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CHAPTER THREE SUMMARY OF WATER AND COMPLIANCE IN SCOTLAND
3.1 The data from this section of the report has been derived from the 2005 DWQR Annual Report.
Overview of compliance
3.2 The drinking water quality results reported by Scottish Water for 2005 show that 345,761 tests were carried out on samples taken from water treatment works, service reservoirs and consumer taps. Of the 153,291 tests on samples taken from consumer taps, 99.56% met the required standard. This is an increase of 0.14% on compliance for 2004. There were 669 tests giving results which did not meet the standard set out in the Water Supply (Water Quality) (Scotland) Regulations 2001. The largest number of fails were for the total coliform and trihalomethane parameters. Map C plots these non compliant tests and shows several zones with more than 9 fails.
3.3 In 2005 there were 42 incidents reported by Scottish Water of events which could affect drinking water quality. These are also mapped on Map D.
Compliance with Key Parameters
3.4 The Water Supply (Water Quality) (Scotland) Regulations 2001 detail fifty-one quality standards that drinking water in Scotland must meet, together with the frequency with which Scottish Water is required to test for each of these standards or parameters. DWQR has identified ten of the standards as being key to measuring drinking water quality in Scotland.
3.5 These ten key parameters have been identified because they:
- Have particular relevance to Scotland and therefore provide a useful indication of water quality; or
- Are parameters which have a higher regulatory frequency of sampling.
3.6 The ten Key Drinking Water Quality Standards are detailed below, together with the Prescribed Concentration or Value ( PCV) at consumer taps set out in the regulations:
1. | Total Coliforms | PCV = 0 per 100ml |
2. | Faecal Coliforms (E. coli) | PCV = 0 per 100ml |
3. | Colour | PCV = 20 mg/l Pt/Co |
4. | Turbidity | PCV = 4 NTU |
5. | Hydrogen Ion (pH) | PCV = 6.5 - 9.5 |
6. | Aluminium | PCV = 200 µg/l |
7. | Iron | PCV = 200 µg/l |
8. | Manganese | PCV = 50 µg/l |
9. | Lead | PCV = 25 µg/l |
10. | Trihalomethanes | PCV = 100 µg/l for a total of four of the compounds |
3.7 Section 6 provides a comparison of water quality compliance in Scotland as a whole with the individual water companies in England and Wales. The following tables detail mean zonal compliance for each of the ten key parameters. Mean Zonal Compliance ( MZC) is a simple calculation reflecting the percentage of samples which met the required standard for any given parameter or supply zone.
3.8 The Overall Compliance figure for Scotland as a whole is derived by taking the mean of the MZC for every parameter for which there is a numerical standard. In 2005 the Overall Compliance for Scotland was 99.42%.
Table 3.1: Mean Zonal Compliance for Microbiological Tests by Region
. | South West | North West | North East | South East | Western Isles, Orkney and Shetland |
|---|
MZC - Coliforms | 99.31 | 97.98 | 99.12 | 99.21 | 97.73 |
|---|
MZC - E. coli | 99.91 | 98.86 | 99.98 | 99.86 | 98.98 |
|---|
3.9 Poorest compliance is in North West and Western Isles, Orkney and Shetland. DWQR attribute this to the number of works with only basic treatment currently in these areas.
Table 3.2: Mean Zonal Compliance for Turbidity by Region
. | South West | North West | North East | South East | Western Isles, Orkney and Shetland |
|---|
MZC - Turbidity | 99.95 | 100.00 | 99.58 | 99.94 | 99.98 |
|---|
3.10 Lowest compliance for turbidity was found in the North East.
Table 3.3: Mean Zonal Compliance for Trihalomethanes by Region
| South West | North West | North East | South East | Western Isles, Orkney and Shetland |
|---|
MZC - Trihalomethanes | 94.93 | 90.67 | 99.58 | 95.03 | 98.72 |
|---|
3.11 Again the North West has the lowest MZC reflecting the large number of works that don't have a treatment process capable of removing the compounds which form THMS when chlorine is added to the water.
Table 3.4: Mean Zonal Compliance for Colour and Hydrogen Ion by Region
| South West | North West | North East | South East | Western Isles, Orkney and Shetland |
|---|
MZC - Colour | 100.00 | 91.61 | 99.93 | 98.73 | 94.81 |
|---|
MZC - Hydrogen Ion | 99.90 | 92.30 | 99.58 | 99.89 | 91.33 |
|---|
3.12 Despite recent improvements in the North West and Island regions, these areas still show lower compliance.
Table 3.5: Mean Zonal Compliance for Aluminium, Iron and Manganese by Region
| South West | North West | North East | South East | Western Isles, Orkney and Shetland |
|---|
MZC - Aluminium | 99.50 | 98.96 | 99.09 | 99.84 | 97.11 |
|---|
MZC - Iron | 99.03 | 96.87 | 99.32 | 95.79 | 92.60 |
|---|
MZC - Manganese | 98.89 | 99.73 | 99.58 | 98.34 | 98.72 |
|---|
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