Lemna gibba and Azolla filiculoides for sewage treatment and plant protein production

Application of duckweed (Lemna gibba) and water fern (Azolla filiculoides) for nutrients recovery and biomass production using municipal sewage supplemented with nitrogen and phosphorous has been investigated. At a temperature range of 15-26 degrees C results of daily biomass production showed a significantly higher rate for Azolla (4.8-5.9 g dry weight (dw)/m(2).d compared to the duckweed (2.1-5.3 g dw/m(2).d) with corresponding monthly dry weight production of 1.3 and 0.9 ton/ha for Azolla and duckweed, respectively. The estimated value of the monthly dry weight production is LE 3250 and 2250 respectively (US $ = LE 7.8). An average protein content of duckweed and Azolla is 26.9% and 25.6%, respectively which make them competitive for many commercial fish and poultry feed ingredients in Egypt. The duckweed and Azolla can be used interchangeably in Summer (duckweed) and Winter (Azolla) to get temperature range suitable for each plant.