Arsenic as source of risk in Bangladesh groundwater

Peshawa Mahmod University of Brighton

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Arsenic as source of risk in Bangladesh groundwater

Introduction

Arsenic contamination of groundwater could happen from diversity source such as wood

preservation, pesticides and glass manufacture; this source could manage and observed

(Ahuja, 2008). However, in case of natural source arsenic not easy to control and mange .the

worst natural contamination of arsenic in the groundwater was found in Bangladesh;

Bangladesh is one of the countries that suffer from different type of hazards for example,

arsenic contamination, cyclones, floods pose, droughts and earthquake. However, arsenic is

conceded as the most hazardous type in Bangladesh which about 59 districts out of all 64

districts under hazard of drinking and using arsenic contaminated water (Yokota et al, 2001).

Arsenic is one of the abundant elements in the surface of the earth and it is inter to the

Bangladesh groundwater by natural geological processes. The concentration of arsenic in

Bangladesh groundwater is higher than the recommended water drinking limit of both world

health organization and Bangladesh National Drinking Water (World Health Organization,

1993). After ten to twenty years of drilling thousand tube wells in Bangladesh the problem was

appears globally and it cause numerous health problem and death of peoples in this country.

This essay describes and discusses the properties of arsenic, the problem in Bangladesh, health

risk in drinking water contaminated by arsenic, source of arsenic in Bangladesh, detection and

some solution.


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Physical and chemical properties of Arsenic

Arsenic arranged as number 20 in the abundant constituent from the surface of the earth

(Ahuja, 2008) and it is naturally presence in soil, air, minerals and rocks (Petrusevski et al,

2007). However, it is not determine as a natural element of water but it transported to the

water by deferent chemical and physical processes (Young et al, 2008). The majority of

Arsenic found in combination with other components for example, Oxygen, Sulfur and

Chorine, and very small amount might found as pure arsenic in nature (Environmental

Toxicology Section, 2002). The atomic number of arsenic is 33 that 33 electrons around the

nucleus interact with other atomic materials; this gives different shape of arsenic in the

nature, gray, shiny and yellow arsenic (Chris, 2007). The arsenic has both metallic and non-

metallic properties and classified in three main groups: Organic, inorganic and gas; it is

insoluble in water in his natural form but it dissolved when it oxidized (World Health

Organization, 2000). The oxidized arsenic is the highly toxic natural form, it is tasteless and

colour less compound (Bentley and Thomas, 2002).

Arsenic and the problem in Bangladesh

The problem started after drilling large numbers of water wells in 1970s and 1980s (Ahuja,

2008) to save peoples in Bangladesh from deadly diarrheal illness that associated with

drinking untreated surface water. A lot of people died due to this disease which the majority

was children and the good solution was to drill water well (Mushtaque and Chowdhury,

2004). The water well (locally called tube well) was not contaminated by bacteria that cause

this disease and in normal analyses show that these well include normal cation and anion;

however, in this time the arsenic test was not included in normal analysis (Younger, 2007).


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Drilled wells were the principle supply water to Bangladesh people for domestic and

agricultural (Shamsudduha et al, 2008). According to UNICEF (2008) and Jakariya (2007) the

approximated number of tube well in Bangladesh is about 8.6 million wells and most of

these wells are hand pumped well which the depth between 20-40 m (Ahuja, 2008). The

Continues drinking of water polluted by arsenic cause an ailment that slowly visible

(Younger, 2007) thus peoples stile drinking this water; unfortunately, someone – everyone

neglected to test theses water wells fro arsenic (Mushtaque and Chowdhury, 2004). The

first report about the presence of arsenic in south west Bangladesh groundwater was done

by the department of public health engineering in 1993 (Shamsudduha et al, 2008).while,

the problem got a global attention in 1995 during international conference on arsenic in

subsurface water (Yokota et al, 2000).

According to the United State of Environmental protection Agency (2006) the limited range

of existence arsenic in drinking water is 10 ppb (part per billion) and the World Health

Organization (WHO) advised that the limited range of arsenic in drinking water is 10

millionths of a gram per litre of water (10 μg/L). However, the Bangladesh National Drinking

Water was limited the Arsenic in drinking water to level of 50 millionths of a gram per litre

of water (50 μg/L) (Mukherjee, 2006).

According to the UNICEF report in (2006) in total of 8.6 million water wells, 4.7 million of

these well had been analysed for arsenic; the data show that 1.4 million water well was

above the limited of drinking (50 μg/L) and considered to be unsafe. Approximately,

between 30% and 60% of the total population in Bangladesh (which equal to 125 million)

now under risk of drinking subsurface water polluted by arsenic (Younger, 2007; Jakariya,

2007). Furthermore, about 20 million people used water well that above (50 μg/L) of arsenic


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in Bangladesh (UNICEF, 2006). About 10% of the Bangladesh people drink water from

tube wells that the concentration six time more than (50 μg/L) (Mushtaque and

Chowdhury, 2004). According to Karim (2000) about 52 districts in Bangladesh was

contaminated by arsenic out of 62 districts which is a larger disaster of contamination of

arsenic in the world.


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Health risk

Arsenic in drinking water effecting on the human health and observation depend on a

mount and extent of exposure (National Research Council, 2001). Drinking water of very

high concentration of arsenic could cause to diarrhea and abdominal (Mushtaque and

Chowdhury, 2004). However, during long term drinking of low arsenic concentration in

water (more than limited) is considered one of health hazards (Petrusevski et al, 2007).

After drinking contaminated water by arsenic as long as 10 years, primary symbol of

poisoning might become visible as black spot in arms, chest and back which known as

Melanosis (Mushtaque and Chowdhury, 2004) and (Petrusevski et al, 2007). With hardly

exposed to the arsenic in drinking water lead to Warts, Hyperkeratosis and Melanosis of the

human skin (World Health Organization, 2000) and if the drinking arsenic continues the skin

de-pigmentation appear and it called medically Leukomelanosis (Petrusevski et al, 2007).

The Continues drinking and exposure to polluted water by arsenic cause symptoms which

called also Arsenicosis and in the end cause death of the exposure (Smith et al, 2000).

According to UNICEF (2006) about 40,000 people in Bangladesh have a skin symptoms and

characteristic of Arsenicosis was recognized and it include dark spots among feet and hand,

lesions, swollen limbs and also loss of emotion from both hand and foot; this also could lead

to gangrene. Some time arsenic assault interior organism of human and there is no any

visible symptoms in the skin and outer body part. To know the concentration of arsenic in

human body before attack organic part and appearance of the symptoms; assess arsenic

concentration in nails, urine, hair and blood is done (Petrusevski et al, 2007). According to

Farmer and Johnson (1990) between (40 – 60) % of the arsenic consumed keeping in human

body thus with increase the concentration of arsenic in the drinking water lead to increase

arsenic in the human body and increase the risk.


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According to the World Health Organization (2001) the long term espousing to arsenic by

drinking water cause to skin cancer which could appear after symptoms. In addition,

depending on the International Agency for Research on cancer (2004) has concluded that

drinking water that contaminated with arsenic could be a source of cancer of lung, skin and

urinary bladder. Depending on study done by Chen and Ahsan (2004) in Bangladesh show

that about 103.5 people per 100,000 populations were in a death risk of lung, bladder and

liver cancer.

Source of the Arsenic in Bangladesh groundwater

The source of arsenic in subsurface water in Bangladesh is naturally formed and it related

to the interaction between the groundwater and deposited sediment partials (Mukherjee,

2002). The presence of arsenic in the sedimentary groundwater rocks are mostly controlled

by geology, geomorphology, hydrogeology and geochemistry of the groundwater and

sedimentary rocks materials (Shamsudduha et al, 2008). Bangladesh lied on a basin called

Bengal Basin which includes a sequence of Cretaceous rocks to upward of recent deposit

(Morgan and McIntire 1959 cited in Langner, 2002).The recent deposits contain floodplain

and delta deposits that occupied about 100,000 kilometre esquire of land in Bangladesh;

this delta and floodplain deposited by action of the Ganges, Brahmaputra and Meghna

rivers (Welch and Kenneth, 2003). Generally, the sediment in Bangladesh composed of thick

porous orange Sand deposited in Pleistocene age covered by gray Clay bed and it also

overlay by dark gray thick porous Sand and silt deposited in Holocene age that covered by

think Clay of overbank deposition (Ahmed et al., 2004). According to Welch and Kenneth

(2003) the water wells that depth is more than 150m only seldom affected by

contamination of arsenic than the shallow water wells (see table 1), furthermore, the more


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affected area is located in the south east of Bangladesh which the sediment is from

Holocene age and the concentration of arsenic often more than (200 μg/L).

The high concentration and mobility of arsenic in Bangladesh ground water is a contentious

issue and has yet to be determined and different hypothesises were argued.

1- It is originated from physical and chemical erosion of different crystalline rocks of

Himalayan and other surrounded uplift area and deposited over 18,000 years ago in

this place (Mushtaque and Chowdhury, 2004).

2- Some argue that occurrence and mobility of arsenic in the subsurface water in

Bangladesh might come due to use of fertilization of Phosphate in agricultural area

(Shamsudduha et al, 2008). However, according to Ravenscroft et al (2001) there is

no fundamental link between phosphate fertilization and arsenic in groundwater and

only reasons of this hypothesis is that test shows that 5 μg/L of phosphorus could

release 2 μg of arsenic and the maximum amount of Phosphorus in Bangladesh

groundwater is less than this amount.

3- The arsenic is linked with Arsenopyrite (pyrite rich arsenic) that with over use of

subsurface water in agriculture and domestic caused to decrease of water table; this


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decrease let air to reach Arsenopyrite and release arsenic by oxidation (Dhar et al,

1997 cited in Karim, 2000) and (Mushtaque and Chowdhury, 2004). Some tube well

that was arsenic free before, at now it contaminated by arsenic with increasing

consumption in these wells (Mushtaque and Chowdhury, 2004). This release arsenic

transport to the groundwater by the infiltration and wash out during rainy season;

according to Yokota et al (2001) during the rainy season the concentration of arsenic

in the tube well is higher than in dry season. However, according to Langner (2001)

the oxidation of pyrite rich arsenic that release arsenic also release Sulphate and in

this cause it is not associated with arsenic oxidation. Furthermore, in shallow well

that the depth is less than 10m the arsenic contamination is rare where the air rich

oxygen are common to oxidize pyrite (Ravenscroft et al, 2001).

4- Recent research approved that primary release of arsenic associated with biogenic

reduction of Fe-oxyhydroxides and this mechanism could pot arsenic in to the

Bangladesh groundwater (Shamsudduha et al, 2008). According to Stollenwerk et al

(2007) and Langner (2001) this hypothesis is mainly wide satisfactory mechanism

which cause due to reduction of Fe-oxyhydroxides (FeOOH) and release arsenic to

the groundwater. This mechanism occurs in the Holocene alluvial sediment that is

rich in ferric minerals associated with deposition of Sand and Gravel (Younger, 2007).


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Detection

Quick and accurate method to determine groundwater contamination by arsenic in field is

stile technical challenge (Ahuja, 2008) however, field Kits test is used to determine arsenic

contamination (see fig1). This test depends on the mercuric bromide stain technique and it

has been established that this technique is insufficient for water that contain arsenic

concentration between 55-100 μg/L (Langner, 2004). This method depends on field

experience of the user because it has a visual identification depending of different colours.

Another method that used to determine arsenic depend on a principle of Atomic

Absorption, this method are more of higher cost than the field Kits but it is more accurate

and depend on laboratory works. The user of this method could not exposure to toxic gases

while in the field kits method the user exposed to toxic gas which is cause hazard (Rahman

et al. 2002).


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Solution and remediation

With occur of large concentration of the arsenic in Bangladesh tube well, several

alternative and technologies has been used to remove arsenic from water that could be

useful to drinking (Ahmed, 2001). However, according to Langner (2004) the arsenic

pollution in Bangladesh is still acute and it is not easy to mange. Some solution and

remediation methods are described as follow.

1- Use alternative source of drinking and cooking water instead of tube well water that

was recognized to be arsenic free for example, using surface water after treatment

and using rain fall water (Davis, 2003 and Jakariya, 2007). According to (Welch and

Kenneth, 2003) and (Mushtaque and Chowdhury, 2004) there is a raped change of

concentration of arsenic in some deep water well which the depth more than (150-

200) m; these wells could also used as one of the alternative source of drinking

water. This solution was argued by UNICEF and Scientists in University of Columbia

and has a possibility to be used for some area according to the geological situation

but it is not available in all places (Wilson, 2009).

2- Arsenic could be removed by use chemical solution and coagulants such as

aluminium salt and high dissolved iron, the iron precipitate arsenic forming

ferrihydrite; this method used only for domestic water use (Safiuddin and Karim,

2001). Relatively, this method is simple in use and of low cost but it creates toxic

materials and it also approved that have lower effect in removing arsenic (III)

(Ahmed, 2001).

3- Using oxidation method to remove arsenic; two type of oxidation are used, air and

chemical oxidation; the type of oxidant that is used is Hypo-chlorite, permanganate


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and ozone. This method as compared with others is simple and have low cost but it

only removes some type of arsenic (Ahmed, 2001).

4- Iron oxide-coated coal ash, this method used successfully in Bangladesh to remove

arsenic in drinking water. This method is tack place in two steps by using ash bottom

covered with ferric hydroxide (Gadgil et al, 2008).

5- Using some type of filter for example, the Shapla filter, the 3Kolshi filter and

Nanofiltration. The Shapla filter has ability of clear about 3000-4000 litter of arsenic

polluted water (Davis, 2003). According to Ahmed (2001) these type of filter is good

in use and effectiveness in remove arsenic however, it is of high cost, need

maintenance and produce wastewater.

Other additional technologies and methods are developed and used in Bangladesh;

according to Sarkar (2008) any methods to remove contaminated arsenic from water should

remove arsenic in safe method and not cause other ecological impact.


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Conclusion

The common type of arsenic in the nature was found combined with other elements and it

is transported to the Bangladesh groundwater by natural geological process from the deltaic

and floodplain deposits. The problem appears after thousand tubes well have been drilled

to find new source of drinking water that is not contaminated by Bactria and it became

known globally as a hazard to Bangladesh people during 1993. Currently, global awareness

concerning arsenic poisoning in Bangladesh is increased and several solutions were argued.

The source and method of entering arsenic in to Bangladesh groundwater derive several

argument however, the formation of arsenic due to oxidation of pyrite rich arsenic and

reduction from iron ox- hydroxide are more concentrated by Scientifics. Field laboratory

test are used to detect arsenic concentration in drinking water and several method and

solution are described; using alternative source of drinking water and using different

technological method could solve this problem but it could be in the way that not cause

waste deposits.


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Arsenic as source of risk in Bangladesh groundwater

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