Role of Al13 species in removal of natural organic matter from low specific UV absorbance surface water and the aggregates characterization

The effect of coagulant dose and pH on the coagulation behaviors of nano-Al13 polymer (Al13O4(OH)247+) was studied with respect to the treatment of low specific UV absorbance (SUVA) surface water. The removal of fine particles and natural organic matter (NOM) was investigated under different coagulation conditions. Polyaluminum chloride (PACl) and traditional aluminum coagulant, alum (Al2(SO4)3) were used for purpose of comparison. Floc size, strength and fractal structure were investigated under different coagulation conditions. The results showed that fine particles and hydrophobic NOM with large molecular weight (MW) could be easily removed by the three coagulants in a wide dose range (5–17 mg/L); while the proportion of hydrophilic NOM in the removed dissolved organic matter (DOM) was larger in Alm and Al13 species coagulation at low and moderate dose (lower than 11 mg/L). Neutral and alkaline pH facilitated the particle removal, while acidic pH contributed to better hydrophilic NOM removal. The floc strength investigation indicated that the floc strength formed by Al13 under different coagulation conditions was in the following hierarchy: pH 6.5 (15 mg/L) > pH 4.0 (9 mg/L) > pH 8.0 (15 mg/L). For Al2(SO4)3 coagulation, the order was as following: pH 4.0 (9 mg/L) > pH 6.5 (15 mg/L) > pH 8.0 (15 mg/L). Additionally, the fractal dimension of flocs indicated that Al13 species resulted in compact aggregates at low concentration and pH.

► Compare the effect of pre-hydrolyzed Al13 on removing of colloidal particles, UV254 and hydrophilic NOM with low MW.
► Investigate the floc size distribution in low SUVA surface water treatment using Al13 species.
► Evaluate the floc strength and fractal structure formed by Al13 species in low SUVA water coagulation.