Simulation-based assessment of safe operating windows and optimization in full-scale seawater reverse osmosis systems

Abstract

Reverse osmosis (RO) is the most widely used desalination technology for both seawater and brackish water. Unfortunately, RO remains an energy intensive technology despite the efforts being made to overcome this drawback. One of the factors that could help to minimize this issue is the optimal design and operation of RO systems. Membrane manufacturers are continuously improving and releasing new spiral wound membrane modules (SWMMs) that nonetheless need to be studied in order to determine how to achieve the best highest possible performance from them. The aim of this study was to evaluate the safe operating windows (SOWs) of 9 commercial SWMMs in pressure vessels (PVs) with 7 of these elements in a single stage seawater reverse osmosis (SWRO) system. The permeability coefficients of the SWMMs were taken from a novel membrane open database. These coefficients and the characteristics of the SWMMs were introduced in a simulation algorithm to estimate the behavior of the SWRO system. SOWs were determined without considering any energy recovery device, although these were considered for the calculation of the minimum energy consumption. The SWMMs were compared and the optimal operating points were identified for each one. The results showed the highest difference was around 0.2 kWhm−3 between SWMMs in their optimal operating point with respect to the minimum specific energy consumption. It was also found that this difference increases slightly with rises in feedwater concentration. For a wide range of PV power inputs, the SWMMs were able to reach quite similar maximum flux recovery rates. Experimental work is needed to obtain more reliable predictions of SWRO systems working in wide operating ranges.