It is important to note that membrane manufacturer’s Especificaciones for rejection and permeate flux are usually based on testing of large area spiral wound membrane elements operating in Flujo cruzado mode using standardized feed streams and pressures. It is normal, and to be expected, that rejection and permeate flux will be different for feed streams and pressures that are not similar to the standardized test conditions. It is also normal, and to be expected, that rejection and permeate flux will have greater variability from published Especificaciones for devices with membrane active areas that are very much smaller than spiral wound elements, such as Celdas agitadas. Some amount of concentration buildup in the feed for Celdas agitadas is inevitable and this may affect rejection and permeate flux.
There are some tactics that can be used to optimize rejection and permeate flow while using Celdas agitadas. First, the membrane should be pre-conditioned using purified deionized water. Please refer to the operating manual for the pre-conditioning procedure. Second, make sure that the stir bar is turning properly and at an appropriate rate. Third, the operating pressure should correspond to the membrane manufacturer’s recommended pressure. Finally, you may want to stop your experiments while there is still some feed liquid remaining in the Celda agitada to mitigate effects associated with increasing concentrations.
