A COMBINED BIOLOGICAL-CHEMICAL APPROACH TO REMOVING NUTRIENTS FROM EUTROPHIC WATERS

Authors

Levi McKercher, University of Nebraska - LincolnFollow

First Advisor

Steve Comfort

Second Advisor

Tiffany Messer

Date of this Version

7-2021

Citation

McKercher, L. (2021). A COMBINED BIOLOGICAL-CHEMICAL APPROACH TO REMOVING NUTRIENTS FROM EUTROPHIC WATERS. M.S. Thesis 2021. University of Nebraska-Lincoln

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Natural Resource Sciences, Under the Supervision of Professors Steve Comfort and Tiffany Messer. Lincoln, Nebraska: July, 2021

Copyright © 2021 Levi J. McKercher

Abstract

Efforts to improve water quality in eutrophic ponds often involve implementing changes to watershed management practices to reduce external nutrient loads. While this is required for long-term recovery and prevention, eutrophic conditions are often sustained by the recycling of internal nutrients already present within the waterbody. In particular, internal phosphorus loads have been shown to delay lake recovery for decades. Thus, in-situ pond management techniques are needed to not only reduce external nutrient loading over the long-term but also mitigate the effects of internal nutrients already present. Our objective was to demonstrate a biological and chemical approach to remove and sequester nutrients present or entering a eutrophic pond. We designed a novel biological and chemical management technique by constructing a 37 m² (6.1 m x 6.1 m) floating treatment wetland (FTW) coupled with a slow-release lanthanum composite inserted inside an airlift pump. The FTW was incorporated into the treatment strategy to promote microbial denitrification and plant uptake of N and P, while the airlift pump slowly delivered lanthanum to the water column over the season to adsorb and precipitate soluble reactive phosphorus (SRP). The design was tested at the microcosm and field scales, where NO₃-N and PO₄-P removal was significant (α=0.05) at the microcosm scale and validated at the field scale. The proposed treatment provides a unique and effective technology to address internal phosphorus loads and minimize the effects of nutrient runoff entering urban retention ponds.

Advisors: Steven D. Comfort and Tiffany L. Messer