Nitrogen (N) and phosphorus (P) contained in agricultural effluents and industrial wastewaters are mainly responsible for eutrophication (Smith et al., 1999). Both of them are considered to be the limiting elements of primary productivity in most freshwater ecosystems, and therefore to be the control target for the restoration of freshwater ecosystems (Garland et al., 2004). N and P removal by means of the cultivation of aquatic macrophytes is desirable for the restoration of eutrophic water bodies such as lakes, streams, reservoirs, ponds and marshes. Previous studies have demonstrated the effective removal of inorganic nutrients N and P in wastewaters by using aquatic macrophytes in natural or semi-natural systems (Forni et al., 2001). Harvesting aquatic plants with assimilated and stored N and P is effective for controlling freshwater eutrophication, and the utilization of harvested aquatic plants can provide economic returns and generate valuable products, e.g., biogas, biofertilizer, biomaterial, and even animal food (Singhal and Rai, 2003).