Phytoremediation of Maninjau Lake water using Minute Duckweed (Lemna perpusilla Torr.)

Lake Maninjau is a tecto-volcanic lake in West Sumatra, which is currently facing eutrophication problem and urgently needs measures to be recovered. A preliminary experiment was carried out to assess the possibility of using minute duckweed (Lemna perpusilla Torr.) for healing the lake water, while also producing biomass for alternative feed. This experiment was carried out in The Unit for Technology Transfer of Lake Restoration – Indonesian Institute of Sciences, which located next to Maninjau Lake. It employed 9 plastic containers of 30X20X20 cm³ filled with lake water taken from 3 locations of different level nutrient contamination. As much as 10 g minute duckweed was put into each container and let to grow for 9 days. Observation on the plant growth and biomass productivity along with the water nutrient concentration was carried out every 3 days. At the end of experiment duckweed biomass was sampled for proximate analysis. The results shows that Maninjau Lake water supported only sub-optimal growth of the duckweed, indicated by low growth rate (ranged 8-22 %/day) as well as the biomass protein content (13-15 % DW). The duckweed, however, can eliminate up to 94% phosphate and 54% total in-organic nitrogen from the water, which also indicating that phosphorous was the limiting factor for duckweed growth in the lake.