On-Off Control Strategy in a BWRO System under Variable Power and Feedwater Concentration Conditions

Abstract

Although reverse osmosis (RO) is the technology of choice for solving water shortage problems, it is a process that consumes large amounts of energy. Brackish water (BW) desalination is more efficient than seawater desalination due to the lower salinity of the feedwater source. This makes coupling renewable energy sources with BWRO systems attractive. The operation of this type of systems is complex and requires the design of control strategies to obtain optimal operation. The novelty of this work was to propose a simple on-off control strategy for operating a BWRO system that can work with one and two stages and with different configurations considering six spiral wound membrane elements per pressure vessel (PV). The feedwater quality variations of a real groundwater well were used together with a computational tool to simulate the response of the different configurations with the purpose of selecting the most appropriate depending on the input power to the BWRO system. The most suitable configurations were found to be 1:0, 2:1 and 3:2 (PV first stage:PV second stage). It was additionally found that increased feedwater concentrations resulted in shorter operating ranges to maximize permeate water production for the 1:0 and 2:1 configurations, and that the 3:2 configuration was the most suitable for most of the operating range.