Arsenic Contamination in Coastal Zone of Bangladesh

8/14/2019 Arsenic Contamination in Coastal Zone of Bangladesh

http://slidepdf.com/reader/full/arsenic-contamination-in-coastal-zone-of-bangladesh 1/21

Arsenic Contamination in Coastal Zone of Bangladesh

Muhammad Mahadi.

Environmental Science Discipline

1. Introduction :

Extensive Arsenic contamination of the groundwater in the alluvialaquifers of Bangladesh is probably the worst case of water pollution in

the present time. Recent study reported that out of 64 districts,drinking water in 61 districts are contaminated by arsenic though thepercentage of the tubewells contaminated vary from 90% to less then5%, exceeding the Bangladesh standard limit of 0.05 mg/l. About 30million people are either directly or indirectly exposed to arseniccontamination with varying degrees of risk. Experts have put forwardseveral hypotheses regarding the causes of the arsenic contamination.Domestic water supply and irrigated agriculture in Bangladesh isheavily dependent on the use of groundwater. Several options areunder active consideration to mitigate the arsenic contamination in thedrinking water supply. The arsenic contamination of groundwater and

its implications on human health are most important issues to beconsidered for the future development of groundwater resources inBangladesh. Heavy withdrawal of groundwater for irrigation, industryand domestic use needs to be managed in an integrated manner alongwith the surface water for the sustainable development of bothsurfaces and groundwater in this country. The paper reviews the stateof arsenic contamination and mitigation measures in Bangladesh.

2. Coastal zone (CZ) of Bangladesh:

The landmass of Bangladesh is connected to the Indian Ocean through a 700 km, longcoastline. The coastal zone is marked by a vast network of river systems, an ever dynamicestuary, a drainage path of a huge basin covering also parts of India, Nepal, Bhutan and

China and a saline waterfront penetrating inland from the sea.

The boundaries of a coastal area change over time for management purposes, as the

issues to be forged become more extensive or complex and require more far-ranging

solutions. Coastal zone recognized administrative boundaries in Bangladesh. The coastalzone represents an area of transition where terrestrial and marine environments interact to

form unique environmental conditions.

The coastal zone (CZ) covers 19 districts facing or having proximity to the Bay of Bengaland the exclusive economic zone (EEZ).

Barguna Feni Satkhira

Barisal Jhalakhati Shariatpur

Bagerhat Khulna Gopalgonj

Bhola Lakshipur Jessor

Chittagong Noakhali Narail

Cox’s Bazar Pirojpur

Chandpur Patuakhali1




Muhammad Mahadi.


Total Bangladesh area is 147,570 Km2 of which 47,203 Km2 falls under coastal zone. This

is roughly 32% of the whole country. According to 2001 census, total population of Bangladesh is 123,151,246 of which 34,846,215 live in coastal area. This is

approximately 28% of the total population of Bangladesh. The national population

density of Bangladesh is 861/Km2 whereas; population density in the coastal area is959/Km2. From 1901, coastal population increases in following manner:

Year Population

1901 7.2 million

1991 24 million

1998 32 million

2001 34 million

2050 50 million (projected)

Fig-1: Map of the coastal zone of Bangladesh

3. Arsenic Contamination in Coastal Zone of Bangladesh:

Arsenic contaminated groundwaters have emerged as a catastrophicproblem across much of Bangladesh. Specifically in the coastal zone,

2




Muhammad Mahadi.


arsenic levels in tubewell water ranges from “clean” to some of thehighest known concentrations. There are 12 district with high % of arsenic concentration, of which 7are in coastal zone: chandpur(90%), Gopalgonj(79%), Noakhali(69%),Satkhira(67%), Saritpur(65%), Bagerhat(60%), and Laxmipur(56%). There are 12 district with less problem arsenic, three of which arelocated in the coastal zone: Barguna(0%), Patuakhali(0%), and Cox’s-Bazar(2%).

High levels of arsenic in groundwater used for drinking and cookingwater cause serious human health problems over time (5 to 15 years). The problem is acute for tubewells abstracting groundwater fromdepths betweens 10 and 100 m depth in the southeast, south central(northern part only) and southwest regions. The most seriouslyaffected areas are chandpur and surrounding districts.

Table-1: Arsenic contamination area of coastal zone of Bangladesh

Total number of Districts of Bangladesh 64Coastal Districts of Bangladesh 19 Total Area of Bangladesh 147,570km 2

Coastal area of Bangladesh 47,203 Km2

Total population of Bangladesh 123,151,246

Coastal population of Bangladesh 34,846,215

Population density of Bangladesh 861/Km2

Population density of Coastal zone of Bangladesh 959Highly arsenic affected district of Bangladesh 12Highly arsenic affected district in coastal zone of Bangladesh

7

Less arsenic affected district of Bangladesh 12Less arsenic affected district in coastal zone of Bangladesh

3

3




Muhammad Mahadi.


Fig-2: Arsenic Crisis Map of Bangladesh

4. World Health Organization ( WHO) guidelines for drinking-water quality:

The WHO Guidelines for Drinking-water Quality are intended as a basis for the

development of national standards in the context of national environmental, social,economic and cultural conditions. The last edition of WHO guidelines for drinking water

quality (1993) established 0.01 mg/l as a provisional guideline value for arsenic in

drinking water.

WHO has had a public position on arsenic in drinking water since 1958 when the first

version of International Standards for Drinking-Water was published. In this instance theterm "standards" was used to be applied to the suggested criteria of water quality. It

established 0.20 mg/l as an allowable concentration in the category of toxic substances

which, if present in drinking-water supplies at concentrations above certain levels, maygive rise to actual danger to health. The updated standards set the maximum permissible

limit of arsenic in drinking water for Bangladesh and India as 0.05 mg/L.

1235. Origin and Causes of Arsenic in Groundwater aquifer inBangladesh4A number of causal explanations for the occurrence of arsenic in groundwater have been

considered. Broadly, they fall in two categories:

Anthropogenic, i.e., human-induced causes, and

Natural, geologic causes

5.1 Anthropogenic or human-induced causes:

Human induced causes include diverse sources of arsenic contamination such asagrochemicals, preservative treated Rural Electrification Board (REB) power poles,

industrial wastes, mining and mineral processing, lower aeration beneath irrigated lands,

and phosphate fertilizers.

4




Muhammad Mahadi.


• Agrochemicals: Arsenic can be present in pesticides, insecticides and herbicides

as well as can occur in fertilizers as impurities. Agrochemicals can be pointsources of localized pollution. But, they cannot possibly give rise to the large-

scale contamination as in the case of Bangladesh.

• REB Power Poles: Arsenic compounds have been used in wood preservatives as

chromate copper arsenic (CCA) for years. A study in this regard by NRECA/ICDDR,B concluded that the wooden pylons, capable of releasing only

very small quantities of arsenic, may only pollute on an extremely localized scale,

but these poles can, in no way, be linked to the extensive contamination of groundwater.

• Industrial Wastes: Industrial wastes can be responsible for localized high arsenic

contamination of groundwater. Again, the widespread nature of the contamination

and the fact that most of the arsenic contaminations are found in areas where noor little industrial activities take place rule out this hypothesis.

• Mining and Mineral Processing: It can be the source of arsenic pollution in the

proximity of the mining areas. But, in Bangladesh, absence of metal mines

invalidates the application of the concept.

• Lower Aeration beneath Irrigated Lands: Arsenic may be released at an intense

rate beneath agricultural lands, as conditions in the underlying aquifer becomemore reducing due to cutting-off of air entry by irrigated water. The resulting

enhanced leaching of arsenic may have a long-term effect, but cannot account for the mode of occurrence of current extensive contamination in Bangladesh, whichis not restricted to the upper-most part of the aquifer only.

5.2 Natural causes:

In natural waters, arsenic is usually found in one of four chemical associations, whichoccur in more-or-less predictable geological and climatic settings, and each of these is

associated with a characteristic cause, or mobilization mechanism. These water types and

mobilisation mechanisms are themes that recur throughout the book because they

determine not only where arsenic is found, but also how it may be avoided, how it affectsagriculture, and how it may best be treated. The four mechanisms are described below

in order of decreasing importance:

• Reductive dissolution: occurs when iron oxides, onto which arsenic is adsorbed,

break down under the influence of decaying organic matter (which consumes

oxygen sources) and dissolve, thereby releasing arsenic in the process. The

5




Muhammad Mahadi.


groundwater produced by these processes is always strongly reducing, with high

concentrations of iron and bicarbonate, while nitrate and sulphate are absent.

• Alkali desorption: occurs at high pH (≥8.0) and in the presence of dissolved

oxygen, nitrate or sulphate, producing waters which can be termed ‘alkali-oxic’,and which have low concentrations of iron and manganese.

• Sulphide oxidation: occurs where sulphide minerals such as pyrite or arsenopyrite

are exposed to oxygen, often at the water table, to produce waters that are

typically both acid (pH 1–6) and sulphate-rich, but not necessarily high in iron.

• Geothermal: waters from deep, sometime volcanic, sources leach arsenic from the

country rocks. The waters are distinguished primarily by elevated temperature,

and usually also by a correlation of arsenic with chloride.

6. Availability of Arsenic in Coastal Zone of Bangladesh:

In Khulna division at least 67.84 per cent tubewells have been affected with arseniccontamination. It has posed .as a health hazard of the people of the people of Khulna

division. Out of 1,213 arsenic affected tubewells, 838 tubewells have been marked as

dangerous and its percentage in 46.87. The authorities concerned said, zero point zerofive milligram arsenic in a liter of water is acceptable, but if its quantity is more than that

it is unfit for human consumption.

In Khulna district 393 tubewells have been examined and presences of arsenic in 199

tubewells have been detected. Water of 126 tubewells have been found dangerous.

In Bagerhat district 115 tubewells water have been examined and presence of arsenic wasfound in 79 tubewells. A total of 58 tubewells out of 79 have been declared dangerous.

In Satkhira district arsenic contamination is very alarming. After examining 313tubewells water of 258 tube wells have been found arsenic contamination in excess

quantity.

In Jessore district 389 tubewells have been examined. Arsenic was found in 257

tubewells.Out of them 185 tubewells have been declared unfit for taking water.

In Narail district 82 tubewells have been examined and presence of arsenic was found in61 tubewells. A total of 50 tubewells have been declared as unfit.

In Jhenidah district 64 tubewells have been examined. Presence of arsenic was found in42 tubewells, out of which 27 tubewells have been declared unfit for use.

In Magura presence of arsenic was found in 42 tubewells, out of which 35 tube- wellshave been declared dangerous.

6




Muhammad Mahadi.


In Kushtia 162 tubewells were examined and presence of arsenic was found in 105

tubewells. A total of 64 tubewells have been declared dangerous and unfit for use.

In Chuadanga district 144 tubewells have been examined and presence of arsenic was

found in 109 tubewells. A total of 68 tubewells have been declared unfit for use.

In Meherpur 71 tubewells have been examined where presence of arsenic has been found

in 61 tubewells. A total of 35 tubewells contained excessive quantity of arsenic and those

are declared unfit for use.

Source:The Daily Star -July 19, 1998-Arsenic detected in many tubewells in Khulna division

In Chandpur is among the five districts in the country severely affected by arsenic

contamination of groundwater. A preliminary survey by the Department of Public Health

and Engineering (DPHE) showed that water of about 40 per cent of the tubewells testedso far in Chandpur contained arsenic and 83 per cent of those 40 per cent had

concentration of arsenic above the permissible level of 0.05 mg per litre, according to

sources in the DPHE. On an average, there are about 30 tubewells in a village in thedistrict. But no arsenic contamination was found in deep tubewell water.

Siurce:The Daily Star -November 10, 1997 -Arsenic affected Chandpur - Villagers don't know what to do next

Arsenic detected in water in Jhalakati, High level arsenic contamination was found inwaters of four shallow tubewells in the district, according to a report of Public Health

Engineering Department. Water of four shallow tubewells in Nalchhiti, sadar and Rajapur

thanas contained arsenic above the acceptable level of 0.01 milligram.

Source:The Daily Star- Sept 26; 1997

17. State of Arsenic in the Coastal Zone of Bangladesh:

Until 1998, a total of 31,651 water samples were tested by field and laboratory tests by

different organizations. Out of these, 30,742 were collected from shallow wells (<200 m)and 909 from deep wells (>200 m). It has been found that 7,942 samples out of the

30,742 from shallow wells and 34 samples out of the 909 from deep wells are

contaminated with the percentages 25.8 and 4, respectively. The arsenic contaminateddistricts of Bangladesh are shown in Figure 3. From Figure 3, it is apparent that all the

surveyed districts (61 out of 64) show the presence of arsenic contamination. However,

nine contaminated districts out of 61 show that a very limited percentage (<1%) of wells

are contaminated.

7




Muhammad Mahadi.


Table-2: Arsenic Contamination-by Division and Nationally

Division Total

districts

Arsenic

affected

districts

Total

thanas

Arsenic

affected

thanas

Affected

thanas, % of

total thanas

Affected

thanas, % of

all thanas incountry

Dhaka 17 16 134 61 45% 12%

Chittagong 11 9 93 21 22 % 4%

Rajshahi 16 16 127 35 27% 7%

Khulna 10 10 63 42 66% 9%

Slhet 4 4 35 34 97% 7%

Barisal 6 6 38 18 47% 4%

Bangladesh 64 61 490 211 43%

Note: Table shows affected thanas, where Arsenic Concentration in groundwater is > 0.05 mg/l.

Source: DPHE/DFID Regional Arsenic Survey, 1998

Three districts (i.e., Rangamati, Khagrachhari, and Bandarban) were not surveyed by any

organization. One reason may be that these three districts are mainly hilly areas, with

8.73 percent of the total area of Bangladesh and only 0.92 percent of the total population.Another reason may be that no primary symptoms of arsenic patient were found there. In

Bangladesh, there are 64 districts and 490 thanas. Out of 465 thanas of the surveyed 61

districts, 54 were not surveyed at all by any organization. Figure 3 shows that almost the

whole of the country is contaminated with arsenic. The severe problem is in the southern

(coastal area) and northeast parts of the country. The badly affected districts areBrahmanbaria, Comilla, Feni, Narayanganj, Sariatpur, Narail, Satkhira, and Nawabganj.

The disastrous situation is in the districts of Laksmipur, Noakhali, Madaripur andChandpur (Figure 3). The Ganges, Megna, and Atri Floodplains, the tidal regions and the

coastal plains are the major physiographic regions vulnerable to arsenic contamination. In

April 2000, SOES and DCH jointly published a report on Bangladesh groundwater arsenic contamination (SOES-DCH, 2000), which shows figures different from those in

the BGS report. Figure 4 shows arsenic contaminated districts according to the SOES-

DCH survey. The main difference between the combined analysis (Figure 3) and theSOESDCH survey (Figure 4) is that Figure 3 shows all 61 sur-veyed districts were

contaminated with concentration of > 0.05 mg/L, whereas Figure 4 shows seven

completely safe districts (i.e., Panchagarh, Thakurgaon, Dinajpur, Naogaon,Moulabibazar, Patuakhali, and Cox’s Bazar), and seven districts (i.e., Nilphamari,Lalmonirhat, Gaibanda, Joypurhat, Dhaka, Barguna, and Bhola) were over the WHO

safety limit but under the maximum permissible limit. Three no-surveyed districts of

combined analysis (Khagrachhari, Rangamati, and Bandarban) were found contaminationfree by the SOES-DCH survey.

8




Muhammad Mahadi.


8. Survey Results of Different Organization

in the Coastal Belt of Bangladesh:

Medical evidence of arsenicosis was first discovered in West Bengal in1987, although the connection with groundwater contamination wasnot recognized until some years later. Further surveys were carried outduring the 1980s (eg Chakraborty et al, 1987; Mazumder et al, 1988),culminating in a national report by PHED, India, in 1991. In 1993,DPHE, Bangladesh, tested for and identified arsenic at ChapaiNawabganj, near the border with West Bengal, but it was not until 1995that the existence of arsenic in Bangladesh became widely known.;

In 1997 DPHE with the assistance of UNICEF made a nation widesurvey using field test kit and produce a database of some 23,000tests. NGO forum and Grameen Bank carried out extensive surveys,while BRAC tested all 12,000 wells in Hajiganj upazila of Chandpurdistrict where 93% of drinking water wells are contaminated by

arsenic. In December 1996, Asia Arsenic Network (Japan based NGO)carried out a detailed survey in Samta village of Jessore of southwestregion and reported that 90% of the tubewells are arseniccontaminated. In early 1997 BUET made a random survey in Northeastpart of Bangladesh under East Minor Irrigation Project (NEMIP) andtested 1210 water samples of which 61% of the samples were above0.01 mg/l and 33% were above 0.05 mg/l of arsenic. A further sample

9

Figure-3




Muhammad Mahadi.


was analyzed by BCSIR of which 42% contain above 0.05 mg/l of arsenic.

Available laboratory analytical results compiled under the project byBritish Geological Survey (BGS) and Mott Mecdonald limited BGS-MML1999, shows that out of 9271 analysis, arsenic concentration in 3243samples exceeded the limit of 0.05 mg/l., which is 35% of all samplesexamined.

Table-3: arsenic contamination in drinking water

DistrictAvera

geLevel

(g/l)

No.of Sampl

es

tested

% of walls

Exceedi

ng50(g/l)

% age of wells in givenarsenic concentration

class

<10 10-50 50-200 >200Bagerhat 156 62 60 19 21 31 29Barguna 1 33 0 97 3 0 0Barisal 92 92 30 58 12 12 18Bhola 10 48 4 96 0 2 2Chandpur 366 59 90 8 2 10 80Chittagong 32 44 16 68 16 11 5Cox’s Bazar 3 43 2 95 2 2 0Feni 54 53 28 49 23 24 4Gopalganj 187 42 79 17 5 43 36

Jessore 70 69 46 29 25 39 7 Jhalokati 23 33 9 76 15 6 3Khulna 35 76 24 61 16 21 3Lakshimpur 179 34 56 24 21 26 29Narail 88 24 42 37 21 25 17Noakhali 162 49 69 16 14 37 33Patuakhali 3 42 0 93 7 0 0Pirojpur 30 47 17 66 17 11 6Satkhira 133 61 67 18 15 41 26Shariatpur 151 49 65 24 10 35 31Source:BGS & DPHE,200lb

The study called “Groundwater Studies for Arsenic Contamination inBangladesh”, conducted by BGS-MML reported that out of 64 districts,drinking water in 61 districts are contaminated by arsenic though thepercentage of the tubewells contaminated vary from 90% to less then5%. The results indicated that it is strongly concentrated in parts of thesoutheast and southwest region of the country.

10




Muhammad Mahadi.


The distribution of arsenic is systematically related to both depth andgeological unit. The very shallowest groundwater as encountered indug-well is mostly uncontaminated. It is observed that the highestconcentration occurs at depth of 20 to 70 meters below ground. Wellsused in Bangladesh rarely goes below 70 to 100 m, with very fewbelow 150 to 200 meter below ground. Most of the wells deeper thanabout 150 to 200 m have been found to contain very low concentrationof arsenic. So in general, it appears to be an improvement of quality interms of arsenic as well as iron and other with depth of borehole.Results from a British Geological Survey of 253 samples showed thefollowing results.

About 51% of groundwater sampled have found more than 0.01 mg/larsenic (WHO standard), while 35% of groundwater sampled have been

found more than 0.05 mg/l arsenic (Bangladesh standard). About 30million people are either directly or indirectly exposed from arseniccontamination with varying degrees of risk. Under the BangladeshArsenic Mitigation Water Supply Project (BAMWSP), so far 13,48,362tube-wells used for drinking water source have been tested for arsenic,48% of which contains arsenic above 0.05 mg/l.

9. Effects of Arsenic Contamination:

9.1 Effects on Human Health

The data collected by the governmental bodies, NGOs and private organizations reveal

that a large number of populations in Bangladesh are suffering from melanosis, leuco-

melanosis, keratosis, hyperkeratosis, dorsum, non-petting oedema, gangrene and skincancer18. Melanosis (93.5%) and keratosis (68.3%) are the most common presentations

among the affected people. Patients of Leucomelanosis (39.1%) and hyper-keratosis

(37.6%) have been found in many cases. Few cases of skin cancer (0.8%) have also beenidentified among the patients seriously affected by the arsenicals (arsenite and arsenate).

11




Muhammad Mahadi.


Fig-5: Skin Lesions in Soles due to Arsenic Intake in Drinking Water

The occurrence of arsenic diseases depends on the ingestion of arsenic compounds and

their excretion from the body. It has been reported that 40% to 60% arsenic can be

retained by the human body. It indicates that the level of hazards will be higher with thegreater consumption of arsenic contaminated water. The daily consumption of arsenic

contaminated water is very high in Bangladesh, especially in villages. The villagers

consume about five liters water per day due to manual labor. Moreover, they consume plenty of rice-water and all of their foods are also cooked using arsenic polluted water.

Therefore, the people of villages in the affected areas are getting more arsenic than

expected. So far SOES and DCH had analyzed 11000 hair, nail, urine and skin-scale

samples collected from the affected villages in Bangladesh. The analysis shows thataround 90% of people have arsenic in their hair, nail and urine above the normal level.

The normal concentration of arsenic in hair is 0.08-0.25 mg/kg and 1 mg/kg indicates the

toxiclevel. The normal arsenic content in nails is 0.43-1.08 mg/kg and the normal amountof arsenic in urine ranges from 0.005 to 0.040 mg/day. Table shows that the arsenic

contents in hairs, nails, urine and skin scales of the affected people are very high in

Bangladesh.

12

Table-4: arsenic contents in hairs, nails, urine and skin scales




Muhammad Mahadi.


There are several factors may have been responsible for triggering off the arsenicrelateddiseases in Bangladesh. The primary reason appears to be the malnutrition, a state that

describes 80 percent of the population of Bangladesh. Having less immunity, a huge

number of people are suffering from the chronic arsenic poisoning. Many People have

died, many are dying and many will die of arsenic diseases. In brief, the majority of the people in Bangladesh are grappling with the massive health crisis caused by the arsenic

diseases

9.2 Social Effects

Although what is causing arsenic contamination in groundwater is not clear indisputably,

its effect on people is well known. The sudden increase in arsenic related diseases has panicked the local people. The native people consider the arsenic diseases contagious. In

many instances, the people suffering from arsenic diseases have been ostracized byneighbors, friends and relatives. The affected people are either avoided or discouraged toappear in public places. The affected children are often barred from attending schools and

the adults are discouraged from attending offices and any public meetings. Qualified

persons are refused jobs when found suffering from arsenicosis. Those affected with ahigher level of contamination are considered incapable of working and hence victimized

by the growing poverty. The situation is worse for women. The women suffering from

arsenic diseases are increasingly facing ostracization and discrimination. Young womensuffering from arsenicosis are often compelled to stay unmarried. Married women

affected by arsenic are no longer considered acceptable as wives due to skin lesions and

sent back to their parents with children. Thus, the unaffected parents and children are also

suffering socially with the affected females. Above all, the affected people are losing their as usual social relation with the neighbors and relatives.

9.3 Effects on Soils, irrigation and agriculture

Combined exposure from food and water can significantly increase the disease burden

from arsenic. In many affected areas, moderately high levels of arsenic are found innatural soils. Arsenic may be taken up through the roots of plants to accumulate in the

edible parts. Where soil is the only source of arsenic, uptake by plants declines over time.

However, greater problems may develop where arsenic in irrigation water accumulates inthe soil and leads to increasing uptake by plants. In general, as a proportion of dry mass,

leafy vegetables and some spices may take up the most arsenic, but when adjusted for

13




Muhammad Mahadi.


dietary intake, grains such as rice make the largest contribution to human exposure. In

some Asian countries this can be a larger source of exposure than drinking water. High

concentrations of arsenic in soil can be toxic to rice, and can dramatically reduce yields.This worrying phenomenon has recently been recognised in South Asia ( Duxbury and

Panaullah, 2007), but as Reed and Sturgis (1936) noted ‘Arsenic toxicity in soils is no

new problem’.

10. Options for Mitigation of Arsenic in drinking water

Mitigation program is however not very significant as compared to theseverity of arsenic contamination for several reasons. Several optionsare considered to mitigate the arsenic contamination in the drinkingwater.

1a) Surface water supply;2b) Dug wells3c) Deep tube wells;4d) Ponds and Pond Sand Filter;5e) Rainwater harvesting;6f) Alkam Enhanced Activated Alumina filter;7g) BUET filter;8h) Arsenic removal at household level;9i) Rural and Peri-urban piped water supply based on Mini-STW’s, etc

10.1 Dug wellDug well is the oldest method of groundwater withdrawal of watersupplies. Most of the dug wells are either free from arsenic or iron orconcentration is well below the acceptable limit. Dug wells areconstructed at least 1m in diameter to facilitate manual excavationand sunk to a depth of at least 1m deeper than the lowest water level. To protect it from bacteriological contamination can be achievedthrough sealing the well top and the upper part of the well lining andthe space between the wall and soil. Water can be withdrawn byinstalling manually operated handpump.

10.2 Pond sand filter Traditionally rural water supply to a large extent was based onprotected ponds before and after the installation of tubewell. There areabout 1,288,222 nos of ponds in Bangladesh (BBS, 1996) having anarea of 0.114ha per ponds and 21.5 ponds per mouza, nearly 17 to 20

14




Muhammad Mahadi.


percent of them dries up in the dry season. In general these arebiological quality of water is extremely poor. If one pond per mouzacould be protected from contamination, it would provide a source of drinking water with minimal treatment.Slow sand filters are package type filter units developed to treatsurface waters for domestic consumption in the coastal saline belt. Inthis system surface water is discharges in a small reservoir underlainby a sand bed and the filtered water is collected through taps. Thesystem popularly known as Pond Sand Filter (PSF) is one of thealternative technologies for supplying arsenic free potable water,suitable for the household level at village level.

10.3 Rainwater harvestingBeside rainwater may be collected 5 minutes after rain starts, at

household level through the pre-fabricated jar or containers, whichrequire no treatment (except filtration for separation of suspendedsolids, if any) before domestic use.

10.4 Deep tube wellsIn areas where arsenic free groundwater can be abstracted safely fromdeeper aquifer further expansion of DTW’s fitted with suction modehand pump, TARA pumps for individual household or with motorizedpumps for community based piped water supply system are beingconsidered. Government under the urgent mitigation program hasprepared a protocol for drilling deep hand tubewell from arsenic

affected areas where arsenic is within tolerable limit.

11. Arsenic Removal Technologies Used in Coastal Zone of Bangladesh:

Although a number of treatment technologies exist that are capable of efficient removalof arsenic from water, but the socio-economic conditions that prevail in Bangladesh do

not permit the implementation of most of them on the cost ground. Individual households

or small groups have their own or community tube-wells. Therefore, solution to the

problem of arsenic contamination, in most situations, in Bangladesh demands the

development technology/ technologies that can be implemented at household or smallcommunity level relatively at a very lower cost. Recently a number of researches have

been conducted to identify such novel technologies for arsenic removal to implement inrural isolated communities. A brief overview of some of these documented technologies

is presented here.

15




Muhammad Mahadi.


11.1 Iron (and Manganese) Oxidation

Passive sedimentation

Since a large part of Bangladesh (about 65% areas) contains iron in excess of 2 mg/L andin many acute iron problem areas, the concentration of iron is as high as 15 mg/L,

therefore, arsenic has been found to co-exists with iron in many situation. In such

situation, arsenic can be removed by both co -precipitation and adsorption onto the

precipitated Fe(OH)3 by oxidation of this water during collection and subsequentlystoring them in household level. Mamtaz and Bache (2000) from their bench-scale tests

demonstrated that arsenic can be removed by co-precipitation with naturally occurring

iron but removal rate largely controlled by the arsenic concentration, the iron/arsenicratio, and pH. It is evident from their test result that up to 88% of the arsenite in water

could be removed by settlement over a period of 24h. Authors collected arsenic

contaminated natural groundwater having very high iron content from Manikgonj area.Samples were shaken during the time of collection and transportation, and allowed to

settle in the laboratory. This process removed more than 60% arsenic, where raw

groundwater arsenic and iron concentrations were in the range of 150 μg/L to 713 μg/L

and 8 mg/L to 14 mg/L respectively. The rapid assessment of this technology byBAMWSP, DFID and WaterAid(2001) showed that it failed to reduce arsenic to the

desired Bangladesh standard for Drinking Water of 50 μg/L in most of their teste d tube-

wells.

11.2 In-situ oxidation

In-situ oxidation of iron and arsenic in the aquifer has been tested under DPHE-Danida

Arsenic Mitigation Pilot Project where the aerated tube-well water is stored in a tank and

then stored water is discharged into the aquifers through tube-well pipe under the pump

head. Water collected by tube -well from such aquifers, followed by in-situ oxidation iron

and arsenic, showed about 50% removal of arsenic.

11.3 Solar oxidation

In this process, transparent bottle containing water are exposed to sunlight for solar oxidation of arsenic in presence other oxidants like oxygen, followed by precipitation of

arsenic with naturally occurring iron. Experiments in Bangladesh showed that the process

on average could remove arsenic content of water to about one-third, and removalefficiency increased to about 45 -78% when 50 μM citrate or 100-200 μL (4-8 drops) of

lemon juice/L is added.

11.4 Arsenic and iron removal plants (AIRP)

The conventional small-community type iron removal plants, which operate on the principles of aeration of ferrous iron to convert them to ferric iron to co-precipitate

arsenic.Groundwater drawn by hand tube-well drops into storage (aeration/sedimentation) chamber for oxidation of iron and arsenic with air to co-precipitate. Water

from storage chamber passes through filtration chamber due to the pressure head of

aeration/ sedimentation chamber and subsequently collected into a storage tank for public

uses. Filtration media comprises of brick chips, charcoal and sands. Filtration media is periodically (3 to 4 times a year) back washed, and sludge is collected in a holding pond.

16




Muhammad Mahadi.


The DPHE, with support from Dutch Government, constructed 3 arsenic and iron

removal plants for piped water supply system in small municipalities, where arsenic co-

exits with iron in tube-well water. In these plants, groundwater is pumped over a series of cascades to aerated water and then passes through filtration unit which removes iron and

arsenic precipitates. Iron and arsenic removal efficiencies of 18-DTP (1999) arsenic

Most of the AIRP plants shown here have good arsenic removal performance and have been treating water to the satisfactory level except in those areas, where arsenic

concentrations are high. It is evident from field survey that these AIRP plants are well

accepted by the community. Thus, some of the above described arsenic and iron removal plants have good potentials for small isolated communities and densely populated

communities respectively where arsenic co-exists with iron at suitable concentrations.

11.5 Bucket treatment unitBucket treatment unit developed by DPHE-Danida a project consists of two buckets

(about 20 L capacity) placed. Chemicals (200 mg/L aluminum sulfate and 2 mg/L potassium permanganate) are mixed manually with arsenic contaminated water in upper

bucket by vigorous stirring with a wooden sticks for about 30-60 seconds and then

flocculated by gentle stirring for about 90 seconds. Mixed water is then allowed settle for

about 1-2 hours and top supernatant is allowed to flow into the lower bucket via a plastic pipe and sand filter installed in the lower bucket. Although this technology perform well

(with arsenic removal efficiencies in the range of 67% to 83%) in many situation but in

some cases under rural operating condition it fails to remove to desired Bangladeshstandard level. Presently, BUET modified the system and used 100 mg/L of ferric

chloride and 1.4 mg/L potassium permanganate, and it perform very well with arsenicremoval; efficiency up to 94%.

11.6 Steven Institute technology

This unit consists of two buckets. Chemicals (reported to be iron sulfate and calciumhypochloride) supplied in packets are mixed in one bucket and the mixture is transferred

to another bucket to separate flocs by the processes of sedimentation and filtration.The

rapid assessment of this technology by BAMWSP, DFID and WaterAid(2001) showed

17

Table-5




Muhammad Mahadi.


that this technology was effective in reducing arsenic levels to less than 50 μg/L in case

of 80% to 95% of the samples tested.

11.7 Pitcher treatment

A pitcher filter unit or small sand filters at the household level can clarify surface water

containing impurities. This method of water purification was primarily in use by the rural people of Bangladesh. With the introduction of tube wells for village water supply these

processes of water treatment have been phased out at household level. Raw water is poured in the top pitcher and filtered water is collected from the bottom one. Other

pitchers contain same filtration media, sands and brick chips. This system has been tried

to remove arsenic from groundwater, collected from contaminated tube-wells. Sono 3- pitchers filter uses zero valent iron filling and coarse sand in the top pitcher, charcoal and

fine sand in the middle pitcher. The bottom pitcher is used to store treated water. The

arsenic removal efficiencies of this system are in the range of 59% to 95% but it dependson the maintenance of the system and the quality of water. But if batches are left for too

long, dissolved iron concentrations become unacceptably high (Ramaswami et al, 2000).

The rapid assessment of this technology by BAMWSP, DFID and WaterAid(2001)showed that this technology was effective in removing arsenic, but the system may be

quickly clogged if groundwater contains excessive iron.

11.8 Activated Alumina

Water passes through the packed column of activated alumina, impurities present in water

including arsenic are adsorbed on the surface of activated alumina grains. At some stage,the alumina becomes saturated and then exposing the medium to 4% caustic soda

regenerates these. The residual caustic soda is then washed out and the medium is

neutralized with a 2% solution of sulfuric acid rinse. Number activated alumina based

sorptive media are used in Bangladesh including:

• BUET Activated Alumina

• Alcan Enhanced Activated Alumina• Arsenic Removal Unit of Project Earth Industries Inc., USA

• Apyron Arsenic Treatment Unit

The rapid assessment of these technology by BAMWSP, DFID and WaterAid(2001)

showed that BUET Activated Alumina and Alcan Activated Alumina are more effective

in removing arsenic. BRAC, a nongovernment organization has experimented a number of alternative technologies including two Alcan Activated Alumina filter.

11.9 Ion Exchange

Tetrahedron ion exchange resin filter tested under rapid assessment program inBangladesh (BAMWSP, DFID and WaterAid, 2001) showed promising result in arsenic

removal. The performance and applicability these arsenic removal units should be

determined through closed field monitoring.

18




Muhammad Mahadi.


11.01 Membrane Technique

A nanofiltration process coupled with bicycle pumping system was examined by Oh et al(2000a) using arsenic contaminated tube-well water in rural area of Bangladesh. Arsenite

was found to have lower rejection than arsenate in ionized form. Therefore low-pressure

nanofiltration with pre-oxidation or reverse osmosis with a bicycle pump device can beused for the treatment of arsenic contaminated groundwater where electricity supply is

not efficient or feasible. The capital and operational cost of this system is relatively high.

11.11 Other Arsenic Removal Technologies

To mitigate arsenic contamination problems in Bangladesh, numbers of organizations and

industries have been trying to develop arsenic removal system and chemicals including:

• Bangladesh Council of Scientific and Industrial Research (BCSIR) Filter Unit

• DPHE-Danida Fill and Draw Unit

• Read-F Aresenic Removal Unit• Sapla Filter

• Granet Home-made Filter

• Adarsha Filter • Safi Filter

• Bijoypur Clay Filter

• Several Cartridge Filter

• Iron coated sand• Granular ferric hydroxide

• Tourmaline mineral

19




Muhammad Mahadi.


12. Recommendations:

Although groundwater arsenic contamination in Bangladesh has been declared a national

disaster by the government, its seriousness is yet to be fully comprehended. If the

following recommendations for research and development are successfully carried out,the remediation of arsenic contamination will be much easier.

1. It is highly desirable to form a research group with geologists, hydrologists, geo-chemists, water supply and environmental engineers, and public health experts to conduct

in-depth investigation on the sources and causes of arsenic contamination in groundwater.

2. A comprehensive research plan should be developed to determine the geological, hydro

geological and geochemical factors controlling the chemical reactions generating and

releasing arsenic to groundwater.

3. A national groundwater resources management policy is established in order to limit

the indiscriminate abstraction of groundwater.

4. It is highly recommended that every donor projects in arsenic mitigation bylaw ensure

community participation for smooth running in future.

5. A comprehensive water distribution system should be implemented and an efficient

monitoring system should be established to provide potable water and to prevent future

arsenic contamination in drinking water.

6. An effective sewage disposal system should also be established to accompany any

deployment of water distribution system.

7. Guidelines on the disposal of arsenical wastes should be established to minimize the

contamination in soil and water.

8. An estimate of annual arsenic use in agriculture is required and the short-term or long-

term environmental impact of arsenic use in cultivation should be assessed.

9. The population exposed to the arsenic contamination should be advised about the

arsenic in drinking water, the sources of arsenic-free water, and the importance of compliance with treatment programs including the nutrition.

20




Muhammad Mahadi.


13. Concluding Remarks:

Arsenic contamination is not peculiar to Bangladesh alone. This is a global problem.

Thousands of arsenic affected patients have already been identified. If the people

continue to use arsenic contaminated water, millions will lose their health or die within a

few decades. Those who will survive are in a danger of carrying genetic diseases to future

generation. Unfortunately, the basic facts in Bangladesh are that the people in the affected

regions are still unaware of arsenic contamination and its hazardous effects. The

governmental efforts are much less than needed to mitigate the crisis. Hence, the

immediate involvement of international community is urgent to combat the slow onset

disaster and save the poor people. Economically and technologically, Bangladesh is not in

a firm position to solve the arsenic crisis herself. Environmental experts and funds are

desperately needed to save the lives of millions of people affected by deadly arsenic. The

international community has the economic resources, environmental experts, and

technologies to mitigate the arsenic contamination in groundwater. The support of United

Nations, donor countries, donor organizations, agencies, and individuals is essential to

save the suffering people from the devastating arsenic disaster.

Date post:	30-May-2018
Category:	Documents
Upload:	muhammad-mahadi
View:	218 times
Download:	0 times

Arsenic Contamination in Coastal Zone of Bangladesh

Documents