Arsenic contamination of groundwater
It is a high-profile problem due to the use of deep tube wells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people.
Gold processing releases arsenic from mine tailings, and contaminated groundwater may be unsafe to drink for decades.
The wells consist of tubes 5 cm in diameter inserted less than 200 m into the ground and capped with an iron or steel hand pump.
[9] This lack of precaution led to one of the largest mass poisoning of a population because the ground water used for drinking was contaminated with arsenic.
Since the 1970s, non-governmental organisations in India have focused on sinking tube wells to provide drinking water uncontaminated by diseases, with the unforeseen side effect of exposing some people to arsenic-contaminated groundwater.
The problem is most severe in the Terai region, the worst being near Nawalparasi District, where 26 percent of shallow wells failed to meet WHO standard of 10 ppb.
[22] A drinking water standard of 0.05 mg/L (equal to 50 parts per billion, or ppb) arsenic was originally established in the United States by the Public Health Service in 1942.
[25] A 2017 Lancet Public Health study found that this rule change led to fewer cancer deaths.
[32] A study conducted in a contiguous six-county area of southeastern Michigan investigated the relationship between moderate arsenic levels and 23 disease outcomes.
[33] Various studies have also shown that arsenic exposure during pregnancy can result in infant death, cancer, heart attacks, kidney failure, lung complications, as well as reduced intelligence, memory, and cognitive development in the child.
In practice, many water treatment strategies tend to be temporary fixes to a larger problem, often prolonging the social issues while treating the scientific ones.
[38] It is claimed that thousands of these systems are in use and can last for years while avoiding the toxic waste disposal problem inherent to conventional arsenic removal plants.
Although novel, this filter has not been certified by any sanitary standards such as NSF, ANSI, WQA and does not avoid toxic waste disposal similar to any other iron removal process.
The most common types of domestic treatment use the technologies of adsorption (using media such as Bayoxide E33, GFH, activated alumina or titanium dioxide)[39] or reverse osmosis.
Current density, the amount of charge delivered per liter of water, of the process is often manipulated in order to achieve maximum arsenic depletion.
Activated alumina columns connected to shallow tube wells in India and Bangladesh have removed both As(III) and As(V) from groundwater for decades.
Traditional anion exchange resins are effective in removing As(V), but not As(III), or arsenic trioxide, which doesn't have a net charge.
Effective long-term ion exchange removal of arsenic requires a trained operator to maintain the column.
No chemicals are used and almost no sludge is produced during operational stage since iron and arsenic compounds are rendered inactive in the aquifer itself.
Six such SAR plants, funded by the World Bank and constructed by Ramakrishna Vivekananda Mission, Barrackpore & Queen's University Belfast, UK are operating in West Bengal.
The first community water treatment plant based on SAR technology was set up at Kashimpore near Kolkata in 2004 by a team of European and Indian engineers led by Bhaskar Sen Gupta of Queen's University Belfast for TiPOT.
The SAR Project was selected by the Blacksmith Institute – New York & Green Cross- Switzerland as one of the "12 Cases of Cleanup & Success" in the World's Worst Polluted Places Report 2009.
Using nanomaterials, it is possible to effectively destroy microorganisms, adsorb arsenic and fluoride, remove heavy metals and degrade pesticides usually found in water.
A product called AMRIT, meaning elixir in Indian languages, developed by the Indian Institute of Technology Madras, is an affordable water purification technology based on advanced materials, which has been validated through research articles[52][53] and patents[54] and has been approved for national implementation in India.
[55] In 2008, the Swiss Aquatic Research Institute, Eawag, presented a new method by which hazard maps could be produced for geogenic toxic substances in groundwater.
This offers specialists worldwide the possibility of uploading their own measurement data, visually displaying them and producing risk maps for areas of their choice.
