Textual Amendments
F1Sch. 3 substituted (27.10.2017) by The Public Water Supplies (Scotland) Amendment Regulations 2017 (S.S.I. 2017/281), reg. 1(1), sch. 2 (as amended by The Public and Private Water Supplies (Miscellaneous Amendments) (Scotland) Regulations 2017 (S.S.I. 2017/321), regs. 1, 3(3)(a)(b))
1.—(1) Subject to paragraph 3, for a parameter in Table 1, the method of analysis used must, as a minimum, be capable of measuring concentrations equal to the prescribed concentration or value for the parameter with—S
(a)a limit of quantification of 30 % or less of the prescribed concentration or value for the parameter; and
(b)an uncertainty of measurement as specified in Table 1 for the parameter.
(2) The result of the analysis for a parameter in Table B or Table C must be expressed using at least the same number of significant figures as the prescribed concentration or value for the parameter in the table.
2. The uncertainty of measurement specified in Table 1 for a parameter must not be used as an additional tolerance to the prescribed concentration or value for the parameter.S
3. Until 31st December 2019, Scottish Water may, for a parameter in Table 2, use the corresponding ‘trueness’, ‘precision’ and ‘limit of detection’ in that table as an alternative set of performance characteristics (instead of using the limit of quantification and the uncertainty of measurement referred to in paragraph 1(1)).S
| Parameter | Uncertainty of measurement (% of prescribed concentration or value, except pH) (Note 1) | Notes |
|---|---|---|
| Aluminium | 25 | |
| Ammonium | 40 | |
| Antimony | 40 | |
| Arsenic | 30 | |
| Benzo(a)pyrene | 50 | Note 5 |
| Benzene | 40 | |
| Boron | 25 | |
| Bromate | 40 | |
| Cadmium | 25 | |
| Chloride | 15 | |
| Chromium | 30 | |
| Conductivity | 20 | |
| Copper | 25 | |
| Cyanide | 30 | Note 6 |
| 1,2-dichloroethane | 40 | |
| Fluoride | 20 | |
| Hydrogen ion concentration (in pH) | 0.2 | Note 7 |
| Iron | 30 | |
| Lead | 25 | |
| Manganese | 30 | |
| Mercury | 30 | |
| Nickel | 25 | |
| Nitrate | 15 | |
| Nitrite | 20 | |
| Oxidisability | 50 | Note 8 |
| Pesticides | 30 | Note 9 |
| Polycyclic aromatic hydrocarbons | 50 | Note 10 |
| Selenium | 40 | |
| Sodium | 15 | |
| Sulphate | 15 | |
| Tetrachloroethene | 30 | Note 11 |
| Trichloroethene | 40 | Note 11 |
| Trihalomethanes: total | 40 | Note 10 |
| Total organic carbon | 30 | Note 12 |
| Turbidity | 30 | Note 13 |
| Parameter | Trueness (% of prescribed concentration or value, except for pH) (Note 2) | Precision (% of prescribed concentration or value, except for pH) (Note 3) | Limit of detection (% of prescribed concentration or value, except for pH) (Note 4) | Notes |
|---|---|---|---|---|
| Aluminium | 10 | 10 | 10 | |
| Ammonium | 10 | 10 | 10 | |
| Antimony | 25 | 25 | 25 | |
| Arsenic | 10 | 10 | 10 | |
| Benzo(a)pyrene | 25 | 25 | 25 | |
| Benzene | 25 | 25 | 25 | |
| Boron | 10 | 10 | 10 | |
| Bromate | 25 | 25 | 25 | |
| Cadmium | 10 | 10 | 10 | |
| Chloride | 10 | 10 | 10 | |
| Chromium | 10 | 10 | 10 | |
| Conductivity | 10 | 10 | 10 | |
| Copper | 10 | 10 | 10 | |
| Cyanide | 10 | 10 | 10 | Note 6 |
| 1,2-dichloroethane | 25 | 25 | 10 | |
| Fluoride | 10 | 10 | 10 | |
| Hydrogen ion concentration (in pH) | 0.2 | 0.2 | Note 7 | |
| Iron | 10 | 10 | 10 | |
| Lead | 10 | 10 | 10 | |
| Manganese | 10 | 10 | 10 | |
| Mercury | 20 | 10 | 20 | |
| Nickel | 10 | 10 | 10 | |
| Nitrate | 10 | 10 | 10 | |
| Nitrite | 10 | 10 | 10 | |
| Oxidisability | 25 | 25 | 10 | Note 8 |
| Pesticides | 25 | 25 | 25 | Note 9 |
| Polycyclic aromatic hydrocarbons | 25 | 25 | 25 | Note 10 |
| Selenium | 10 | 10 | 10 | |
| Sodium | 10 | 10 | 10 | |
| Sulphate | 10 | 10 | 10 | |
| Tetrachloroethene | 25 | 25 | 10 | Note 11 |
| Trichloroethene | 25 | 25 | 10 | Note 11 |
| Trihalomethanes: total | 25 | 25 | 10 | Note 10 |
| Turbidity | 25 | 25 | 25 | |
| Notes to Table 1 and Table 2 | ||||
| Note 1: Uncertainty of measurement is a non-negative parameter characterising the dispersion of the quantity values being attributed to a measurand, based on the information used. The performance criterion for measurement uncertainty (k = 2) is the percentage of the prescribed concentration or value for the parameter stated in the table or better. Measurement uncertainty must be estimated at the level of the prescribed concentration or value for the parameter, unless otherwise specified. | ||||
| Note 2: Trueness is a measure of systematic error, i.e. the difference between the mean value of the large number of repeated measurements and the true value. Further specifications are those set out in international standard ISO 5725 entitled “Accuracy (trueness and precision) of measurement methods and results”. | ||||
| Note 3: Precision is a measure of random error and is usually expressed as the standard deviation (within and between batches) of the spread of results from the mean. Acceptable precision is twice the relative standard deviation. This term is further specified in international standard ISO 5725 entitled “Accuracy (trueness and precision) of measurement methods and results”. | ||||
| Note 4: Limit of detection is either three times the standard deviation within a batch of a natural sample containing a low concentration of the parameter, or five times the standard deviation of a blank sample (within a batch). | ||||
| Note 5: If the value of uncertainty of measurement cannot be met, the best available technique should be selected (up to 60 %). | ||||
| Note 6: The method determines total cyanide in all forms. | ||||
| Note 7: Values for trueness, precision and uncertainty of measurement are expressed in pH units. | ||||
| Note 8: Reference method European standard EN ISO 8467:1995 entitled “Water quality - Determination of permanganate index (ISO 8467:1993)”. | ||||
| Note 9: The performance characteristics for individual pesticides are given as an indication. Values for the uncertainty of measurement as low as 30 % can be achieved for several pesticides, higher values up to 80 % may be allowed for a number of pesticides. | ||||
| Note 10: The performance characteristics apply to individual substances, specified at 25 % of the prescribed concentration or value for the corresponding parameter in Table B. | ||||
| Note 11: The performance characteristics apply to individual substances, specified at 50 % of the prescribed concentration or value for the corresponding parameter in Table B. | ||||
| Note 12: The uncertainty of measurement should be estimated at the level of 3 mg/l of the total organic carbon in accordance with European standard EN 1484:1997 entitled “Water analysis - Guidelines for the determination of total organic carbon and dissolved organic carbon”. | ||||
| Note 13: The uncertainty of measurement must be estimated at the level of 1.0 nephelometric turbidity units in accordance with European standard EN ISO 7027-1:2016 entitled “Water quality - Determination of turbidity - Part 1: Quantitative methods (ISO 7027-1:2016)”.] | ||||