In the United States, 400 billion gallons of water are used per day.1 Taking a published estimate of 14 kilowatt hours of energy to desalinate 1,000 gallons of water leaves us with 5,600,000,000 kilowatt hours per day if we wanted to replace all 400 billion gallons of water with desalinated water. Current yearly electricity use in the United States is 3,741 billion kWh per year, or 10.2 billion kWh per day.2 This means that desalinating all water would leave us with an increase in electricity consumption of about 50%.
This isn’t to suggest that energy demands will make desalination unfeasible. Rather, it’s a demonstration of the Red queen effect, as the use of resources that take a long period to regenerate requires us to substitute with increasingly large amounts of other resources, often energy. These estimates depend on initial variables as well. Brackish water takes less energy to desalinate than seawater, but the problem with brackish water is that the effect of the desalination plant on the local ecosystem would likely be even larger.
More worrisome to look at are the effects that desalinated water has on human health. Desalination is a process that removes salt from the water, but it removes other benevolent minerals as well, while some harmful minerals prove difficult to remove from the water.
Israel’s government begrudgingly accepted adding Magnesium to the drinking water, as although necessary for healthy water, artificially adding magnesium back to the water is quite costly as well. It increases the cost of water by an estimated 20 dollar cents per cubic meter of water.3 This represents a significant increase over the 49 cent per cubic meter that water desalination costs in Singapore.4 This is important to remember when it comes to hyped up desalination projects. Does the low cost used to market the project as feasible come at the cost of quality of water?
To produce high quality water, calcium would have to be added back into the water as well, but as far as I’m aware, this is not done so far anywhere. Different proposals for this include mixing back a small amount of untreated salt water with desalinated water and treating the water with lime. The prior solution has a number of problems, including an increase in the water’s concentration of boron, the latter solution is believed to be carbon intensive.
For now, the effect that the lack of calcium added back to the Israeli water supply has is a significant increase in the number of people whose calcium intake falls below the desired intake for optimal health, with rates of deficient calcium intake seen at 62% in those who only have access to desalinated water.5
We can not expect the problem to be adequately addressed by dietary supplements, because water low in calcium has a variety of undesirable effects. Food begins to leach nutrients into water when cooked in water that’s low in calcium. It’s also believe that calcium in water has a protective effect against metals also present in the water. Furthermore, water low in calcium causes metals to leach from material in contact with the water.6 All these factors are believed to play a role in the observation of worse health outcomes in populations exposed to water low in calcium.
In agriculture, a variety of problematic effects are seen as a result of the use of desalinated water as well. High boron concentrations in water are believed to be damaging to the health of humans as well as plants. Current very energy intensive techniques allow us to reduce boron to 0.8 mg per liter.7 The ideal concentration of boron for human health would probably be less than 0.1 mg per liter of drinking water however.8 A median published estimate for boron in river water is 0.0063 mg per liter.9
In other words, if we do our best, desalinated water is going to expose plants and humans to two orders of magnitude more boron than river water would. The impact this interesting experiment has on agriculture remains to be seen. Studies have found that there is a relatively small range between levels of soil boron causing deficiency and toxicity symptoms in plants.10 Israel has so far found that desalinated water is proving to be harmful for its crops.11
1 – http://www.livescience.com/4510-desalination-work.html
2 – http://www.indexmundi.com/g/g.aspx?c=us&v=81
3 – http://www.haaretz.com/news/national/health-ministry-failure-to-add-magnesium-to-tap-water-could-kill-up-to-250-israelis-a-year-1.420686
4 – http://www.edie.net/news/3/Black–Veatch-Designed-Desalination-Plant-Wins-Global-Water-Distinction/11402/
5 – http://www.ncbi.nlm.nih.gov/pubmed/23781750
6 – http://www.who.int/water_sanitation_health/dwq/nutrientschap12.pdf
7 – http://www.tandfonline.com/doi/abs/10.5004/dwt.2011.2334?journalCode=tdwt20#.VSPho_msWSo
8 – http://www.theage.com.au/it-pro/warning-the-desalination-plant-may-be-bad-for-your-health-20111016-1lrg9.html
9 – http://ceqg-rcqe.ccme.ca/download/en/324
10 – http://link.springer.com/chapter/10.1007%2F978-1-4612-5046-3_7#page-1
11 – http://www.haaretz.com/print-edition/news/desalinated-water-can-harm-crops-researchers-warn-1.232848