Assessing Nutrient Transport from Onsite Wastewater Systems and Efficacy of a Subsurface Bioreactor to Remediate Nutrients in Surficial Aquifers in the Falls Lake Watershed Grant uri icon

abstract

  • Researchers at East Carolina University (ECU) have studied onsite wastewater system (OWS) inputs to tributaries of the Falls Lake Watershed for the past 6 years and found evidence to support that OWSs can be significant contributors of nutrients to streams draining to the reservoir. Brown and Caldwell partnered with Systech Water Resources, Inc. and ECU to develop a model to estimate the nutrient inputs from OWSs and they estimated that there are approximately 50,000 OWSs within the watershed. Watershed-scale nutrient models rely on inputs that are representative and comprehensive of the variables that influence nutrient transport dynamics. Past research conducted by our team has allowed us to sample surface water from sub-watersheds in various geological and soil settings. Additionally, much of our previous work from individual OWS occurred at residences located in Triassic Basin geological regions, which is characteristic of finer-textured soils with lower hydraulic conductivities. Preliminary surface water nutrient data from sub-watersheds utilizing OWS suggest that nutrient transport from OWTS varies by geologic setting. However, there have been limited studies that characterize site transport from households served by OWS located in the Carolina Slate Belt and/or Raleigh Belt geologic settings. These geologic settings tend to higher hydraulic conductivities, which may influence nutrient loads. New data collected from these geological settings will be leveraged with past studies funded by the NC Policy Collaboratory and other funding agencies to further understanding of nutrient transport from household OWSs in the Falls Lake Watershed. Furthermore, additional research is needed to quantify nutrient treatment of engineered best management practices that mimic nature-based features to improve on-site attenuation of nutrients. The proposed project will generate data to address the aforementioned gaps by: 1) identifying OWSs located in the Carolina Slate and Raleigh Belts where data are not readily available; and 2) leverage results from the bioreactor mesocosm pilot study (funded by the NC Policy Collaboratory, 2020 - 2021) to install a subsurface bioreactor in groundwater downgradient from OWS to improve nutrient attenuation.*Note: The funds for this project were delayed and the subsurface bioreactor component could not be completed. The results and scope of this project was modified to accommodate the delayed receipient of funds.

date/time interval

  • March 2020 - March 2021