Containerized Desalination: A Freshwater Solution for the United States
Usable water is a rapidly-diminishing resource in the United States. Conservation aside, containerized industrial desalination systems present an ideal method for producing reliable, clean water.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.
Energy Consumption
picture 6 Desalination
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.
Containerized reverse osmosis desalination system.
Desalination plants (particularly RO facilities) struggle with many of the same problems that exist with traditional water production plants: These facilities are expensive to plan, complicated to build and unable to address dramatic changes in the product environment -- problems that must continually be addressed when a water plant is built in the U.S. However, recent developments in technology have resulted in the containerized desalination system, an RO plant built out of a 20- or 40-foot storage container. This system not only addresses the environmental challenges associated with large-scale desalination but also the logistical problems associated with building a plant.
picture 7 Containerized desalination
Laying the foundation of a plant is complicated and costly. Oceanfront property in California, for example, is extremely expensive. Compared to a traditional desalination plant, a containerized system has a dramatically reduced footprint, requiring only a concrete foundation for the container. Containerized systems are also modular and therefore easy to set up in a series if additional capacity is required.
A containerized desalination system, comprising an energy-recovery system and all the necessary contained pretreatment, can produce a half-million gallons of water per day. While traditional desalination plants in the U.S. produce tens of millions of gallons of water per day, space for these large facilities is at a premium. Storage containers, by contrast, can fit almost anywhere.
To put it into perspective, if there was one containerized desalination plant for every 10 miles of California's 840-mile coastline, they would produce 42 million gallons of water per day -- enough to provide a drought-proof water supply for 47,000 people annually.
Adaptability
The quality of source water can change dramatically in a short amount of time. Spills, algae blooms, marine migrations, and other events can halt water production for an extended period. A containerized desalination system, however, can be moved to a new location and begin processing water again in less than a day, giving the area time to recuperate. These portable systems are also ideal for disaster relief, directing the water where it is needed as soon as possible. In summary, a containerized system can be as temporary or as permanent as its owner needs.
Customizability
For a dependable, predictable source of water that's independent of rainfall and doesn't impact available freshwater sources, containerized desalination systems offer a modular approach that could very well revolutionize the way we purify water.