the South East region.

Table 5.5d Summary of Incidents in the South East

Figure 5.5e Consumer Complaints about Drinking Water Quality in the South East

In the South East region in 2005, the water supply zones in the Newton Stewart area of Dumfries and Galloway reported the highest rate of complaints about discolouration. This is partly due to the condition of the distribution system, with cast iron mains and iron sediment causing discolouration, but also to iron passing through the water treatment works due to a lack of appropriate treatment. Authorised Departures have been granted in Barclye and Penwhirn Barclye supply zones. Scottish Water is undertaking work to ensure compliance with the standards for iron, THMs and colour by September 2007.

The Newton Stewart area, supplied by Penwhirn and Barclye water treatment works also appears to be a particular "hotspot" for chlorine taste and odour complaints. Some of the Edinburgh supply zones supplied by Fairmilehead and Marchbank water treatment works also recorded a large number of taste and odour complaints. This is surprising, given that these supplies are disinfected by chloramination; a process which would normally be expected to produce reduced numbers of complaints about chlorinous tastes and odours.

Hopes supply zone in East Lothian recorded an unusually large number of complaints about metallic tastes and odours.

5.6 Drinking Water Quality in the Western Isles, Orkney Islands and Shetland

5.6.1 Drinking Water Quality at Treatment Works in the Western Isles, Orkney Islands and Shetland

Table 5.6a Summary of Samples Taken from Water Treatment Works in the Western Isles, Orkney Islands and Shetland

Mid Yell WTW on Shetland reported three of the 19 coliform failures. Percentage compliance with the turbidity indicator standard across the islands was by far the poorest of any region in 2005.

Figure 5.6e Consumer Complaints about Drinking Water Quality in the Western Isles, Orkney Islands and Shetland

As with other areas, discolouration forms the largest single complaint category in this region. The region recorded a relatively large number of complaints about chlorine tastes and odours compared to the size of the population. Many of the small sites on the islands have minimal treatment which does not remove natural colour and iron present in the source water. Ness on the Western Isles and Lerwick and Bigton supply zones on Shetland experience notably large numbers of complaints about discolouration.

The region reported a relatively large number of complaints about tastes and odours. As with the North West region, this is probably partly due to the large number of very small treatment works with simple treatment processes which have difficulty in ensuring that the chlorine dose keeps pace with rapidly varying source water quality.

A significant number of supply zones in the Western Isles have relatively high complaint rates for chlorine. This is all the more notable given that some of these supplies are chloraminated; a process which would normally be expected to produce reduced numbers of complaints about chlorinous tastes and odours.

Tolsta on the Western Isles and Boardhouse and Kirbister on the Orkney Islands showed a relatively high rate of complaints of metallic tastes. The latter two supply zones also recorded an exceptionally large number of complaints about earthy/musty type tastes in 2005. It is likely that the numbers in both categories reflect the incident in late summer 2005 when an algal bloom resulted in taste-causing compounds passing through the treatment process and reaching consumers' taps.

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