In most cases, samples need to arrive at the laboratory on Monday, Tuesday, Wednesday or Thursday. Be sure the form accompanying the sample is accurate and complete. If there is no date or time of collection on the form, it will be assumed the sample is over 48 hours old. If there is no return address, test results cannot be sent to you. The plates then are removed from the incubator and the number of coliform bacteria colonies are counted.
Bacterial contamination falls under the category of pathogens.
The number of coliform colonies found in the incubated water sample, if any, is reported and the form is checked to indicate whether or not the water meets the EPA bacteriological standard of zero. At times, excessive numbers of other bacteria in a sample can interfere with the counting of coliform types. If you suspect bacterial contamination in your water supply, use an alternative water supply or disinfect your water supply while waiting for test results. If laboratory tests confirm the presence of coliform bacteria in your water supply, use an alternative water supply or disinfect your water supply until the problem can be corrected. For short term disinfection of small amounts of water, two options exist.