Evaluating the Amount of Residual Aluminum from Conventional and Enhanced Coagulation Using Poly-aluminum Chloride in Refined Water

Poly-aluminum chloride (PACL) is an inorganic coagulant used in recent years for the removal of color and turbidity in refining water industry. When coagulants are added to water, some amount of this material dissolves in water and remains in the final refined water. Aluminum is also a material that is found in aluminum coagulants base (Alum and PACL), and little amounts of this material in the water causes many health problems such as dialysis encephalopathy and Alzheimer. Environmental Protection Agency (EPA), has determined the maximum concentrations level (MCL) allowable in drinking water as 0.2 mg/l. Advanced coagulation process is defined as the addition of excess coagulant for the removal of natural organic matter (NOM), as precursors of disinfection by products. It is expressed as the best available process for the treatment and removal of this material. The amount of residual aluminum was studied in conventional and advanced coagulation after adding PACL in jar test. Results showed that mean residual aluminum in enhanced coagulation was more than conventional coagulation. But the amount of residual aluminum in both processes was lower than the MCL recommended by EPA. It can be conclude that using enhanced coagulation by PACL in water, not only causes turbidity and NOM removal, but even with multiplying the coagulant dose, the residual aluminum is less than the recommended maximum concentration level.