Cellulose acetate is a widely used polymer with good characteristics and its very important in the modern age which faces major problems, among which the shortage of drinking water, accompanied by fatal human activities, climate changes and the rapid increase of the world population. The problem of drinking water is trying to be solved with modern membrane technologies, and among them is reverse osmosis, for which membranes made from cellulose acetate are often used because they are cheap, easy to produce, highly permeable to water and retain a high percentage of salt. However, cellulose acetate membrane also have shortcomings: they are sensitive to pH changes, their selectivity decrease over time due to susceptibility to hydrolysis, and salt retention also decreases with increasing temperature. In order to obtain the best possible membranes with improved properties, it is necessary to modify them with other substances. In this work, cellulose acetate membranes were modified with poly (methyl-methacrylate-co-dimethylaminoethyl-methacrylate) (briefly P(MMA-ko-DMAEMA)) copolymer and silver nanoparticles in order to obtain membranes with better properties. Membranes containing mass 17% and 20% pure cellulose acetate and membranes containing 17% polymer mixture CA/P(MMA-ko-DMAEMA) in the mass ratios 95/5 and 90/10 were prepared. In addition, all prepared membranes were modified with silver nanoparticles. The prepared membranes were characterized using a scanning electron microscope (SEM) which investigated the morphology of the membranes, infrared spectroscopy (FTIR) which investigated the chemical structure of the membranes, and measuring the contact angle as a way of determining the hydrophilicity/hydrophobicity of the membranes. The membranes were also tested in a reverse osmosis device in order to determine their flux values and retention coefficient. The test was conducted in three series: 1) pressure treatment of membranes, 2) thermic and pressure treatment of membranes and 3) modification of membranes with silver nanoparticles (AgNPs).