Regulation 11
SCHEDULE 3E+WSampling and analysis
PART 1 E+WGeneral
Samples: generalE+W
1.—(1) The local authority must ensure that each sample is—
(d)taken by a competent person using suitable equipment;
(e)representative of the water at the sampling point at the time of sampling;
(f)not contaminated in the course of being taken;
(g)kept at such temperature and in such conditions as will secure that there is no material change in what is to be measured; and
(h)analysed without delay by a competent person using suitable equipment.
(2) It must ensure that the sample is analysed using a system of analytical quality control.
(3) The system must be subjected to checking by a person who is—
(a)not under the control of either the analyst or the local authority; and
(b)approved by the Welsh Ministers for that purpose.
Analysing samplesE+W
2.—(1) The local authority must ensure that each sample is analysed in accordance with this paragraph.
(2) For each parameter specified in the first column of Table 1 in Part 2 of this Schedule the method of analysis is specified in the second column of that table.
(3) For each parameter specified in the first column of Table 2 in Part 2 of this Schedule the method is one that is capable of—
(a)measuring concentrations and values with the trueness and precision specified in the second and third columns of that table, and
(b)detecting the parameter at the limit of detection specified in the fourth column of that table.
(4) For hydrogen ion, the method of analysis must be capable of measuring a value with a trueness of 0.2 pH unit and a precision of 0.2 pH unit.
(5) The method of analysis used for odour and taste parameters must be capable of measuring values equal to the parametric value with a precision of 1 dilution number at 25°C.
(5) For these purposes—
“limit of detection” is —
(a)three times the relative within-batch standard deviation of a natural sample containing a low concentration of the parameter; or
(b)five times the relative within-batch standard deviation of a blank sample;
“precision” (the random error) is twice the standard deviation (within a batch and between batches) of the spread of results about the mean;
“trueness” (the systematic error) is the difference between the mean value of the large number of repeated measurements and the true value.
Authorisation of alternative methods of analysisE+W
3.—(1) The Welsh Ministers may authorise a method different from that set out in paragraph 2(2) if satisfied that it is at least as reliable.
(2) An authorisation may be time-limited and may be revoked at any time.
Sampling and analysis by persons other than local authoritiesE+W
4.—(1) A local authority may enter into an arrangement for any person to take and analyse samples on its behalf.
(2) A local authority must not enter into an arrangement under paragraph (1) unless—
(a)it is satisfied that the task will be carried out promptly by a person competent to perform it, and
(b)it has made arrangements that ensure that any breach of these Regulations is communicated to it immediately, and any other result is communicated to it within 28 days.
PART 2 E+WAnalytical methods
Table 1
Prescribed methods of analysis
| Parameter | Method |
|---|---|
| Clostridium perfringens (including spores) | Membrane filtration followed by anaerobic incubation of the membrane on m-CP agar* at 44 ± 1°C for 21 ± 3 hours. Count opaque yellow colonies that turn pink or red after exposure to ammonium hydroxide vapours for 20 to 30 seconds. |
| Coliform bacteria | BS-EN ISO 9308-1 |
| Colony count 22°C — enumeration of culturable microorganisms | BS-EN ISO 6222 |
| Colony count 37°C — enumeration of culturable microorganisms | BS-EN ISO 6222 |
| Enterococci BS-EN ISO 7899-2 | |
| Escherichia coli (E. coli) | BS-EN ISO 9308-1 |
| Pseudomonas aeruginosa | BS-EN-ISO 12780 |
Use the following method to make m-CP agar :
Make a basal medium consisting of—
| Tryptose | 30.0g |
| Yeast extract | 20.0g |
| Sucrose | 5.0g |
| L-cysteine hydrochloride | 1.0g |
| MgSO4.7H2O | 0.1g |
| Bromocresol purple | 40.0mg |
| Agar | 15.0g |
| Water | 1,000.0ml |
Dissolve the ingredients of the basal medium, adjust pH to 7.6 and autoclave at 121°C for 15 minutes. Allow the medium to cool.
Dissolve—
| D-cycloserine | 400.0mg |
| Polymyxine-B sulphate | 25.0mg |
| Indoxyl-β-D-glucoside | 60.0mg |
into 8ml sterile water and add it to the medium.
Add to the medium—
| Filter-sterilised 0.5% phenolphthalein diphosphate solution | 20.0ml |
| Filter-sterilised 4.5% FeCl3.6H2O | 2.0ml |
Table 2
Prescribed performance characteristics for methods of analysis
Notes: | |||
1 The method of analysis should determine total cyanide in all forms. | |||
2 The performance characteristics apply to each individual pesticide and will depend on the pesticide concerned. | |||
3 The performance characteristics apply to the individual substances specified at 25% of the parametric value in Part I of Table B in Schedule 1. | |||
4 The performance characteristics apply to the individual substances specified at 50% of the parametric value in Part I of Table B in Schedule 1. | |||
5 The performance characteristics apply to the prescribed value of 4 NTU. | |||
6 The performance characteristics apply to the specification of 1 NTU for surface waters or ground waters influenced by surface water. | |||
| Parameters | Trueness % of prescribed concentration or value or specification | Precision % of prescribed concentration or value or specification | Limit of detection % of prescribed concentration or value or specification |
|---|---|---|---|
| Aluminium | 10 | 10 | 10 |
| Ammonium | 10 | 10 | 10 |
| Antimony | 25 | 25 | 25 |
| Arsenic | 10 | 10 | 10 |
| Benzene | 25 | 25 | 25 |
| Benzo(a)pyrene | 25 | 25 | 25 |
| Boron | 10 | 10 | 10 |
| Bromate | 25 | 25 | 25 |
| Cadmium | 10 | 10 | 10 |
| Chloride | 10 | 10 | 10 |
| Chromium | 10 | 10 | 10 |
| Colour | 10 | 10 | 10 |
| Conductivity | 10 | 10 | 10 |
| Copper | 10 | 10 | 10 |
| Cyanide 1 | 10 | 10 | 10 |
| 1,2-dichloroethane | 25 | 25 | 10 |
| Fluoride | 10 | 10 | 10 |
| 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 |
| Pesticides and related products 2 | 25 | 25 | 25 |
| Polycyclic aromatic hydrocarbons 3 | 25 | 25 | 25 |
| Selenium | 10 | 10 | 10 |
| Sodium | 10 | 10 | 10 |
| Sulphate | 10 | 10 | 10 |
| Tetrachloroethene 4 | 25 | 25 | 10 |
| Tetrachloromethane | 20 | 20 | 20 |
| Trichloroethene 4 | 25 | 25 | 10 |
| Trihalomethanes: | |||
| Total 3 | 25 | 25 | 10 |
| Turbidity 5 | 10 | 10 | 10 |
| Turbidity 6 | 25 | 25 | 25 |
[F1PART 3E+WMonitoring for indicative dose and analytical performance characteristics
Textual Amendments
F1Sch. 3 Pt. 3 inserted (14.4.2016) by The Private Water Supplies (Wales) (Amendment) Regulations 2016 (S.I. 2016/411), reg. 1(1), Sch. 3
Monitoring for compliance with the indicative doseE+W
5. A local authority may use reliable screening strategies to indicate the presence of radioactivity in water intended for human consumption.
6. The strategies referred to in paragraph 5 may include screening for–
(a)certain radionuclides or individual radionuclide; or
(b)gross alpha activity or gross beta activity (where appropriate gross beta activity may be replaced by residual beta activity after subtraction of the K-40 activity concentration).
Screening for certain radionuclides, or screening for an individual radionuclideE+W
7. If one of the activity concentrations exceeds 20% of the corresponding derived value or the tritium concentration exceeds its parametric value listed in Part 3 of Schedule 1 an analysis of additional radionuclides is required.
8. A local authority must, in deciding which radionuclides require to be measured for each supply, take into account all relevant information about likely sources of radioactivity.
Screening strategies for gross alpha activity and gross beta activityE+W
9. Subject to paragraph 10 the recommended screening values are–
(a)0,1Bq/l for gross alpha activity; and
(b)1,0Bq/l for gross beta activity.
10. If the gross alpha activity exceeds 0,1Bq/l or the gross beta activity exceeds 1,0Bq/l, analysis for specific radionuclides is required.
11. The Welsh Ministers may set alternative screening levels for gross alpha activity and gross beta activity where it can be demonstrated by the local authority that the alternative levels are in compliance with an indicative dose of 0,1 mSv.
12. The radionuclides to be measured must be based on all relevant information about likely sources of radioactivity.
Calculation of the indicative doseE+W
12. The indicative dose must be calculated from–
(a)the measured radionuclide concentrations and the dose coefficients laid down in Annex III, Table A of Directive 96/29/Euratom; or
(b)more recent information recognised by the Welsh Ministers, on the basis of the annual intake of water (730 1 for adults).
13. Where the following formula is satisfied, it can be assumed that the indicative dose is less than the parametric value of 0,1 mSv and no further investigation is required–
where:
Ci(obs) = observed concentration of radionuclide i
Ci(der) = derived concentration of radionuclide i
n = number of radionuclides detected.
Derived concentrations for radioactivity in water intended for human consumption
(1) This table includes values for the most common natural and artificial radionuclides; these are precise values, calculated for a dose of 0,1 mSv, an annual intake of 730 litre and using the dose coefficients laid down in Annex III, Table A of Directive 96/29/ Euratom; derived concentrations for other radionuclides can be calculated on the same basis, and values can be updated on the basis of more recent information recognised by the Welsh Ministers. | ||
(2) This table allows only for the radiological properties of uranium, not for its chemical toxicity. | ||
| Origin | Nuclide | Derived concentration |
|---|---|---|
| Natural | U-238 | 3,0 Bq/1 |
| U-234 | 2,8 Bq/1 | |
| Ra-226 | 0,5 Bq/1 | |
| Ra-228 | 0,2 Bq/1 | |
| Pb-210 | 0,2 Bq/1 | |
| Po-210 | 0,1 Bq/1 | |
| Artificial | C-14 | 240 Bq/1 |
| Sr-90 | 4,9 Bq/1 | |
| Pu-239/Pu-240 | 0,6 Bq/1 | |
| Am-241 | 0,7 Bq/1 | |
| Co-60 | 40 Bq/1 | |
| Cs-134 | 7,2 Bq/1 | |
| Cs-137 | 11 Bq/1 | |
| 1-131 | 6,2 Bq/1 | |
Performance characteristics and methods of analysisE+W
14. For the following parameters and radionuclides, the method of analysis used must, as a minimum, be capable of measuring activity concentrations with a limit of detection specified below:
(Note 1) The limit of detection must be calculated according to the ISO standard 11929: Determination of the characteristic limits (decision threshold, detection limit, and limits of confidence interval) for measurements of ionising radiation – Fundamentals and application, with probabilities of errors of 1st and 2nd kind of 0,05 each. | ||
(Note 2) Measurement uncertainties must be calculated and reported as complete standard uncertainties, or as expanded uncertainties with an expansion factor of 1,96 according the ISO Guide for the Expression of Uncertainty in Measurement. | ||
(Note 3) The limit of detection for tritium and for radon is 10% of its parametric value of 100 Bq/1. | ||
(Note 4) The limit of detection for gross alpha activity and gross beta activities are 40% of the screening values of 0,1 and 1,0 Bq/1 respectively. | ||
(Note 5) This limit of detection applies only to initial screening for indicative dose for a new water source; if initial checking indicates that it is not plausible that Ra-228 exceeds 20% of the derived concentration, the limit of detection may be increased to 0,08 Bq/1 for routine Ra-228 nuclide specific measurements, until a subsequent re-check is required.] | ||
| Parameters and radionuclides | Limit of detection | Notes |
|---|---|---|
| Tritium | 10 Bq/1 | |
| Radon | 10 Bq/1 | |
| gross alpha | 0,04 Bq/1 | |
| gross beta | 0,4 Bq/1 | |
| U-238 | 0,02 Bq/1 | |
| U-234 | 0,02 Bq/1 | |
| Ra-226 | 0,04 Bq/1 | |
| Ra-228 | 0,02 Bq/1 | |
| Pb-210 | 0,02 Bq/1 | |
| Po-210 | 0,01 Bq/1 | |
| C-14 | 20 Bq/1 | |
| Sr-90 | 0,4 Bq/1 | |
| Pu-239/Pu-240 | 0,04 Bq/1 | |
| Am-241 | 0,06 Bq/1 | |
| Co-60 | 0,5 Bq/1 | |
| Cs-134 | 0,5 Bq/1 | |
| Cs-137 | 0,5 Bq/1 | |
| I-131 | 0,5 Bq/1 | |