Brittany Hicks,
PhD Student

Pathogens are very small organisms that cause disease. Some pathogens don’t usually infect healthy individuals; however, they can pose a threat to people with weaker immune systems. The pathogens that I study are “opportunistic pathogens.” Often, they are resistant to antibiotics which makes it difficult to treat infected individuals.  In my previous work, I found higher numbers of pathogens in drinking water pipes that had a higher water “age”. What is high water age? It occurs when drinking water that is pumped from the treatment plant to user taps remains in pipes for a long time. Water utilities add chemical disinfectants into water to kill pathogens. Enough disinfectant is added so that residual amounts are present in tap water at the point of use. This is done in order to prevent growth of pathogens that find their way into the pipes from the environment. Unfortunately,  the amount of chemical disinfectant present will decrease as water travels from the treatment plant, through pipes, and out the faucet.   If the level of disinfectant drops too low, the likelihood of pathogens growing increases. I investigate the chemistry behind high water age environments and how it favors the growth of pathogens.  By understanding this relationship, we can develop better methods to prevent pathogen survival in high water age drinking water pipes.

Members of my research team collected drinking water samples to understand high water age chemistry; specifically, the organic carbon that is normally present in all drinking water. These samples came from regions of Flint, MI, which is experiencing depopulation. Engineers design drinking water distribution systems for population growth, but the water demand decreases when people move away from a city, and the distribution system becomes too big for the population it serves.   As a result, water will spend more time sitting within the pipes; this is called stagnation. In our work with Flint water, we compared the type of organic carbon present in both a low water age and a high water age sample. Interestingly, the type of organic carbon present shifted significantly between these samples. This is important because organic carbon serves as food for pathogens. My current work looks at how opportunistic drinking water pathogens grow with low versus high water age forms of organic carbon. I am investigating pathogen growth using lab experiments and a method called flow cytometry. Flow cytometry allows me to count how many bacteria are present in a sample. These methods allow me to model the pathogen’s growth over time. Later, I will grow opportunistic pathogens along with common, non-harmful bacteria also found in drinking water. If the opportunistic pathogens grow better in a high water age environment than the common bacteria, it may justify monitoring the pathogens. Additionally, flushing drinking water pipes may need to occur in high water age regions to improve water quality. My work could impact academics, engineers, public health officials, and the general public.