Suitability of Lemna Trisulca (Duckweed) in Water Purification

Abstract

The research was aimed at studying the effectiveness of duckweed as a coagulant/disinfectant in the treatment of water and wastewater. Water sample was obtained from River Benue and duckweed was harvested near a residential area in Makurdi Town, Nigeria. Laboratory experiments were carried out using dosage, pH, temperature, initial concentration and Flocculating Speed as variables for both disinfection and coagulation. Results obtained revealed that, the optimum conditions with respect to disinfection (bacteria load removal) were; Dosage=0.4ml, pH=9, Temperature=30°C, Initial concentration=300µm and Flocculating speed=90rev/min, with highest percentage removal of 91% and 82% for the filtrate and powder respectively. For coagulation (turbidity and suspended solid removal), the optimum conditions were; Dosage=0.2ml, pH=5, Temperature=30°C, Initial concentration=633FTU and Flocculating Speed=90rev/min with the highest percentage removal at 84.3% and 80.4% for duckweed filtrate and powder respectively. It is recommended that, duckweed filtrate and powder should be used in water purification for drinking and greywater respectively.