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4.1 Drinking Water Quality in the South West

Treatment Works

Table 4.1-a Samples Taken from Water Treatment Works Supplying the South West

As in 2006, E.coli was not detected in any samples taken from water treatment works in the South West region. Three samples, all from different treatment works, contained coliform bacteria. The proportion of treatment works with turbidity failures was largely unchanged in 2007 (Table 4.1-a).

Table 4.1-b Summary of Disinfection Indices at Treatment Works Supplying the South West

The disinfection index ( DI) is used by the DWQR to track the progress being made by Scottish Water in improving control of its disinfection processes. This is to make sure that all supplies are thoroughly disinfected to keep them safe, whilst at the same time, limiting the extent to which chlorine concentrations fluctuate. Inconsistent chlorine residuals in water leaving treatment works are a major cause of taste and odour complaints from consumers. The higher the DI, the less consistent the chlorine level in water leaving the treatment works.

Scottish Water has been funded to undertake work to ensure all water treatment works have a DI of less than 100 by 2010. Once again, disinfection indices at works in the South West have not changed significantly overall in 2007 (Table 4.1-b), although only one site had a DI in excess of 100.

Distribution System

Table 4.1-c Summary of Samples taken from Service Reservoirs in the South West

*95% samples shall not contain coliforms; 100% shall not contain E.coli

The number of samples taken from service reservoirs in the South West that contained coliforms increased from 40 to 45 in 2007, in contrast to an overall trend of improved microbiological compliance (Table 4.1-c). The two service reservoirs not meeting the standard of 95% of samples free from coliforms were Kerse and Maukinhill, both in Ayrshire. E. coli detections at service reservoirs remained the same as last year.

Table 4.1-d DMI in the South West - Supply Zones not scoring 100%

Distribution Maintenance Index ( DMI) is a measure of the performance of the distribution system for the parameters likely to cause discolouration at consumers' taps (Turbidity, Iron and Manganese). The overall DMI for the South West region in 2007 was 99.54, a slight improvement on the 2006 figure of 99.4% (Table 4.1-d).

Although Killin is at the top of the list, the DMI is a consequence of one failing sample for manganese, highlighting a shortcoming in the statistical method used for calculating DMI for smaller zones where fewer samples are taken. Poor manganese compliance also affected four zones in Ayrshire: Castlehill, Camphill and Bradan A and B. Extensive work is underway in all these zones and DWQR expects improved compliance in the Castlehill and Camphill zones in 2008, However, visible improvement in the compliance for Bradan A and B may take a little longer to materialise.

Figure 4.1-a DMI and Consumer Discolouration Contacts in the South West

Consumer Contacts

Figure 4.1-b Consumer Contacts about Drinking Water Quality in the South West

Scottish Water's South West region generated 14,549 contacts from consumers about water quality, giving a rate of 57.1 per 10,000 population, which is slightly higher than the average for Scotland as a whole. Finlas water supply zone on the Argyll / Dunbartonshire border generated the largest complaint rate, with nearly one fifth of the 1,141 people in the zone having contacted Scottish Water about their water quality. Almost all of these contacts were concerning discoloured supplies.

In terms of absolute numbers of discolouration contacts (Figure 4.1-b), Camphill and Bradan A and B zones in Ayrshire, and Carron Valley A zone in central Scotland had some of the highest numbers of contacts in the whole of Scotland. Extensive work is underway in all of these areas to rehabilitate old water mains. In the case of Camphill, work to install manganese removal at the treatment works is complete, with work on the distribution system due to be completed in Summer 2008.

Milky or cloudy water continues to be the second largest category of contacts for the South West region. Camps supply zone in Lanarkshire and Rosebery in Midlothian recorded a large number of contacts about this issue during 2007, although the totals in this category can fluctuate from year to year.

The region does not generally experience high volumes of contacts about the taste and smell of the water. Elsrickle supply zone in South Lanarkshire recorded seven contacts about chlorine. As the zone has a population of only 101, this gave the highest chlorine contact rate in Scottish Water. Disinfection at Elsrickle is achieved using ultra-violet light ( UV), so no chlorine is used under normal circumstances, however an incident in September caused the UV disinfection system to fail temporarily and it may be that Scottish Water used temporary chlorine dosing or brought in chlorinated supplies from another area until it was restored.

Muirdykes supply zone in Renfrewshire recorded 16 metallic taste contacts. Although a relatively small number, this is an unusual category, and the zone featured for this reason in DWQR's analysis of 2006 data.

Incidents

In 2007, there were seven water quality incidents in the South West Region, a decrease of two on the previous year.

Bradan, Ayrshire 21 April 2007 - Treatment Failure

This incident occurred due to a failure of one of the two air compressors providing air to drive the Dissolved Air Flotation clarifiers due to a lack of lubrication. The other compressor had failed just over two weeks previously, also due to lubrication problems, and had been deemed uneconomical to repair. The compressors were 15 years old. The failure of the second compressor resulted in the filters being overloaded and elevated concentrations of aluminium in the water entering supply. Aluminium concentrations in the distribution system breached the prescribed concentration or value ( PCV) at several locations in the hours following the incident.

Camphill, N.Ayrshire 05 June 2007 - Discoloured Supplies

A local discolouration of water supplies was caused by the unauthorised operation of a valve by a contractor working for Scottish Water. This disturbed manganese sediment in the area, which discoloured the water. Approximately 230 consumer calls were taken by Scottish Water in response to this incident. Scottish Water followed established protocols to clean the distribution system by flushing and deliver alternative supplies. Extensive mains rehabilitation is under way in order to prevent this type of incident, which has affected the area for a number of years.

Camphill, N.Ayrshire 09 July 2007 - Treatment Failure

On Wednesday 4th July 2007, a quantity of mineral oil was mistakenly put into hydraulically operated equipment used to drive the valves on the rapid gravity filters at Camphill WTW. Following a burst which occurred on the high pressure side of the hydraulic power pack it was discovered that the oil used was not of food grade type. A persistent small oil leak meant there was the potential for a very small quantity of mineral oil to have seeped into the clarified water. Sampling and checks revealed that in fact no oil entered the water. DWQR viewed this incident very seriously and has requested ongoing Scotland wide checks by Scottish Water on oil types.

Amlaird, 16 July 2007 - Treatment Failure

A ferric sulphate dosing pump failed at the works, but an alarm was not generated immediately since the pump continued to run. Turbidity alarms were generated about an hour after the initial failure and this was followed by a high iron alarm about half an hour after that. Once the operator arrived on site, a number of different actions were taken to find the cause of the problem and fix it. The works was shut down, and water stored in the two clear water tanks was used to maintain supply. Iron concentrations in excess of the PCV were recorded at a few points in the distribution system but the action of shutting the works down probably reduced the number of failures and the number of customer complaints. DWQR noted that the site staff initially failed to realise the impact of the failure of the dosing system, acting reactively rather than stepping back to consider the impact on the works as a whole and water quality generally. It was also noted that changing over the ferric dosing pumps is a scheduled monthly task but that this task had not been carried out for at least two months prior to the incident. A number of actions by Scottish Water were agreed to prevent a recurrence.

Touch, Stirling 07 October 2007 - Disinfection Failure

The warning system at Touch Water Treatment Works that indicates which bank of chlorine cylinders is operational had reset itself following a power failure. Failure to spot this resulted in both banks of cylinders running empty, although chlorine stock records should have made it obvious to site operators that the second bank of cylinders was not full. A low level chlorine alarm alerted operators to the situation and following resolution of the problem the operators left the site once chlorine residuals were increasing, but crucially, before they were sufficient to reset the original low chlorine alarm. Consequently, when a subsequent blockage of the chlorination pipework occurred, no further alarm was raised. Scottish Water was fortunate that this problem was discovered when an operator attended to deal with a different alarm. Although no water quality failures were recorded following this incident, it is noted that the sampling that took place may not have been truly representative of water directly supplied by Touch Water Treatment Works. In response to the incident, Scottish Water has implemented a number of actions. These include improvements to chlorine stock control at the site and inclusion of the chlorination pipework on the maintenance schedule.

Elsrickle, S.Lanarkshire 06 September 2007 -UV Disinfection Failure

A failure of a mains circuit breaker led to a short interruption to the disinfection process at this site which is achieved by ultra-violet light. On the advice of the Consultant in Public Health Medicine, a boil notice was issued for two days until clear sample results were obtained. Scottish Water investigated the cause of the failure and the provision of alternative means of power generation to the site.

Water Quality in Local Authorities in the South West

Clackmannanshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

East Ayrshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

East Dunbartonshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

East Renfrewshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Glasgow City Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Glasgow City have no private water supplies

Inverclyde Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

North Ayrshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

North Lanarkshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Renfrewshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

South Ayrshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

South Lanarkshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Stirling Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

West Dunbartonshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

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