JWSS - Journal of Water and Soil Science

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Soltani Margani S, Abedi Koupai J, Heidarpour M, Gohari S A. Evaluation of the Efficiency of Vetiver and Reed Plants in Reducing Nitrate, Phosphate, BOD, and COD in Urban Wastewater Using Floating Island Systems. jwss 2026; 30 (1) :87-102
URL: http://jstnar.iut.ac.ir/article-1-4487-en.html

This research focuses on evaluating the efficiency of constructed wetlands in treating municipal wastewater using two plants: vetiver (Chrysopogon zizanioides) and common reed (Phragmites australis). Given the increasing pollution of water resources and water scarcity in Iran, the application of nature-based solutions (NBS), particularly constructed wetlands, is a crucial approach for effective wastewater management and treatment. This study concentrates on the wastewater from the treatment plant of Isfahan University of Technology and, over a period of six months, assesses the impact of four different treatments in a completely randomized design: 1) wetland planted with vetiver (V), 2) wetland planted with reed (N), 3) control wetland without plants (B), and 4) control wetland without plants but with a supporting substrate (P), on chemical parameters of wastewater and plants. The measured parameters include BOD₅, COD, nitrate, and phosphate. Results indicated the highest levels of BOD₅ and COD in the control treatments (without plants) and a significant reduction in these parameters in the treatments planted with vetiver and reed. The best removal performance for these two parameters was observed in the sixth month at a hydraulic retention time of 30 days, with reductions of 67% and 65% for BOD₅ and 85% and 84% for COD in the vetiver and reed treatments, respectively. In the sixth month, at a retention time of 15 days, nitrate levels decreased by 25% and 34% in the vetiver and reed treatments, respectively, and by 39% and 59% at 30 days retention time. These differences were statistically significant at the 5% level for both retention time and plant type. Phosphate reductions in the sixth month at 15-day retention were 65% and 81% in vetiver and reed treatments, respectively, and at 30 days, 82% and 87%, with these decreases being statistically significant for both retention times and plant types at the 5% level. Retention time results showed that the reduction of BOD₅ and COD is directly related to retention time, with longer retention times yielding higher removal percentages. Regarding nitrogen and phosphorus, the reed demonstrated the highest performance, effectively reducing these pollutants. The total nitrogen uptake in the shoots and roots of the reed after 30 days was 33.4 and 22.51 mg/kg dry plant matter, respectively, indicating the high capacity of the reed for nitrogen absorption from wastewater. This study demonstrates that planting vetiver and reed can serve as sustainable solutions for improving water quality and effective water resource management in Iran