AbstractFor a RO pilot plant the study and determination of the operative parameters were accomplished. The semiautomatizedwork for the plant allows us the election of different modular configurations serial/parallel. The systemwas characterized with NaCl solutions, with concentrations between 3-11 g/l. For the different configurations, thevalues of the working parameters were obtained as a function of the brine flow, corresponding the optimal design to asingle stage with the two modules in parallel for the concentration range studied. For all configurations, some threedimensionalgraphs were drawn representing fresh water flow versus feed stream concentration and brine flow.