The report determines the phosphate retention of lake sediments in relationship to their mineralogical and chemical composition and physical properties, the effect of phosphate equilibrium concentration, pH, reaction time, solid to solution ratio and phosphate to sediment ratio on phosphate retention, the different forms of phosphorus in lake sediments, and elucidates the mechanism of phosphate retention using model substances such as pure clay minerals, hydroxides of iron and aluminum, and clay minerals with hydroxy-iron and hydroxy-aluminum interlayers. The findings also include the development of a method for phosphate removal from waste effluents.