We describe a novel strategy to control the release of silver from polyethylene-based water purification membranes by suitably modifying the membrane surface by a biocidal macromolecule (poly(ethylene imine), PEI) before depositing silver on the surface. The PE membranes were first treated with ozone and then PEI was covalently grafted. The distribution of silver was mapped by EDAX, and the antibacterial activity assessed by standard plate count method and by estimating the reactive oxygen species. The new membrane allows controlled release of silver ions which otherwise would contaminate the water source if used in excess. Leaching in the final permeate is lower than 0.03 ppm opening the route to antibacterial polyolefin-based membranes for water decontamination. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim