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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 6920-2.4: 2000 ICS 07.
2、100.20; 13.060.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water Part 2: Methods of test Section 2.4: Growth of aquatic mi
3、croorganisms test This British Standard, having been prepared under the direction of the Health and Environment Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 May 2000 BSI 05-2000 The following BSI references relate to the work on this stan
4、dard: Committee reference EH/3/7 Draft for comment 99/560129 DC ISBN 0 580 33109 1 BS 6920-2.4:2000 Amendments issued since publication Amd. No.DateComments Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee EH/3, Water qual
5、ity, to Subcommittee EH/3/7, Effects of materials on water quality, upon which the following bodies were represented: Association of Manufacturers of Domestic Electrical Appliances Automatic Vending Association of Britain British Bathroom Council British Cement Association British Coatings Federatio
6、n Ltd. British Malleable Tube Fittings Association British Non-Ferrous Metals Federation British Plastics Federation British Plumbing Fittings Manufacturers Association British Precast Concrete Federation Ltd. British Rubber Manufacturers Association British Valve and Actuator Manufacturers Associat
7、ion British Water Department of the Environment for Northern Ireland The Drinking Water Inspectorate Galvanizers Association Laboratory of the Government Chemist Lead Development Association Pipeline Industries Guild UK Steel Association UK Water Byelaws Scheme Water Research Centre Water UK Zinc De
8、velopment Association BS 6920-2.4:2000 BSI 05-2000i Contents Page Committees responsibleInside front cover Forewordii Introduction1 1Scope1 2Normative references1 3Terms and definitions2 4Principle2 5Test premises2 6Safety2 7Reagents2 8Apparatus3 9Samples4 10Test procedures4 11Expression of results5
9、 12Test report6 Table 1 Quality criteria for inoculum water2 Table 2 Quality criteria for test water3 Table 3 Test container calibration mark3 Table 4 Volume of inoculum4 Annex A (informative) Test sequence7 Bibliography8 Figure A.1 Test sequence7 ii BSI 05-2000 BS 6920-2.4:2000 Foreword This sectio
10、n of BS 6920 has been prepared by Subcommittee EH/3/7 under the direction of the Health and Environment Sector Committee. This section of BS 6920 supersedes BS 6920-2.4:1996, which is withdrawn. This edition introduces technical changes but it does not reflect a full review or revision of the standa
11、rd. BS 6920 is published in several parts, namely Part 1: Specification, Part 2: Methods of test, Part 3: High temperature tests and Part 4: The GCMS identification of water leachable organic substances. Part 2 is further subdivided into a number of sections and subsections as follows. Section 2.1:
12、Samples for testing; Section 2.2: Odour and flavour of water; Subsection 2.2.1: General method of test; Subsection 2.2.2: Method of testing odours and flavours imparted to water by hoses and composite pipes and tubes; Subsection 2.2.3: Method of testing odours and flavours imparted to water by hoses
13、 for conveying water for food and drink preparation; Section 2.3: Appearance of water; Section 2.4: Growth of aquatic microorganisms; Section 2.5: The extraction of substances that may be of concern to public health; Section 2.6: The extraction of metals. Annex A is informative. A British Standard d
14、oes not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an in
15、side front cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. BSI 05-20001 BS 6920-2.4:2000 Introduction WARNING The tests described in this section of BS 6920 should be carried
16、out only in laboratories with suitable facilities and by suitably qualified persons with an appropriate level of chemical and microbiological expertise. Standard microbiological procedures should be followed throughout. Organic substances present in non-metallic materials (either as ingredients, con
17、taminants or process by-products) which are capable of being utilized by microorganisms can give rise to a noticeable deterioration in the quality of the water with which they are in contact. This deterioration may manifest itself as a change in either the organoleptic, physical or microbiological c
18、haracteristics of the water. Microbial growth may occur in the water itself or at the material/water interface. The phenomenon is distinct from that of microbial attachment which can occur on the surface of any material type. If utilizable substances leach out of the material into the water, then th
19、e growth will be self-limiting and decline in proportion to the rate of leaching. In practical situations, growths on such materials have been found to persist for periods from 18 months to 3 years. Where the utilizable substance is bound within or to the material, then growths have been found to pe
20、rsist indefinitely. Materials capable of supporting microbial growth are unlikely to give rise to an observable deterioration in water quality in every situation. This is due to the influence of various environmental factors, particularly temperature and the presence of residual chlorine. However, i
21、n plumbing systems the water temperature is rarely low enough to inhibit microbial growth and the low residual chlorine concentration present in public water supplies will not exert any appreciable bactericidal or bacteriostatic action once the water is within the customers pipework. Water intended
22、for human consumption has been treated to ensure the absence of microbial pathogens but it is not sterile. The numbers and types of harmless microorganisms present in water intended for human consumption vary considerably and the natural flora comprises many strains that are adapted to living in a r
23、elatively hostile environment. Such organisms differ in their physiological capacity from strains of the same organisms found in other environments or grown in the laboratory. Tests using natural strains of aquatic organisms have given responses that correlate well with the occurrence of problems in
24、 practice, whereas the responses of laboratory cultures have not given reliable predictions of the performance of a material in practice. No single technique, based on growing microorganisms on or in culture media, exists to enumerate all the aquatic microorganisms present in a sample of water. Thus
25、, overall numbers of microorganisms can only be assessed by an indirect measurement of their activity. The method of assessing microbial activity in the test system described in this section of BS 6920 is the measurement of dissolved oxygen uptake. All the organisms which give rise to appreciable mi
26、crobial growth respire aerobically and exert an influence on the concentration of oxygen dissolved in the water in the test systems. Other indirect measurement techniques are currently being developed. A variety of factors may influence the capacity of living organisms to respond in a predictable ma
27、nner and thus validation procedures are an essential part of any biological assay. A validation procedure fulfils a similar role to a calibration procedure in a physico-chemical test method. The validation procedure in this method is designed to identify the use of unsuitable test reagents or an err
28、or in the undertaking of the assay or chance occurrences. (These may occur at random when large numbers of assays using living organisms are performed over an extended time period.) Validation is achieved through the use of reference materials. 1 Scope This section of BS 6920 specifies a method for
29、assessing the ability of a product to promote the multiplication of aerobic aquatic microorganisms in water intended for human consumption. The method is applicable to all types of non-metallic product used in contact with water intended for human consumption. NOTEUnder the requirements of the Water
30、 Supply (Water Quality) Regulations (Regulation 25) and the Water Supply (Water Fittings) Regulations (Clause 2 of Schedule 2), the National Regulator may specify additional provisions in some cases and will assess the significance of the results obtained. 2 Normative references The following normat
31、ive documents contain provisions which, through reference in this text, constitute provisions of this part of BS 6920. For dated references, subsequent amendments to or revisions of any of these publications do not apply. For undated references, the latest edition of the publication referred to appl
32、ies. BS 6920-1:2000, Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water Part 1: Specification. BS 6920-2.2.1:2000, Suitability of non-metallic products for use in contact with water intended for hu
33、man consumption with regard to their effect on the quality of the water Part 2: Methods of test Section 2.2: Odour and flavour of water Subsection 2.2.1: General method of test. BS EN 25814, Method for determination of dissolved oxygen in water: electrochemical probe method. BS EN ISO 3696:1995, Wat
34、er for analytical laboratory use Specification and test methods. 2 BSI 05-2000 BS 6920-2.4:2000 Table 1 Quality criteria for inoculum water ParameterUnitsMinimum valueMaximum value pH5.59.0 Coppermg/l0.05 Total presumptive coliformsper 100 ml10 Presumptive pseudomonadsper 100 ml1100 3 Terms and defi
35、nitions 3.1 product manufactured item, in its finished form, that comes into contact with water, including a component part of a manufactured item 3.2 composite product product whose water-contact surface is made from a material that differs from those comprising the remainder of the product 3.3 sam
36、ple product, or a part of a product, submitted for testing for suitability for use in contact with water intended for human consumption 4 Principle Tap water in contact with a sample of the product is inoculated with a mixture of naturally occurring aquatic microorganisms. The overall growth/activit
37、y of the microbial population is determined indirectly by the measurement of dissolved oxygen depletion in the test system and a control. Validation of the results is achieved by the assessment of reference materials tested in parallel with the sample. NOTEA flow diagram showing the sequence of the
38、test procedures is given in annex A. 5 Test premises Carry out the tests in premises as free as practicable from the presence of any volatile organic chemicals in the atmosphere, as such chemicals can dissolve in exposed water surfaces in sufficient quantities to produce abundant microbial slimes wh
39、ich will mask similar growths due to the test samples. NOTEThe volatile chemical most frequently responsible for such slimes is ethanol, but many other volatile chemicals used in or near the test premises can produce this effect. Even though the containers are sealed during incubation, their content
40、s may become contaminated during water changes. 6 Safety As well as statutory and general consideration of safety, particular care shall be taken in microbiological laboratories because the organisms present may be pathogenic. Media not being used specifically for tests for pathogens may enable path
41、ogens to grow until present in large numbers, so care shall be exercised in the handling and disposal of all media after incubation. Any written safety guidance shall be supplemented by thorough training and supervision. NOTEThe tests presented in this section of BS 6920 fall within the scope of the
42、 report entitled Categorization of pathogens according to hazard and categories of containment published by the Health and Safety Executive (1990) 1. Generally, Containment Level 2 facilities are required. 7 Reagents 7.1 General Except where otherwise specified, only reagents of analytical grade sha
43、ll be used. 7.2 Inoculum water, consisting of a fresh sample taken from a lowland surface water suitable for abstracting for water intended for human consumption preparation and that conforms to Table 1. Conformity of the inoculum water with the criteria in Table 1 shall be determined on the basis o
44、f analysis of samples of the surface water. Analyses of the water shall be performed in accordance with the appropriate sections of BS 6068 or, if none exist, with Methods for the Examination of Water and Associated Materials 2. The inoculum water shall be used within 6 h of collection. If suspended
45、 solids are present, the water shall be filtered (using filters of average pore size 10 mm) before use. NOTEIf necessary, the criteria in Table 1 may be met by dilution with test water (7.3). 7.3 Test water, obtained from a tap connected directly to a service pipe at mains pressure. Before collectio
46、n of the water, the tap shall be flushed until the temperature of the flowing water does not vary by more than 1 8C over a period of 1 min and does not exceed 25 8C. NOTEFor measurements of water temperature, an instrument should be used which shows values to the first decimal place. The test water
47、shall exhibit the characteristics specified in Table 2 so that it can be added directly to the test container. BSI 05-20003 BS 6920-2.4:2000 Table 2 Quality criteria for test water ParameterUnitsMinimum valueMaximum value pH5.59.0 Total presumptive coliformsper 100 ml1.69 but 1.69 mg/l to 2.9 mg/l,
48、then test two further samples for a period of seven weeks only. Do not extend this test to 9 weeks (10.3). Calculate the mean of the three MDOD values. If the value is greater than 2.3 but less than 2.4 mg/l, express the result to 2 decimal places. 11.2 Validation of results Glass reference material
49、s shall have an MDOD value of (0.0 0.6) mg/l. Paraffin wax reference materials shall have an MDOD value of (7.5 2.5) mg/l. The control shall have a dissolved oxygen value (mean value) of (8.5 2.5) mg/l. If any reference material or the control gives results that do not conform to these values, repeat the tests using fresh reagents and samples. NOTEThe quality characteristics of the test and inoculum waters should be carefully assessed when an out-of-range result occurs. If the results for the cementitious or bactericidal/bacterios