The following photo is of a R-Card of unknown origin. It is included for demonstration purposes only. Each blue dot indicates the presence of E.coli in a 1 ml sample row 1 = 1 row 2 = 12 row 3 = 49 row 4 = 43 row 5 = 45 row 6 = 13 total = 163 Because the accepted unit of measurement is colony forming units of E.coli per 100 ml sample, we multiply 163 x 100 giving 16300 cfu/100ml In practice we will be examining 3 cards for each test and recording the mean/average of the 3 cards. Because 16300 is greater than 900 the Environment Agency would classify this sample as "poor", and advise against swimming. Me too ( I hope samples from the Thames are not a polluted as this ).
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