Seventy-one percent of the Earth’s surface is water. The question many have is why then do we have a global water crisis? The answer is that 2.5%-3% of all water is freshwater; the balance is saltwater and brackish (salt-laden) water. Why hasn’t the world focused on desalination if all around us is water?
Two simple reasons: 1)Desalination uses vast amounts of energy, which is expensive; and 2) disposal of the byproduct, brine. All that is on the cusp of changing.
Traditional desalination is by either a thermal process (heating water to steam and then distillation) or membrane filtration. Heating water to steam requires substantial energy. Forcing water by pumps through membranes also requires significant energy. Generally, it takes 6-7 kilowatts to desalinate one cubic meter (264.17 gallons). Energy costs these days have seldom been higher; the cost of electricity has risen 13-18% a year in just the past eighteen months.
The second impediment has been disposal of the byproduct, brine. The residue contains sodium chloride (salt), magnesium, calcium, potassium, and even trace elements of lithium. The obvious answer is so what? Why not just put it back in the sea, from whence it came? The answer is that unless it is effectively dispersed, concentrated brine results in lower ocean oxygen leading to dead zones. It can be effectively disbursed to avoid this, but, that costs money (and more energy).
For some, the only option has been desalination. Islands without abundant freshwater sources for example. The Middle East accounts for 42% of all freshwater desalination: 99% for Qatar, 90% for Kuwait and Bahrain, 86% for Oman, and 70% for Saudi Arabia. The Middle East has always had abundant energy and has never been a model of environmental consciousness. But, what about places that have stringent environmental controls on energy use and residue disposal? California has pivoted to innovative offshore technologies, inland brackish plants, and has a number of coastal traditional plants. Texas is another state that has a significant number of inland brackish water plants and has coastal plants on the horizon.
Still, the percentage of freshwater from desalination in the US is minimal, less than four percent. Recent technological advances may change that. Energy costs and environmental impacts stand to be slashed by the new technologies.
China’s Beijing based Institute of Process Engineering at China’s Academy of Science at Shenzhen University is pioneering a new medium consisting of ultra-black nanomaterials embedded with organic polymers that absorb up to 90.2% of incoming sunlight to evaporate water with 47.5% less energy. The promise is of drinking water at lower cost than bottled water.
The University of Rochester is working on a new technology to make freshwater without brine by separating salts and other minerals as solids and even collecting rare lithium in the process.
California based OceanWell has launched a unique offshore desalination technology that mirrors the way traditional land based well fields collect water. By using the natural pressures of water at depth (for those of you who scuba dive, recall Boyles law: At sea level, one atmosphere of pressure surrounds you; for each ten meters of depth, an additional atmosphere is gained). Water under pressure tries to get into a series of pods that have membranes at openings that allow only freshwater to enter, filtering out all salts and minerals in a marine friendly way. It is deceptively simple: Natural pressure is traded for the traditionally energy intensive means of pumping water through a membrane. The result would be a 42% reduction in energy demand and desalination without brine disposal. A pilot Well Farm has been launched 4.5 miles off Malibu.
So, when you doom scroll through the negative news, know that it’s the loudest and dumbest that garners the media attention. There are some innovative folks out there quietly solving the big problems.