Guidance
Monitoring discharges to water: CEN and ISO monitoring methods
Updated 18 January 2023
Applies to England
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General determinands
These are the monitoring methods for general wastewater quality indicators and inorganic parameters (excluding metals).
Ammonia
See also BS ISO 15923-1.
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of ammonium nitrogen by flow analysis (CFA and FIA) and spectrometric detection. You can vary the limit of detection (LOD) and range by using a different instrument configuration. |
BS EN ISO 11732 | V0.1 to 1 mg/l | 0.1 to 1 mg/l |
| Determination of ammonium: manual spectrometric method. Many laboratories use an automated version of this method using a discrete analyser (BS ISO 15923-1). |
BS 6068-2.11 ISO 7150-1 | 0.2 mg/l | 0 to10 mg/l extended by dilution |
| Water quality. Determination of ammonium: distillation and titration method. | BS 6068-2.7 ISO 5664 | 0.2 mg/l | 0 to 10 mg/l extended to 1,000 mg/l by dilution |
| Water quality. Determination of ammonium: potentiometric method. | BS 6068-2.10 ISO 6778 | 0.2 mg/l | 0 to 50 mg/l extended by dilution |
Anions by ion chromatography
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of dissolved anions by liquid chromatography of ions – part 1: determination of bromide, chloride, fluoride, nitrate, nitrite, orthophosphate and sulfate. | BS EN ISO 10304-1 | Up to 20 mg/l or up to 50 mg/l depending on anion | |
| Water quality. Determination of dissolved anions by liquid chromatography of ions – part 3: determination of chromate, iodide, sulfite, thiocyanate and thiosulfate. | BS EN ISO 10304-3 | Up to 50 mg/l |
Biochemical oxygen demand (BOD)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Determination of biochemical oxygen demand after n days (BODn) – part 1: dilution and seeding method with allylthiourea addition. Includes the procedures for 5 and 7 day incubation periods. In the UK the 5 day test is normal. This standard supercedes BS EN 1899-1. |
BS EN ISO 5815-1 | 3 mg/l O | 0 to 6,000 mg/l O |
| Determination of biochemical oxygen demand after n days (BODn) – part 2: method for undiluted samples. | BS EN 1899-2 | 2 mg/l O | 0.5 to 6 mg/l O |
Chemical oxygen demand (COD)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Physical, chemical and biochemical methods. Method for the determination of the chemical oxygen demand. If the chloride concentration in the sample is >1,000mg/l then it should be diluted until it is less than this. This will affect the LOD that can be quoted. |
BS 6068-2.34 (same as ISO 6060) | 30 mg/l | 30 - 700 mg/l O, extended by dilution |
| Water quality. Determination of the COD index (ST-COD). Small-scale sealed-tube method. If the chloride concentration in the sample is >1,000 mg/l then it should be diluted until it is less than this. This will affect the LOD that can be quoted. Commercial test kits are available that use this method – one is now available that can analyse saline matrices. |
BS ISO 15705 | 6 to 15 mg/l | 0 to 1,000 mg/l O extended by dilution |
Chloride
See also BS ISO 15923-1.
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality: Determination of chloride by flow analysis (CFA and FIA) and photometric or potentiometric detection. Range and LOD depend on the configuration of the analyser. |
BS EN ISO 15682 | 1 to 10 mg/l | Up to 1,000 mg/l |
Chlorine
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of free chlorine and total chlorine. Iodometric titration method for the determination of total chlorine. | BS EN ISO 7393-3 | - | 0.7 to 15 mg/l |
| Water quality. Determination of free chlorine and total chlorine. Colorimetric method using N, N-diethyl-1, 4-phenylenediamine for routine control purposes. | BS EN ISO 7393-2 | 0.05 mg/l | 0.03 to 5 mg/l |
| Water quality. Determination of free chlorine and total chlorine. Titrimetric method using N, N-diethyl-1, 4-phenylenediamine. | BS EN ISO 7393-1 | 0.05mg/I | 0.03 to 5 mg/l |
Conductivity
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Method for the determination of electrical conductivity. | BS EN 27888 (same as ISO 7888) |
Cyanide
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of total cyanide and free cyanide using flow analysis (FIA and CFA). Method using flow injection analysis (FIA). | BS EN ISO 14403-1 | 20 to 200 µg/l can be extended by dilution | |
| Water quality. Determination of total cyanide and free cyanide using flow analysis (FIA and CFA). Method using continuous flow analysis (CFA). Free cyanide results by EN ISO 14403-1 are not equivalent. |
BS EN ISO 14403-2 | 10 to 100 µg/l, can extend by dilution | |
| Water quality. Determination of available free cyanide (pH 6) using flow injection analysis (FIA), gas-diffusion and amperometric detection. | BS ISO 17690 | 5 to 500 µg/l | |
| Water quality. Determination of total cyanide. Method using segmented flow injection, in-line ultraviolet digestion analysis by gas diffusion and amperometric detection. | BS ISO 22066 | From 5 µg/l to 50 µg/l, from 50 µg/l to 500 µg/l, from 0,5 mg/l to 5 mg/l, from 5 mg/l to 50 mg/l, from 50 mg/l to 500 mg/l and from 500 mg/l to 2 000 mg/l |
Inorganic parameters by discrete analyser
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of selected parameters by discrete analysis systems – part 1: Ammonium, nitrate, nitrite, chloride, orthophosphate, sulfate and silicate with photometric detection. This method is favoured by high throughput laboratories as it carries out multiple colorimetric determinations simultaneously. The individual methods for each determinand usually closely follow an existing standard. |
BS ISO 15923-1 | ||
| Water quality. Determination of selected parameters by discrete analysis systems. Chromium (VI), fluoride, total alkalinity, total hardness, calcium, magnesium, iron, iron (II), manganese and aluminium with photometric detection. | PD ISO/TS 15923-2 |
Nitrate, nitrite and total oxidised nitrogen (TON)
See also anions by ion chromatography and inorganic parameters by discrete analyser.
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of nitrite, nitrogen and nitrate nitrogen, and the sum of both by flow analysis (CFA and FIA) and spectrometric detection. | BS EN ISO 13395 | TON:0.2 mg/l NO2:0.01 mg/l | 0 to 1 mg/l |
| Water quality. Determination of nitrite: molecular absorption spectrometric method. | BS EN 26777 (same as ISO 6777) | 0.002 mg/l | 0 to 0.25 mg/l |
Nitrogen (total)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of total organic carbon (TOC), dissolved organic carbon (DOC), total bound nitrogen (TNb) and dissolved bound nitrogen (DNb) after high temperature catalytic oxidative combustion. This standard supersedes BS EN 12260. |
BS EN 20236 | ||
| Water quality. Determination of nitrogen. Method using oxidative digestion with peroxodisulfate. This method may not oxidise all organonitrogen compounds completely. It will not 100% recover some common compounds found in crude sewage such as creatinine. |
BS EN ISO 11905-1 | 0.02 mg/l | 0 to 5 mg/l extended by dilution |
| Water quality. Determination of total nitrogen after UV digestion. Method using flow analysis (CFA and FIA) and spectrometric detection. | BS ISO 29441 | 0 to 20 mg/l | |
| Total nitrogen can be monitored by adding TON and Kjeldahl nitrogen results. |
Orthophosphate and total phosphorus
See also inorganic parameters by discrete analyser.
For total phosphorus see also trace metals (BS EN ISO 11885).
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of orthophosphate and total phosphorus contents by flow analysis (FIA and CFA) – part 1: Method by flow injection analysis (FIA). This method recommends a manual digestion procedure for total phosphorus using ISO 6878. |
BS EN ISO 15681-1 | Ortho P: 0.01 mg/l Total P: 0.1mg/l | Ortho P: 0.01 to 1 mg/l Total P: 0 to 10 mg/l |
| Water quality. Determination of orthophosphate and total phosphorus contents by flow analysis (FIA and CFA) – part 2: Method by continuous flow analysis (CFA). This method includes a digestion procedure for total phosphorus using an integrated UV digestion and hydrolysis unit. It alternatively suggests a manual method using ISO 6878. |
BS EN ISO 15681-2 | Ortho P: 0.01mg/l Total P: 0.1mg/l | Ortho P: 0.01 to 1 mg/l Total P: 0 to 10 mg/l |
| Water quality, Determination of phosphorus. Ammonium molybdate spectrometric method. | BS EN ISO 6878 |
pH
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Physical, chemical and biochemical methods. Determination of pH. Covers laboratory and continuous monitoring instruments. |
BS ISO 10523 |
Suspended Solids
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of suspended solids. Method by filtration through glass fibre filters. The method does not specify filter size and filter type. UK practice is to use a Whatman GF/C paper or equivalent glass fibre paper with a nominal pore size of 1 to 1.2 µm. |
BS EN 872 | Quoted as 2 mg/l |
Sulfate
See anions by ion chromatography and inorganic parameters by discrete analyser.
Total organic carbon (TOC) and dissolved organic carbon (DOC)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water analysis. Guidelines for the determination of total organic carbon (TOC) and dissolved organic carbon (DOC). Results and LOD will be instrument-dependant. |
BS EN 1484 | Up to 1,000 mg/l | |
| Water quality. Determination of total organic carbon (TOC), dissolved organic carbon (DOC), total bound nitrogen (TNb) and dissolved bound nitrogen (DNb) after high temperature catalytic oxidative combustion. | BS EN ISO 20236 |
Turbidity
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of turbidity - quantitative methods. | BS EN ISO 7027-1 | 0 to 40 FNU |
Trace metals
These are the monitoring methods for trace metals.
Arsenic
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of arsenic and antimony. Method using hydride generation atomic fluorescence spectrometry (HG-AFS). This method will need to be fully validated for wastewater. |
BS ISO 17378-1 | 0.02 to 100 µg/l | |
| Water quality. Determination of arsenic and antimony. Method using hydride generation atomic absorption spectrometry (HG-AAS). This method will need to be fully validated for wastewater. |
BS ISO 11378-2 | 0.5 to 20 µg/l | |
| Total arsenic: silver diethyldithiocarbamate spectrophotometric method. An extra digestion step is required if the effluent is likely to contain silicon fluoride or organic arsenic compounds that are difficult to decompose. |
BS EN 26595 (same as ISO 6595) | 1 to 100 µg/l |
Cadmium
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of cadmium by atomic absorption spectrometry (AAS). Methods given – flame AAS (FAAS) and electrothermal atomisation AAS (EAAAS). Method largely superseded by multi determinand methods. |
BS EN ISO 5961 | FAAS 0.05 mg/l EAAAS 0.3 µg/l | FAAS 0.05 to 1 mg/l EAAAS 0.3 to 3 µg/l |
Chromium
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of chromium. Atomic absorption spectrometric methods. Two methods are given, FAAS and EAAAS. These methods have largely been superseded by multi determinand methods. |
BS EN 1233 | Ranges FAAS 0.5-20 mg/l EAAAS 5-100 µg/l |
Chromium VI
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of chromium (VI). Spectrometric method using 1,5-diphenylcarbazide. |
|||
| Susceptible to interference – you should analyse the sample as soon as possible after sampling. | BS 6068-2.47 (same as ISO 11083) | 0.05 to 30 mg/l | |
| Water quality. Determination of chromium (VI). Photometric method for weakly contaminated water. | BS EN ISO 18412 | ||
| Water quality. Determination of chromium (VI). Method using flow analysis (FIA and CFA) and spectrometric detection. Best for large numbers of samples. Samples may be stored for a maximum of 24 hours at 2°C to 5°C. |
BS EN ISO 23913 | 20 to 2,000 µg/l, flow system dependent |
Mercury
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of mercury – a method using atomic absorption spectrometry (AAS) with and without enrichment. | BS EN 12846 | ||
| Water quality. Determination of mercury – method using a combined preservation and digestion step followed by atomic fluorescence spectrometry. Highly sensitive method that may require an additional digestion step for wastewater samples. |
BS EN ISO 17852 | 1 to10 ng/l | up to 10µg/l |
Selenium
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of selenium. Method using hydride generation atomic fluorescence spectrometry (HG-AFS). | PD ISO/TS 17379-1 | 0.02 to 100 µg/l | |
| Water quality. Determination of selenium. Method using hydride generation atomic absorption spectrometry (HGAAS). | PD ISO/TS 17379-2 | 0.5 to 20 µg/l |
Trace metals (multi determinand methods)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of selected elements by inductively coupled plasma optical emission spectroscopy (ICPOES). ICPOES is also known as ICPAES (inductively coupled plasma atomic emission spectroscopy). The LOD may not be adequate for some elements, for example cadmium and arsenic. This will be the method of choice at many laboratories. |
BS EN ISO 11885 | ||
| Water quality. Application of inductively coupled plasma mass spectrometry (ICP-MS) – part 2: Determination of 62 elements. Very low detection limits possible in clean samples. Linear over several orders of magnitude. |
BS EN ISO 17294-2 | 0.1 - 10μg/l | |
| Water quality. Determination of trace elements using atomic absorption spectrometry with graphite furnace. Method covers Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn. Validation data is limited on wastewaters for some elements. This method tends not to be used for routine samples due to low throughput, but it is acceptable. |
BS EN ISO 15586 |
Organics
These are the monitoring methods for organic determinands.
Acid herbicides
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of selected phenoxyalkanoic herbicides, including bentazones and hydroxybenzonitriles by gas chromatography and mass spectrometry after solid phase extraction and derivatization. The LOD and range depend on the linear range of calibration curve and the instrument used. Not validated on effluents. |
BS EN ISO 15913 |
Adsorbable organically bound halogens (AOX)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of adsorbable organically bound halogens (AOX). | BS EN ISO 9562 | 10 to 300 µg/l |
Chlorophenols
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Gas chromatographic determination of some selected chlorophenols in water. Includes pentachlorophenol. |
BS EN 12673 | 0.1 µg/l to 1 mg/l |
Complexing agents
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of 6 complexing agents. Gas-chromatographic method. Includes: EDTA — ethylenedinitrilotetraacetic acid NTA — nitrilotriacetic acid DTPA — diethylenetrinitrilopentaacetic acid MGDA — methylglycinediacetic acid β-ADA — β- alaninediacetic acid 1,3-PDTA — 1,3-propylenedinitrilotetraacetic acid |
BS EN ISO 16588 | 0.5 to 200 µg/l |
Dioxins, furans and dioxin-like polychlorinated biphenyls (PCBs)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of tetra to octa-chlorinated dioxins and furans – method using isotope dilution HRGC/HRMS. The LOD and range are very dependent on interference levels in the sample. |
BS ISO 18073 | ||
| Water quality Determination of dioxin-like polychlorinated Biphenyls. Method using gas-chromatography/mass spectrometry. | BS ISO 17858 |
Hydrocarbon oil index
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of hydrocarbon oil index – method using solvent extraction and gas chromatography. | BS EN ISO 9377-2 | 0.1 mg/l |
Organic nitrogen and phosphorus compounds
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of parathion, parathion-ethyl and some other organophosphorus compounds in water by dichloromethane extraction and gas chromatographic analysis. | BS EN 12918 | up to 1 µg/l | |
| Water quality. Determination of selected organic nitrogen and phosphorus compounds – gas chromatographic methods. Atrazine, fenpropimorph, dimethoate, vinclozolin, metolachlor, isochloridazon, metazachlor,and simazine have been validated. Samples should contain <50 mg/l suspended solids. |
BS EN ISO 10695 | 0.5 µg/l or 0.05 µg/l depending on extraction |
Organochlorine compounds
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of certain organochlorine insecticides, polychlorinated biphenyls and chlorobenzenes – gas chromatographic method after liquid-liquid extraction. May not be suitable for samples with high suspended solids (>50 mg/l). |
BS EN ISO 6468 | 1 to 50 ng/l | |
| Water quality - Determination of organochlorine pesticides (OCP) in whole water samples - Method using solid phase extraction (SPE) with SPE-disks combined with gas chromatography mass spectrometry (GC-MS). Will require verification of suitability for wastewater matrix. |
BS EN 16693 |
Organotin compounds
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of selected organotin compounds. Gas chromatographic method. | BS EN ISO 17353 | 1 to 50 ng/l | |
| Water quality. Determination of tributyltin (TBT) in whole water samples. Method using solid phase extraction (SPE) with SPE disks and gas chromatography with triple quadrupole mass spectrometry. | PD CEN/TS 16692 |
Nonylphenols
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of individual isomers of nonylphenols. Methods using solid phase extraction (SPE) and gas chromatography with mass spectrometry (GC-MS). | BS ISO 24293 | 0.1 µg/l | 0.1 to 50 µg/l |
Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) — Method for unfiltered samples using solid phase extraction and liquid chromatography/mass spectrometry. Needs to be matrix validated when used for wastewaters. |
BS ISO 25101 | 2 to 10,000 µg/l for PFOS and10 to 10,000 µg/l for PFOA |
Phenol Index
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of phenol index by flow analysis (FIA and CFA). The relative response of these methods to substituted phenols depends on their molecular structure. It is usually less than the response for phenol itself. The results are reported as mg/l phenol. |
BS EN ISO 14402 | 0.01 to 1 mg/l | |
| Water quality. Physical, chemical and biochemical methods. Determination of phenol index: 4- aminoantipyrine (4-aminophenazone) spectrometric methods after distillation. 2 methods are presented. | BS 6068-2.12. (same as ISO 6439) | 0.1 or 0.01 mg/l |
Phthalates
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of selected phthalates using gas chromatography and mass spectrometry. | BS EN ISO 18856 | 0.02 to 0.15 µg/l |
Polybrominated diphenyl ether (PBDE)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of selected PBDE in whole water samples. Method using solid phase extraction (SPE) with SPE-disks combined with gas chromatography-mass spectrometry (GC-MS). | BS EN 16694 |
Polycyclic aromatic hydrocarbons (PAHs)
These methods do not have performance data for effluents. They can be modified for determining PAHs in wastewater, and for other species of PAHs. They will need validating when modified.
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of 15 polycyclic aromatic hydrocarbons (PAHs) in water by HPLC with fluorescence detection after liquid-liquid extraction. | BS EN ISO 17993 | ||
| Water quality. Determination of 16 polycyclic aromatic hydrocarbons (PAHs) in water. Method using gas chromatography with mass spectrometric detection (GC-MS). | BS ISO 28540 | ||
| Water quality. Determination of selected polycyclic aromatic hydrocarbons (PAH) in whole water samples. Method using solid phase extraction (SPE) with SPE-disks combined with gas chromatography mass spectrometry (GC-MS). | BS EN 16691 |
Short-chain polychlorinated alkanes (SCCP)
| Method and comments | Standard | Reported | LOD | Reported range |
|---|---|---|---|---|
| Water quality. Determination of short-chain polychlorinated alkanes (SCCP) in water. Method using gas chromatography-mass spectrometry (GC-MS) and negative-ion chemical ionization (NCI) | BS EN ISO 12010 |
Volatile organic carbons (VOCs)
| Method and comments | Standard | Reported LOD | Reported range |
|---|---|---|---|
| Water quality. Determination of highly volatile halogenated hydrocarbons. Gas-chromatographic methods. Highly volatile halogenated hydrocarbons are defined as fluorinated, chlorinated, brominated or iodinated, mainly nonaromatic hydrocarbons. They are composed of 1 to 6 atoms of carbon – boiling points are usually 20°C to 220°C. |
BS EN ISO 10301 | ||
| Water quality. Gas-chromatographic determination of a number of monocyclic aromatic hydrocarbons, naphthalene and several chlorinated compounds using purge-and-trap and thermal desorption. | BS EN ISO 15680 | typically 10 µg/l | up to 100 µg/l |
| Water quality. Determination of selected highly volatile organic compounds in water - Method using gas chromatography and mass spectrometry by static headspace technique (HS-GC-MS). | BS EN ISO 20595 |