The environmental pollution resulting from natural resources acquisition is one of the most severe problems nowadays. New environmental friendly and economically attractive techniques are proposed, using the ability of microorganisms (bioremediation) or plants (phytoremediation) for detoxification of their substrate. Depending on the type of pollutant and the mechanism of its immobilisation (accumulation or decomposition), several techniques are proposed. The specialised plant species are called hyperaccumulators, e.g. Brassica juncia, Helianthus annuus, Nicotiana tabacum or genetically modified Arabidopsis thaliana. Azolla caroliniana Willd. (Azollaceae) is an aquatic fern occurring in temperate and tropical climates. Recently, some natural stands of it were found in western Poland. The fern lives in symbiosis with cyanobacterium Anabaena azollae which is capable of fixing atmospheric nitrogen. Besides numerous application of Azolla in agriculture, e.g. as green manure, it was found that this plant possess a huge ability for phytoremediation. Our studies showed its ability for removal and accumulation of Hg, Cd, Pb, Cr, As, Ag, Pt and Au from waters (up to 100% of applied doses). These promising results open a new application of Azolla spp. for the purification of water polluted by heavy metals, for example as an additional step of wastewater purification.