Development of a SWRO-PRO hybrid desalination system: pilot plant investigations

Abstract

Seawater reverse osmosis (SWRO) desalination technology accounted for 78% of annual new contracted desalination capacity from 2006 to 2012, due of its lower electrical power consumption (3–5 kWh/m³) versus thermal desalination technologies (up to 18 kWh/m³), such as multistage flash and multiple effects. However, the existing SWRO desalination process still needs further improvement to lower the energy consumption. Recently, a novel hybrid SWRO desalination system using pressure-retarded osmosis (PRO) technology has been studied, which can recover a large amount of osmotic power from the concentrated brine. In this study, GS Engineering & Construction Corp. (GS E&C) developed an advanced SWRO-PRO process to economically couple this PRO technology with a conventional SWRO desalination process. To investigate the SWRO-PRO process, pilot and demonstration plants, of 20 m³/d and 240 m³/d PRO treatment capacity, were constructed and thin-film composite spiral-wound PRO membrane modules (8 inches) were assessed. The operating parameters of the pilot plants, such as pressure, temperature, and flow rates of the draw solution and the feed solution, were found to be important factors determining the plant energy consumption and operating efficiency. An economic analysis of a large-scale SWRO-PRO hybrid desalination is also described.