BS EN ISO 7027:2000 pdf – Water quality Ð Determination of turbidity.
1? Scope This International Standard specifies four methods for the determination of turbidity of water. Two semiquantitative methods, employed for example in field work, are specified: a)? measurement of turbidity using the transparency testing tube (applicable to pure and lightly polluted water); b)? measurement of turbidity using the transparency testing disk (especially applicable to surface water). Two quantitative methods, using optical turbidimeters, are specified: c)? measurement of diffuse radiation, applicable to water of low turbidity (for example drinking water); Turbidity measured by this method is expressed in formazin nephelometric units (FNU); results typically range between 0 FNU and 40 FNU. Depending on the instrument design, it may also be applicable to waters of higher turbidity. d)? measurement of the attenuation of a radiant flux, more applicable to highly turbid waters (for example waste or polluted waters). Turbidity measured by this method is expressed in formazin attenuation units (FAU); results typically range between 40 FAU and 4000 FAU. 2? Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 3864:1 984, Safety colours and safety signs. ISO 5667-3:1 994, Water quality — Sampling — Part 3: Guidance on the preservation and handling of samples.
4? Sampling and samples Maintain all containers that come into contact with the sample in a scrupulously clean condition. Wash with hydrochloric acid or surfactant cleaning solution. Collect samples in glass or plastics bottles, and carry out the determinations as soon as possible after collection. If storage is unavoidable, store the samples in a cool, dark room but for not longer than 24 h. If the samples have been stored cool, allow them to come to room temperature before measurement. Prevent contact between the sample and air, and avoid unnecessary changes in the temperature of the sample. 5? Semiquantitative methods of turbidity measurement 5.1? Measurement using the transparency testing tube 5.1.1? Apparatus 22.214.171.124? Transparency testing tube, consisting of a colourless glass tube 600 mm ? 1 0 mm long and of internal diameter 25 mm ? 1 mm, graduated in divisions of 1 0 mm. 126.96.36.199? Shield, close-fitting, to protect the transparency testing tube from lateral light. 188.8.131.52? Print sample to place under the tube (5.1 .1 .1 ), consisting of black print on a white background (height of characters 3,5 mm; line width 0,35 mm) or a test mark (for example, a black cross on white paper), provided with the apparatus. 184.108.40.206? Constant light source, 3 W low voltage tungsten lamp, to illuminate the print sample or test mark (5.1 .1 .3). 5.1.2? Procedure It is absolutely essential that tests conducted according to this International Standard be carried out by suitably qualified staff. Thoroughly mix the sample and transfer it to the transparency testing tube (5.1 .1 .1 ). Steadily lower the sample level until the print sample or test mark (5.1 .1 .3) is clearly recognizable as viewed from above. Read the liquid height from the graduations on the tube. 5.1.3? Expression of results Report the measured liquid height, to the nearest 1 0 mm, together with the apparatus used (name of the manufacturer).
5.2.3? Expression of results Report the depth of immersion. For values less than 1 m, report the result to the nearest 1 0 mm. For values greater than 1 m, report the result to the nearest 0,1 m. 6? Quantitative methods of turbidity measurement using optical turbidimeters 6.1? General principles It is absolutely essential that tests conducted according to this International Standard be carried out by suitably qualified staff.