Two different approaches to treat municipal landfill leachate with reverse osmosis membranes are evaluated and discussed. Possibilities are evaluated to radically reduce concentrate flow by a value that does not exceed 0,5-1 % of initial feed water flow to withdraw all rejected impurities together with dewatered sludge. Experimental procedure is developed and described to evaluate reduction of membrane flux and rejection during leachate treatment and recovery increase. Results of experimental investigations are presented that enable us to determine main characteristics of membrane process such as: membrane flux, ammonia rejection, membrane types, number of stages, and recovery. Experimental relationships are obtained to determine the required membrane recovery values that correspond to ammonia concentration in the feed water to meet required regulation values in the product water.