Abstract
Reverse osmosis (RO) technology requires high energy input in order to extract freshwater from seawater. Improvements in RO technology have led to seawater RO (SWRO) becoming the dominant form of large scale desalination around the world. However, the specific energy consumption (SEC) of SWRO remains substantially higher than that for surface water treatment and indirect potable recycling, making SWRO less cost effective than other alternatives for producing potable water. Furthermore, where non-renewable energy sources are used to supply SWRO energy demand, higher levels of greenhouse gas are emitted compared with lower energy alternatives. The purpose of this paper is to review the RO process configurations currently available and their impact on reducing SWRO energy consumption. This paper highlights the main factors contributing to SWRO energy consumption and presents some of the commonly adopted approaches to reducing SEC in SWRO plants. The use of energy recovery devices (ERDs) in SWRO is explored and the relative effectiveness of the various types of ERDs in reducing SEC presented.
Highlights
Population growth and urbanization of cities worldwide is placing ever-greater stress on existing water supplies
By 2016, there were 18,983 commercial-scale desalination plants supplying over 95 million m3 day−1 to cities worldwide [Global Water Intelligence (GWI), 2016], with desalination projects increasing in number and size by 5–6% internationally since 2010 (Voutchkov, 2018)
The energy needed for high pressure pumping makes seawater RO (SWRO) an expensive option for producing potable water when compared with common alternatives such as surface water treatment and indirect potable reuse (IPR)
Summary
Population growth and urbanization of cities worldwide is placing ever-greater stress on existing water supplies. ERD efficiency (change in feed pressure divided by change in concentrate pressure) for various ERDs has been found to be Turbine 75%, Turbocharger 80%, Pelton Wheel 85%, while isobaric chambers are around 95–97% (Kim et al, 2019; Urrea et al, 2019). The earliest ERDs used in SWRO plants were centrifugal-type devices such as the Francis Turbine, Pelton Wheel and Turbocharger (Urrea et al, 2019). These devices convert the hydraulic energy of the concentrate into mechanical energy to drive a piston or pump, which transfers hydraulic energy back into the feed.
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