# The Water Supply (Water Quality) Regulations (Northern Ireland) 2017, Schedule 4: ANALYTICAL METHODOLOGY


TABLE A
Parameters for which, subject to regulation 18(12), methods of analysis are prescribed
(1) Parameter
(2) Method
Clostridium perfringens (including spores)
EN ISO 14189
Coliform bacteria
EN ISO 9308-1 or EN ISO 9308-2
Colony count 22°C-enumeration of culturable microorganisms
ENISO 6222
Colony count 36°C-enumeration of culturable microoganisms
EN ISO 6222
Enterococci
EN ISO 7899-2
Escherichia coli (E. coli)
EN ISO 9308-1 or EN ISO 9308-2
Pseudomonas aeruginosa
EN ISO 16266
TABLE B
Minimum performance characteristic: “uncertainty of measurement”
1 Acrylamide, epichlorohydrin and vinyl chloride to be controlled by product specification.
2 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 parametric value stated in the table or better. Measurement uncertainty must be estimated at the level of the parametric value, unless otherwise specified.
3 If the value of uncertainty of measurement cannot be met, the best available technique should be selected (up to 60%).
4 The method determines total cyanide in all forms.
5 Values for trueness, precision and uncertainty of measurement are expressed in pH units.
6 Reference method EN ISO 8467.
7 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
8 The performance characteristics apply to individual substances, specified at 25% of the parametric value in Table B in Schedule 1.
9 The performance characteristics apply to individual substances, specified at 50% of the parametric value in Table B in Schedule 1.
10 The uncertainty of measurement should be estimated at the level of 3 mg/l of the total organic carbon. CEN 1484 Guidelines for the determination of total organic carbon and dissolved organic carbon must be used.
11 The uncertainty of measurement must be estimated at the level of 1.0 NTU (nephelometric turbidity units) in accordance with EN ISO 7027.
(1) Parameter1
(2) Uncertainty of measurement (% of parametric value, except pH)2
Aluminium
25
Ammonium
40
Antimony
40
Arsenic
30
Benzo(a)pyrene3
50
Benzene
40
Boron
25
Bromate
40
Cadmium
25
Chloride
15
Chromium
30
Conductivity
20
Copper
25
Cyanide4
30
1,2-dichloroethane
40
Fluoride
20
Hydrogen ion concentration pH (expressed in pH units)5
0.2
Iron
30
Lead
25
Manganese
30
Mercury
30
Nickel
25
Nitrate
15
Nitrite
20
Oxidisability6
50
Pesticides7
30
Polycyclic aromatic hydrocarbons8
50
Selenium
40
Sodium
15
Sulphate
15
Tetrachloroethene9
30
Tetrachloromethane
30
Trichloroethene9
40
Trihalomethanes: total8
40
Total organic carbon10
30
Turbidity11
30
TABLE C
Minimum performance characteristics: trueness, precision and limit of detection- may be used until 31 December 2019
1 Acrylamide, epichlorohydrin and vinyl chloride to be controlled by product specification.
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 ISO 5725.
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 ISO 5725.
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).
5 The method determines total cyanide in all forms.
6 Values for trueness, precision and uncertainty of measurement are expressed in pH units.
7 Reference method EN ISO 8467 1995.
8 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
9 The performance characteristics apply to individual substances, specified at 25% of the parametric value in Table B in Schedule 1.
10 The performance characteristics apply to individual substances, specified at 50% of the parametric value in Table B in Schedule 1.
11 The performance characteristics apply to prescribed value 4 NTU.
12 The performance characteristics apply to prescribed value 1 NTU for water leaving surface water treatment works.
(1) Parameter1
(2) Trueness2
(3) Precision3
(4) Limit of detection4
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
Cyanide5
10
10
10
1,2-dichloroethane
25
25
10
Fluoride
10
10
10
Hydrogen ion concentration pH (expressed in pH units)6
0.2
0.2
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
Oxidisability7
25
25
25
Pesticides8
25
25
25
Polycyclic aromatic hydrocarbons9
25
25
25
Selenium
10
10
10
Sodium
10
10
10
Sulphate
10
10
10
Tetrachloroethene10
25
25
10
Tetrachloromethane
20
20
20
Trichloroethene10
25
25
10
Trihalomethanes: total9
25
25
10
Turbidity11
10
10
10
Turbidity12
25
25
25

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Source: https://www.legislation.gov.uk/nisr/2017/212/schedule/4 (the official version)
Page: https://openlegislation.uk/water-supply-water-quality-regulations-northern-ireland-2017/schedule-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.