ISO INTERNATIONAL STANDARD 6222 Second edition 1999-05-15 Water quality Enumeration of culturable micro-organisms Colony count by inoculation in a nutrient agar culture medium Qualite de I'eau Dénombrement des micro-organismes revivifiables - Comptage des colonies par ensemencement dans un milieu de culture nutritif gélosé Reference number ISO 6222:1999(E) No r y IHS under ted without license from IHS Not for Resale ISO 6222:1999(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (isO member bodies). The work of preparing International Standards is normally carried out through IsO technical committees. Each member body interested in a subject for which atechnicalcommitteehasbeenestablishedhastherighttoberepresented on that committee. International organizations, governmental and non- governmental, in liaison with isO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this held responsible for identifying any or all such patent rights. International S StandardISO 6222 2waspreparedbythe European Committee for Standardization (CEN) in collaboration with ISO Technical Committee TC 147, Water quality, Subcommittee SC 4, Microbiological methods, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement). Throughout the text of this document, read "..this European Standard..." to mean "...this International Standard...". whichhasbeentechnicallyrevised. @ISO1999 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International OrganizationforStandardization Casepostale56·CH-1211Geneve20·Switzerland Internet [email protected] Printed in Switzerland Not for Resale @ ISO ISO 6222:1999(E) Foreword of which is held by DIN, in collaboration with Technical Committee ISO/TC 147 "Water quality". This EuropeanStandard shall begiventhestatusofa national standard,eitherbypublicationofanidenticaltextorby endorsement, at the latest by November 1999, and conflicting national standards shall be withdrawn at the latest by November 1999. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries the United Kingdom. Introduction Waters of all kinds invariably contain a variety of micro-organisms derived from various sources, such as soil and vegetation,andestimationoftheoverall numbersprovideuseful informationfortheassessr mentandsurveillanceofwate quality. Separate counts are usually made of the micro-organisms which are able to grow and form colonies on nutrient agar media at 36 °C and 22 °C. processes such as coagulation, filtration and disinfection and provide an indication of the cleanliness and integrity of the distribution system. They can also be used to assess the suitabillty of a supply for the preparation of food and drink, where the water supply should contain few micro-organisms to avoid contaminating the product with spoilage organisms. The main value of colony counts lies in the detection of changes from those expected, based on frequent, long term monitoring. Any sudden increase in the count can be an eariy warning of serious pollution and calls for immediate investigation. 1 Scope This European Standard specifies a method for the enumeration of culturable micro-organisms in wate