Containerized Desalination: A Freshwater Solution for the United States

By Kevin Lindmark

Usable water is a rapidly- diminishing resource in the United States. In states like Florida, Texas and California where freshwater is scarce to begin with, communities are being compelled to consider alternative sources of potable water. Conservation aside, containerized industrial desalination systems present an ideal method for producing reliable, clean water.

Critics of desalination are not necessarily wrong when they refer to it as a "last resort" -- when not handled responsibly, desalination presents a number of issues that need to be addressed.

Energy Consumption

There is no corner-cutting when it comes to energy consumption: desalination is the least cost-effective solution when it comes to providing freshwater, especially in an industrial setting. Depending on the type of desalination, the cost can grow to extremely high levels by comparison, sometimes even 100 times more expensive in electrical energy alone. In this regard, reverse osmosis (RO) desalination is ideal at only 15 times more expensive than groundwater treatment. To put this in a practical perspective, if the U.S. received all of its freshwater from RO desalination, it would mean an energy increase of 10 percent -- roughly equivalent to an additional refrigerator in each household (as stated by an article released by the AMTA in 2009).

Also, large-scale RO desalination systems can use energy-recovery systems to reduce the amount of horsepower needed for their pumps, reducing energy requirements by more than half in ideal situations. The increase in energy consumption still bears a hefty price tag, but taken into consideration with energy-recovery systems in place, an industrial RO desalination system is less expensive than pumping clean water over state lines. With very few rainfall-independent sources of water to choose from, desalination may be more expensive, but a consistently reliable water source is provided in return. Without a dependency on rain, industrial desalination makes drought a non-issue.

Wastewater Disposal

Compared to other desalination systems, RO desalination offers many benefits. The difficulty, however, comes with the disposal of wastewater. For every gallon of freshwater produced by RO, an equivalent amount of brine waste is discharged. This waste is essentially a sludge of salt and minerals, and dumping it into the ocean would not only be hazardous to local seawater habitats but also illegal in the U.S.

However, like most industrial processes, RO desalination produces a waste product that can be disposed of responsibly with minimal impact on the environment, and there are naturally-occurring locations where this is possible, such as where a freshwater source meets a saltwater source. Dumping extra-salty water in a region where salt water and freshwater are already mixing lessens its impact on the environment. Likewise, releasing brine waste over a large area of the seafloor (via a network of pipes, for example) also minimizes its impact on the environment. If neither of these is an option, brine waste can be naturally evaporated into commercial salt -- a common practice for existing desalination plants

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Taxonomy

• Technical Equipment
• Desalination