Posted by: drazizul | November 21, 2009

Lecture 5: Arsenic contamination of groundwater

Arsenic contamination of groundwater is a natural occurring high concentration of arsenic in deeper levels of groundwater, which became a high-profile problem in recent years due to the use of deep tubewells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people. A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning of drinking water.[1] Arsenic contamination of ground water is found in many countries throughout the world, including the USA. [2]
Approximately 20 incidents of groundwater arsenic contamination have been reported from all over the world. [3] Of these, four major incidents were in Asia, including locations in Thailand, Taiwan, and Mainland China.[4][5] South American countries like Argentina and Chile have also been affected. There are also many locations in the United States where the groundwater contains arsenic concentrations in excess of the Environmental Protection Agency standard of 10 parts per billion adopted in 2001. According to a recent film funded by the US Superfund, “In Small Doses”. http://www.dartmouth.edu/~toxmetal/InSmallDoses/., millions of private wells have unknown arsenic levels, and in some areas of the US, over 20% of wells may contain levels that are not safe.
Arsenic is a carcinogen which causes many cancers including skin, lung, and bladder as well as cardiovascular disease.
Some research concludes that even at the lower concentrations, there is still a risk of arsenic contamination leading to major causes of death. A study was conducted in a contiguous six-county study area of southeastern Michigan to investigate the relationship between moderate arsenic levels and twenty-three selected disease outcomes. Disease outcomes included several types of cancer, diseases of the circulatory and respiratory system, diabetes mellitus, and kidney and liver diseases. Elevated mortality rates were observed for all diseases of the circulatory system. The researchers acknowledged a need to replicate their findings.[6]
A study preliminarily shows a relationship between arsenic exposure measured in urine and Type II diabetes. The results supported the hypothesis that low levels of exposure to inorganic arsenic in drinking water may play a role in diabetes prevalence.[7]
Arsenic in drinking water may also compromise immune function “Scientists link influenza A (H1N1) susceptibility to common levels of arsenic exposure”. http://www.eurekalert.org/pub_releases/2009-05/mbl-sli052009.php..

Contamination specific nations and regions
Bangladesh and West Bengal

The story of the arsenic contamination of the groundwater in Bangladesh is a tragic one. Many people have died from this contamination. Diarrheal diseases have long plagued the developing world as a major cause of death, especially in children. Prior to the 1970s, Bangladesh had one of the highest infant mortality rates in the world. Ineffective water purification and sewage systems as well as periodic monsoons and flooding exacerbated these problems. As a solution, UNICEF and the World Bank advocated the use of wells to tap into deeper groundwater for a quick and inexpensive solution. Millions of wells were constructed as a result. Because of this action, infant mortality and diarrheal illness were reduced by fifty percent. However, with over 8 million wells constructed, it has been found over the last two decades that approximately one in five of these wells is now contaminated with arsenic above the government’s drinking water standard.
In the Ganges Delta, the affected wells are typically more than 20 m and less than 100 m deep. Groundwater closer to the surface typically has spent a shorter time in the ground, therefore likely absorbing a lower concentration of arsenic; water deeper than 100 m is exposed to much older sediments which have already been depleted of arsenic.[4][8]
Dipankar Chakraborti from West Bengal brought the crisis to international attention in 1995.[9] [10][11] Beginning his investigation in West Bengal in 1988, he eventually published, in 2000, the results of a study conducted in Bangladesh, which involved the analysis of thousands of water samples as well as hair, nail and urine samples. They found 900 villages with arsenic above the government limit.
Chakraborti has criticized aid agencies, saying that they denied the problem during the 1990s while millions of tube wells were sunk. The aid agencies later hired foreign experts, who recommended treatment plants which were not appropriate to the conditions, were regularly breaking down, or were not removing the arsenic.[12]
Chakraborti says that the arsenic situation in Bangladesh and West Bengal is due to negligence. He also adds that in West Bengal water is mostly supplied from rivers. Groundwater comes from deep tubewells, which are few in number in the state. Because of the low quantity of deep tubewells, the risk of arsenic patients in West Bengal is comparatively less. [13]
According to the World Health Organisation, “In Bangladesh, West Bengal (India) and some other areas, most drinking-water used to be collected from open dug wells and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhoea, dysentery, typhoid, cholera and hepatitis. Programmes to provide ‘safe’ drinking-water over the past 30 years have helped to control these diseases, but in some areas they have had the unexpected side-effect of exposing the population to another health problem—arsenic.” [14] The acceptable level as defined by WHO for maximum concentrations of arsenic in safe drinking water is 0.01 mg/L. The Bangladesh government’s standard is at a slightly higher rate, at 0.05 mg/L being considered safe. WHO has defined the areas under threat: Seven of the nineteen districts of West Bengal have been reported to have ground water arsenic concentrations above 0.05 mg/L. The total population in these seven districts is over 34 million, with the number using arsenic-rich water is more than 1 million (above 0.05 mg/L). That number increases to 1.3 million when the concentration is above 0.01 mg/L. According to a British Geological Survey study in 1998 on shallow tube-wells in 61 of the 64 districts in Bangladesh, 46% of the samples were above 0.01 mg/L and 27% were above 0.050 mg/L. When combined with the estimated 1999 population, it was estimated that the number of people exposed to arsenic concentrations above 0.05 mg/L is 28-35 million and the number of those exposed to more than 0.01 mg/L is 46-57 million (BGS, 2000). [14]
Throughout Bangladesh, as tube wells get tested for concentrations of arsenic, ones which are found to have arsenic concentrations over the amount considered safe are painted red to warn residents that the water is not safe to drink.
The solution, according to Chakraborti, is “By using surface water and instituting effective withdrawal regulation. West Bengal and Bangladesh are flooded with surface water. We should first regulate proper watershed management. Treat and use available surface water, rain-water and others. The way we’re doing at present is not advisable.”[13]
United States
There are many locations across the United States where the groundwater contains naturally high concentrations of arsenic. Cases of groundwater-caused acute arsenic toxicity, such as those found in Bangladesh, are unknown in the United States where the concern has focused on the role of arsenic as a carcinogen. The problem of high arsenic concentrations has been subject to greater scrutiny in recent years because of changing government standards for arsenic in drinking water.
Some locations in the United States, such as Fallon, Nevada, have long been known to have groundwater with relatively high arsenic concentrations (in excess of 0.08 mg/L).[15] Even some surface waters, such as the Verde River in Arizona, sometimes exceed 0.01 mg/L arsenic, especially during low-flow periods when the river flow is dominated by groundwater discharge.[16]
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. The Environmental Protection Agency (EPA) studied the pros and cons of lowering the arsenic Maximum Contaminant Level (MCL) for years in the late 1980s and 1990s. No action was taken until January 2001, when the Clinton administration in its final weeks promulgated a new standard of 0.01 mg/L (10 ppb) to take effect January 2006.[17] The incoming Bush administration suspended the midnight regulation, but after some months of study, the new EPA administrator Christine Todd Whitman approved the new 10 ppb arsenic standard and its original effective date of January 2006.[18]
Many public water supply systems across the United States obtained their water supply from groundwater that had met the old 50 ppb arsenic standard but exceeded the new 10 ppb MCL. These utilities searched for either an alternative supply or an inexpensive treatment method to remove the arsenic from their water. In Arizona, an estimated 35% of water-supply wells were put out of compliance by the new regulation; in California, the percentage was 38%.[19]
The proper arsenic MCL continues to be debated. Some have argued that the 10 ppb federal standard is still too high, while others have argued that 10 ppb is needlessly strict. Individual states are able to establish lower arsenic limits; New Jersey has done so, setting a maximum of 0.005 mg/L for arsenic in drinking water.[20]
A study of private water wells in the Appalachian mountains found that 6% of the wells had arsenic above the US MCL of 0.010 mg/L.[21].
Water purification solutions
Small-scale water treatment

Chakraborti claims that arsenic removal plants (ARPs) installed in Bangladesh by UNDP and WHO were a colossal waste of funds due to breakdowns, inconvenient placements and lack of quality control.[13]
A simpler and less expensive form of arsenic removal is known as the Sono arsenic filter, using 3 pitchers containing cast iron turnings and sand in the first pitcher and wood activated carbon and sand in the second.[22] Plastic buckets can also be used as filter containers.[23] It is claimed that thousands of these systems are in use 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.
In the United States small “under the sink” units have been used to remove arsenic from drinking water. This option is called “point of use” treatment. The most common types of domestic treatment use the technologies of adsorption (using media such as Bayoxide E33, GFH, or titanium dioxide) or reverse osmosis. Ion exchange and activated alumina have been considered but not commonly used.
Large-scale water treatment
In some places, such as the United States, all the water supplied to residences by water utilities must meet primary (health-based) drinking water standards. This may necessitate large-scale treatment systems to remove arsenic from the water supply. The effectiveness of any method depends on the chemical makeup of a particular water supply. The aqueous chemistry of arsenic is complex, and may affect the removal rate that can be achieved by a particular process.
Some large utilities with multiple water supply wells could shut down those wells with high arsenic concentrations, and produce only from wells or surface water sources that meet the arsenic standard. Other utilities, however, especially small utilities with only a few wells, may have no available water supply that meets the arsenic standard.
Coagulation/filtration removes arsenic by coprecipitation and adsorption using iron coagulants. Coagulation/filtration using alum is already used by some utilities to remove suspended solids and may be adjusted to remove arsenic.
Iron oxide adsorption filters the water through a granular medium containing ferric oxide. Ferric oxide has a high affinity for adsorbing dissolved metals such as arsenic. The iron oxide medium eventually becomes saturated, and must be replaced.
Activated alumina is another filter medium known to effectively remove dissolved arsenic. It has also been used to remove undesirably high concentrations of fluoride.
Ion Exchange has long been used as a water-softening process, although usually on a single-home basis. It can also be effective in removing arsenic with a net ionic charge. (Note that arsenic oxide, As2O3, is a common form of arsenic in groundwater that is soluble, but has no net charge.)
Both Reverse osmosis and electrodialysis (also called electrodialysis reversal) can remove arsenic with a net ionic charge. (Note that arsenic oxide, As2O3, is a common form of arsenic in groundwater that is soluble, but has no net charge.) Some utilities presently use one of these methods to reduce total dissolved solids and therefore improve taste. A problem with both methods is the production of high-salinity waste water, called brine, or concentrate, which then must be disposed of.
SAR Technology: A new solution to this pressing problem has been proposed in the form of Subterranean Arsenic Removal (SAR) process where aerated groundwater is recharged back into the aquifer to create an oxidation zone which would coprecipitate iron & arsenic. The oxidation zone created by aerated water boosts the activity of the arsenic oxidizing microorganisms which can enzymatically oxidize arsenic from +3 to +5 state. Six such treatment plants, funded by the World Bank and constructed by Ramakrishna Vivekananda Mission, Barrackpore are in full scale operation in West Bengal. Each plant has been delivering more than 3000 litres of arsenic & iron free water everyday to the rural people. The first community water treatment plant based on SAR technology was set up near Kolkata by a team of European and Indian engineers led by Dr. Bhaskar Sen Gupta of Queen’s University Belfast for TiPOT Consortium which was funded by the European Commission TiPOT. This technology is expected to provide a long term solution to arsenic contamination in groundwater and is targeted towards treatment of the aquifer as a whole. Moreover, this technology has been used in Germany for the past hundred years to remove iron from groundwater without any negetive effectSAR Technology.
A summary of SAR Technology, entitled ‘A simple chemical free arsenic removal method for community water supply – A case study from West Bengal, India’ has been published in Environmental Pollution Journal (Elsevier) by the TiPOT team. SAR Technology is a chemical and waste free solution to low cost arsenic removal from groundwater.
In November 2009, the Blacksmith Institute – New York & the Green Cross – Switzerland selected the SAR Technology as one of the 12 Cases of Cleanup & Success in their World’s Worst Polluted Places Report 2009. (Read the report here)The only other project from India that has been selected in this list is that of “Delhi Metro Rail Project & CNG Conversion of cars at Delhi”. Press releases are available at Scientific American &
Researchers from Bangladesh and the United Kingdom have recently claimed that dietary intake of arsenic adds a significant amount to total intake, where contaminated water is used for irrigation.

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Responses

  1. Hi,
    this is subho das I am into ground water investigation & rainwater harvesting & relevent topics.your idea & outlook is very noval & interesting .looking forward to you in this connection .
    thanks !
    subho das

    • Dear Dr. Das
      Thanks for your comments.Please keep in touch.
      Wish you all the best.
      azizul

  2. Hi Dr.M.Azizul
    i am interest your paper.
    i have experiences of Fe removal (10ppm to WHO standards) by using appropriate technology such as Ariation, contact to fabric, filered by burned paddy shell (like wooden activated carbon) and than finally filtered by Coarse sand and / or findgrain fresh water gravel in Myanmar.
    Now in Myanmar also facing As problem.
    NGO are trying but not positive rsult and effect to puple in village at Arrawaddy delta.
    I want to keep in touch with you.
    Now i am working in Singapore. BUT i want to do something such as As removal (portable units) to mitigate for those peples who are using As contaminated GW in this area.

  3. Hello Dr.Azizul,
    Am proposing bioremediation using concurrent pipes as a method to remove Arsenic from water.This particular bacteria has been tested to accumulate within it high quantities of Arsenic and thus just the pipe needs to be changed every week and what comes out is a heavy metal free water that can be drunk.
    Your suggestions needed.
    Regards
    Suhasini

    • Hi Suhasini
      Thank you for your mail. I hope your system should be fine to deal with the practical solution of Arsenic contaminated ground water as an in-situ technology.
      No problem.
      With regards.
      Azizul

  4. Thank you for your message. Can you please email me by detailing of the experimental conditions.


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