Regulations 2 and 4
SCHEDULE 1E+WPRESCRIBED CONCENTRATIONS AND VALUES
Table A
Microbiological Parameters
1 Note: Compliance required as to 95% of samples from each service reservoir (regulation 4(6)).
|
Part I: Directive requirements |
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Item | Parameters | Concentration or Value (maximum) | Units of Measurement | Point of compliance |
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1 | Enterococci | 0 | number/100 ml | Consumers' taps |
2 | Escherichia coli (E coli) | 0 | number/100 ml | Consumers' taps |
Part II: National requirements |
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Item | Parameters | Concentration or Value (maximum) | Units of Measurement | Point of compliance |
---|
1 | Coliform bacteria | 0 | number/100 ml | Service reservoirs1 and water treatment works |
2 | Escherichia coli (E coli) | 0 | number/100 ml | Service reservoirs and water treatment works |
Table B
Chemical Parameters
Notes:
|
1 The parametric value refers to the residual monomer concentration in the water as calculated according to specifications of the maximum release from the corresponding polymer in contact with the water. This is controlled by product specification.
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2 See also regulation 6(6).
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3 See also regulation 4(2)(d).
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4 See the definition of “pesticides and related products” in regulation 2.
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5 The parametric value applies to each individual pesticide.
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6 “Pesticides: Total” means the sum of the concentrations of the individual pesticides detected and quantified in the monitoring procedure.
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7 The specified compounds are:
The parametric value applies to the sum of the concentrations of the individual compounds detected and quantified in the monitoring process.
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8 The parametric value applies to the sum of the concentrations of the individual compounds detected and quantified in the monitoring process.
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9 The specified compounds are:
— chloroform
— bromoform
— dibromochloromethane
— bromodichloromethane.
The parametric value applies to the sum of the concentrations of the individual compounds detected and quantified in the monitoring process.
|
Part I: National requirements |
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Item | Parameters | Concentration or Value (maximum) | Units of Measurement | Point of compliance |
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1 | Acrylamide | 0.10 | μg/l | 1 |
2 | Antimony | 5.0 | μgSb/l | Consumers' taps |
3 | Arsenic | 10 | μgAs/l | Consumers' taps |
4 | Benzene | 1.0 | μg/l | Consumers' taps |
5 | Benzo(a)pyrene | 0.010 | μg/l | Consumers' taps |
6 | Boron | 1.0 | mgB/l | Consumers' taps |
7 | Bromate | 10 | μBrO3/l | Consumers' taps |
8 | Cadmium | 5.0 | μgCd/l | Consumers' taps |
9 | Chromium | 50 | μgCr/l | Consumers' taps |
10 | Copper 2 | 2.0 | mgCu/l | Consumers' taps |
11 | Cyanide | 50 | μgCN/l | Consumers' taps |
12 | 1, 2 dichloroethane | 3.0 | μg/l | Consumers' taps |
13 | Epichlorohydrin | 0.10 | μg/l | 1 |
14 | Fluoride | 1.5 | mgF/l | Consumers' taps |
15 | Lead 2 | (a)25, from 25th December 2003 until immediately before 25th December 2013
| μgPb/l | Consumers' taps |
(b)10, on and after 25th December 2013
| μgPb/l | Consumers' taps |
16 | Mercury | 1.0 | μgHg/l | Consumers' taps |
17 | Nickel 2 | 20 | μgNi/l | Consumers' taps |
18 | Nitrate 3 | 50 | mgNO3/l | Consumers' taps |
19 | Nitrite 3 | 0.50 | mgNO2/l | Consumers' taps |
0.10 | | Treatment Works |
20 | Pesticides 45 | | | |
Aldrin) | 0.030 | μg/l | Consumer's taps |
Dieldrin) |
Heptachlor) |
Heptachlor |
epoxide) |
other pesticides | 0.10 | μg/l | Consumers' taps |
21 | Pesticides: Total 6 | 0.50 | μg/l | Consumers' taps |
22 | Polycyclic aromatic hydrocarbons 7 | 0.10 | μg/l | Consumers' taps |
23 | Selenium | 10 | μgSe/l | Consumers' taps |
24 | Tetrachloroethene and Trichloroethene 8 | 10 | μg/l | Consumers' taps |
25 | Trihalomethanes: Total 9 | 100 | μg/l | Consumers' taps |
26 | Vinyl chloride | 0.50 | μg/l | 1 |
Part II: National requirements |
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Item | Parameters | Concentration or Value (maximum unless otherwise stated) | Units of Measurement | Point of compliance |
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1 | Aluminium | 200 | μgAl/l | Consumers' taps |
2 | Colour | 20 | mg/l Pt/Co | Consumers' taps |
3 | Iron | 200 | μgFe/l | Consumers' taps |
4 | Manganese | 50 | μgMn/l | Consumers' taps |
5 | Odour | Acceptable to consumers and no abnormal change | .................... | Consumers' taps |
6 | Sodium | 200 | mgNa/l | Consumers' taps |
7 | Taste | Acceptable to consumers and no abnormal change | .................... | Consumers' taps |
8 | Tetrachlorome-thane | 3 | μg/l | Consumers' taps |
9 | Turbidity | 4 | NTU | Consumers' taps |
Regulations 2 and 4
SCHEDULE 2E+WINDICATOR PARAMETERS
Notes:
|
1 The water should not be aggressive.
|
2 . . . |
3 May be monitored from samples of water leaving treatment works or other supply point, as no significant change during distribution.
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Item | Parameters | Specification Concentration or Value (maximum unless otherwise stated) or State | Units of Measurement | Point of compliance |
---|
1 | Ammonium | 0.50 | mgNH4/l | Consumers' taps |
2 | Chloride 1 | 250 | mgCl/l | Supply point3 |
3 | Clostridium perfringens (including spores) | 0 | Number/100 ml | Supply point3 |
4 | Coliform bacteria | 0 | Number/100 ml | Consumers' taps |
5 | Colony counts | No abnormal change | Number/1 ml at 22°C | Consumers' taps, service |
Number/1 ml at 37°C | Reservoirs and treatment works |
6 | Conductivity 1 | 2500 | μS/cm at 20°C | Supply point3 |
7 | Hydrogen ion | 9.5 | pHvalue | Consumers' taps |
6.5 (minimum) | pH value | |
8 | Sulphate 1 | 250 | mgSO4/l | Supply point3 |
9 | . . . | . . . | . . . | . . . |
10 | Total organic carbon (TOC) | No abnormal change | mgC/l | Supply point3 |
11 | . . . | . . . | . . . | . . . |
12 | Turbidity | 1 | NTU | Treatment works |
Regulation 6A
[SCHEDULE 2AE+WRadioactive substances parameters
Parametric values for radon, tritium and ID of water intended for human consumption
Parameters | Maximum concentration or value | Units of measurement |
---|
|
|
Indicative dose (for radioactivity) | 0,10
| mSv
|
Radon | 100 | Bq/1 |
Tritium (for radioactivity) | 100 | Bq/l |
SCHEDULE 3E+WMONITORING
PART IV
Table 1 E+WParameters and Circumstances for Check Monitoring
(1) | (2) | (3) |
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Item | Parameter | Circumstances |
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1 | Aluminium | When used as flocculant or where the water originates from, or is influenced by, surface waters |
2 | Ammonium | |
3 | Clostridium perfringens (including spores) | Where the water originates from, or is influenced by, surface waters |
4 | Coliform bacteria | |
5 | Colony counts | |
6 | Colour | |
7 | Conductivity | |
8 | Escherichia coli (E coli) | |
9 | Hydrogen ion | |
10 | Iron | When used as flocculant or where the water originates from, or is influenced by, surface waters |
11 | Manganese | Where the water originates from, or is influenced by, surface waters |
12 | Nitrate | When chloramination is practised |
13 | Nitrite | When chloramination is practised |
14 | Odour | |
15 | Taste | |
16 | Turbidity | |
Regulation 9
Table 2 E+WAnnual Sampling Frequencies: Water Supply Zones
Note: This table sets out the annual sampling frequencies for all the substances and parameters in column 1. These are determined for each water supply zone according to its estimated population (column 2). The number of samples is either the standard number in column 4 or the reduced number in column 3 (if one is given). Regulation 9 provides for the circumstances in which the reduced number of samples may be taken.
1 Where the population is not an exact multiple of 5,000, the population figure should be rounded up to the nearest multiple of 5,000.
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2 Sampling for these parameters may be within water supply zones or at supply points as specified in Table 3, subject to notes (iii) and (iv) below.
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3 Check monitoring in water supply zones is required only where chloramination is practised. In other circumstances audit monitoring is required.
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4 Audit monitoring in water supply zones is required only where sodium hypochlorite is added after water has left the treatment works. In other circumstances, audit monitoring is required at supply points.
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5 ...
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(1) | (2) | (3) | (4) |
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Substances and parameters subject to check monitoring | Estimated population of water supply zone | Reduced | Standard |
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Subject to check monitoring | | | |
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E coli | <100 | | 4 |
Coliform bacteria | ≥100 | | 12 per 5,000 population1 |
Residual disinfectant | | | |
Aluminium | | | |
Ammonium |
Clostridium perfringens (including spores)2 |
Colony counts |
Colour |
Conductivity2 |
Hydrogen ion |
Iron |
Manganese |
Nitrate 3 |
Nitrite 3 |
Odour |
Taste |
Turbidity |
Subject to audit monitoring | | | |
---|
Aluminium | | | |
Antimony |
Arsenic |
Benzene2 |
Benzo(a)pyrene |
Boron2 |
Bromate 4 |
Cadmium |
Chromium |
Clostridium perfringens (including spores) |
Copper |
Cyanide2 |
1,2 dichloroethane2 |
Enterococci |
Fluoride2 |
Iron |
Lead |
Manganese |
Mercury2 |
Nickel |
Nitrate 3 |
Nitrite 3 |
Pesticides and related products 2 |
Polycyclic aromatic hydrocarbons |
[Radon(b)] |
Selenium |
Sodium |
Trichloroethene /Tetrachloroethene2 |
Tetrachloromethane2 |
Trihalomethanes |
Chloride2 |
Sulphate2 |
Total organic carbon2 |
Tritium2 |
[Indicative dose (for radioactivity)(b)] |
|
Regulation 9
Table 3 E+WAnnual Sampling Frequencies: Treatment Works or Supply Points
Note 1: Sampling is at treatment works for the substances and parameters shown in column (1) of the Table as items (1) to (6) and at supply points for the other substances and parameters, except nitrate subject to footnotes (ii) and (ii)(a) to the Table below. Note 2: This table sets out the annual sampling frequencies for all the substances and parameters in column 2 at treatment works or supply points. The frequencies are determined according to the volume of water supplied at each treatment works or supply point (column 3). The number of samples is either the standard number in column 5 or the reduced number in column 4 (if one is given). Regulation 9 provides for the circumstances in which the reduced number of samples may be taken.
1 Sampling at treatment works when chloramination is practised.
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2 Check monitoring is required only in respect of surface waters (see regulation 6(2) and Table 1 in Schedule 3).
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3 Audit monitoring at supply points is required only where sodium hypochlorite is not added after water has left the treatment works. In other circumstances, audit monitoring is required in water supply zones.
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4 Sampling at treatment works when chloramination is not practised.
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5...
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(1) | (2) | (3) | (4) | (5) |
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Item | Substances and parameters | Volume of water supplied m3/d | Reduced | Standard |
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1. | E Coli | | | |
2. | Calliform bacteria |
3. | Colony counts |
4. | Nitrite 1 |
5. | Residual disinfectant |
6. | Turbidity |
Subject to check monitoring |
---|
7. | Clostridium perfringens2 | | | |
8. | Conductivity |
Subject to audit monitoring |
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9. | Benzene | | | |
10. | Boron |
11. | Bromate 3 |
11A. | Clostridium perfringens (including spores) |
12. | Cyanide |
13. | 1,2 dichloroethane |
14. | Fluoride |
15. | Mercury |
16. | Nitrite 4 |
17. | Pesticides and Related products |
[17A | Radon] |
18. | Trichloroethene |
Tetrachloroethene |
19. | Tetrachloromethane |
20. | Chloride |
21. | Sulphate |
22. | Total organic carbon |
23. | Tritium |
24. | [Indicative dose (for radioactivity)(b) |
25.] | |
Regulation 6A
[SCHEDULE 3AE+WMonitoring of radioactive substances
RadonE+W
1.—(1) In relation to the radon parameter in the radioactive substances parameters table, a water undertaker—
(a)must ensure that a representative survey is carried out in accordance with sub-paragraph (2) to determine the likelihood of a supply failing to comply with the relevant parametric concentration or value specified in the radioactive substances parameters table; and
(b)must carry out monitoring where there is reason to believe, on the basis of the results of the representative surveys or other reliable information, including any risk assessment carried out in accordance with regulation 28, that the parametric value for the radon parameter laid down in the radioactive substances parameters table might be exceeded.
(2) A representative survey must be designed in such a way—
(a)as to be capable of determining the scale and nature of likely exposure to radon in water intended for human consumption originating from different types of groundwater sources and wells in different geological areas; and
(b)that underlying parameters, especially the geology and hydrology of the area, radioactivity of rock or soil, and well type, can be identified and used to direct further action to areas of likely high exposure.
TritiumE+W
2.—(1) In relation to the tritium parameter in the radioactive substances parameters table, a water undertaker—
(a)must carry out monitoring where an anthropogenic source of tritium or other artificial radionuclides is present within a water supply zone and it cannot be shown on the basis of other surveillance programmes or investigations, including any risk assessment carried out in accordance with regulation 28, that the level of tritium is below the parametric value listed in the radioactive substances parameters table; and
(b)must carry out an investigation of the presence of other artificial radionuclides if the concentration of tritium exceeds the parametric value listed in the radioactive substances parameters table.
(2) Where monitoring is required by sub-paragraph (1) samples must be taken in accordance with regulation 9(1) and (3).
Indicative DoseE+W
3.—(1) In relation to the indicative dose (“ID”) parameter in the radioactive substances parameters table, a water undertaker must carry out monitoring where a source of artificial radioactivity or elevated natural radioactivity is present in a water supply zone and it cannot be shown on the basis of other surveillance programmes or investigations, including any risk assessment carried out in accordance with regulation 28, that the level of ID is below the parametric value listed the radioactive substances parameters table.
(2) Where monitoring is required by sub-paragraph (1) in relation to artificial radionuclides samples must be taken in accordance with regulation 9(1) and (3).
(3) Where monitoring is required by sub-paragraph (1) in relation to a source of elevated natural radioactivity—
(a)the Welsh Ministers must specify, by notice in writing to the water undertaker, the frequency of the monitoring required of—
(i)gross alpha activity;
(ii)gross beta activity; or
(iii)individual natural radionuclides,
depending on the screening strategy adopted by the water undertaker pursuant to Schedule 5; and
(b)the frequency of monitoring required under sub-paragraph (a) may vary from a single check measurement to the frequencies required for sampling in accordance with regulation 9(1).
(4) Where a single check for natural radioactivity is specified under paragraph (3)(a), the water undertaker must carry out a further check if any change occurs in relation to the supply which is likely to influence the concentrations of radionuclides in the supply.
Water treatmentE+W
4. Where treatment to reduce the level of radionuclides in a water supply zone has been undertaken, to verify the continued efficacy of that treatment, the water undertaker must—
(a)monitor the supply for total indicative dose, radon and tritium in accordance the provisions of this Schedule; and
(b)take samples in accordance with regulation 9(1) and (3).
AveragingE+W
5. Where a parametric value in the radioactive substances parameters table is exceeded in relation to a particular sample taken by a water undertaker, the Welsh Ministers must specify, by notice in writing to the water undertaker, the extent of resampling necessary to ensure that the measured values are representative of an average activity concentration for a full year.]
Regulation 16
SCHEDULE 4E+WANALYTICAL METHODOLOGY
Regulation 16
Table A1 E+WParameters for which, Subject to Regulation 16(7), Methods of Analysis are Prescribed
(1) | (2) |
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Parameter | Method |
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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 | ISO 9308-1 |
Colony count 22°C-enumeration of culturable microorganisms | prEN ISO 6222 |
Colony count 37°C-enumeration of culturable microorganisms | prEN ISO 6222 |
Enterococci | ISO 7899-2 |
Escherichia coli (E coli) | ISO 9308-1 |
*The composition of m-CP agar is: | |
Basal medium | |
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 and add: | |
D-cycloserine | 400.0mg |
Polymyxine-B sulphate | 25.0mg |
Indoxyl-[beta]-D-glucoside to be dissolved in 8 ml sterile water before addition | 60.0mg |
Filter-sterilised 0.5% phenolphthalein diphosphate solution | 20.0 ml |
Filter-sterilised 4.5% FeCl3·6H2O | 2.0 ml |
Table A2 E+WParameters for which, Subject to Regulation 16(7), Methods of Analysis are Prescribed
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 4NTU.
|
6 The performance characteristics apply to the specification of 1NTU for water leaving treatment works.
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(1) | (2) | (3) | (4) |
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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 |
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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 |
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 |
Regulation 6A
[SCHEDULE 5E+WMonitoring for indicative dose and analytical performance characteristics
Monitoring for compliance with the indicative doseE+W
1. A water undertaker may use reliable screening strategies to indicate the presence of radioactivity in water intended for human consumption.
2. The strategies referred to in paragraph 1 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
3. If one of the activity concentrations exceeds 20% of the corresponding derived value or the tritium concentration exceeds its parametric value listed in Schedule 2A an analysis of additional radionuclides is required.
4. A water undertaker 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
5. Subject to paragraph 6 the recommended screening values are–
(a)0,1Bq/l for gross alpha activity; and
(b)1,0Bq/l for gross beta activity.
6. If the gross alpha activity exceeds 0,1Bq/l or the gross beta activity exceeds 1,0Bq/l, analysis for specific radionuclides is required.
7. The Welsh Ministers may set alternative screening levels for gross alpha activity and gross beta activity where it can be demonstrated by the water undertaker that the alternative levels are in compliance with an indicative dose of 0,1 mSv.
8. The radionuclides to be measured must be based on all relevant information about likely sources of radioactivity.
Calculation of the indicative doseE+W
9. 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).
10. 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
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
11. 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:
Parameters and radionuclides | Limit of detection (Notes 1,2) | Notes |
---|
Tritium
| 10 Bq/1
| Note 3
|
Radon
| 10 Bq/1
| Note 3
|
gross alpha
| 0,04 Bq/1
| Note 4
|
gross beta
| 0,4 Bq/1
| Note 4
|
U-238
| 0,02 Bq/1
| |
U-234
| 0,02 Bq/1
| |
Ra-226
| 0,04 Bq/1
| |
Ra-228
| 0,02 Bq/1
| Note 5
|
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
| |
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.]