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DesalData Weekly - May 5th, 2016

Posted 05 May, 2016 by Mandy

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The coastline along San Diego County North   Credit: JRo [3]

San Diego currently imports 57 percent of its water supply—compared to 95 percent a quarter of a century ago.[1]  As reported in the Wall Street Journal, San Diego transformed from being “one of the most vulnerable areas” during drought in California—to “one of the best prepared.”  Rather than transporting water hundreds of miles from Northern California and the Colorado River, the city now relies on treated water.  Although this has come at a great cost.  Water officials have managed more than $2 billion in investments, and users now pay more than twice the amount they used to pay ($1,365 per acre-foot in 2015 compared to $505 in 1990).[2] 

The $1 billion Carlsbad desalination plant was one of the new, and expensive sources of water for San Diego. Another source, which now provides 15 percent of San Diego’s water supply, are two irrigation canals that the water authority helped to line with material to prevent leaks.  Completed in 2010, the canals transport water from the Colorado River to agricultural areas in southeastern California.[4]  Water authority officials paid $400 million towards the cost of this project.  Between 2009 and 2014, San Diego also completed one of the world’s largest reservoir-expansion projects.  The San Vicente Dam’s depth was raised from 117 feet to 220 feet, increasing the capacity of the reservoir increased from 90,000 to 242,000 acre-feet at a cost of $400 million. 

 

Israeli scientists have been working on two recent studies that associate health risks to the consumption of treated and reclaimed water or desalinated water. 

One study, which is currently ongoing at Bar Ilan University and Tel Hashomer Hospital, connects the lack of magnesium in desalinated water to a higher death rate in cardiac patients.  Researchers based their findings on 4,700 cases in the Acute Coronary Syndrome Israeli Survey, a study conducted between 2002 and 2013 that gathered data about cardiac patients across Israeli hospitals.[5]  According to this survey, “the lower consumption of magnesium is liable to increase fatal heart disease”; and the study’s researchers hope that their work will bring public and political attention to this issue—ideally, to add magnesium and other essential minerals to desalinated water.

 

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However, these findings need to be looked into further and critically assessed by other university and water experts (they have not yet been published, so the information about the study is limited).  As reported in GWI’s Water Desalination Report, a 2011 World Health Organization report, “Safe Drinking-water from Desalination,” referred to a 2006 symposium that assessed the links between magnesium in hard water (i.e. high in calcium and magnesium) and heart health.[6]  The report concluded that “there does not appear to be an association between drinking-water magnesium and myocardial infarction (heart attacks), although the studies do show a negative association (i.e. protective effect) between CVD (acute myocardial infarction, stroke and hypertension) mortality and drinking-water magnesium.”  Dr Joe Cotruvo, a contributor to the WHO report and the chair of the symposium and meeting, told WDR that “there could be a link between low dietary magnesium and CVD mortality, but the question is much larger than desalinated water.”  An individual’s “total exposure” to magnesium is determined by their diet, of which water is one component is water. 

More broadly, there are several factors to consider when analysing this study—which has not yet been published: these factors include the “type/amount of daily water consumption, dietary patterns, age distribution, whether it was an observational ecological data survey or an analytical study, the specific types of CVD related deaths, the power of the study regarding the population sizes and numbers compared to comparison and background deaths, and whether it has been through peer review.”[7]

 

The other Israeli study was published in the journal Environmental Science and Technology, and was conducted by researchers at the Hebrew University of Jerusalem and the Hadassah Medical Centre.  The study concluded that “vegetables and fruits grown in soils irrigated with reclaimed wastewater exposes consumers to minute quantities of pharmaceuticals”—according to the Times of Israel.  The researchers found traces of carbamazepine—a common anti-epileptic medicine—in the urine of a test group of 34 men and women. 

At the first measurement, most of the participants had low or undetectable levels of carbamazepine in their systems.  However, after these individuals consumed “wastewater irrigated produce” for one week, the traces of the pharmaceutical were “markedly higher” than they were for the control group.  The study suggested that there may be other pharmaceuticals in recycled water that are problematic; and it concluded that more research needs to be conducted on filtration technology.

 

 

 

[1] Jim Carlton, “Cities Look for New Ways to Meet Demand for Water Supplies,” The Wall Street Journal, April 24, 2016, <http://www.wsj.com/articles/cities-look-for-new-ways-to-meet-demand-for-water-supplies-1461550181> accessed April 26, 2016.

[2] Ibid.

[3] “San Diego Coast,” July 23, 2013. Image available at: < http://www.wellhowdidigethere.com/san-diego-coast/> accessed April 27, 2016.

[4] Across the U.S., household leaks account for the loss of a trillion gallons of water—enough to supply more than 11 million homes. To address this issue, inspectors find and patch leaks, using corrosion-resistant valves on water lines.

[5] David Shamah, “Israeli Water Recycling, Desalination Tech Needs Work, Studies Show,” Times of Israel, April 28, 2016, <http://www.timesofisrael.com/israeli-water-recycling-desalination-tech-needs-work-studies-show/> accessed May 5, 2016.

[6] “Tossing the Baby Out with the Bathwater,” Water Desalination Report, Volume 52, Number 15, April 11, 2016, <https://www.desalination.com/articles/tossing-out-the-baby-with-the-bathwater>, p.1.

[7] Ibid., p. 2.

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