Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory Results
Urban and storm water retention ponds eventually become eutrophic after years of receiving runoff water. In 2020, a novel biological and chemical treatment was initiated to remove accumulated nutrients from an urban retention pond that had severe algae and weed growth. Our approach installed two 6.1...
Saved in:
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-09-01
|
| Series: | Nitrogen |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2504-3129/5/4/53 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850058542025801728 |
|---|---|
| author | Jenna McCoy Matt Chaffee Aaron Mittelstet Tiffany Messer Steve Comfort |
| author_facet | Jenna McCoy Matt Chaffee Aaron Mittelstet Tiffany Messer Steve Comfort |
| author_sort | Jenna McCoy |
| collection | DOAJ |
| description | Urban and storm water retention ponds eventually become eutrophic after years of receiving runoff water. In 2020, a novel biological and chemical treatment was initiated to remove accumulated nutrients from an urban retention pond that had severe algae and weed growth. Our approach installed two 6.1 m × 6.1 m floating treatment wetlands (FTWs) and two airlift pumps that contained slow-release lanthanum composites, which facilitated phosphate precipitation. Four years of treatment (2020–2023) resulted in median nitrate-N concentrations decreasing from 23 µg L<sup>−1</sup> in 2020 to 1.3 µg L<sup>−1</sup> in 2023, while PO<sub>4</sub>-P decreased from 42 µg L<sup>−1</sup> to 19 µg L<sup>−1</sup>. The removal of N and P from the water column coincided with less algae, weeds, and pond muck (sediment), and greater dissolved oxygen (DO) concentrations and water clarity. To quantify the sustainability of this bio-chemical approach, we focused on quantifying nitrate removal rates beneath FTWs. By enclosing quarter sections (3.05 × 3.05 m) of the field-scale FTWs inside vinyl pool liners, nitrate removal rates were measured by spiking nitrate into the enclosed root zone. The first field experiment showed that DO concentrations inside the pool liners were well below the ambient values of the pond (<0.5 mg/L) and nitrate was quickly removed. The second field experiment quantified nitrate loss under a greater range of DO values (<0.5–7 mg/L) by including aeration as a treatment. Nitrate removal beneath FTWs was roughly one-third less when aerated versus unaerated. Extrapolating experimental removal rates to two full-sized FTWs installed in the pond, we estimate between 0.64 to 3.73 kg of nitrate-N could be removed over a growing season (May–September). Complementary laboratory mesocosm experiments using similar treatments to field experiments also exhibited varying nitrate removal rates that were dependent on DO concentrations. Using an average annual removal rate of 1.8 kg nitrate-N, we estimate the two full-size FTWs could counter 14 to 56% of the annual incoming nitrate load from the contributing watershed. |
| format | Article |
| id | doaj-art-101078bfd15f4ac7ae4716b262f97520 |
| institution | DOAJ |
| issn | 2504-3129 |
| language | English |
| publishDate | 2024-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Nitrogen |
| spelling | doaj-art-101078bfd15f4ac7ae4716b262f975202025-08-20T02:51:07ZengMDPI AGNitrogen2504-31292024-09-015480882710.3390/nitrogen5040053Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory ResultsJenna McCoy0Matt Chaffee1Aaron Mittelstet2Tiffany Messer3Steve Comfort4School of Natural Resources, University of Nebraska-Lincoln, 205 Kiesselbach Hall, Lincoln, NE 68583, USADepartment of Biological Systems Engineering, University of Nebraska-Lincoln, 200 L.W. Chase Hall, Lincoln, NE 68583, USADepartment of Biological Systems Engineering, University of Nebraska-Lincoln, 200 L.W. Chase Hall, Lincoln, NE 68583, USADepartment of Biosystems and Agricultural Engineering, University of Kentucky, 128 CE Barnhart, Lexington, KY 40506, USASchool of Natural Resources, University of Nebraska-Lincoln, 205 Kiesselbach Hall, Lincoln, NE 68583, USAUrban and storm water retention ponds eventually become eutrophic after years of receiving runoff water. In 2020, a novel biological and chemical treatment was initiated to remove accumulated nutrients from an urban retention pond that had severe algae and weed growth. Our approach installed two 6.1 m × 6.1 m floating treatment wetlands (FTWs) and two airlift pumps that contained slow-release lanthanum composites, which facilitated phosphate precipitation. Four years of treatment (2020–2023) resulted in median nitrate-N concentrations decreasing from 23 µg L<sup>−1</sup> in 2020 to 1.3 µg L<sup>−1</sup> in 2023, while PO<sub>4</sub>-P decreased from 42 µg L<sup>−1</sup> to 19 µg L<sup>−1</sup>. The removal of N and P from the water column coincided with less algae, weeds, and pond muck (sediment), and greater dissolved oxygen (DO) concentrations and water clarity. To quantify the sustainability of this bio-chemical approach, we focused on quantifying nitrate removal rates beneath FTWs. By enclosing quarter sections (3.05 × 3.05 m) of the field-scale FTWs inside vinyl pool liners, nitrate removal rates were measured by spiking nitrate into the enclosed root zone. The first field experiment showed that DO concentrations inside the pool liners were well below the ambient values of the pond (<0.5 mg/L) and nitrate was quickly removed. The second field experiment quantified nitrate loss under a greater range of DO values (<0.5–7 mg/L) by including aeration as a treatment. Nitrate removal beneath FTWs was roughly one-third less when aerated versus unaerated. Extrapolating experimental removal rates to two full-sized FTWs installed in the pond, we estimate between 0.64 to 3.73 kg of nitrate-N could be removed over a growing season (May–September). Complementary laboratory mesocosm experiments using similar treatments to field experiments also exhibited varying nitrate removal rates that were dependent on DO concentrations. Using an average annual removal rate of 1.8 kg nitrate-N, we estimate the two full-size FTWs could counter 14 to 56% of the annual incoming nitrate load from the contributing watershed.https://www.mdpi.com/2504-3129/5/4/53floating treatment wetland (FTW)water qualitynitrate-Nphosphate-Pdissolved oxygen concentrations |
| spellingShingle | Jenna McCoy Matt Chaffee Aaron Mittelstet Tiffany Messer Steve Comfort Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory Results Nitrogen floating treatment wetland (FTW) water quality nitrate-N phosphate-P dissolved oxygen concentrations |
| title | Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory Results |
| title_full | Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory Results |
| title_fullStr | Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory Results |
| title_full_unstemmed | Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory Results |
| title_short | Nitrate Removal by Floating Treatment Wetlands under Aerated and Unaerated Conditions: Field and Laboratory Results |
| title_sort | nitrate removal by floating treatment wetlands under aerated and unaerated conditions field and laboratory results |
| topic | floating treatment wetland (FTW) water quality nitrate-N phosphate-P dissolved oxygen concentrations |
| url | https://www.mdpi.com/2504-3129/5/4/53 |
| work_keys_str_mv | AT jennamccoy nitrateremovalbyfloatingtreatmentwetlandsunderaeratedandunaeratedconditionsfieldandlaboratoryresults AT mattchaffee nitrateremovalbyfloatingtreatmentwetlandsunderaeratedandunaeratedconditionsfieldandlaboratoryresults AT aaronmittelstet nitrateremovalbyfloatingtreatmentwetlandsunderaeratedandunaeratedconditionsfieldandlaboratoryresults AT tiffanymesser nitrateremovalbyfloatingtreatmentwetlandsunderaeratedandunaeratedconditionsfieldandlaboratoryresults AT stevecomfort nitrateremovalbyfloatingtreatmentwetlandsunderaeratedandunaeratedconditionsfieldandlaboratoryresults |