The effect of grafts length on flocculation effectiveness of PAA-grafted silica for kaolin suspension (R = 6.5 mu m, C = 30 kg . m(-3)) comparing with PAA and commercial flocculant Magnafloc LT-27 have been studied. It has been ascertained that nanocomposite with longer grafts is markedly better flocculant. The results of treatments of PAA-grafted silica which have been performed on the waterworks together with different nonionic (A227), anionic (A1020, A1050) and cationic (DB45SSH, KP555) commercial flocculants known in Ukraine are considered. It is shown that PAA-grafted silica alone removes up to 37% and in pair with coagulant up to 75% of pesticide during water clearing.