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Desalination with ECLIPSE MEMBRANES™

ECLIPSE : Contacting and Separation : Degassing and Debubbling

The Problem

Desalination is a form of membrane distillation where clean, mineral and pollutant-free water is extracted from salt water, brackish water, or water that is otherwise contaminated with solids, minerals or high boiling organic compounds.

 

Why then treat desalination as a section of its own? Simply put, the importance of the topic and opportunity with membrane desalination to contribute to the solution of some significant issues that will become increasingly important in the years to come.

 

Approximately 97.3% of the world’s water supply is in the form of salt water or polar ice caps. Of the remaining 2.7% much of it is undrinkable in its present form or inaccessible to those who need it.

 

Evans and Miller1 report that over half the world’s population is impacted by water shortages. Roughly 80 – 90% of all diseases and 30% of all deaths result from poor water quality. To compound matters, the total number of people in the world impacted by water shortages is expected to increase fourfold over the next 25 years.

 

The number of research publications on the topic have become so large that journals dedicated to the subject of desalination have cropped up in recent years.

 

1. Evans, Lindsey R., and James E. Miller, "Sweeping Gas Membrane Desalination using Commercial Hydrophobic Hollow Fiber Membranes," Sandia National Laboratories, January 2002.

The Opportunity

To generate potable water from salt water or waste water requires an energy driving force, which may either be pressure or thermal energy. Micro-, ultra-, and nano-filtration have all been used to clean water of impurities. The ultimate pressure-driven membrane process, Reverse Osmosis, has been employed for many years removing salts and other contaminants from water.

 

Thermally driven processes all involve heating the feed stream, allowing water to pass to a separate region as a vapor, and condensation of the clean water. Conventional multi-stage flash distillation, evaporative processes and membrane distillation all fall into this category.

 

The advantages of membrane distillation over more conventional thermal means are:

• No potential contact between the feed steam and the distillate, ensuring no carry-over of minerals, etc.

• Ability to employ lower energy levels, waste energy, solar energy, etc. for membrane desalination

• Smaller footprints and easier operation

 

While a full discussion of the advantages of membrane desalination are not practical here, it is important to note that the requirements for good membrane distillation systems outlined in the discussion on membrane distillation are true for membrane desalination as well.

 

Membrane desalination requires a hydrophobic, porous membrane, a module capable of withstanding harsh cleaning systems, elevated temperatures and most importantly a system that can provide the design flexibility to accommodate the variety of conditions in which one might employ membrane desalination.

 

The Markel porous PTFE hollow fiber and fluoropolymer potting system is such a system. Operable at temperatures in excess of 150°C, the extremely strong and chemical resistant fiber-potting system will handle the most severe conditions with ease.

More Information about Porous PTFE Membranes for Desalination

 

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