Nutrient and Heavy Metal Removal Efficiencies Using Floating Wetland Treatment Techniques Of Polluted Hanumante River Water, Nepal

Abstract

Floating treatment wetlands (FTWs) offer a promising solution for wastewater treatment, particularly in river water remediation. This study evaluated the performance of FTWs constructed with various floating and emergent aquatic and medicinal plants. Laboratory mesocosm experiments were conducted under ambient conditions to assess nutrient and heavy metal removal efficiencies. Results demonstrated that FTWs using floating macrophytes effectively removed phosphate and nitrate. Azolla filiculoides, Pistia stratiotes, and Zephyranthes grandiflora achieved phosphate removal efficiencies of 90.9%, 86.4%, and 83.3%, respectively. Nitrate removal rates were similarly high, ranging from 86.3% to 87.5% for these species. While ammonium removal was less efficient (30–50%), the FTWs effectively captured heavy metals. Pistia stratiotes and Chrysopogon zizanioides exhibited zinc and manganese removal rates of 90% and 80%, respectively. Zephyranthes grandiflora removed zinc and manganese at rates of 65% and 67%. Additionally, floating aquatic plants like Azolla filiculoides and Pistia stratiotes demonstrated iron removal efficiencies exceeding 60%. These findings suggest that FTWs constructed with Azolla filiculoides, Pistia stratiotes, and Zephyranthes grandiflora can be a viable option for treating polluted river water, given their ability to efficiently remove nutrients and heavy metals.