Improved analytic modeling and experimental validation for brackish-water reverse-osmosis desalination

We derive an expanded analytical model for the performance of brackish-water reverse-osmosis desalination systems, and conduct extensive measurements on a modest-sized laboratory system, over broad ranges of feedwater salinity and system driving pressure toward establishing good agreement between theory and experiment. The model has no adjustable parameters, captures the essential physics, casts the analysis in terms of the system's natural physically-transparent variables, and accounts for how permeate flow rate and permeate concentration vary with the principal control parameters: system driving pressure, feedwater flow rate and feedwater salinity. By explicitly and analytically incorporating salt diffusion across the membrane into the model, we show how accurate performance predictions can be made with no more input information than is commonly provided in manufacturer specifications. The predictive capabilities of the improved model are also elaborated — a cardinal point being the ability to predict permeate concentration rather than having to assume it as a known input parameter.