[CAIRO] A controversial water project in Jordan that is due to begin operation this month has highlighted an issue of concern to many countries in the Middle East and North Africa.
Because of the region's lack of rain, the millions of cubic metres of water pumped daily from ancient aquifers are of crucial importance, but studies have revealed that some of the groundwater contains potentially hazardous radioactive elements.
Groundwater constitutes about 15 per cent of available water resources in the Arab world, but the overall average conceals big differences.
"Libya, Tunisia, and Saudi Arabia are 100 per cent dependent on groundwater reservoirs. Kuwait, Bahrain, Yemen and the United Arab Emirates are 90 per cent dependent, while Jordan and Egypt are 60 per cent and 20 per cent dependent respectively," Fatma Abd El-Rahman Attia, professor emeritus in the Egyptian National Water Research Center, tells SciDev.Net.
Aquifers are either renewable or non-renewable depending on whether they are still recharged by rainwater. Attia says that water in the non-renewable aquifers has been exposed far longer to the natural phenomenon of radioactivity caused by particles of elements in the sedimentary rocks.
"The level of contamination by these radioactive elements depends on many factors, such as the thickness of the layer of sedimentary rocks and the radioisotope concentration, which can differ from place to place, even in the same aquifer," she explains.
WHO guidelines on drinking-water quality note that such water may contain radioactive substances, or radionuclides, that could cause health risks, including bone cancer and leukaemia.
However, the guidelines point out that "these risks are normally small compared with the risks from micro-organisms and chemicals that may be present in drinking water. Except in extreme circumstances, the radiation dose resulting from the ingestion of radionuclides in drinking water is much lower than that received from other sources of radiation." 
“The water could be purified of the radioactive isotopes in many ways but it is not affordable for developing countries.”
Hamed Bakir, adviser on health and environment at the WHO's Eastern Mediterranean Office, emphasises that radioactivity guidance levels are conservative and not mandatory: "Exceeding a guidance level should be taken as a trigger for further investigation, but not necessarily as an indication that the drinking water is unsafe."
This is not a new debate, but it has been given fresh impetus by the Disi Water Conveyance Project, a US$1 billion scheme to pump up to 100 million cubic metres of water a year from 55 wells in the largest of Jordan's two non-renewable aquifers. A 325-kilometre pipeline will carry the water to the capital, Amman.
Demand for water in Jordan — which has one of the lowest levels of water resource availability per capita in the world, according to the WHO — increased six per cent last year and the Ministry of Water and Irrigation expects demand to increase further this year. The Disi aquifer, which lies 500 metres under the desert in southern Jordan and north-west Saudi Arabia, will help meet this demand.
The increase in demand caused by development is being further boosted by the flow of Syrian refugees to Jordan, according to Tawfiq Al Habashneh, the secretary-general of the Water Authority of Jordan.
The European Investment Bank has approved loans totalling US$225 million for the Disi scheme. Construction is by a subsidiary of the Turkish company GAMA Energy.
Work began in 2009 "and will be completed in July 2013", says Anwar Battikhi, president of the Jordan Society for Scientific Research and professor of soil physics at the University of Jordan.
Controversy erupted in 2009 when a study led by Avner Vengosh of Duke University in the United States found that the water the scheme would tap was highly radioactive. The study tested 37 existing wells in the aquifer and found that all but one had concentrations of radioactive radium isotopes that exceeded international standards for drinking water. 
Battikhi confirms that further tests last year in 55 wells found radioactivity levels of one millisievert (mSv) a year, compared with the WHO guidelines of 0.1mSv. But he says it is up to each country to set its own guidelines and look for appropriate solutions.
Similarly, Mohammad Najjar, a former minister of water and irrigation in Jordan, says that the WHO guidelines are "only guidance indicators and any country can adopt these indicators or adopt stronger or weaker indicators according to the data and expertise".
Australia, he says, puts the upper limit of human exposure to radiation at 1mSv a year, while Jordan has set the level at 0.5mSv.
Hamed Bakir says it is essential that the judgement of what is an acceptable level of risk takes costs and benefits into account. That is, water supplies of generally safe quality but with characteristics that are slightly different from the guidelines' minimum requirement should be weighed against the health cost of not having water supplies.
Another option is to treat the radioactivity — but this is costly. "The water could be purified of the radioactive isotopes in many ways but it is very expensive and so not affordable for developing countries," says Mohamed Gad, a hydrology professor at the Desert Research Center in Egypt.
One method is to force the water through a membrane that prevents the passage of radium, a process called reverse osmosis. Another option is ion-exchange purification, in which water is fed through columns of porous materials that capture the radium.
Nadia Sharara, professor of mineralogy at Assiut University, Egypt, says that purification is complex and costly "and the biggest challenge is how to get rid of the radioactive elements resulting from purification".
Battikhi says that Jordan's Ministry of Water and Irrigation plans to dilute the Disi aquifer water with non-radioactive contaminated water from other sources. But the difficulty of obtaining enough water to do so has forced the authorities to reduce their planned extraction rate from 100 million cubic metres a year to about 70 million cubic metres.
Nevertheless, the water authority's Tawfiq Al Habashneh is confident that the country's water situation will improve significantly when Disi starts pumping
This article has been produced by SciDev.Net's Middle East & North Africa desk.