Aluminum Fractions in Drinking Water from Reservoirs

To provide insight into aluminum speciation in raw and in finished water and to investigate the factors that can affect it, specific aluminum fractions have been isolated and analyzed in water samples from three drinking water reservoirs in Sardinia (Italy) and at the outlet of their treatment plants. All water treatment plants employed polyaluminum chloride as coagulant. The results demonstrate that the treatment of raw water with the aluminum-based coagulant did not increase the concentration of the metal in the finished water. Aluminum fractions were quite different in raw water and in finished water. More than 80% of the aluminum in raw water was in the particulate form. In the dissolved fraction, organic forms were present at higher concentrations in the raw water, while following water treatment (coagulation, flocculation, filtration) most of the aluminum was in the inorganic form. Most of the dissolved Al in raw water was strongly bound or polymeric colloidal, while percentages of monomeric Al ranging from 40 to 62% were present in the finished water.