Assessing the Efficiency and Role of Duckweed (Lemna Minor) in the Removal of Pollutants from Wastewater Treatment Plant Secondary Clarifier Tanks: A Comprehensive Review

Abstract

Aquatic plants, including duckweed (Lemna minor), are increasingly utilized in sewage and wastewater treat-ment to improve pollution parameters and organic matter removal. This study aimed to investigate the impacts and efficacy of duckweed in secondary clarifier tanks in a conventional biological treatment facility. The per-formance of four secondary clarifiers with and without duckweed was compared based on water quality efflu-ent and settling characteristics. As per the experiment results, the secondary clarifier tank with duckweed demonstrated higher removal efficiency for chemical oxygen demand (COD), biological oxygen demand (BOD5), ammonium, phosphate, total nitrogen (TN), and total phosphorus (TP) – of 70%, 75%, 72%, 82%, 67%, and 96%, respectively, compared to the tank without duckweed. The concentration of suspended solids in the effluent and sludge volume index (SVI) values were similar in both settings. The research findings suggest that duckweed can contribute to the treatment efficiency of conventional biological treatment plants, thus re-ducing the need for tertiary nutrient removal. Additionally, the cost-effectiveness of treatment with duckweed and its reuse as fertilizer and animal fodder make it a valuable resource. The optimal temperature for duck-weed growth is approx. +26°C, and it is influenced by sunlight and temperature more than nutrient concentra-tions.