Superstructure based optimization of reverse osmosis desalination systems fed by decarbonated high-pH seawater under boron restrictions

This paper presents a superstructure based optimization of reverse osmosis (RO) system fed by decarbonated seawater (DS) at high pH value under boron restrictions. Each RO stage/pass could be operated with high boron rejection. The permeate split (PS) design allows permeates with different quality collecting from both sides of pressure vessel (PV). The pH variations are fitted by experiment and simulated results from the literature. The accuracy of the RO model is also validated. Results showed that about 3.48%-18.31% water cost and 3.04%-14.61% energy consumption savings are achieved by permeate split with decarbonated seawater (PSDS) design. Water cost is less influenced by pH values for PSDS design, which might be a robust solution for pH control. A two-stage stochastic model is performed to obtain robust and flexible designs considering uncertainties of the RO design problem. Both operational conditions and process flow are adjusted to save water cost and energy consumption.