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~~ i <br />., <br />•~ <br />.. ~ ~, <br />:a <br />There are two basic methods for analyzing water samples <br />for bacteria: <br />1) The membrane. filtration method involves filtering water <br />samples using standard filters, placing each filter on a nutrient <br />medium in a petri plate, incubating the plates at a specified <br />temperature and time period, and then counting the colonies that <br />have grown on the filter. This method varies for different <br />bacteria types. Some tests use high temperature incubation or <br />substances in the medium to inhibit the growth of unwanted <br />colonies. Others use dyes that are keyed to the byproducts <br />produced when the bacteria consume nutrients. Bacteria are <br />counted and reported as colony forming units (cfu) pet 100 mL. <br />2) The multiple-tube fermentation method involves adding <br />specified quantities of the water sample zo tubes containing a <br />nutrient broth, incubating the tubes at a specified temperature and <br />`time period, and then looking for the development of gas and/or <br />turbidity that the bacteria produce. The presence or`absence of gas" <br />in each tube is used to calculate an index known as the Mosr " <br />Probable Number (MPN)' A recent. variation on this is the <br />Quanti-Tray Method. ` <br />There are many. variations on these two :basic methods. <br />Bacteria results are usually compared with state water quality cri- <br />teria, which describe levels that should not be exceeded for differ- <br />ent forms of recreation or drinking water. Monitoring for fecal <br />bacteria, and using these criteria... as benchmarks, might enable <br />your group to help people decide whether it's safe to jump in. <br />Service Provider Directory <br />Rivers Council of Minnesotas Service Provider Directory <br />has been developed for citizen volunteers (and their lead- <br />ers) monitoring rivers and lakes of Minnesota. The Service <br />Providers are the people and organizations that assist citi- <br />zenvolunteer monitoring programs. Service Providers may <br />provide technical services (such as training), direct services <br />(such as analyzing data}, or resources (such as equipment, <br />loans, or grants}. This directory is a free resource, designed <br />to link you to these services. For a searchable Directory, <br />check out the Rivers Council of Minnesota website: <br />www riversmn.org/directoryhtml <br />Equipment and Supply Sources' <br />To help. narrow your search for water quality monitoring <br />equipment or supplies, checkout the Equipment Supply <br />Directory on the Rivets Council of Minnesota website: <br />http://www riversmn.org/Monitoring_List.html <br />__.__ <br />_~ <br />MlN YESOT.4 <br />L~~.S ~ ~ ~,- ~ ~ ~~~ <br />i <br />~~~ <br />