Grantee Research Project Results
Final Report: Adaptation of Hydroponics to Remove Excess Phosphorus from Urban Lakes
EPA Grant Number: SU835725Title: Adaptation of Hydroponics to Remove Excess Phosphorus from Urban Lakes
Investigators: Small IV, Gaston Elvin , Brundrett, Ashley , Adamich, Ben , Sisombath, Brendan , Spangenberg, Claire , Thoresen, Douglas , Kellner, Jack , Griffith, Joseph , Hunt, Kirsten , Foster, Malia , Dahmus, Maria , Sciamanda, Marianne , Lauzon, Megan , Rivard, Tyler
Institution: University of St Thomas
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2014 through August 14, 2015
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2014) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
Urban lakes offer societal benefits including recreational opportunities, aesthetic value, sources of drinking water, enhanced property values, and wildlife habitat. However, in many urban areas, lakes are impaired due to phosphorus (P) pollution and excessive algal growth. Management practices focus on reducing P inputs from the watershed, often through expensive stormwater engineering projects, but these efforts may not lead to improved water quality because of internal P loading (P released from lake sediments), which can continue for decades and offset reductions in external loading. In order to achieve improvements in urban lake water quality, active removal of P from the lake may be required to supplement watershed nutrient management.
Our project explores a novel approach to urban lake remediation, using hydroponic gardens to sequester excess nutrients in lake water. The lakeside hydroponic gardens produce vegetables that can offset the cost of this system, while also creating a uniqueplatform for public education and community participation. Hydroponic gardens have previously been used to remove nutrients from aquaculture facilities and even from wastewater treatment facilities, but ours is the first application of hydroponic gardens to urban lakes.
Our Phase I research has focused on Como Lake in Saint Paul, which is the most visited lake in Minnesota and is listed as impaired due to excess P and algae. Our project has focused on determining how to optimize both crop growth and nutrient sequestration. We have conducted a series of experiments measuring nutrient limitation and maximum P sequestration rates for a variety of different crops growing in lake water. We have also constructed a lake ecosystem model, which we are using to conduct cost-‐benefit analyses for hydroponic garden implementation compared to other lake management strategies.
The output from this project is an innovative application of hydroponic plant production used to remove nutrient pollution from an urban lake. Project outcomes include: improved lake water quality; the production of nutritious, locally-‐grown vegetables; catalyzing educational opportunities for the public related to urban water quality; and training a team of students to be leaders in environmental problem-‐solving.
Summary/Accomplishments (Outputs/Outcomes):
Our initial experiments showed that some crops are capable of sequestering significant amounts of P, but we also found that nitrogen (N) becomes limiting in Como Lake during the late summer, inhibiting crop growth in our hydroponic gardens. Follow-‐up experiments are focusing on the most efficient way to provide supplemental nutrients to crops in hydroponic gardens while still maximizing P sequestration from lake water. We are currently measuring the potential of legumes (peas and beans) to fix atmospheric N to supplement nutrients available in the lake water. We are also testing several other strategies for delivering additional nutrients to crops including foliar nutrient application, periodically soaking rafts of crops in a nutrient-‐rich solution, and growing crops on a “floating island” in which crop roots can access nutrients in both soil and in lake water. We will assess which of these techniques provides the best results for crop production while also assessing the feasibility of implementation on a larger scale. We have also measured elemental composition of crops grown in lake water and determined that they do not contain elevated levels of heavy metals.
Another major focus of our current work is in developing a lake ecosystem model, which we will use to conduct comparative cost-‐benefit analyses of lakeside hydroponic gardens as well as other management practices that have been implemented in Como Lake. Preliminary results suggest that the cost per kg of P removed using hydroponic gardens compares favorably to other management strategies implemented in the lake. Interestingly, our model has also shown that stormwater infiltration projects in the watershed, while effective at reducing nutrient loading, also reduce Como Lake’s flushing rate, which partially offsets any benefits to actual dissolved P levels in the lake.
Understanding how any management practices would affect lake nutrient levels requires understanding the dynamics of P exchange with the sediment. Despite its importance, this process had not previously been measured by management agencies, so we conducted sediment P extractions and measured P sorption isotherms to characterize the capacity of the sediment to bind and release dissolved P, and have implemented these results into our model.
Recently, we have begun examining the social, economic, and political feasibility of using hydroponics to remove existing nutrients from lake water while creating social value through growing produce, building community, and creating a unique platform for education about water quality. We are developing potential models for an economically and socially viable food distribution system from the hydroponic garden as well as education and outreach materials to inform and engage the public about water quality issues on Como Lake. We are also examining the larger policy context of environmental decision-‐making through a policy analysis of different environmental regulations relating to the water quality of Como Lake from federal, state, and local agencies as well as participatory equity in local environmental engagement, planning and decision-‐making, and education, with a focus on Como Lake.
Conclusions:
The results of our Phase I research indicate that hydroponic gardens can be part of an integrated lake nutrient management strategy. The cost of implementation is small relative to other nutrient management projects, and can be partially offset by the value of the crops produced. Importantly, lakeside hydroponic gardens provide a tangible way for citizens to be involved with improving water quality in their watershed, in a way that underground infiltration trenches, for example, do not. We plan to install a prototype lakeside hydroponic garden at Como Lake during the summer of 2015, with the goals of collecting additional data and providing a unique platform for public education.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 1 publications | 1 publications in selected types | All 1 journal articles |
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Small G, Niederluecke E, Shrestha P, Janke B, Finlay J. The effects of infiltration-based stormwater best management practices on the hydrology and phosphor budget of a eutrophic urban lake. LAKE AND RESERVOIR MANAGEMENT 2019;35(1):38-50 |
SU835725 (Final) |
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Supplemental Keywords:
cost benefit assessment, bioremediation, treatment technologies, computer models, urban water planning, water treatmentRelevant Websites:
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.