Removal of Orthophosphate from Municipal Wastewater Using Chemical Precipitation Process in Ahvaz Wastewater Treatment Plant, Iran

Phosphate removal such as orthophosphate, from municipal wastewater has become an environmental necessity; since the excessive phosphate ion content in municipal wastewater causes water eutrophication. According to environmental protection organization of Iran; Maximum permissible concentration of residual phosphorus in treated municipal wastewater is 1 mg/L P. Almost all the phosphorus in natural water and wastewater is available in the form. of phosphate. Phosphorus compounds in wastewater, after hydrolysis and biodegradation; Change to solution orthophosphates. In this research, poly aluminium chloride and bentonite clay as nature coagulant were added and with low chemical cost; bentonite effect in improving poly aluminium chloride in municipal wastewater treatment; has been investigated: The research is a bench Scale experimental type. Samples : were collected, from influent wastewater to primary and effluent of secondary Clarifier and-then effect of pH and dose of coagulant investigated on orthophosphate removal efficiency. The result show optimal conditions Of compound of polyaluminium chloride and bentomite for removal of arthophosphate, COD, BOD and TSS in pH = 7 and optimal dose. 15.55 mg/L polyaluminium chloride and 5.55 mg/L bentonite in influent wastewater to primary clarifier has been obtained 71.83, 46.1, 48.9 and 63.5 %, respectively. Under optimal condition, orthophosphate concentration was reached to 1 mg/L. SO this compound coagulant;, in lowest dose and consequently chemical cost decrease was selected as suitable Coagulant in removal of orthophosphate of-effluent of treatment plant.