Optimizing the Removal of Stormwater Pollutants in Small-Scale, Constructed Treatment Wetlands

Natural wetlands use plants to absorb and break down harmful pathogens and water pollutants. This process improves water quality in a natural and efficient way. By mimicking natural wetlands with constructed wetlands, we are able to perform the same functions. We used the two small-scale treatment wetlands in the Cook Laboratory for Bioscience Research to perform experiments to optimize the removal of stormwater pollutants. These two treatment wetlands consist of three connected basins each with the goal of removing harmful pollutants in each basin. These stormwater pollutants include total suspended solids, biochemical oxygen demand (organic carbon), and nitrate. Past studies led us to expect greater pollutant removal with a greater hydraulic retention time. In our project, to lengthen the retention time and test its effect, we recycled water that had gone through the wetland once already. We placed a pump at each end of the constructed wetlands to circulate water through the system, and a basin with the proper tubing to capture this water before it was cycled through again. We performed several experiments by pumping stormwater through the wetlands while measuring the turbidity, nitrate concentration, temperature, and pH of the water. We measured these parameters with instruments available in the Environmental Engineering lab. Our findings indicated that the updated wetland setup was successful in removing turbidity. Further work should be conducted now that the recycle line is in place. This project provides insight on how to improve the efficiency and effectiveness of the two constructed wetlands. This information can be used to for the design of wetlands stormwater treatment