Floating wetland mesocosm assessment of nutrient removal to reduce ecotoxicity in stormwater ponds|
Chang, N.B.; Islam, M.K. & Wanielista, M.P.
A grouped mesocosm study was conducted with different water holding capacities and conditions to determine nutrient removal efficiency using floating wetland macrophytes. Different scenarios were created by changing water depth, littoral vegetation, sorption media and area coverage to observe how they affect nutrient removal efficiencies. Plant species were screened and selected based on the literature, local availability and previously performed microcosm studies. Sorption media were warped using geotextile filter fostering microbial colonization in the rhizospheric zone to enhance denitrification and plant growth. Water quality parameters included total nitrogen, total phosphorus, orthophosphate, nitrate–nitrogen and ammonia–nitrogen in addition to in situ parameters such as pH, dissolved oxygen, temperature and chlorophyll-a. Composite samples across several locations were collected periodically to understand the spatial distribution or aggregation of nutrients. After 3 months of water quality monitoring, plants were analyzed for tissue nutrient concentrations, and the average uptake rate was calculated as 36.39 and 1.48 mg m-2 day-1 for nitrogen and phosphorus, respectively, by the floating treatment wetland system. Finally, considering the higher nutrient aggregation in the rhizospheric zone, the removal rate with 5 % area coverage and water quality improvement by littoral zone, the optimized design, placement and maintenance of the whole system were recommended.
Best management practice; Littoral zone; Nutrient aggregation; Rhizospheric zone; Sorption media