TP037 - Pravilnik o pitni vodi

This document
— introduces conditions, constraints and resources necessary to evaluate a measurement method or a result;
— defines an organizational scheme for the acquisition of trueness and precision data by study;
— provides the necessary definitions, statistical model and principles for ISO 5725 (all parts).
— is not applicable to proficiency testing or production of the reference item that has their own standards (ISO 13528, respectively and ISO Guide 35).
This document is concerned exclusively with measurement methods which yield results on a continuous scale and give a single value as the test result, although this single value may be the outcome of a calculation from a set of observations.
It defines values which describe, in quantitative terms, the ability of a measurement method to give a true result (trueness) or to replicate a given result (precision). Thus, there is an implication that exactly the identical item is being measured, in exactly the same way, and that the measurement process is under control.
This document may be applied to a very wide range of test items, including gas, liquids, powders and solid objects, manufactured or naturally occurring, provided that due consideration is given to any heterogeneity of the test item.
This document does not include methods of calculation that are described in the other parts.

This document provides
a) a discussion of alternative experimental designs for the determination of trueness and precision measures including reproducibility, repeatability and selected measures of intermediate precision of a standard measurement method, including a review of the circumstances in which their use is necessary or beneficial, and guidance as to the interpretation and application of the resulting estimates, and
b) worked examples including specific designs and computations.
Each of the alternative designs discussed in this document is intended to address one (or several) of the following issues:
a) a discussion of the implications of the definitions of intermediate precision measures;
b) a guidance on the interpretation and application of the estimates of intermediate precision measures in practical situations;
c) determining reproducibility, repeatability and selected measures of intermediate precision;
d) improved determination of reproducibility and other measures of precision;
e) improving the estimate of the sample mean;
f) determining the range of in-house repeatability standard deviations;
g) determining other precision components such as operator variability;
h) determining the level of reliability of precision estimates;
i) reducing the minimum number of participating laboratories by optimizing the reliability of precision estimates;
j) avoiding distorted estimations of repeatability (split-level designs);
k) avoiding distorted estimations of reproducibility (taking the heterogeneity of the material into consideration).
Often, the performance of the method whose precision is being evaluated in a collaborative study will have previously been assessed in a single-laboratory validation study conducted by the laboratory which developed it. Relevant factors for the determination of intermediary precision will have been identified in this prior single-laboratory study.

1.1 This document
— specifies basic methods for estimating the bias of a measurement method and the laboratory bias when a measurement method is applied;
— provides a practical approach of a basic method for routine use in estimating the bias of measurement methods and laboratory bias;
— provides a brief guidance to all personnel concerned with designing, performing or analysing the results of the measurements for estimating bias.
1.2 It is concerned exclusively with measurement methods which yield measurements on a continuous scale and give a single value as the measurement result, although the single value can be the outcome of a calculation from a set of observations.
1.3 This document applies when the measurement method has been standardized and all measurements are carried out according to that measurement method.
NOTE In ISO/IEC Guide 99:2007(VIM), "measurement procedure" (2.6) is an analogous term related to the term "measurement method" used in this document.
1.4 This document applies only if an accepted reference value can be established to substitute the true value by using the value, for example:
— of a suitable reference material;
— of a suitable measurement standard;
— referring to a suitable measurement method;
— of a suitable prepared known sample.
1.5 This document applies only to the cases where it is sufficient to estimate bias on one property at a time. It is not applicable if the bias in the measurement of one property is affected by the level of any other property (i.e. it does not consider interferences by any influencing quantity). Comparison of the trueness of two-measurement methods is considered in ISO 5725-6.

1.1 This document
— amplifies the general principles for designing experiments for the numerical estimation of the precision of measurement methods by means of a collaborative interlaboratory experiment;
— provides a detailed practical description of the basic method for routine use in estimating the precision of measurement methods;
— provides guidance to all personnel concerned with designing, performing or analysing the results of the tests for estimating precision.
NOTE Modifications to this basic method for particular purposes are given in other parts of ISO 5725.
1.2 It is concerned exclusively with measurement methods which yield measurements on a continuous scale and give a single value as the test result, although this single value can be the outcome of a calculation from a set of observations.
1.3 It assumes that in the design and performance of the precision experiment, all the principles as laid down in ISO 5725-1 are observed. The basic method uses the same number of test results in each laboratory, with each laboratory analysing the same levels of test sample; i.e. a balanced uniform-level experiment. The basic method applies to procedures that have been standardized and are in regular use in a number of laboratories.
1.4 The statistical model of ISO 5725-1:1994, Clause 5, is accepted as a suitable basis for the interpretation and analysis of the test results, the distribution of which is approximately normal.
1.5 The basic method, as described in this document, (usually) estimates the precision of a measurement method:
a) when it is required to determine the repeatability and reproducibility standard deviations as defined in ISO 5725-1;
b) when the materials to be used are homogeneous, or when the effects of heterogeneity can be included in the precision values; and
c) when the use of a balanced uniform-level layout is acceptable.
1.6 The same approach can be used to make a preliminary estimate of precision for measurement methods which have not reached standardization or are not in routine use.

This document specifies a method for the enumeration of Pseudomonas aeruginosa in water. The method is based on the growth of target organisms in a liquid medium and calculation of the most probable number (MPN) of organisms by reference to MPN tables.  
This document is applicable to a range of types of water. For example, hospital waters, drinking water and non‑carbonated bottled waters intended for human consumption, groundwater, swimming pool and spa pool waters including those containing high background counts of heterotrophic bacteria.  
This document does not apply to carbonated bottled waters, flavoured bottle waters, cooling tower waters or marine waters, for which the method has not been validated. These waters are, therefore, outside the scope of this document. Laboratories can employ the method presented in this document for these matrices by undertaking appropriate validation of performance of this method prior to use.
The test is based on a bacterial enzyme detection technology that signals the presence of P. aeruginosa through the hydrolysis of a 7‑amino‑4‑methylcoumarin aminopeptidase substrate present in a special reagent. P. aeruginosa cells rapidly grow and reproduce using the rich supply of amino acids, vitamins and other nutrients present in the reagent. Actively growing strains of P. aeruginosa have an enzyme that cleaves the 7‑amido‑coumarin aminopeptidase substrate releasing a product which fluoresces under ultraviolet (UV) light. The test described in this document provides a confirmed result within 24 h with no requirement for further confirmation of positive wells.

This document specifies the following semi-quantitative methods for the assessment of transparency of waters:
a)    measurement of visual range using the transparency testing tube (applicable to transparent and slightly cloudy water),  see Clause 4;
b)    measurement of visual range in the upper water layers using the transparency testing disc (especially applicable to surface, bathing water, waste water and often used in marine monitoring), see 5.1;
c)    measurement of visibility by divers in a destined depth, see 5.2.
NOTE       The quantitative methods using optical turbidimeters or nephelometers are described in ISO 7027-1.

ISO/IEC 17025:2017 specifies the general requirements for the competence, impartiality and consistent operation of laboratories.
ISO/IEC 17025:2017 is applicable to all organizations performing laboratory activities, regardless of the number of personnel.
Laboratory customers, regulatory authorities, organizations and schemes using peer-assessment, accreditation bodies, and others use ISO/IEC 17025:2017 in confirming or recognizing the competence of laboratories.

ISO 14189:2013 specifies a method for the enumeration of vegetative cells and spores of Clostridium perfringens by the membrane filtration method in samples of water intended for human consumption. However, the method can be applied to all types of water samples provided they do not contain particulate or colloidal matter that interferes with filtration.

ISO 7027-1:2016 specifies two quantitative methods using optical turbidimeters or nephelometers for the determination of turbidity of water:
a)    nephelometry, procedure for measurement of diffuse radiation, applicable to water of low turbidity (for example drinking water);
b)    turbidimetry, procedure for measurement of the attenuation of a radiant flux, more applicable to highly turbid waters (for example waste waters or other cloudy waters).
Turbidities measured according to the first method are presented as nephelometric turbidity units (NTU). The results typically range between <0,05 NTU and 400 NTU. Depending on the instrument design, it can also be applicable to waters of higher turbidity. There is numerical equivalence of the units NTU and formazin nephelometric unit (FNU).
Turbidity measured by the second method is expressed in formazin attenuation units (FAU), results typically range between 40 FAU and 4 000 FAU.

ISO 9308-1:2014 specifies a method for the enumeration of Escherichia coli (E. coli) and coliform bacteria. The method is based on membrane filtration, subsequent culture on a chromogenic coliform agar medium, and calculation of the number of target organisms in the sample. Due to the low selectivity of the differential agar medium, background growth can interfere with the reliable enumeration of E. coli and coliform bacteria, for example, in surface waters or shallow well waters. This method is not suitable for these types of water.
ISO 9308-1:2014 is especially suitable for waters with low bacterial numbers that will cause less than 100 total colonies on chromogenic coliform agar (CCA). These may be drinking water, disinfected pool water, or finished water from drinking water treatment plants.
Some strains of E. coli which are β-D-glucuronidase negative, such as Escherichia coli O157, will not be detected as E. coli. As they are β-D-galactosidase positive, they will appear as coliform bacteria on this chromogenic agar.

ISO 9308-2:2012 specifies a method for the enumeration of E. coli and coliform bacteria in water. The method is based on the growth of target organisms in a liquid medium and calculation of the "Most Probable Number" (MPN) of organisms by reference to MPN tables. This method can be applied to all types of water, including those containing an appreciable amount of suspended matter and high background counts of heterotrophic bacteria. However it must not be used for the enumeration of coliform bacteria in marine water. When using for the enumeration of E. coli in marine waters, a 1→10 dilution in sterile water is typically  required, although the method has been shown to work well with some marine waters that have a lower than normal concentration of salts. In the absence of data to support the use of the method without dilution, a 1→10 dilution is used.
This method relies upon the detection of E. coli based upon expression of the enzyme b‑D‑glucuronidase and consequently does not detect many of the enterohaemorhagic strains of E. coli, which do not typically express this enzyme. Additionally, there are a small number of other E. coli strains that do not express b‑D‑glucuronidase.
The choice of tests used in the detection and confirmation of the coliform group of bacteria, including E. coli, can be regarded as part of a continuous sequence. The extent of confirmation with a particular sample depends partly on the nature of the water and partly on the reasons for the examination. The test described in ISO 9308-2:2012 provides a confirmed result with no requirement for further confirmation of positive wells.

This European Standard describes the principles of a risk management approach to improve the integrity of the drinking water supply system.
This European Standard addresses all entities and stakeholders sharing responsibility in the provision of safe drinking water throughout the entire supply chain from the source to the point of use.

ISO 5667-5:2006 establishes principles to be applied to the techniques of sampling water intended for human consumption. For the purposes of ISO 5667-5:2006, water intended for human consumption comprises: all water either in its original state or after treatment, intended for drinking, cooking, food preparation, or other domestic purposes, regardless of its origin, plus all water used in any production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form.
The guidance given in ISO 5667-5:2006 is confined to those circumstances where water is drawn from municipal or similar distribution systems (including individual systems) where prior treatment and/or quality assessment has resulted in the water being classified as suitable for drinking or potable process purposes. Specifically, ISO 5667-5:2006 is applicable to water that is in continuous supply relative to any stage of use up to and including the point of consumption in a distribution system. This includes distribution within large buildings in which additional water quality management might be applicable.
ISO 5667-5:2006 is also applicable to sampling situations that can arise relative to the investigation of system defects or emergency situations where the safety of sampling operatives is not compromised.
ISO 5667-5:2006 does not provide guidance for water sources or for products generated by using drinking water. The followings items are examples of cases not addressed by the present document: the sampling of source water, for example groundwater and surface water impoundments; sampling of drinking water supplies derived from non-continuous sources (for example, from road tankers); sampling of bulk storage of water on airplanes, trains and ships; the sampling of beverage products (including bottled waters) or food containing potable water used in its preparation; sampling of drink vending machines that dispense unsealed cups of drinks.

ISO 19458:2006 provides guidance on planning water sampling regimes, on sampling procedures for microbiological analysis and on transport, handling and storage of samples until analysis begins. ISO 19458:2006 focuses on sampling for microbiological investigations.

The purpose is to give some indications of the way in which accuracy data can be used in various practical situations by: giving a standard method of calculating the repeatability limit, the reproducibility limit and other limits, providing a way of checking the acceptability of test results obtained under repeatability or reproducibility conditions, describing how to assess the stability of results within a laboratory over a period of time, describing how to assess whether a given laboratory is able to use a given standard measurement method in a satisfactory way, describing how to compare alternative measurement methods.

This part of ISO 5725
— provides detailed descriptions of alternatives to the basic method for determining the repeatability and
reproducibility standard deviations of a standard measurement method, namely the split-level design and a
design for heterogeneous materials;
— describes the use of robust methods for analysing the results of precision experiments without using outlier
tests to exclude data from the calculations, and in particular, the detailed use of one such method.
This part of ISO 5725 complements ISO 5725-2 by providing alternative designs that may be of more value in some
situations than the basic design given in ISO 5725-2, and by providing a robust method of analysis that gives
estimates of the repeatability and reproducibility standard deviations that are less dependent on the data analyst's
judgement than those given by the methods described in ISO 5725-2.

Migrated from Progress Sheet (TC Comment) (2000-07-10): TC 230 Res. 87: // approval procedure on the revision of ISO 7899-2:1984. ++ N315: New TD (TA/980915)

This European Standard specifies a method for the enumeration of culturable micro-organisms in water by counting the colonies formed in a nutrient agar culture medium after aerobic incubation at 36 °C and 22 °C. The method is intended to measure the operational efficiency of the treatment process of public drinking water supplies and for general application to all types of water. It is particulary applicable to the examination of water intended for  human consumption, including water in closed containers and to natural mineral waters.

The principle of the method specified is heating a sample in a boiling water-bath with a known amount of potassium permanganate und sulfuric acid for a fixed period time (10 min), reducing part of the permanganate by oxidizable material in the sample and determining the consumed permanganate by addition of an excess of oxalate solution, followed by titration with permanganate. Applies to waters having a cloride ion concentration of less than 300 mg/l. Samples having a permanganate index over 10 mg/l should be diluted before analysis. The lower limit of the optimum range of the test is 0,5 mg/l.

Specifies four intermediate measures due to changes in observation conditions (time, calibration, operator and equipment) within a laboratory. These intermediate measures can be established by an experiment within a specific laboratory or by an interlaboratory experiment. Furthermore, discusses the implications of the definitions of intermediate precision measures, presents guidance on the interpretation and application of the estimates of intermediate precision measures in practical situations, discusses the connections between trueness and measurement conditions.