A new theoretical approach to estimate the specific energy consumption of reverse osmosis and other pressure-driven liquid-phase membrane processes

The specific energy consumption (SEC) of pressure-driven liquid-phase membrane processes, in particular the reverse osmosis (RO) process, has usually been estimated using a phenomenological approach, which does not explicitly consider the membrane properties and operating parameters. This paper presents a new analytical approach that has been derived, from a well-established theory, to estimate the SEC and to quantify the effect of membrane properties; namely, membrane permeability and surface area as well as the effect of process parameters such as feed pressure, recovery rate, membrane element permeate rate, and feed osmotic pressure. The SEC is also presented in terms of a dimensionless parameter, namely, the specific energy indicator (SEI), which can be used as a membrane property to indicate the SEC of the membrane element for a given process recovery rate and feed osmotic pressure. The SEC calculations are presented for desalting a NaCl solution with a salinity of 35,000 mg/L over a wide range of re...