Measurement of Enterococci and Other Water Quality Parameters as an Active Learning Module in Introductory Life Science Courses
Authors: Spence Coleman Dewitt , Leri Alessandra 
Published: June 2021

Like many cities, New York utilizes a combined sewer system where wastewater, sewage, and runoff are pooled together before being carried to a treatment plant. The system can become overwhelmed during storms, resulting in discharge of excess wastewater into nearby water bodies in a phenomenon known as Combined Sewage Overflow (CSO). New York is surrounded by biologically productive waterways that are used for commerce, recreation, and fishing. Excess nutrients and bacteria that enter the ecosystem from CSOs negatively affect the river's biodiversity and aquatic health. An important indicator bacterium is Enterococcus, which is abundant in human feces. Biological nutrients such as nitrate and phosphate from CSOs can cause eutrophication, decreasing the dissolved oxygen for the ecosystem.

We have developed an active learning module for students in introductory science courses to measure water quality in New York City's East River, an estuary near our campus. In order to assess fecal contamination from CSOs in the East River, a section of the river between East 63rd and East 71st Streets in Manhattan is sampled. There are three CSO sites along this stretch, varying in average quantity of outflow. Samples are taken from five locations in a gradient moving away from the dominant CSO outflow in the direction of the river current. Each water sample is tested for pH, dissolved oxygen (DO), temperature, nitrate, and phosphate using field equipment before being brought back to the lab for analysis using the Enterolert system to count the Most Probable Number (MPN) of Enterococci cells in a given volume of sample. This experiment is performed twice, on a dry‐weather and wet‐weather day, to assess the effects of rainfall/CSOs on water quality. After periods of rainfall, we have measured Enterococci counts of >20,000 cells/L, well above the levels acceptable for human exposure. In general, we find that the MPN of Enterococci is highest in areas directly downstream of the CSO outflows. Results also indicate a strong positive correlation between Enterococci and prior four‐day rainfall, consistent with the CSOs acting as the source of bacterial contamination. The data also show a negative correlation between Enterococci and dissolved oxygen, suggesting that the CSO contamination has a deleterious effect on the overall health of the aquatic ecosystem. Students present their original data in the form of a scientific paper and an oral presentation that is open to the college community.

This module provides an effective way for students in introductory science courses to learn about the impact of human waste on aquatic health. It is suitable for courses in ecology, environmental science, and chemistry, for science majors and non‐majors alike. It could also be adapted for use in high school courses. Using straightforward techniques and equipment, beginning students are able to collect original data that they present to the wider community. Similar projects could be carried out in any area that has CSOs or other sources of sewage contamination to local water bodies.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.