Coagulation or dense membrane processes, i.e. nanofiltration (NF) and reverse osmosis (RO), are intensively used in surface water treatment. Conventional coagulation process is used to remove colloids and particles, while the dense membrane processes are used to remove trace dissolved contaminants. This paper applied an in-situ surface modification technique by directly depositing the laboratory synthesized coagulant, aluminium tridecamer ([AlO4Al12(OH)(24)(H2O)(12)]Cl-7, Al-13), as a coating solution for two NF and one RO membranes. The dense membranes can completely reject the Al-13 compounds; while the coated membranes were effectively removing humic acid and 17 beta-estradiol (E2) from waters. The coated Al-13 layer revealed structural stability subjected to salt (NaCl), acid (pH 5) and base (pH 9) challenges. (C) 2011 Elsevier B.V. All rights reserved.