Water Desalination Methods
suggests that nearly 98 percent of all the water on earth is salty. Through
desalination, the process used to remove salt from water, over 16 billion
gallons of desalinated water are produced daily, primarily for drinking. There
are several methods by which this can be accomplished, but unfortunately,
they’re all quite expensive.
methods used to filter large quantities of water produce byproducts that are
considered hazardous. One such byproduct is concentrated brine, which is
harmful to both animals and fresh water. Large-scale desalinization methods
- Carbon Nanotube Enhanced Membrane Distillation (CNT)
- Vapor Pressure
- Forward Osmosis
- Reverse Osmosis
- Solar Desalination
a closer look at the water desalination techniques mentioned:
Carbon Nanotube Enhanced Membrane Distillation (CNT)
nanotubes are revolutionary new materials that aid in the preparation of new
membranes with highly selective, low-fouling properties. In layman’s terms,
carbon nanotubes exhibit ultra-high salt absorption capacity. Long carbon
nanotube membranes can remove salt and any other metal or organic contaminants.
Studies reveal that this method of desalination may lead to the next generation
of water purification appliances and researchers are working hard to perfect
the entire process.
this process, pressure is inserted into the thermodynamic equilibrium by vapor
in its condensed state. The vapor is then subjected to pressure either in a
liquid or a solid state at specific temperatures within a closed system. The
liquid’s evaporation rate is indicated by the equilibrium’s vapor pressure.
an incremental increase in temperature, vapor pressure is forced to overcome
atmospheric pressure, at which point the liquid turns to vapor. The formation
of vapor bubbles requires an even higher temperature, allowing pure water to
escape the salt in vapor form. These vapor bubbles are then collected to form
osmosis is a process that utilizes a semi-permeable membrane to separate water
efficiently from dissolved solutes. An osmotic pressure gradient is the chief
element that makes this process work.
osmotic pressure gradient induces a net flow of water via the membrane and into
the draw solution. The process effectively separates feed water from solutes.
opposed to forward osmosis, reverse osmosis utilizes hydraulic pressure as the
element to aid in the separation process. The hydraulic pressure actually
counteracts the osmotic pressure gradient. As a result, the entire purification
process uses more energy than forward osmosis.
desalination is a method that utilizes the sun’s energy to remove salt from
water. The two primary methods used in solar desalination are the direct method
and the indirect method.
solar desalination involves a solar collector joined to a distilling mechanism.
The entire process takes place in a single cycle. The water produced by this
method is proportional to the solar surface area.
solar desalination employs either a solar collection array or a separate
conventional desalination plant. A solar collection array typically consists of
fluid-based thermal collectors or photovoltaic collectors. If a separate plant
is used, the separation of water and solutes is heavily dependent on the
plant’s efficiency. The per-unit cost of the process goes down as the scale of
the operation increases.
processes listed above are methods currently available for large-scale water
desalination. Although their high cost and hazardous byproducts are serious
concerns, the earth’s growing population and changing needs have created water
shortages that need to be addressed. It’s also likely that solutions to these
and other problems will be uncovered by further research, at some point.