Examining the Effects of Green Infrastructure on Water Quality

By Annie Block

As a rising senior in Columbia College studying sustainable development and environmental science, I have always been interested in water quality, specifically within urban environments. This summer, I am taking part in an REU program that focuses on just that. I’m working with the Urban Water Innovation Network as an undergraduate researcher, which has me traveling between Fort Collins, CO and Brooklyn, NY. During the program’s opening conference at Colorado State University, I examined how the city of Fort Collins could implement sustainable water management practices. After this opening conference, I started my own individual research project at Brooklyn College under the guidance of Brianne Smith and Jennifer Cherrier.

My research specifically examines how green infrastructure affects water quality. Many of the coastal waterways in the United States are prone to nutrient overloading. These nutrients come from surface runoff from fertilizer, combined sewage overflow events, and subsurface runoff from septic tanks. Due to climate change and urbanization, nutrient overloading will pose even more of a challenge in the future—unless we attempt to address it now.

Green infrastructure is gaining recognition as a way to solve these problems. Yet at the same time, current green infrastructure is passive in water retention and inconsistent in nutrient removal. EcoWEIR, a new hybrid active form of green infrastructure, makes up for these limitations. Developed by Cherrier and her team, ecoWEIR allows for the active control of water. This two-layered system creates anaerobic and aerobic environments, allowing for the processes of both nitrification and denitrification to occur. In theory, this means that nutrients are removed from the water before it enters coastal waterways.

The goal of my project is to compare these two forms of green infrastructure. Specifically, I will compare active hybrid green infrastructure (ecoWEIR) and standard green infrastructure in regard to their nutrient removal capacities. For the past six weeks, I have been constructing these two systems. I gathered all of the materials (including six seven-foot barrels and 30 tons of sand) and built the systems from scratch. Then, after constructing the two systems, I ran my first rain event through both. I am now currently analyzing the outflow and inflow water samples in a laboratory; I am testing for phosphorus, ammonium, fecal coliform, dissolved organic carbon and total nitrogen to determine which system is the most effective. During my last two weeks in Brooklyn, I hope to run another rain event. In this second rain event, I plan to have grass planted within these systems, which will allow me to see how vegetation affects nutrient removal processes.

At the end of the summer, I will head back to Colorado to present my results to other UWIN researchers, environmental scientists, environmental engineers, and various stakeholders. The program has allowed me to gain more insight into the specifics of green infrastructure as well as what it means to work in a research setting. I hope to take these skills and knowledge and further apply them to my senior thesis this year.

Annie Block is a current student in Columbia University’s Undergraduate Program in Sustainable Development.