A desalination system with efficiency approaching the theoretical limits

Philip A. Davies*, James Wayman, Chioma Alatta, Kim Nguyen, Jamel Orfi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The objective of this project is to design a new desalination system with energy efficiency approaching the theoretical thermodynamic limit—even at high recovery ratio. The system uses reverse osmosis (RO) and a batch principle of operation to overcome the problem of concentration factor which prevents continuous-flow RO systems from ever reaching this limit and thus achieving the minimum possible specific energy consumption, SEC. Batch operation comprises a cycle in three phases: pressurisation, purge, and refill. Energy recovery is inherent to the design. Unlike in closed-circuit desalination (CCD), no feedwater is added to the pressure circuit during the pressurisation phase. The batch configuration is compared to standard configurations such as continuous single-stage RO (with energy recovery) and CCD. Theoretical analysis has shown that the new system is able to use 33% less energy than CCD at a recovery ratio of 80%. A prototype has been constructed using readily available parts and tested with feedwater salinities and recovery ratios ranging from 2,000 to 5,000 ppm and 17.2–70.6%, respectively. Results compare very well against the standard configurations. For example, with feedwater containing 5,000 ppm NaCl and recovery ratio of 69%, a hydraulic SEC of 0.31 kWh/m3 was obtained—better than the minimum theoretically possible with a single-stage continuous flow system with energy recovery device.

Original languageEnglish
JournalDesalination and Water Treatment
VolumeLatest articles
Early online date9 May 2016
Publication statusPublished - 2016

Bibliographical note

This is an Accepted Manuscript of an article published by Taylor & Francis in Desalination and Water Treatment on 9/5/16, available online: http://www.tandfonline.com/10.1080/19443994.2016.1180482


  • batch desalination
  • brackish water
  • high efficiency
  • high recovery
  • RO
  • solar
  • sustainable development


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