Source substitution and treatment can help tackle naturally occurring arsenic.
By Arslan Ahmad and Prosun Bhattacharya*
Of all the ways to die, one most lends itself to murderous intent. Arsenic is a highly toxic chemical that has no taste, colour or smell. A victim’s symptoms from a single effective dose will resemble food poisoning: abdominal cramping, diarrheoa, vomiting, followed by death from shock. There’s no simple or easy cure. From the Roman Empire through to the Victorian Age, such a fatal combination made arsenic the perfect killing agent.
Now the so-called king of poisons is threatening public health on an unprecedented scale. While there may be no individual culprit, 130 million people around the world are suffering from exposure to naturally occurring high concentrations of arsenic in drinking water.
Many have no clue they are even at risk, especially if they rely on private wells and don’t go beyond microbial testing. Water professionals must improve on this tragic trend.
Consider the scope of the challenge. “High concentrations” is itself a subjective and highly contested term. Since 1993 the World Health Organization has set a provisional ‘unsafe’ threshold at 10 microgrammes per litre (10 ug/L, or 10 parts per billion). Yet multiple studies in the last quarter century have shown adverse health effects building at much lower levels. In a significant development with implications for health officials and responses worldwide, the Netherlands recently agreed to target concentrations at or above 1 ug/L.
Geographic scale matters. Regions with high arsenic issues range from Chile and the western US to pockets of southern Africa and the UK. But no region has a more severe naturally poisoning hotspot than Bangladesh, where arsenic afflicts 20 million and kills 43,000 people each year.
Arsenic is naturally present in the Earth’s crust. It gets released into groundwater both by natural and anthropogenic processes. While no “silver bullet” can remove it, two pragmatic approaches can mitigate the suffering from arsenic: substitute a new source where you can, and treat the old source if you must.
First let’s look at substitution. The handling and disposal of residuals may introduce additional complications, which make treatment often prohibitively expensive. That’s another reason to simply replace an existing unsafe source with a safe alternative: groundwater, rainwater or surface water, as technical, economic and social factors allow.
In Bangladesh, the fastest and most promising solutions enable poor rural communities to target and secure arsenic-safe aquifers by themselves. Indeed, local drillers have a vital role to play. They are the main driving force in tube-well installation, and if they can target safe aquifers, what else does one need?
Through the Sustainable Arsenic Mitigation (SASMIT) project, we have developed a tool that links the colour and textural attributes and the geochemical characteristics of the targeted aquifer sediments to the groundwater pH, redox and a series of water quality parameters. Since prevention is the best treatment, abstraction of water from deep aquifers in Bangladesh must not be blindly adopted. In fact, groundwater overuse can push arsenic deeper, making the problem worse, and rendering future costs high in terms of health and water-purification.
Treatment is a backup option. Remediation requires specialised expertise, a good understanding of arsenic’s complex aqueous chemistry, and funds for the more expensive tools and methods. Arsenic removal techniques can be broadly grouped into: precipitation, absorption and ion exchange, membranes, oxidation and bioremediation.
How do you decide which technique is the most appropriate? Carefully pre-evaluate water quality characteristics, target finished water arsenic concentration, and consider ease of implementation. To optimise treatment variables and avoid the wrong technology, conduct a pilot for potential mitigation processes.
Socio-economic realities shape the strategy for arsenic remediation. It is hard to apply advanced arsenic treatment tools in rural settings, given the de-centralised nature of the populations. But the basic principles of many conventional water treatment technologies can be shared, reduced in scale and conveniently applied at community and household levels.
*￼Arslan Ahmad is a water systems and technology researcher at KWR Watercycle Research Institute in The Netherlands; Prosun Bhattacharya is a professor of groundwater chemistry at KTH Royal Institute of Technology, Sweden. They are respectively vice-chair and chair of the IWA Specialist Group, Metals and Related Substances in Drinking Water
He was born in Samsun in 1958. He was graduated from İstanbul Technical University Civil Engineering Faculty in 1981. After completing his military service in 1983 he began to work in State Hydraulic Works Technical Research and Quality Control Department. While working here he participated graduate professional education and investigation programs in Holland and USA Bureu of Reclamation and US Army Corps of Engineers.
In 1998 he participated first “EU Master Education” program and later “International Affairs Proficiency” program in Ankara University European Union Research and Application Center. In 2000 he completed his MS thesis in the topic of water politics in Hacettepe University Hydropolitics and Strategy Research Center. He worked for five years as the section head and for following 10 years as department deputy head in State Hydraulic Works Technical Research and Quality Control Department. During this period he published more than 100 technical and scientific reports and papers. Then he worked as the department deputy head in State Hydraulic Works Domestic Water Supply Department and worked at the Planning and Investigation Department of the same institution and retired in 2007.
Dursun YILDIZ while working in State Hydraulic Works he lectured in the topics of water works in Gazi University Engineering and Architectural Faculty, Civil Engineering Department and water resources and hydropolitics in Hacettepe University, Hydropolitics and Strategy Research Center.
Dursun YILDIZ worked also as a executive committee member , Vice President in Turkish Chamber of Civil Engineers and Vice President of the Union of Chambers of Turkish Engineers and Architects . He worked in execution committee of “Water Politics Congress” held by the Civil Engineers Chamber in several times.
Dursun YILDIZ, experienced in water management, water development ,hydraulic research and consultancy for 30 years, wrote 15 books (Water Report,Water Problems in the Mediterranean Basin and Turkey,Strategical İmportance and Water Related İssues in Eastern Meditterranean Water Security 2050, etc.) and besides published several papers and technical reports in the topics of water engineering,water development,hydraulic research and hydro-politics in national and international periodicals.
He has awarded Successful Water Resarcher Prize of Year of 2008 by Agriculturers Associations of Türkiye .He was also awarded continuously success on water research prize of 2016 by Central Union of Irrigation Cooperatives of Turkey.
He is a member of Scientific Committee of Turkish Foundation for Combating Soil Erosion (TEMA). He is now the director of an NGO called Hydropolitics Association, and runs a company, Ada Hydro-Energy, Strategy & Engineering Consultancy Co.
He is head of Ada Hydro-Energy , Strategy & Engineering Consultancy Co. Since 2007.He is president of Hydropolitics Association.