March 19, 2012
The pursuit of freshwater is quickly becoming a concern comparable to oil shortages. The average American uses more than 300 liters of water a day, but of all the water that exists on earth, we can only use easily accessible freshwater. That’s .3% of the earth’s water, and that isn’t a lot to work with. By 2030, exponential population growth and accompanying industrial and agriculture needs are predicted to outstrip water supply by 40%.
California, with a population of 37,690,000 is poised to have some of the worst water supply issues, particularly because most of the population is concentrated in the driest portions of the state. However, the state’s saving grace might be the very thing that induced much of its initial population growth, its 840 miles of coastline. Because of advancements in desalination technology, Californians can now utilize our access to ocean water to produce freshwater.
Desalination is not a new concept. Two methods to desalinize water are distillation and the more popular reverse osmosis. Reverse osmosis is a riff on the principle of osmosis, which states that water naturally moves from low to high concentrations of solutes through a membrane. Reverse osmosis utilizes external pressure to reverse the flow of osmosis, so that water moves from high to low solute concentration. External pressure comes in the form of cylindrical rotors that spin 1,200 times per minute to reduce solute concentration. The Sand City Desalination Plant, for example uses this reverse osmosis system and achieves 99% reduction of solutes. The water is then disinfected by ultraviolet light and chlorination, achieving 99.99% elimination of potentially harmful bacteria and viruses.
Due to these new technologies, the environmental concerns associated with desalination are low, especially compared to the costs of current water acquisition methods. The main way that Southern California currently attains water is through water diversion, reallocating water from lakes and rivers and diverting them into aqueducts. These often depletes lakes and rivers, negatively altering important ecosystems and potentially destroying them, as in the case of Owens Valley. The sea life that desalination plants may affect due to impingement and entrainment of animals would likely be no more seriously damaged than the organisms disrupted by extensively damming and diverting bodies of water like the Colorado River. Damming and diverting are severely detrimental to local ecosystems, harming plant and animal species diversity.
Other causes for concern for water desalinization plants are the energy usage and brine residue left after the distillation process. Environmentalists claim that brine residue can be harmful to sea life by making waters too saline for native species to survive in, but it is possible to mitigate damage. In Sand City’s desalination plant, brine solution is effectually pumped into the naturally high saline Monterey Bay. In regards to high-energy usage, desalinization plants have added energy recovery devices to increase output and decrease energy consumption by using pressure exchangers. The PX Pressure Exchanger used in Sand City recovers up to 98 percent of the energy from the stream of concentrate and uses opposing forces of fresh sea and salt-heavy waters to power a rotor that moves water around and out of the system.
These environmental concerns are not to be dismissed, but to be taken into account when considering improvements to current desalination technology. Nonetheless, the prospect of providing “drought-free” fresh water to humans outweighs the environmental costs. Desalination produces a reliable and locally available source of water, especially useful in places that experience drought regularly, just like Southern California. With looming water shortages the daily 50 million gallons produced by the potential Huntington Beach plant is a not something that Californians can afford to pass up.
Sarah Beshir and Ashley Lukashevsky are undergraduates in the USC Dana and David Dornsife College of Letters, Arts and Sciences.