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4.3 Drinking Water Quality in the North East

Treatment Works

Table 4.3-a Samples Taken from Water Treatment Works Supplying the North East

Whilst the number of samples containing coliforms and E.coli has reduced dramatically in 2007, the number of treatment works not meeting regulatory requirements remains the same as in 2006 (Table 4.3-a). Invercannie WTW, serving Aberdeen, recorded two coliform failures in 2007, as well as the E.coli failure. DWQR has noted that this site continues to produce a disproportionate number of microbiological failures and has raised the issue with Scottish Water. Although investigations are continuing, Scottish Water suspects that the failures may be due to inappropriate siting of the sample tap and will act as necessary.

The 31 failures of the ex-works turbidity standard are disappointing, as the equivalent figure for 2006 was 10. Invercannie produced seven of the failures, and Clatto, which supplies Dundee, was responsible for three.

Table 4.3-b Summary of Disinfection Indices at Treatment Works Supplying the North East

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, while 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 is funded to undertake work to ensure all water treatment works have a DI of less than 100 by 2010. Table 4.3-b shows the North East sites generally achieve good DI scores, although DWQR is keen to see continued improvement.

Distribution System

Table 4.3-c Summary of Samples taken from Service Reservoirs in the North East

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

In 2007, coliforms were detected in 49 samples taken at storage points in the North East (Tabel 4.2-c). Only one storage point, Forebank in Angus, failed to meet the 95% compliance standard, however the number of coliform failures is extremely disappointing as it represents an increase on the 28 failures from 2006. The number of E. coli failures has also increased, doubling from last year's three. These failures all occurred at different storage points.

Table 4.3-d DMI in the North East - Supply Zones not scoring 100%

Table 4.3-d shows all supply zones in the North East not scoring 100% for DMI in 2007. This index is a measure of the performance of the distribution system in relation to the parameters likely to cause discolouration of supplies. The small supply zones at Killin and Rhynie scored highly due to one failure occurring in a small dataset of compliance samples. The poor compliance for iron in Whitehillocks supply zone in Angus has dragged down the overall DMI score for the region. Rehabilitation work is ongoing, and it is expected that this work should address the issue.

Figure 4.3-a DMI and Consumer Discolouration Contacts in the North East

Figure 4.3-b Consumer Contacts about Drinking Water Quality in the North East

The North East region continues to generate lower rates of consumer contacts about water quality than the other regions. Discolouration remains the largest category (Figure 4.3-b), and the contact rate increased in 2007 from nearly 25 contacts per 10,000 population to just over 30. Supply zones with notably large numbers of discolouration contacts in the North East include Lintrathen and Whitehillocks in Angus, Mannofield East in Aberdeen and Turret C in the Perthshire and Stirling area. Further mains rehabilitation is required in these areas. In the case of Mannofield, treatment improvements are also necessary in order to reduce these contacts and ensure compliance with the manganese standard. Scottish Water has committed to replacing the current temporary measures for manganese removal at Mannofield with a permanent solution by August 2009. Figure 4.3-a relates discolouration contacts to DMI.

Although taste and odour seems to be less of an issue in the North East than for other regions, the supply zones served by Glendevon water treatment works in Fife recorded a notable number of contacts in all categories for taste and odour. Forehill supply zone, covering Peterhead, was reported as being a "hotspot" for taste and odour contacts in 2006. The situation in 2007 improved significantly, possibly due to operational changes made at the treatment works.

Glendye supply zone covering Stonehaven recorded a notable number of milky water contacts, probably due to air in the supply.

Incidents

In 2007 there were eight water quality incidents in the North East Region, a increase of three on the previous year.

Invercannie, Aberdeen 01 February 2007 - Vandalism

This incident involved unauthorised access by vandals to three access hatches on the old aqueduct, which runs between Invercannie and Mannofield water treatment works. There was an obvious risk of contamination of the treated water supply as a result. DWQR expressed concern at the four day delay between the initial notification to Scottish Water from a member of the public, and the time the incident was eventually investigated. The subsequent sampling programme indicated no contamination had taken place.A number of actions were taken by Scottish Water as a result of this incident in order to improve reporting mechanisms and review the security provided to this asset.

Kenmore, Perthshire 08 February 2007 - Disinfection Failure

An intermittent fault with a relay switch in the control panel for the disinfection system at Kenmore borehole resulted in an intermittent problem with the Sodium Hypochlorite dosing pumps. The system should have been configured so that such a fault automatically shut down the works but it did not. Furthermore, the treated water chlorine residual monitor was not responding to the low dose and as such did not generate an alarm on the telemetry system. Samples were taken relatively promptly, and although not all samples were totally clear of coliforms as suggested in Scottish Water's report, the levels were low and not of significance for public health.

Scottish Water committed to undertake a number of actions in response to this incident, to improve maintenance at the site and ensure that the works will shutdown in the event of a further disinfection failure.

Lintrathen Supply Zone, Angus 04 August 2007 - Mains Repair Microbiological Failure

A bacteriological failure in the distribution system may have been caused when a burst on a short length of a two-inch diameter pipe was repaired. The repair was carried out while the system was pressurised so the risk of contamination during the repair should have been less than if the repair had been carried out with the water turned off. Following investigation by DWQR, Scottish Water was unable to provide evidence of compliance with procedures other than a statement to the effect that an interview took place with the relevant staff, which confirmed that procedures had been followed. Scottish Water state that the lack of a chlorine residual in the sample that failed suggests that there may be an issue with the condition of the main. However, two resamples taken 4 days later from the same location showed reasonable levels of chlorine residuals. DWQR concluded that there is a strong possibility that the failed sample was caused by contamination due to the lack of strict adherence to the relevant procedures. There was also an unacceptable delay by Scottish Water in taking resample's.

DWQR has asked Scottish Water to review its procedures in respect of ensuring hygienic conditions during any work on the distribution system, including ensuring that there is a satisfactory chlorine residual in the system prior to work commencing. DWQR undertook a number of audits of work in the distribution system during 2007 and issued a number of procedural recommendations to Scottish Water, which are being followed up.

Windyfield Rhynie, Aberdeenshire 07 August 2007 - Cryptosporidium

This incident occurred when a routine Cryptosporidium sample taken on 7 August 2007 was reported on 10 August as containing 0.371 oocysts per 10 litres. Samples from Rhynie WTW do not normally contain oocysts, therefore this was an exceptional result for the site. The Consultant in Public Health Medicine was concerned that the community had had no previous exposure to Cryptosporidium so they requested that Scottish Water issue advice to consumers in the area to boil their water. This boil notice was subsequently lifted on 16 August.

Investigation by Scottish Water showed that on the morning of 6 August, the chlorine residual in water leaving the treatment works fell away to zero due to an extremely sudden increase in water flow through the works. Scottish Water consider that the likeliest route by which surface water containing Cryptosporidium could have suddenly infiltrated the system was through the spring collection chambers following exceptionally heavy rainfall. DWQR considers that the sudden loss of chlorine at the site should have triggered further investigation by operational staff. A turbidity monitor installed in 2006 at the site, which could have triggered an alarm, had never functioned correctly.

Work has been undertaken to ensure the turbidity monitor is operating correctly and disinfection at the site has been significantly improved. Additionally, a temporary filtration system is in place at the site to provide an effective barrier against Cryptosporidium. DWQR visited the site in January 2008 as part of the investigations and to verify that actions were complete.

Turriff, Aberdeenshire 08 November 2007 - Coagulation Process Failure

A failure of the power supply to Turriff Water Treatment Works caused a corruption of the computer programme that controlled the lime dosing. This resulted in a more concentrated lime slurry being produced. Although the pH control system at the site responded correctly, it was insufficient to prevent overdosing of lime and a failure of the pH standard. DWQR is still investigating this incident due to late notification by Scottish Water.

Glenfarg Water Supply Zone, Fife 14 December 2007 - Failure to Follow Water Quality Procedures

A contractor carrying out preliminary work on a 5" distribution main in Kirkcaldy operated a valve and isolated the network without undertaking an impact assessment and without liaising with Scottish Water Operations. This left a number of consumers without water and Scottish Water unable to explain the situation as they had not been warned of the work. Additionally, the necessary sampling to confirm that water quality was satisfactory following the work was not undertaken in a timely manner. Scottish Water has committed to improved enforcement of its DOMS procedures.

Windyfield Rhynie, Aberdeenshire 17 December 2007 - Disinfection Failure

A sodium hypochlorite dosing line froze on the night of 17 December leading to loss of disinfection for a period of over three hours. Although an alarm was generated, its dispatch to Scottish Water Operations was delayed. No water quality sampling was undertaken in response to the failure due to a misunderstanding over whether a routine sample was already scheduled to be taken.

Since the incident, a new chlorine dosing system has been installed at the site, including provision of trace heating to prevent freezing. Scottish Water has investigated the delay in passing out the alarm and the lack of a water quality sample.

Water Quality in Local Authorities in the North East

Aberdeen City Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Aberdeenshire Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Angus Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Dundee City Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Fife Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Perth and Kinross Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

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