Mrirt, a small mountain town in Morocco, sources its drinking water from the Oum Errabia River, which has a high salinity level exceeding the World Health Organization's (WHO) and Moroccan standard limits. Remarkably, too much sodium can lead to both short-term and long-term health issues. Membrane processes are a promising solution for lowering the salinity and Na+ concentration of Mrirt water. This study investigated the use of reverse osmosis (RO) and nanofiltration (NF) techniques to remove sodium ions from the drinking water in Mrirt City. Three NF membranes (NF270*4040, NF90*4040, and TR60*4040) and two RO membranes (BW30LE4040, TM710) were tested. Numerous factors, including applied pressure and recovery rate, were studied. The results showed that permeate flow increases almost linearly with the applied pressure in compliance with Darcy's law, and NF membranes yielded a higher permeate flux than the RO membranes. The Hermia model was used to identify fouling mechanisms. Among the five membranes assessed, fouling was of the cake type, characterized by the accumulation of molecules on the membrane's surface, leading to the promotion of surface fouling.