Floating Treatment Wetlands for Brackish Waters: Plant Selection and Nutrient Uptake Potential.
Date of Award
Master of Science (MS)
Sarah A. White
Peter van den Hurk
Brackish water bodies in coastal regions provide critical ecosystem services that support human and environmental health. Anthropogenic activities such as agricultural and industrial activities, construction, urban settlements, and tourism contribute to increased inputs of nitrogen (N) and phosphorus (P) in brackish coastal ecosystems. Excess nutrients can lead to impaired water quality and affect marine organisms. Floating treatment wetlands (FTWs) are a vegetated-base technology used to remove contaminants from water column, that has been mainly studied and applied in freshwater systems. Application of FTWs in brackish systems requires further investigation, as high salinity in brackish waters could result in toxicity to many plant species.
The goal of this research was to 1) evaluate the salinity tolerance of four plant species established in FTWs at different salinity levels, and 2) quantify the nutrient removal efficiency of two plant species in FTWs established in brackish waters. First, a mesocosm-scale FTW experiment was conducted to evaluate survival and characterize plant growth in Distichlis spicata, Juncus roemerianus, Spartina alterniflora and Spartina patens plants, and plant tissue nutrient concentrations of plants deployed in 0.5, 5.0, and 18 parts per thousand (ppt) salinity. Then, a mesocosm-scale FTW experiment was conducted to evaluate plant growth in J. roemerianus and S. alterniflora plants, plant tissue nutrient concentrations, and N and P removal efficiency, in plants deployed in three different salinity levels (0.5, 5.0, and 18 ppt) and two nutrient concentrations (Low and High).
These experiments showed that saltmarsh plants evaluated behaved differently when exposed to different salinity concentrations. D. spicata was negatively influenced by higher salinity, producing the least biomass. Development and biomass production of J. roemerianus was affected by transplant shock, age-response of plant tissue, and salinity. S. alterniflora grew similarly across all salinities, and S. patens grew similarly in all salinities but presented salinity stress symptoms (e.g., leaf chlorosis) at higher salinities.
These experiments showed that J. roemerianus and S. alterniflora both had high N and P removal efficiency across all salinities and nutrient concentrations. Floating treatment wetlands had up to 99% N removal in the presence of J. roemerianus and S. alterniflora. Phosphate removal was from 75-97% with J. roemerianus and 54-97% with S. alterniflora. These results indicate that J. roemerianus and S. alterniflora are suitable species that could be used in FTWs for N and P removal from brackish water bodies.
Landaverde, Andrea, "Floating Treatment Wetlands for Brackish Waters: Plant Selection and Nutrient Uptake Potential." (2022). All Theses. 3736.
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