Desalination is a process by which salt water is converted to fresh water fit for drinking. The word is starting to enter mainstream vocabulary as desalination plants take root across the globe as a solution for shrinking supplies of water. However, it is not without controversy.
Desalination is an energy intensive process, and many people advocate that water efficiency measures, true cost pricing for water, and a smart water grid are all more intelligent solutions for minimizing our water waste. Desalination is often viewed as an extravagant band-aid solution for low water supplies.
Still, desalination is taking hold in places like Australia where severe drought has limited any other option in certain areas. And, for one tiny town on the coast of California, desalination became the only option to provide enough water for residents when the state clamped down on local groundwater pumping for drinking water.
The diminutive plant is barely noticeable, plunked at the end of a row of industrial offices. But it only needs to produce enough fresh water for a small town. Sand City has just 330 residents, though as many as 40,000 people visit each day to take advantage of shopping centers, hotels, and golf courses, and the town employs 4,000 people.
Despite the fact that Sand City has done all it can for water efficiency since the 1950s, from residents minimizing their consumption to using recycled water for the golf course irrigation, new requirements from the state of California that would cut the groundwater pumping limit by half meant that the city faced a tough choice - find a new source of water, or cease to exist. As a tourist and shopper destination, the town already feels the pinch of a down-turned economy, and according to City Engineer Richard Simonitch, if they didn't find a new source of fresh water, there would be no way to keep up the hotels and shopping centers that attract the visitors that keep the city afloat, and thus no way to spare the small seaside town from urban blight. A desalination plant was the only solution.
The planners did all they could to minimize the energy consumption and environmental impact of the plant. It produces just 300 acre feet of water, or around 600,000 gallons when running at full capacity. Residents only need about 94 acre feet, so the rest enters the water grid and benefits the surrounding cities. (In comparison, the Poseidon desalination plant proposed for Carlsbad, California aims to produce 56,000 acre feet - a scale at which the pros and cons of energy consumption start to weigh in much more heavily.)
Though the Sand City desalination plant chose not to run on renewable energy, it took measures to maximize energy efficiency, including using energy recovery devices from Energy Recovery Inc. which cut the energy required to run the plant by an impressive 60%.
According to Water & Waste Digest, "Permitting for seawater desalination facilities has been a complex process in California, delaying the implementation of nearly all of the currently planned facilities. The Sand City desalination facility is the first full-scale, municipal desalination plant in California to receive permitting under the new surface water treatment regulations."
While the plant solves the water problems for the city, the environmental impact was carefully considered in planning out how the plant would operate.
Another major drawback for desalination plants is the environmental impact of both pulling water from the ocean as well as the chemistry of the water dumped back into the sea, called brine. The plant pulls water from 200 feet inland and about 80 feet underground, where salt and fresh water mix. Called brackish water, the plant needs much less energy to purify it than it would if it pulled directly from the ocean. The brine it releases is the same salinity level as the water in Monterey and it is released at the same depth as where it is pulled, 200 feet inland and 80 feet deep, so the impact on the ecology is effectively zero.
We took a tour of the plant with City Engineer Richard Simonitch who walked us through how the plant operates as well as why this was the best, and only, option for Sand City.