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4.4 Drinking Water Quality in the South East

Treatment Works

Table 4.4-a Summary of Samples Taken from Water Treatment Works in the South East

The number and proportion of works with coliform fails shows an improvement compared with the previous year but E.coli and turbidity fails were unchanged in 2007 compared with 2006. It is pleasing to see that there were no nitrite fails in 2007, which is an improvement over the three fails noted in 2006 (Table 4.4-a).

Table 4.4-b Summary of Disinfection Indices at Treatment Works in the South 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. The South East sites generally achieve good DI scores, although DWQR is always keen to see continued improvement (Table 4.4-b).

Distribution System

Table 4.4-c Summary of Samples taken from Service Reservoirs in the South East

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

Only one service reservoir failed in 2007 for coliforms and there was an improvement in the number of fails for E.coli , which reduced from 4 in 2006 to 1 in 2007 (Table 4.4-c). The one E.coli failure is associated with Kingston Service Reservoir which is supplied from Castle Moffat Water Treatment Works in East Lothian.

Table 4.4-d DMI in the South East - Supply Zones not scoring 100%

Table 4.3-d shows all supply zones in the South East not scoring 100% for DMI in 2007. DMI is a measure of the performance of the distribution system in relation to the parameters likely to cause discolouration of supplies. Rehabilitation work is ongoing in many of the worst scoring areas in the South East, including Penwhirn and Barclye in Dumfries and Galloway. It is expected that this work should address the issue.

Consumer Contacts

Figure 4.4-a Consumer Contacts about Drinking Water Quality in the South East

Scottish Water's South East region generated 8,257 contacts from consumers about water quality, giving a rate of 47.5 per 10,000 population, which is slightly lower than the average for Scotland a whole. The majority of these contacts were related to discoloured water (Figure 4.4-a) and many of the zones where these contacts came from also feature in Table 4.4-d above, which gives the DMI results. Areas which have a low DMI and which also received a high number of complaints about discolouration include Penwhirn, Winterhope and Glendevon. Figure 4.4-b co-relates DMI and consumer discolouration contacts.

Figure 4.4-b DMI and Consumer Discolouration Contacts in the South East

Incidents

There were five water quality incidents in the South East region. Two of these related to coagulation failures and the other three were for high levels of Cryptosporidium, two of which were at the same works. DWQR is promoting work to improve the treatment at both Langholm and Southdean Mill. Therefore, Scottish Water is developing proposals to reduce the risk of Cryptosporidium getting into these supplies. In the short term, Scottish Water has introduced temporary filtration systems at both sites, which appear to be helping the situation.

Langholm, 22 June 2007 - High levels of Cryptosporidium

Adverse weather caused high levels of Cryptosporidium to get into the water supply. Advice was given to customers to boil their water before consuming it. The treatment at Langholm is disinfection only and DWQR is promoting the introduction of appropriate treatment to reduce the risk of Cryptosporidium from getting into the supply. In the meantime, Scottish Water has introduced a temporary filtration system which is helping to reduce the risk.

Southdean Mill, 26 June 2007 - High levels of Cryptosporidium

Adverse weather caused high levels of Cryptosporidium to get into the water supply. Advice was given to customers to boil their water before consuming it. The treatment at Southdean Mill is disinfection only and DWQR is promoting the introduction of appropriate treatment to reduce the risk of Cryptosporidium from getting into the supply. In the meantime, Scottish Water has introduced a temporary filtration system which is helping to reduce the risk.

Langholm, 17 August 2007 - High levels of Cryptosporidium

Adverse weather again caused increased levels of Cryptosporidium in the catchment. A temporary filtration plant was put in place following the earlier incident on 22 June, but due to operational issues this was not as effective as it should have been for a period of 24 hours. Unfortunately, this resulted in further advice to customers to boil their water before consuming it.

Lochenkit, 23 November 2007 - Coagulation Failure

A burst on the inlet main to one of the service reservoirs caused an increase in demand for treated water, which caused the clear water tank at the works to drain down. A filter backwash fault at the works, together with several communication and IT issues amongst operational staff, including some missed water quality alarms, meant that the flow through the treatment works was not restored before the clear water tank drained down. As a result of the interruption in the treatment process, the quality of the water leaving the works did not initially meet regulatory standards due to elevated turbidity and aluminium levels. Scottish Water scoured the system at a number of points in the distribution system in order to remove the non-compliant water as quickly as possible. Scottish Water proposed a number of actions in response to this incident, including measures to improve awareness and communications amongst operational staff involved with networks and treatment. The possibility of providing a larger service water tank at the works has been considered and discounted but Scottish Water has investigated ways of reducing the demand for service water placed on the tank. Scottish Water's actions following the deterioration in treated water quality were appropriate, except that operational staff did not inform the Public Health Team of the event as per procedure. This meant that external stakeholders such as the NHS Board and Local Authority were not informed as they should have been. Scottish Water realise that they were deficient in this respect and DWQR acknowledges that this omission was not typical of the South East region.

Carron Valley, 8 December 2007 - Coagulation failure

This incident was due to a malfunction of the lime pump. The site has a standby lime pump, but at the time of the incident this had to be brought on line manually. A delay in Scottish Water's Operational Management Centre passing out the alarm resulted in an operator being called to site too late to prevent the final water quality being affected. Once on site, DWQR considers that appropriate actions were taken by Scottish Water to minimise the impact of the failure. These included shutting down the flow through the plant temporarily until water quality was restored. A discrepancy between readings on hand-held and on-line water quality instrumentation caused initial confusion as to the actual effect of the failure on treated water quality, although laboratory analysis of a sample taken from the clear water tank showed that a failure of the aluminium standard did, in fact, occur.

In response to the incident, Scottish Water has improved the arrangement at the site so that the standby lime dosing pump will start automatically. It has also committed to investigating why there was a delay in passing out the alarm and investigating the reason behind the discrepancy between instrumentation readings.

Water Quality in Local Authorities in the South East

Dumfries and Galloway Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

East Lothian Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

City of Edinburgh Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Falkirk Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Midlothian Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

Scottish Borders Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

West Lothian Council

Water Supply Zones in Area

Quality of Public Water Supply

Summary of Private Water Supplies

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