Evaluation of the fern Azolla for growth, nitrogen and phosphorus removal from wastewater

Water Fern (Azolla filiculoides Lam.) has been assessed for nitrogen and ph osphorus removal in outdoor experiments comparing sewage water (S) from an experimental aquaculture plant, well water (W) and mineral growth medium Ho agland (H). The experiments were undertaken during the spring and the summe r. The yield of fern biomass and nitrogenase activity was higher in PI than in W and S waters. The enzyme activity had a decreasing trend with signifi cant differences (p <0.05) in the three waters. Peroxidase (POD) activity i n April decreased with significative differences in W and S waters (p <0.05 ). The electrical conductivity and the concentrations of NO3- in the three waters decreased significantly (p <0.05). The highest removal of nitrate fr om the media was obtained in July. In S water, NOT concentration decreased, while it increased in W water. PO43- concentration was very low in W and S waters and decreased in H medium. The results obtained confirm the ability of the fern to grow in sewage water. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.