Massachusetts Health Department

E. Coli Testing

For my internship I worked with the Acton, Massachusetts Health Department where my main duty was to test natural water sources for E. Coli contamination. I sampled natural water sources for E. Coli on a daily basis. Each day, I first figured out what natural water source locations I would be testing, usually six to ten different sites. Then, I would gather up tools that I needed to collect the samples from the natural water sources. All I needed to collect these samples was one container for the water from each site, a marker to label the sites on the container, a map, and an extended arm pickup tool so I could retrieve samples without touching the water with my hand (almost like a robot arm). Then, I would drive the Department of Health’s company car (a Toyota Prius) to each natural water source location, collect the water samples, and bring them back to the Health Department.

Once I was back, I would run each sample through a filter, then put the filter paper into a petri dish and let that petri dish sit in an incubator over night. Then I would take out the petri dish samples we had in the incubator from the previous day and count the number of specs or dots on the petri dish filter paper. The number of dots on the filter paper shows how much E. Coli was in that water: the more dots the more E. Coli. This entire sampling process is known as the petri dish filtration method. After this process, I would put the data in an Excel spreadsheet that shows every natural water source test site in Acton, with the date and the amount of E. Coli contamination on that day. Lastly, I would analyze the data for trends and natural water sources that had too much E. Coli contamination.

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My internship didn’t directly deal with an environmental problem, but some of the results of my E. Coli water testing could have been an effect of an environmental problem. Runoff from nearby farms and agricultural areas can increase the amount of E. Coli in natural water sources. In agricultural and farm areas there is a large amount of fecal matter from both the animals and the soil in general. E. Coli comes from fecal matter and can then make its way from farms to natural water sources, causing an unnaturally high level of E. Coli in a natural water source. The highlight for me from this internship was that I actually got to be outside doing hands on work for the majority of each day. I love being outdoors; not being cooped up in an office all day was very enjoyable.


by Trevor MacDonald ’15

Environmental and Natural Resource Economics Major + Business Minor

May 6th, 2014