In order to preserve the environmental quality of a landfill site, it is necessary to collect and properly treat the leachate produced by the landfill. Given the complexity of these leachates and increasingly stringent environmental standards, it is difficult to purify them using just one treatment technology. A combination of different treatment processes is often required to effectively treat leachates and comply with the strict discharge standards to which they are subject.The aim of this work is to convey to waste management decision-makers an approach for the adequate treatment of leachates using a combination of biological treatment and the reverse osmosis system, and to meet the requirements of effluent discharge standards in the natural environment. It will also be of benefit to municipalities planning to build new controlled landfills, drawing on experience gained from the Moulay Abdellah controlled landfill.