Highly charged cations destabilize any colloidal particles by the formation of polyvalent polyhydroxide estates (8, 9).
This experimental research has been performed in Wastewater Treatment Plant of Bu-Ali Industrial Estates in Hamadan City from April to September 2006. The system of treatment at this estate is based on aeration lagoons, so significant amounts of algae are always discharged with effluent especially in warm and mild seasons.