Released on 31 January, the review compares the effectiveness and costs of technologies tested in laboratories or through field trials to remove arsenic in groundwater — a health threat to at least 140 million people in 50 countries, according to the World Health Organisation.
The report says any arsenic removal technology must bring drinking water up to the WHO standard, which limits maximum arsenic concentration per litre of water to 10 micrograms.
Technologies that were developed most recently, in 2017, and passed the WHO standard came from the United States (using a ZeroWater® water pitcher filter) and India (using aluminum electrode).
Of the 14 removal technologies that were tested in the field, efficiency levels ranged from 60 to 99 per cent, with only five achieving the WHO standard.
Four of these technologies were developed in India: using an electro-chemical arsenic remediation (ECAR) reactor; activated laterite; a combination of sodium bicarbonate, potassium manganite and ferrous chloride; and one that uses ferric hydroxide as arsenic absorbent.
The fifth technology that achieved the WHO standard came from China, using iron minerals and limestone.. Arsenic contamination areas.
Photo credit: Wikimedia Commons.
For field-tested technologies, the cost of treating one cubic metre of water ranged from almost zero to about US$70.
Apart from cost limitations, some of the lab-tested technologies were shown to have harmful impacts such as producing sludge, or to require more research.
Soumya Balasubramanya, a senior researcher at the Sri Lanka-based International Water Management Institute – CGIAR, tells SciDev.Net that the recommendations outlined in the UNU report are important for policy-making in developing countries battling the arsenic crisis.