Biomass characterization of Azolla filiculoides grown in natural ecosystems and wastewater

The aquatic pteridophyte Azolla, a small-leaf floating plant, which lives i n symbiosis with a nitrogen fixing cyanobacteria, Anabaena azollae, was wid espread throughout water channels and hydrographic basins of Portugal. Azol la is also the aim of a study for its utilization as a biofilter for wastew ater purification, namely for phosphorus removal (+/- 36%). The goal of thi s work is to compare the growth characteristics and biomass composition of this water fern in natural ecosystems with those obtained in some wastewate rs. Plant growth rate (0.107 +/- 0.037 d(-1)) and productivity (5.8 g dw m( -2) d(-1)) suggest that Azolla can grow well in partially treated domestic wastewater, but not in diluted pig wastes. This fact, associated to its bio mass composition, namely in phosphorus content (1.38 +/- 0.20%), increase t he possibility of this plant being used to improve wastewater discharge qua lity. It may also be possible to use the biomass as a biofertiliser or as a feed supplement for aquatic and terrestrial animals due to its protein, cr ude fiber and mineral content.