Why Desalination is Not the Answer to the World’s Water Issues
Water is the foundation of life. Not only are our bodies made up of over 60% of water but we require clean, safe drinking water to survive as well as to grow our food and move our waste stream. While our population has exploded the amount of freshwater on the planet has stayed constant. Water use has grown more than twice the rate of population increase in the last century. Today nearly 700 million people worldwide suffer from water scarcity. And that number is expected to grow to 1.8 billion in just 10 years.
Water scarcity is a worldwide issue. California’s epic drought has shone a bright light on this alarming problem. The lack of rain in California has resulted in 80% of the state to be extreme or exceptional drought, forcing water restrictions in urban areas and cutoffs to some farmers. Historical observations point to this drought being among the worst ever. Levels of rainfall, snowpack, reservoirs, and streamflow are all at record lows.
If you are currently living in a drought stricken area, you have been experiencing first- hand the impact of a water shortage. For many of us we occasionally hear about it in the news but it hasn’t really affected our daily lives. Well that is all about to change. Water shortages are real and with climate changes are going to be more widespread and frequent. Water shortages will impact everything in our daily lives – from where we vacation to how we do our laundry.
As scientists and government agencies seek answers to this crisis, desalination has been touted as the solution. But desalination is not a silver bullet. It is exorbitantly expensive, requires large amounts of energy, it is environmentally damaging plus it is only really viable for coastal communities.
To put it simply, desalination removes salt and other minerals from water. Most desalination technology follows one of two methods thermal distillation and membrane filtration. Based on methods used for thousands of years, distillation involves boiling sea water to produce steam—purified water vapor. The steam is collected in a separate container and cooled so it will condense back into water.
The most common type of membrane separation is called reverse osmosis. It involves pushing the water through a series of microscopic sieves rolled up into larger cylindrical filters. The energy-intensive process separates pure water from both salt molecules and impurities.
All desalination methods produce a concentrated waste product composed of the salts found in seawater and chemicals used in the process. Disposal methods for the concentrate include dumping it back in the ocean, injecting it into deep underground wells, storing it in above-ground evaporation ponds, and zero-liquid discharge procedures that produce a solid waste product.
Seawater desalination is one of the most expensive sources of fresh water. The total costs of desalination, including the costs of planning, permitting, and concentrate management, are high, both in absolute terms and in comparison with the costs of other alternatives.
Because desalination requires a lot of energy the plants are also very expensive to maintain. Energy is reported to be the largest single expense for desalination plants, accounting for as much as half of the costs to make drinking water from the sea viable. According to a report from Pacific Institute, “Desalination plants on average use about 15,000 kilowatt- hours of power for every million gallons of fresh water that’s produced.” And these high energy requirements raise concerns about emissions.
There costs of desalination are not just monetary but environmental as well. Sea life can get sucked into desalination plants, killing small ocean creatures like baby fish and plankton, upsetting the food chain. Also, there is concern of what happens to the separated salt, which is left over as a very concentrated brine. Pumping this super salty water back into the ocean can harm local aquatic life. Reducing these impacts is possible, but it adds to the costs.
Excessive costs, energy consumption and the threat to fisheries and marine should make communities think twice about desalination as their solution.
Conservation and recycling programs are usually much less expensive and less risky alternatives to building desalination plants. Companies today are helping homes and business make more efficient use of their water. By using water-efficient product choices—with no sacrifice to quality or product performance we can help conserve our most precious natural resource.