{
  "url": "https://openlegislation.uk/water-supply-water-quality-regulations-northern-ireland-2017/schedule-4",
  "json_url": "https://openlegislation.uk/water-supply-water-quality-regulations-northern-ireland-2017/schedule-4.json",
  "legislation": "nisr/2017/212",
  "legislation_title": "The Water Supply (Water Quality) Regulations (Northern Ireland) 2017",
  "legislation_url": "https://openlegislation.uk/water-supply-water-quality-regulations-northern-ireland-2017",
  "path": "schedule/4",
  "kind": "schedule",
  "number": "4",
  "heading": "ANALYTICAL METHODOLOGY",
  "text": "TABLE A\nParameters for which, subject to regulation 18(12), methods of analysis are prescribed\n(1) Parameter\n(2) Method\nClostridium perfringens (including spores)\nEN ISO 14189\nColiform bacteria\nEN ISO 9308-1 or EN ISO 9308-2\nColony count 22°C-enumeration of culturable microorganisms\nENISO 6222\nColony count 36°C-enumeration of culturable microoganisms\nEN ISO 6222\nEnterococci\nEN ISO 7899-2\nEscherichia coli (E. coli)\nEN ISO 9308-1 or EN ISO 9308-2\nPseudomonas aeruginosa\nEN ISO 16266\nTABLE B\nMinimum performance characteristic: “uncertainty of measurement”\n1 Acrylamide, epichlorohydrin and vinyl chloride to be controlled by product specification.\n2 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.\n3 If the value of uncertainty of measurement cannot be met, the best available technique should be selected (up to 60%).\n4 The method determines total cyanide in all forms.\n5 Values for trueness, precision and uncertainty of measurement are expressed in pH units.\n6 Reference method EN ISO 8467.\n7 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\n8 The performance characteristics apply to individual substances, specified at 25% of the parametric value in Table B in Schedule 1.\n9 The performance characteristics apply to individual substances, specified at 50% of the parametric value in Table B in Schedule 1.\n10 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.\n11 The uncertainty of measurement must be estimated at the level of 1.0 NTU (nephelometric turbidity units) in accordance with EN ISO 7027.\n(1) Parameter1\n(2) Uncertainty of measurement (% of parametric value, except pH)2\nAluminium\n25\nAmmonium\n40\nAntimony\n40\nArsenic\n30\nBenzo(a)pyrene3\n50\nBenzene\n40\nBoron\n25\nBromate\n40\nCadmium\n25\nChloride\n15\nChromium\n30\nConductivity\n20\nCopper\n25\nCyanide4\n30\n1,2-dichloroethane\n40\nFluoride\n20\nHydrogen ion concentration pH (expressed in pH units)5\n0.2\nIron\n30\nLead\n25\nManganese\n30\nMercury\n30\nNickel\n25\nNitrate\n15\nNitrite\n20\nOxidisability6\n50\nPesticides7\n30\nPolycyclic aromatic hydrocarbons8\n50\nSelenium\n40\nSodium\n15\nSulphate\n15\nTetrachloroethene9\n30\nTetrachloromethane\n30\nTrichloroethene9\n40\nTrihalomethanes: total8\n40\nTotal organic carbon10\n30\nTurbidity11\n30\nTABLE C\nMinimum performance characteristics: trueness, precision and limit of detection- may be used until 31 December 2019\n1 Acrylamide, epichlorohydrin and vinyl chloride to be controlled by product specification.\n2 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.\n3 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.\n4 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).\n5 The method determines total cyanide in all forms.\n6 Values for trueness, precision and uncertainty of measurement are expressed in pH units.\n7 Reference method EN ISO 8467 1995.\n8 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\n9 The performance characteristics apply to individual substances, specified at 25% of the parametric value in Table B in Schedule 1.\n10 The performance characteristics apply to individual substances, specified at 50% of the parametric value in Table B in Schedule 1.\n11 The performance characteristics apply to prescribed value 4 NTU.\n12 The performance characteristics apply to prescribed value 1 NTU for water leaving surface water treatment works.\n(1) Parameter1\n(2) Trueness2\n(3) Precision3\n(4) Limit of detection4\nAluminium\n10\n10\n10\nAmmonium\n10\n10\n10\nAntimony\n25\n25\n25\nArsenic\n10\n10\n10\nBenzene\n25\n25\n25\nBenzo(a)pyrene\n25\n25\n25\nBoron\n10\n10\n10\nBromate\n25\n25\n25\nCadmium\n10\n10\n10\nChloride\n10\n10\n10\nChromium\n10\n10\n10\nColour\n10\n10\n10\nConductivity\n10\n10\n10\nCopper\n10\n10\n10\nCyanide5\n10\n10\n10\n1,2-dichloroethane\n25\n25\n10\nFluoride\n10\n10\n10\nHydrogen ion concentration pH (expressed in pH units)6\n0.2\n0.2\nIron\n10\n10\n10\nLead\n10\n10\n10\nManganese\n10\n10\n10\nMercury\n20\n10\n20\nNickel\n10\n10\n10\nNitrate\n10\n10\n10\nNitrite\n10\n10\n10\nOxidisability7\n25\n25\n25\nPesticides8\n25\n25\n25\nPolycyclic aromatic hydrocarbons9\n25\n25\n25\nSelenium\n10\n10\n10\nSodium\n10\n10\n10\nSulphate\n10\n10\n10\nTetrachloroethene10\n25\n25\n10\nTetrachloromethane\n20\n20\n20\nTrichloroethene10\n25\n25\n10\nTrihalomethanes: total9\n25\n25\n10\nTurbidity11\n10\n10\n10\nTurbidity12\n25\n25\n25",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/nisr/2017/212/schedule/4",
    "retrieved_at": "2026-10-29T00:51:01.047970+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}