Enhancement of brackish water desalination using hybrid membrane distillation and reverse osmosis systems

PLoS One. 2018 Oct 9;13(10):e0205012. doi: 10.1371/journal.pone.0205012. eCollection 2018.

Abstract

Desalination of geothermal brackish water by membrane distillation (MD) provides a low recovery rate, but integrating MD with reverse osmosis (RO) can maximize the production rate. In this study, different design configurations of a hybrid system involving brine recycling and cascading are studied via simulations, and the performance improvement due to the process integration is substantiated via the increased recovery rate and reduced specific energy consumption. Brine recycling is also found to improve the recovery rate considerably to 40% at an energy cost of 0.9 $/m3. However, this achievement is only valid when the final brine is recycled to the RO feed: when the final brine is recycled to the MD feed, the overall performance degrades because the recycled brine cools the feed and causes a serious reduction in the driving force and the consequent production rate. Configuring the hybrid system in multiple stages connected in series increases the recovery rate to 90% and reduces the specific energy consumption to 0.9 MJ/kg. Although the specific energy cost increases dramatically because external inter-stage heating is implemented, using a free energy source (such as a geothermal or waste-energy source) for inter-stage heating could provide the optimum configuration.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Membranes, Artificial
  • Osmolar Concentration
  • Saline Waters / chemistry*
  • Water Purification / methods*

Substances

  • Membranes, Artificial

Grants and funding

The research is funded by the deanship of scientific research at King Saud University through the research group program number 1438-93. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.