A complete tertiary process in the wastewater treatment aimed at removing nitrogen and phosphorus is estimated to be about four times more expensive than primary treatment (de la Noüe et al.,1992). It is identical that microalgal cultures offer an elegant solution to tertiary treatment due to the ability of microalgae to use inorganic nitrogen and phosphorus for their growth (Oswald, 1988a; Tam and Wong, 1996). And also, their capacity to remove heavy metals, as well as some toxic organic compounds, therefore, does not lead to secondary pollution. In conclusion, microalgae cultures by wastewater can significantly contribute to the management of water ecosystems by providing an inexpensively environment-
friendly system for wastewater treatment.