Science on Tap: Keeping Poop out of Our Potable Water!

Who is responsible for making sure our water is safe? That’s one of the questions that assistant professor of environmental epidemiology Alasdair Cohen addressed at the August 24, 2025, Science on Tap event “Safe Drinking Water Access in Rural Regions: Progress and Pitfalls.” Cohen paired an engaging lecture about the whos and whats of public water safety with a trivia worksheet to challenge audience members.

    Cohen introduced the audience to the concept of water quality safety by holding up two glasses of water, both locally sourced. In his left hand was a full glass of clear water; in his right hand, Cohen held a glass of water tinged brown. He challenged the audience to point out which one is safe to drink. Although the audience quickly stated that they believed the clear water to be safer, Cohen revealed that the brown water just had a dash of beer in it, making the point that we couldn’t judge water quality through sight alone.

    Cohen framed his talk around three vital questions. First: What do we mean by water quality and safety? The two major categories of water quality are microbiological and chemical, he explained. Chemical contaminants comprise elements such as arsenic and lead along with man-made chemicals like insecticides. These contaminants often manifest as chronic exposure in small doses. On the other hand, viruses and other pathogens make up microbiological contaminants; as with food-borne illnesses, the source can be difficult to pinpoint due to time between exposure, infection, and symptoms but can include human or animal feces. Cohen summed up his talk in one sentence: “If you remember nothing else, the goal is to keep poop out of people’s drinking water!”

    The next question Cohen delved into was this: Who is responsible for making sure water is safe? The answer often has an urban-rural divide, with households, individuals,  small communities, and large municipalities all players. While the majority of the U.S. population has water coming from surface water, most rural systems pull from groundwater. This leads to a discrepancy between water quality in urban and rural communities, as groundwater is often safer than surface water. However, Cohen assured the audience that most treatment plants do a great job of treating the water that households use every day. Households without access to municipal water supplies have sources of well water or spring water, or even harvest rainwater.

    Cohen described the many methods of treating water at the community, individual, and household levels. Perceptions of water quality can have big impacts on behaviors. For example, if a household has water that smells of sulphur, the water may be perfectly safe to drink but the unpleasant odor may drive people to use treatment  systems. On the other hand, households who use well or surface water may continue to drink their water untreated because they like the taste, even though the water may contain E.coli – a bacterial indicator of poop in the water. 

    Treatment methods can be as simple as placing water in the sun and letting the ultraviolet light disinfect it, Cohen said. Other popular treatment systems involve boiling or filtering the water, both of which can be highly effective. The final question that Cohen addressed was whether access to clean drinking water is considered a challenge of technology, economics, or adoption. He stated that often the challenge did not pertain to technology but instead concerns what is easy and convenient to adopt. The broader challenge becomes one of resource allocation and knowledge. Despite these challenges, there are many examples of sustainable, affordable water treatment systems. Cohen pointed to areas in Canada that offer free well water testing as an example of potential models for the United States could look like for rural areas.

    Thank you to Alasdair Cohen for sharing water safety and access knowledge and to Rising Silo Brewery for hosting! Science on Tap is a monthly event sponsored and supported by the Center for Communicating Science and by Virginia Tech's chapter of Sigma Xi. Come out to our next event at 5:30 p.m. September 25, 2025, to hear Virginia Tech graduate student in the School of Neuroscience Ainul Huda speak about activating neurons in fruit flies.

By Bria Weisz, Center for Communicating Science graduate assistant