The aquatic fern Azolla, a small-leaf floating plant that lives in symbiosis with a nitrogen fixing cyanobacteria (Anabaena), is an outstanding plant, thanks to its high biomass productivity along with its tremendous rate per unit area for nitrogen-fixation.  The present study investigates the potential growth of Azolla in secondary effluents for removal of COD, phosphorus, and nitrogen. Results have shown that N and P removal at 100 ppm of each component in separate medium turned out to be 36% and 44%, respectively, whereas in case of a mixed solution of these two compounds, N and P removal declined to 33% and 40.5%, respectively. Moreover, results have suggested that in the presence of phosphorus nitrogen absorption decreased. Furthermore, Azolla has revealed a high potential of COD removal by 98.8% in 28 days. Finally, Azolla may be one of the most promising agents to remove COD and treat nitrogen-free and phosphorus-rich wastewaters.