1. Arsenic in Bangladesh: The need for urgent action to reduce major disease impacts. Allan H. Smith
2. General overview of UNICEF and its initiative in Bangladesh and West Bengal. Gourishankar Ghosh
3. Arsenic crisis in Bangladesh: a personal experience. Bibudhendra Sarkar
4. An integrated study of sources, transport and health effects of arsenic in Bangladesh. Y. Zheng, M. Stute, L. van Geen, J. Simpson and J. Graziano, H. Ahsan, P. Brandt-Rauf
5. Groundwater arsenic contamination and sufferings of people in Bangladesh, a report up to January, 1999. B.K. Biswas, U.K. Chowdhury, R.K. Dhar, B.K. Manda, T.R. Chowdhury, G. Samanta, C. R. Chanda. G. K. Basu, D. Lodh, D. Chakraborti and S. Roy, S. Kabir, Q. Quamruzzaman
6. Arsenic disaster in Bangladesh - an urgent call to save a nation. T. E. Bridge and M. T. Husain
7. Arsenic poisoning and remediation: Some unfocussed issues in Bangladesh. Faisal Hossain
8. Analytical science of arsenic: problems and practice in arsenic analysis in the Bangladesh laboratories. A.H. Khan, M. Khaliquzzaman, M. Alauddin, A. Hussam, A.K.M. Munir, A.I.Kazi and M. Aftabuddin
9. Arsine Generation in Arsenic Field Kit: A Health Hazard. A. Hussam, M. Alauddin, A.H. Khan, S.B. Rasul and A.K.M. Munir
10. Arsenic Measurement: The Right Approach for Bangladesh! M. Alauddin, Y. Islam, M. Habibuddowla, A. Hussam
11. Speciation of Inorganic Arsenic in Ground Water of Bangladesh. S.B. Rasul, N. Ahmed, A.K.M. Munir, S. Washe, M. Khaliquzzaman, A.H. Khan, A. Hussam
12. How Serious is the Arsenic Situation in Bangladesh - A recent two week Field Survey Report.    Uttam K. Chowdhury, Bhajan K. Biswas, Ratan K. Dhar, Tarit Roy Chowdhury, Badal K. Mandal, Gautam Samanta, Chitta R. Chanda, Gautam K. Basu, Dilip Lodh, Dipankar Chakraborti and Sibtosh Roy, Bashir Ahmed, Anam Hossain, Quazi Quamruzzaman
13. Groundwater chemistry and arsenic distribution in groundwater of Bangladesh. A.H. Khan, A. Hussam and M. Alauddin
14. Levels of arsenic in some specific areas of the Dhaka city and Sitakund, Chittagong. M. Alauddin, A.H. Khan, S. Nahar, N. Nabi, A. Hussam
15. Cycling of arsenic in ground water of the United States: Processes relevant to the arsenic problem in the Bengal Delta. Alan H. Welch
16. The arsenic disaster in Bangladesh: Causes and remedies. Muhammad A. Miah
17. Groundwater arsenic in the Holocene alluvial aquifers of Bengal Delta Plains: Petrological, geochemical and isotope geochemical studies. Prosun Bhattacharya, K. Matin Ahmed, M. Aziz Hasan, Gunnar Jacks, Debashis Chatterjee, Aftab Alam Khan, S. Humayun Akhter, M. Badrul Imam, Andre Sracek
18. Arsenic Crisis in Bangladesh - Ways to Combat the Situation. Dipankar Chakraborti
19. Arsenic levels in water samples from a village of Bangladesh. Dalilur Rahman and Mohammad Alauddin
20. Appropriate Remediation Technologies for Arsenic-Contaminated Wells in Bangladesh. Susan Murcott
21. Arsenic Crisis in the Indian Sub-continent: a Local Solution to a Global Problem.Arup K. SenGupta
22. Removal of Arsenic from Drinking Water: AsRT Field Trials. Jeffrey A. Lackovic, Nikolaos P. Nikolaidis, Gregory M. Dobbs
23. Arenic Removal from Drinking Water by Low Cost Materials. Abul Khair, Abul Kalam Azad and Gobinda Narayan Paul
24. Reckless Resource USe Intensifies Problem of Arsenic in Groundwater of West Bengal and Bangladesh. Timir B. Hore
25. Health Effects due to Arsenic Contamination in Ground Water in Bangladesh. Sk. Akhtar Ahmad, M.H. Salim, Ullah Sayed, Sk. Abdul Hadi, M.H. Faruquee, Manzurul Haque Khan, Md. Abdul Jalil, Rukshana Ahmed, A. Wadud Khan, M. Shahajada. Chowdhury
26. Arsenic Contamination in the Ground Water of Bangladesh and its removal using Floculation followed by Filtration Technique. Aftabuddin Ahmed, Tahuran Neger, Samiran Bhattacharjee, Meher Nigar Chowdhury and Ashish Kr. Sarker
27. Low-cost UV disinfection of surface water in Bangladesh. Elwyn Ewald, David Greene, Anushka Drescher, Ashok Gadgil
28. Arsenic crisis in Bangladesh. Quazi Quamruzzaman, Mahmuder Rahman, Abul Hasnat Milton, Shibtosh Roy, Dipanker Chakrabarti, Ratan Dhar, Bhajan Biswas and Goutam Samanta
29. Arseniferous groundwater in the Bengal Delta Plains: Appraisal of the low-cost remediation techniques. Gunnar Jacks, Prosun Bhattacharya, Maria Larsson, Andrea Leiss, Debashis Chatterjee, Mattias von Br?mssen

At the same time as awareness of the extent of contamination of drinking water with arsenic in Bangladesh has been increasing, evidence of the serious long term impacts of arsenic in causing human disease has been mounting in exposed populations in different parts of the world. Evidence, primarily from Taiwan and Chile, suggests that arsenic in drinking water poses the highest known environment cancer risks. In the long term, consumption of drinking water containing around 500 m g/l of arsenic may cause 1 in 10 exposed persons to die from arsenic-caused cancers. In the short term, skin lesions resulting from arsenic are well known, but further work is needed to identify less obvious health consequences including neurologic, respiratory, vascular and reproductive effects. Factors related to individual susceptibility to arsenic effects also wait to be identified. But while there are many research questions, the top three priorities in the huge exposed population in Bangladesh relate to stopping exposure. These include providing easily accessible alternative water sources, making sure there is community understanding about the use of the alternative water sources, making sure there is community understanding about use of the alternative sources, and population monitoring to ensure that the exposure have indeed stopped.

The Bangladesh arsenic problem represents a collective failure on the part of the International agencies, the Government and other donor agencies which could have acted faster than what we did in getting a fuller picture and extent of the problem. UNICEF works in Bangladesh, as in all other countries, to support government plans and programs for the children. UNICEF with other partners acted for many years with a fair amount of success to promote tubewells as a viable low cost solution to the critical water problem for reduction of morbidity and mortality due to water borne diseases. The slow effect of the high arsenic contaminated water was not realized till recent years.

The problem is extremely complex and the complete knowledge of the problem is yet to be available. It is a "long term slow emergency" and yet no magic bullet is easily available. The immediate action requires an open collaborative effort of all interested partners in various fronts, scientific, technical, administrative, social and economic fields. The main issue is to create a public awareness without pressing any panic button. The lessons learned from the high Fluoride mitigation strategy in India possibly can offer some direction. A Global Arsenic Information Network (GAIN)

Linking all activities for free information to all will possibly be a good start for global cooperation between interested agencies, academic institutions, donors, individual and existing initiatives. The simple cost of finding alternate sources for these wells is so prohibitive and time consuming that various actions are to be taken at different levels and depending on the gravity of the situation in the ground several mix of actions are to be decided.

UNICEF is committed to facing the challenge of mitigation as a partner to the efforts of the Government, the Civil Society, and other agencies, donors and institutions. Communication, development of simple household filtration systems, water harvesting and treatment of surface water, deep tubewells with regular water quality testing and development of a Global Network will be the major areas for future activities of UNICEF.
 
 

The catastrophic health crisis caused by arsenic poisoning of drinking water in Bangladesh and West Bengal could be the biggest mass poisoning in human history. I have traveled through hundreds of remote villages, crossing the border between Bangladesh and West Bengal in India on foot to gather first hand knowledge of this massive poisoning. Arsenic is a human carcinogen which quietly accumulates in hair, nail, and skin. Common symptoms are depigmentation, rashes on palms and soles of feet which eventually develop to gangrene and cancer. Death is inevitable. I found villagers did not know what was happeningg to them. I have seen seven- and eight-year-old children with melanosis, which is too early for showing the signs of arsenic poisoning. These children looked severely malnourished as well. There are innumerable subclinical cases where people show no physical symptoms, but they will eventually become sick and die. There has been a terrible delay. A well-coordinated, financially accountable group of experts from various disciplines locally and internationally must be drawn, and unlike today, they must cooperate.

The goal of our study is to understand how arsenic (As) is mobilized in sediments and transported by groundwater, and how health effects relate to arsenic exposure. We have assembled a multi-disciplinary team at Columbia University and partner institutions to address these questions ranging from geochemistry and hydrogeology to epidemiology and toxicology.

The exact sequence of processes that leads to the elevated arsenic concentrations in ground water in Bangladesh is not yet well understood, but mobilization followed by transport of naturally-occurring arsenic in delta sediments probably plays an important role. A series of oxidation and reduction reactions that do not proceed at the same rate for As and for Fe (or Mn) could have mobilized and re-concentrated As. We plan to document spatial and temporal variations in As concentrations and speciation in drinking water and relate these variations to geochemical and hydrogeological conditions in order to determine the As exposure of different populations in the biomedical context. The consequences of human arsenic exposure on pregnancy outcomes and infant development are essentially unknown. These health outcomes will likely prove to be the most sensitive adverse health effects associated with arsenic exposure. Thus, utilizing a two-town design, we plan to explore dose-response relationships across a uniquely wide range of arsenic exposures. Similarly, we want to explore dose-response relationships between arsenic exposure and a variety of health outcomes including skin, bladder, lung and liver cancer, as well as vascular diseases. A unique aspect of this project will relate to the exploration of biomarkers of both exposure and effect in adult subjects with a wide range of arsenic exposures.

A Columbia public health/geochemistry team visited Bangladesh in early February, 1999. Samples from shallow and deep wells in areas characterized by different degrees of As contamination were collected and the corresponding exposed populations screened for health effects. We expect to be able to present the first preliminary data at the meeting.

The total area and population of Bangladesh are 148393 sq. km, and 120 million respectively. We are doing our scientific study and survey on Bangladesh almost last 4years. Till to date in our preliminary survey, we have analyzed about 12000 hand tube-well water samples, collected from 64 districts and found arsenic in 52 districts above the WHO recommended value (0.01 mg/1) and in 42 districts above 0.05 mg/l. The area and population of these 42 districts are 92106 sq. km and 79.9 million respectively. This does not mean that the total population in these 42 districts are drinking contaminated water or suffering, but no doubt they are at risk. The analytical results show that in 143 thanas of these 42 districts, 61.9% of the water samples are not suitable for drinking as per the WHO recommended value (0.01 mg/l), and 55.6% of the water samples contain arsenic above the WHO maximum permissible limit (0.05 mg/1).

About 3332 hair, 3321 nail, 373 skin-scale and 1043 urine samples from people living in arsenic affected villages (including patients) have so far been analyzed and 92% samples on average, contain arsenic above the normal value. Thus many may not be showing arsenical skin lesions but may be subclinically affected. Further, if it is true that arsenic toxicity appears after several years of exposure, then the picture may actually be far more grim than it appears at present and children of our future generations are at greater risk. From the affected villages we have so far examined 1351 children (below 11 years) and out of that 17% have arsenical skin lesions. When we compare the magnitude of the arsenic calamity of Bangladesh with West Bengal we find Bangladeshis much more affected. In West Bengal out of the total children examined below 11 years we have found 1.7% having arsenical skin lesions. Out of total 55000 hand tube-wells we had analyzed so far from West Bengal only 45 contains arsenic above 1.0 ppm whereas in Bangladesh it is 211 out of 12000 hand tube-wells analyzed. Out of the 42 districts where arsenic has been found above 0.05 mg/l, we have, so far, surveyed 27 districts for arsenic patients, and in 25 districts we have identified people suffering from arsenic induced skin lesions such as, melanosis, leuco-melanosis, keratosis, hyperkeratosis, dorsum, non-petting edema, gangrene, skin cancer etc. During our preliminary field survey for last the four years, in 118 groundwater arsenic contaminated villages of 54 thanas of 27 districts, we have found arsenic patients in 112 villages in 25 districts.

We have examined, at random in affected villages, 816 people including children, and out of the 29.3% are found to have arsenic skin-lesions. When only adults are considered the affected population is 2504 out of the total examined adults 7364. When we started 4 years ago we knew of only 10arsenic affected villages and now the number reached to 112.

At present, we know several other villages where people are suffering from skin lesions in those 25 districts and they will be included in course of time. More we are surveying more and more affected villages and hence patients are added to our report. We feel still we are at the tip of iceberg.

Bangladesh is located on the Ganges, Brahmaputra and Meghna Delta and has one of the greatest population densities of any country in the world. The people won their independence from Pakistan in 1971.

During the past thirty years millions of people have lost their lives in the many hazards that are common to the area. An attempt to eliminate one of the hazards, disease caused by drinking polluted surface water, millions of shallow surface wells were drilled into the delta alluvium. These wells were or have become contaminated with arsenic. Millions of people drinking water from these contaminated wells are showing the symptoms of arsenic poisoning. Immediate steps must be taken to identify those areas affected by arsenic contaminated water and then supply fresh potable water to the people in those areas.

A research project to map the contaminated waters of the regions affected, find the source of the contamination, and establish a system of water management for the people of Bangladesh that assures a continuing supply and of safe water for domestic use.

This paper attempts to bring to light a few relevant technological and non-technological issues that have escaped the focus of the media and the research community in Bangladesh. An arsenic cycle is proposed for the Bangladeshi context. A hypothesis that extended periods of inundation over the years could be one of the causative factors behind the arsenic contamination of ground water is proposed. Three cost-effective technologies are briefly described which appear very promising for Bangladesh. Finally, it is hoped that dissemination of these issues is Bangladesh will play an important role in devising a country-wide master plan for solving the arsenic problem.
 
 

1. Dept. of Chemistry, University of Dhaka and Intronics Technology Center, Dhaka, Bangladesh

In recent years there are widespread reports in the press media that in large areas of Bangladesh the ground water systems, used for drinking as well as irrigation purposes, are contaminated with arsenic much above the Bangladesh standard of 0.05 mg/l for drinking water. For the correct assessment of the extent of the problem, it is essential that appropriate analytical technology available in the country be used to obtain a quality assured database so that a correct approach can be adopted for mitigation measures to combat the problem. In this context the status of different methods being used in different laboratories in Bangladesh for the analysis of arsenic in different matrices is discussed.

To address the issue of arsenic contamination of ground water in the right perspective, the need for quality assurance of analytical results is emphasized. To accomplish such a task of national importance, it is necessary to build up an institutional framework in order to achieve and maintain the quality and performance of the analytical laboratories. Once this primary task is rightly performed, the services of the tested (tested through intercomparison studies), laboratories can be utilized to monitor the field analysis statistically designed for more than two million tube wells which are in use to supply drinking water throughout Bangladesh, and to develop an overall understanding of the problem, a comprehensive scientific study of the arsenic problem involving professionals of different disciplines is needed where quantity assured analytical information will play the critical role. To this effect our own experience of laboratory analysis vis-a-vis field tests are illustrated.

A large number of arsenic field kits is used for the screening of arsenic in groundwater of Bangladesh and many other parts of the world. The kit operation involves reduction of inorganic arsenic to arsine by Zn and HCl and subsequent visual comparison of color change of a test strip containing HgBr₂ hanging in the headspace of the reaction vessel. It is known that arsine gas is one of the most toxic substances known to man with a threshold limiting value (TLV) of 50 ppbv. The objective of the present work is to understand the analytical aspects of the kit by measuring the concentration of ambient arsine produced during the test and possible safety issues associated with the kit.

Ambient arsine produced by the kit was measured under two different experimental conditions by using a single point digital arsine monitor based on color change and reflectance photometry. Experiments show that a typical test kit produce arsine with 96%efficiency in less than 500 s. This corresponds to a cumulative arsine concentration of 456 ppbv with 14 ppb As(V) in solution. All experiments produced higher than the alarm level (50 ppbv) of arsine more than half the time of the experiment. The analytical method developed in this work can be used to measure very low level of arsenic in water with a precision and accuracy of 10% rsd. The concentration of arsine produced even at this low level was 9 times above the 50 ppbv TLV. Actual kit experiments show that more than 50% of the arsine escapes the reaction cell during the test. Because the arsenic test kit can only detect arsenic concentration above 100 ppb in water, we estimate that arsine concentration in the immediate vicinity of the kit can be more than 35 TLV from a single experiment. Particularly, field workers performing a large number of tests in highly affected areas are exposed to a much higher level of arsine. We suggest the tests should be performed in well ventilated places and the worker should he provided with gas mask to minimize arsine inhalation.

Recently, there have been concerns on the right approach for the measurement of arsenic in drinking water in Bangladesh. It is very unfortunate that during this national calamity of overwhelming proportion there is no consensus as to the appropriate analytical methods for the measurement of arsenic. The problem is compounded by an urgent need of a reliable and inexpensive analytical method applicable for the analysis of hundreds of thousands of samples (there are about 2.5 million tubewell in Bangladesh -WHO).

The present problem is the measurement of total arsenic species in drinking water at 10 ppb level. The measurement methods used in Bangladesh are: arsenic kit, SDDC-spectrophotometry, electrochemical-anodic stripping voltammetry (ASV), hydridegeneration atomic absorption spectroscopy (HGAAS), and total reflection X-Ray fluorescence spectroscopy (TRXRF) are discussed with respect to their availability, sensitivity, cost, validity, and user's safety. It has been shown that the arsenic kit is the least sensitive for the purpose and most unsafe due to high level of toxic arsine generated by the kit. The SDDC method has been disapproved by the EPA due to lack of detection limit. The electrochemical method (EPA method # 7063) performing ASV seems to be very sensitive and a direct approach to measure As(III) at low cost. Techniques based atomic spectroscopy are generally very sensitive and validated extensively but very costly. New performance based method (PBM) such as reflectance photometry, flow injection techniques, gas phase amperometric arsine sensor and solid phase extraction techniques are discussed. Finally, the methods are compared on cost basis and long term guidelines for the measurement issue are proposed.
 
 
 
 
 

1. Hussam

The presence of arsenic in ground water above the maximum permissible limits 10-50ppb (parts-per-billion, 1 ppb = m g/L) has been reported in many parts of the world in last few years. The problem of arsenic contamination of ground water from a very large area of the alluvial aquifer of Bengal deltaic plane is of serious public health concern because it may have affected more than 50 million people in Bangladesh and the neighboring India. In the aquatic environment, inorganic arsenic exists in +5, and +3 oxidation states. In order of toxicity the +3[As(III) as in arsenite] is more toxic to humans than the +5 [As(V) as in arsenate] oxidation state. The present study was motivated by (1) the reed to know the extent of arsenic contamination, (2) to establish speciation information for future studies on bioavailabilty of arsenic, and (3) establish a reliable methodology for the measurement of arsenic in a decentralized way.

Measurement and speciation of inorganic As(III) and As(V) were performed by a custom-made computer controlled electrochemical analyzer performing anodic stripping voltammetry (ASV). ASV is the most direct method for the measurement of As(III) in various matrices (EPA Method # 7063). In ASV, As(0) from As(III) is electrochemically preconcentrated on a thin gold film coated glassy carbon electrode at a constant potential for a known deposition time. The deposited As(0) is then stripped off the electrode surface by a reverse voltage and the stripping current is measured. A standard addition technique is used to calculate the As(III) concentration free from matrix effect. The electroanalytical aspects for speciation measurement are outlined.

Ground water samples were collected from 17 districts covering 63 thanas and were analyzed for arsenic. About 800 samples were analyzed for As(III) and 50 samples were analyzed for both As(III) and As(V) covering wide geographic locations. The overall and regional distribution of As(III) are discussed. About 40% of the sample was found to contain As(III) above 50 ppb - a level showing significant toxicity. It was found that more than 50% of the total arsenic is in the form of more toxic As(III), which is indicative of a very reductive anaerobic aquifer. A depth distribution of As(III) is also presented. Possible consequences of this study are discussed.

During December- January, 1998-1999 we carried out a 2 week field survey in 10 villages of 8 districts in Bangladesh. All the 10 villages we surveyed in these 8 districts are new additions to our list. Further, out of the 8 districts in 3 districts, Bogra, Jamalpur and Jhinaidhah, we did not survey earlier for arsenic patients but in the other 5 districts we have found villages where people are suffering from arsenical skin lesions.

The most important point to mention is the district Bogra we declared earlier from our preliminary survey as the district where groundwater contains arsenic between 0.01-0.05 mg/l and we did not expect patients. However, in our recent survey not only we have found arsenic in groundwater in Ulipur village of Bogra as high as 1.5 mg/l but also 20 patients out of 89 we had examined. From Bogra we have now also the information of other villages (Rameswarpur, Satchua) where arsenic patients are present. The conclusion from this study is the 11 districts we marked earlier having arsenic in groundwater in the range 0.01-0.05mg/l should be thoroughly surveyed to know the situation. For Jamalpur district we had earlier reported arsenic in water above 0.05 mg/l but we had no information about arsenic patients. Present field survey indicates the village Izrapara of Sarisabari is one of the highest affected village so far we have identified in Bangladesh. We surveyed all the residents of the village and out of 145 people examined 73 have arsenical skin lesions (50.3 %) and out of 48 children (below 11 years) 8 are arsenic patients (16.6%). The water they were drinking earlier has the arsenic concentration 1.65 mg/l. At present a deep tubewell is installed. We have analyzed that water and it is safe to drink. From Shenbag Thana village Seladi of Noakhali district we analyzed 72 water samples for arsenic. Arsenic is present in all samples above 0.05 mg/l and 23 have arsenic above 1.0 mg/l and 18 have 0.7-1.0 mg/l. Our group stopped in seladi for a short while and examined 31 people and 13 (41.9%) have arsenical skin lesions and out of 13 children examined 4 have arsenical skin lesions (30.7%) also. From village Chattarpaya of the same Thana Senbag we had examined 42 water samples and out of that 32 samples contain arsenic above 1.0 mg/l. Most probably this is the only example from the groundwater contaminated area of the world where so many tubewells used by the villagers for drinking and cooking have arsenic of so much high concentration. So far from Bangladesh the highest concentration of arsenic in hand tubewell we have found is in Chaterpaya village and concentration 4.7 mg/l. Altogether from Senbag we had analyzed 538 water samples and 517 contains arsenic above 0.05 mg/l.

In Barisal district we surveyed the village Uttar Dehergati in Babugonj Thana. The villagers were not aware that they are suffering from arsenical skin lesions before our team went there. Out of 133 people we had examined 61 (45.8 %) have arsenical skin lesions. In this village181 water samples we had analyzed and 10 contains arsenic above 1.0 mg/l and 23 in the range 0.7-1.0 mg/l. Only 20 water samples safe to drink according to the WHO recommended value of arsenic (0.01 mg/1).

We knew that ground water of the district of Jhinaidhah is arsenic contaminated but we had no information of arsenic patients in this district. This is the first time we have identified village in Jhinaidhah where people are suffering from arsenical skin lesions. In Mahespur Thana the village Krishnachandrapur village is affected and out of 91 people we had examined 24 (26.31 %) have arsenical skin lesions. Although in Bangladesh at present more and more deep tubewells are installed to get safe water but in Mahespur Thana the deep tubewell (160.6 meter) supplying water through pipe line is arsenic contaminated (0.11 mg/1).Table-1 shows our survey report for 2 weeks in 10 villages of 8 districts.

Table I - Two weeks survey report in 10 villages of 8 districts
 

District	Thana	Village Surveyed
		Name of village	No. of tubewell analysed	% tubewells having arsenic >  0.05 mg/l	No. people examined for dermatological symptosm	% people having arsenical skin lesions	% people having arsenic in hair above toxic level* (average of all villages)	% people having arsenic in nail above normal level** (average of all villages
Bogra	Borga Sadar	Ulipur	47	12	89	20	72.5	84
Jhinaidhah	Mahespur	Krishna Chandrapur	113	23	91	26.3
Jamalpur	Sarisa Bari	Izrapara, Baushipara	49	40.8	145	50.3
Jessore	Abhagnagar	Pombagh	63	96.8	188	20.7
Comilla	Chandina	Orain	62	80.6	61	16.4
Barisal	Babugonj	Dehergate (Uttar)	181	78.5	133	45.8
Noakhali	Senbag	Seladi, Chaterpaya	104	99	31	41.9
Chandpur	Matalab	Kaladi	67	88	51	25.5

*Normal amount of arsenic in hair is about 0.08-0.25 mg/kg with 1.0 mg/kg being an indication of arsenic toxicity

** Normal arsenic content of nails 0.43-1.08 mg/kg

_____________

corresponding author, tel: 91 33 4735233, Fax: 91 33 4734266, email: dcsoesju@vsnl.com
 
 
 

From the studies so far carried out on the groundwater systems of Bangladesh for arsenic contamination, it is estimated that more than twenty million people of Bangladesh are drinking water with arsenic contamination above the recommended values of 0.05 mg/l and of the more than 2 two million tubewells across the country, about 26% of them are contaminated. The cause for this widespread contamination is still known to be geologic. It is recognized that deep tubewells with about 300 m depth are not contaminated with arsenic while the shallow tubewells with about 70-100 m depths are contaminated above the permissible level. Some features of this irregular distribution of arsenic in different parts of the country and how they are correlated with the groundwater chemistry will be discussed and the need for further studies would be emphasized.

Arsenic in drinking water from some specific areas of Dhaka city were measured by the techniques of stripping voltammetry and graphite-furnace atomic absorption spectroscopy(GF-AAS) in the laboratories of the Intronics Technology Center (ITC), Dhaka,Bangladesh. These measurements were carried out in ITC's Bangladesh and US laboratory facilities. Some of the measurements were carried out for specific areas of Sitakund hilly areas yet not surveyed by any organization These studies were carried out on behalf of Water Aid in Bangladesh. The data obtained in Dhaka city areas and Sitakund areas will be presented. In addition, another monitoring of tube-wells are being carried for some highly affected areas of Noakhali. These data will be presented to illustrate the extent of arsenic poisoning in highly affected areas of Bangladesh.

Although the cause of widespread arsenic concentrations in ground water of the Bengal Delta is a subject of debate, some basic elements of the problem are well established. Of particular importance, from a geochemical standpoint, is the observation that pyrite (an iron-sulfide mineral) and iron oxide are present in the deltaic sediments and locally contain high arsenic concentrations. The ongoing debate is concerned with the relation between these phases and the arsenic in the ground water. One theory posits that arsenic in the ground water results from iron oxide dissolution. A competing theory suggests that pyrite dissolution is the primary source of the dissolved arsenic. Understanding the cause of the release of arsenic to ground water is vital because water management strategies can either mitigate or exacerbate the problem.

Within the United States, the most prevalent causes of widespread, high arsenic concentrations are release from iron oxide and sulfide minerals. Cycling of arsenic between pyrite, iron oxide, and ground water has been studied inn a variety of geologic, hydrologic, and climatic settings within the United States. These studies provide a basis for an understanding of the arsenic problem in the Bengal Delta.

Arsenic can be released to ground water by desorption from, and dissolution of iron oxide. Many aquifers contain iron oxide with arsenic as an impurity due to co-precipitation or adsorption. Desorption of arsenic can be promoted by either an increase in pH or the concentration of a competing ion, such as phosphorous. Arsenic also can be released from iron oxide because of chemical reduction of the oxide. Deposition of Fe-coated sediment along with organic matter can lead to the dissolution of iron oxide with consequent release of arsenic to ground water. In ground water containing dissolved sulfide, arsenic-rich pyrite can precipitate, resulting in arsenic removal from the water. The rate of sulfide-mineral oxidation is limited by the supply of an oxidizing agent, most commonly molecular oxygen. High nitrate concentrations from agricultural activities also can oxidize sulfide minerals. Human activities that increase the supply of oxygen or another oxidizing agent such as nitrate, to ground water can lead to increased mineral oxidation and, consequently, high arsenic concentrations. A common product of this oxidation is iron oxide with co-precipitated or adsorbed arsenic. Sampling of ground water and deltaic sediments within Bangladesh and the neighboring Indian State of West Bengal suggests that these processes may be occurring in the Bengal Delta.
 
 

The reported groundwater contamination of up to 2 mg/liter in the Ganges delta in Bangladesh is found to be linked with the continued deficient recharging resulting from the reduced discharge in the Ganges from over 2,000 cu m/s to about 400 m/s in over a period of more than 20 years since 1975 and the more than 30% drop in the monsoon rainfall. Shoals formed in the dwindling Ganges and in the choked distributaries obstructed the flow of the scanty water to flood plains and other pools of water that had been the natural wells for ground water recharging. During the virgin flow of the Ganges, an annual evapotranspiration loss of about 3 trillion liters of water would deposit 35-70 kg of arsenic just front its background level of 1-2 micrograms/liter. In the following recharging season, the self-purification property of water would remove arsenic by reaction with iron hydroxides form of the ion cations with the oxygen of recharging water. Any significant drop in recharging would make the regular purification incomplete leaving behind dissolved arsenic in water. In more than the past two decades, inadequate recharging has led to the cumulative addition of arsenic every year in a way similar to the addition of salt to seawater. For the permanent solution of the problem, unobstructed discharge of the Ganges through the delta with accessibility to floodplain areas has to be restored to allow recharging over wide areas and for a long duration. Open wells in which water cleans of its arsenic content have to be introduced as a temporary measure for extraction of ground water. Riparian countries should take lessons out of this man-made disaster not to deprive a downstream country of its natural supply of water by upstream diversion. Donor agencies should notify finance projects on the construction of dams/barrages that may have potential threats to a downstream civilization. Strict international laws should be enforced not to let any country turn a craddle of civilization into a graveyard.

Groundwater abstracted from the vast tract of alluvial aquifers in the Bengal Delta Plains (BDP) is characterized by arsenic concentration above the limits of the drinking water standard of India and Bangladesh (0.05 mg/L) as well as the limits of the WHO drinking water standard (0.01 mg/L). The problem is spread over a large geographical area and a population of nearly 90-100 million in West Bengal and Bangladesh are in potential risk of arsenic exposure. The source of arsenic in these sedimentary aquifers of the BDP is geological and mainly restricted within the meandering alluvial sediments of Holocene age. The sedimentary fills in the BDP is characterized by a thick succession of fluviatile sediments deposited by the Ganges-Brahrmaputra-Meghna (GBM) river systems. The Holocene sediments of the Upper Delta Plains (UDP) are mostly characterized by complete or truncated cycles of fining upward sequences typical of the deposits of the meandering channels and dominated by course to medium sand, fine sand, silt and clay sediments (Bhattacharya et al. 1997). Two distinct facies associations have been identified, i) channel-fill association with a predominant coarse detrital suite and ii) overbank association with fine grained clastic suite (Ahmed et al, 1999). The sedimentary architecture of the BDP is however inadequately known and the lateral and vertical variability of the individual sedimentary facies need detailed investigations.

Petrological and geochemical characteristics

Petrological studies on the clastic units from Chapai Nawabganj in NW Bangladesh reveal that the detrital mode comprises nearly 50-65% quartz, 7-15% feldspar, 5-15% mica (biotite and muscovite)and 7-20% lithic fragments. Sparry calcite is observed in some samples of the channel fill facies. Theheavy mineral content is generally low (<l%) to moderate (<5%), whereas opaque heavies such as pyrite and/or arsenopyrfte are insignificant. Non-opaque heavies include mostly homblende, garnet, tourmaline, epidote and rutile. The striking feature noted in most of the samples is the pronounced development of authigenic ferruginous coatings on the detrital framework grains of quartz and feldspar. Biotite at places show signs of alterations with the development of conspicuous iron stains. The coatings are deep brown to black in color, generally thin but at places thick to very thick. At places the sparry calcites are often seen to be masked by the ferric precipitates (Ahmed et al 1999). The presence of authigenic pyrite and corroded iron oxy-hydroxides are noted in the fine clastic sediments.

Geochemical investigations on the alluvial sediments from Hanspukuria, Mahishbathan and

Ghetugachi in Nadia District in West Bengal have revealed significant enrichment of arsenic. 7M HNO₃ extraction technique used to determine the non-silicate bound chemistry of the sediments reveal arsenic concentrations in the range 20-133 mg/kg in the aquifers at different depths.

Significant positive correlation has been noted amongst the total concentrations of Fe, Al, Mn and PO₄ with arsenic in these sediments. Estimation of leachable As from these sediments has been carried out through sequential leaching batch experiments using deionized water (pH 6.95) and with 0.01 M NaHCO₃ (pH 8.65). The total concentration of arsenic leached by sequential leaching was found to be in the range of 116-383 m g/L strikingly similar to the As concentrations in groundwater (Bhattacharya et al. 1998, 1999). Selective oxalate and pyrophosphate extraction of the sediments have been carried out to understand the relationship of As with the secondary amorphous Fe, Al and Mn phases and organically bound As. Oxalate extraction of the sediments revealed that ferric oxyhydroxides dominate in these sediments (Fes_x = 264-1233 mg/kg) as compared to aluminum hydroxides Als_x =27-294 mg/kg) as secondary inorganic mineral phases in these sediments. The clayey sediments at depths however indicate presence of both Fes_x = (933 mg/kg) and Als_x (294 mg/kg) fractions and complimented by high Sis_x (229 mg/kg) indicate dissolution of the secondary aluminosilicates as a potential adsorbent for arsenic. The concentrations of pyrophosphate extractable Fe, Al, Mn and As are however low and suggest that the bulk of the arsenic is bound to the inorganic fractions of Fe, Al and Mn in the sediments.

Hydrochemical characteristics

Groundwater is in most cases found to be Ca-HCO₃ type although Na-HCO₃ type and Na-Cl type

water are also found in some areas (Bhattacharya et at 1998, 1999; Ahmed, 1999). Groundwater samples from Nadia district in West Bengal are characterized by elevated pH values, in the range

from 7.1 to 7.8 and correspondingly high alkalinity up to 352 mg/L. Concentrations of sulfate (2-12.8 mg/L), phosphate (0.5-3.1 mg/L) and Mn (0.1-0.9 mg/L) are the typical characteristics of the groundwater from the BDP, The total concentrations of arsenic reached up to 370 m g/L. As^3+/As⁵⁺ ratios were generally less than 1.0, but As³⁺ concentrations were still high, from 15 to 122% of the As⁵⁺ concentrations. Concentrations of total iron varied between 1.8-8.8 mg/L and the correlation between the total As and the total Fe was low. Data from discrete aquifer depths however revealed good correlation between total As and total Fe (r² 0.93).

Available data on pore water chemistry from Chapai Nawabganj (BGS/MMI, 1998) and Meherpur (Perrin, 1998), indicate that oxidation of the cores prior the extraction and analysis changed considerably and do not correspond to the local conditions of groundwater chemistry. This is because of the fact that the reduced species such as Fe, NH₄, Mn and As become oxidized and may be removed from dissolved phases altogether. Concentration of Ca and HCO₃ which is generally high in groundwater decreased considerably because of calcite precipitation (BGS/MM, 1998). The pore water arsenic profile from Meherpur shows that high arsenic zone in pore water occurs just below the high arsenic zone in the sediments.

Isotope geochemical characteristics

The d²H and d¹⁸O data for the shallow groundwater typically range between -46 to -24 % and - 8.0 to- 3.0 % and plot close to the World Meteoric Water Line (WMWL) and hence indicate recharge due to precipitation with no evidence of evaporation (Shivanna et al. 1999). There is a striking similarity in the d¹⁸O composition (-6 %) of the groundwater samples from shallow, intermediate and deep aquifers particularly in the UDP of Murshidabad district which indicate the possible zonal interconnections between the aquifers (Bhattacharya et al. 1997). Shallow groundwater are characterized by tritium values of 2.10 TU and ¹⁴C values (87-109 PMC, Shivanna et at 1998)

indicate influence of modem recharge (< 50 years). Isotopic signatures of the deep groundwater however indicate tritium values >2 TU with corresponding ¹⁴C values of 78-85 PMC giving a model age of 500 years. Stable isotope signatures of groundwater from shallow as well as deep aquifers in Nadia district are more or less similar. d³⁴S values in groundwater from shallow aquifers range between +3.2 to +9.5% (Shivanna et al. 1999). The enrichment of d³⁴S is related with decrease in the sulfate concentration in groundwater. In Nadia district low groundwater sulfate concentration is concomitant with increased d³⁴ S values (+7.7% implying the role of sediment organic matter in the sulfate reduction processes. The d¹³C data show that most of the DIC in groundwater are depleted in ¹²C and these values are consistent with methanogenesis under extreme reducing groundwater conditions. These data also suggest that the dissolved inorganic carbon in the groundwater was derived from oxidation of organic matter in the aquifers.

Conclusions

The data generated so far does not support the pyrite oxidation hypothesis as a major source of arsenic contamination in the Holocene sedimentary aquifers in the Bengal Delta Plains. From the petrological investigations, it seems very unlikely that pyrite oxidation is a viable mechanism for the release of arsenic in groundwater. The absence of primary detrital sulfide minerals in the aquifer sediments is ubiquitous as they are unstable under oxidizing conditions during transport well as deposition with in the BDP. At the same time very low concentration of sulfate in groundwater is also contrary to the pyrite oxidation hypothesis. On the other hand, ferruginous grain coatings on the detrital framework grains serve as a potential adsorbent for arsenic within the aquifer sediments. Adsorption of arsenate is facilitated under oxidizing conditions during the sediment-water interaction within the sedimentary basin. Finer sediments always contain high concentrations of arsenic. Presence of framboidal pyrite suggests that they are the potential sinks for arsenic and not the source for arsenic in the fine grained sediments. Corroded iron oxyhydroxides as revealed by the SEM studies have particular relevance to arsenic release and mobilization due to reductive dissolution. Most of the arsenic present in the sediments are oxalate leachable.

Sediment geochemical data support the hypothesis that arsenic in groundwater is released due to desorption as well as reductive dissolution of ferric hydroxides present within the clastic aquifer sediments. Ferric hydroxides with variable pH-dependent surface charge attain a net positive charge at low pH values where the adsorbed arsenic is predominantly in As(V) anionic form and to less extent in As(III) in neutral form. With an increase in pH, the surface charge of ferric hydroxide becomes more negative and arsenic is desorbed. During groundwater development, flow of reducing groundwater through the aquifers results in the dissolution of ferric hydroxide and releases bulk of the arsenic due to reductive dissolution of the ferric oxyhydroxides. Transformation of amorphous ferric hydroxide to goethite with time may also constrain the release of arsenic due to decrease in the available surface adsorption sites in the aquifer sediments. Similar hypothesis has already been published for the origin of arsenic in West Bengal (Bagia and Kaiser, 1996; Bhattacharya et al. 1997) and in Bangladesh (Nickson et at 1998).
 
 

References

Ahmed. K.M. (1999) A review of available geochemical data and their implications to the origin of arsenic in Bangladesh groundwater. Abstract Volume. KTH-Dhaka University Seminar on Groundwater Arsenic Contamination in the Bengal Delta Plains of Bangladesh, February 7-8, 1999, Department of Geology, University of Dhaka, Dhaka, Bangladesh, p.18.

Ahmed. K.M.m Imam, M.B., Akhter, S.H, Hassan, MA. And Khan A.A. (1999). Sedimentary and minerology of the arsenic contaminated aquifers in the Bengal Delta of Bangladesh. Abstract Volume. KTH-Dhaka University Seminar on Groundwater Arsenic Contamination in the Bengal Delta Plains of Bangladesh, February 7-8, 1999, Department of Geology, University of Dhaka, Dhaka, Bangladesh, p.22.

Bagia, P. and Kaiser. J. (1996). India's spreading health crisis draws global arsenic experts. Science 274: 174-175.

BGS/MMI (1998). Groundwater studies for arsenic contamination in Bangladesh. Draft Final Report, volume S4: Hydrogeochemistry of the Special Study Areas.

Bhattacharya, P., Chatterjee, D. and Jacks, G. (1997). Occurrence of arsenic contaminated groundwater in alluvial aquifers from Delta Plains, Eastern India: Options for safe drinking water supply. Int. J. Water Res. Management 13(1): 79-92.

Bhattacharya, P., Jacks, G., Sracek, A., and Chatterjee, D. (1998). Sediment chemistry of alluvial aquifers in part of Bengal Delta Plains, Eastern India: Implications for mobilization of arsenic in groundwater. Applied Geochemistry (in review).

Bhattacharya, P., Jacks, G., Sracek, A., Gustafsson, J.P. and Chatterjee, D. (1998). Geochemistry of the Holocene alluvial sediments in the Bengal Delta Plains and their implications in groundwater arsenic contamination. Abstract Volume. KTH-Dhaka University Seminar on Groundwater Arsenic Contamination in the Bengal Delta Plains of Bangladesh, February 7-8, 1999, Department of Geology, University of Dhaka, Dhaka, Bangladesh, p.12.

Nickson, R., McArthur, J., Burgess, W., Ahmed, K.M. Ravenscroft, P. and Rahman, M. (1998). Arsenic poisoning of Bangladesh groundwater. Nature 395: 338.

Shivanna, K. Sharma, S., Sinha, U.K., Nair, A.R., Navada, S.V., Ray, A., Talukdar, T., Mahta, B.C. and Ghosh, A.K. (1999). Arsenic pollution in groundwater of West Bengal. Workshop on Ground Water Pollution and its Protection with Special Reference to Arsenic Contamination. Science City Calcutta, January 22, 1999, Central Ground Water Board, Eastern Region, Calcutta and UNICEF, pp. 1-16.

Perrin, J. (1998). Arsenic is groundwater at Meherpur, Bangladesh: a vertical pore water profile and rockwater interactions. Unpublishsed M.Sc. Thesis, University College London.
 
 
 

To combat the present arsenic crisis, we badly need the following: (1) proper watershed management; (2) utilization of our huge number of water bodies with people's participation; (3) rain water harvesting; (4) the people should be made aware of the arsenic calamity and they must be made to realize that it is not a curse of god, or the consequence of the 'wrath of god'; (5) we must understand that, safer water, nutritious food and physical exercise are the only medicines for chronic arsenic toxicity at present. For nutritious food it is not necessary, one has to take of egg, fish, and meat. Elephant, the strongest animal, is a vegetarian. We have to teach villagers how they can get nutritious food using seasonal fruits and vegetables. During our survey in affected villages, we have found more than 90% of the population suffering from arsenical skin lesions show signs of vitamin-B deficiency when plenty of vegetables and edible herbs are available and cheap. Although villagers eat vegetables and edible herbs but they cook so hard with strong spices that vegetables no longer taste like vegetables; (6) the scientific community and medical people all over the world must come forward to find a solution to the problem that has put at risk 100 million people only in West Bengal and Bangladesh.

Working on West Bengal's arsenic calamity for the last 10 years, even now we feel we are at the tip of the iceberg. Thus we need to know as early as possible the real magnitude of the arsenic calamity in Bangladesh. For that other than district level work, we need in-depth semi-micro and micro level studies to get an idea of the magnitude of the calamity at Union and village levels. According to WHO, the possibility of getting skin lesions exists among those drinking 1.0 mg of arsenic per day for several years. And our analytical report on water (about 12000) indicates that a large sum of population is consuming above 1.0 mg of arsenic per day. Our thousands of hair, nail and urine analyses from the affected villages indicate that more than 80% of population have higher arsenic body burden. Thus many may not be showing arsenical skin lesions but may be sub-clinically affected. Further if it is true that arsenic toxicity appears after several years of exposure, then the picture may actually be far more grim than it appears at present, and children our future generations are at a greater risk.

The mistake that we made in the past and are persisting with it even today is the merciless exploitation of groundwater for irrigation without ever trying to adopt effective watershed management to harness our huge surface water resources and rainwater. In Bangladesh, we have large area of wetlands, a huge area of flooded river basins, innumerable ox-bow lakes and big lagoons. Per capita available surface water in Bangladesh is about I 1000 cubic meter.Proper watershed management and the use of these water bodies for pisciculture, duck-breeding and growing vegetables on their banks with people's participation could actually help the villagers become more prosperous. Instead of taking this course, we are digging more and more tubewells. From West Bengal experience we now know even deep tube-wells are not safe. Out of 31 deep tube-wells (above 350 feet) installed in Gaighata block in district North 24-Parganas West Bengal during last 2 years, 19 are now arsenic contaminated which were safe when installed. During our survey in January, 1999 to Maheshpur thana, Jhinaidaha district, Bangladesh we have found that there is only one deep tube-well (530 feet) in that thana and supplying drinking water to thousands, is arsenic contaminated (0.11 mg/1). In the long run these deep tube-wells may ran the risk of contamination. In many districts of W. Bengal and Bangladesh most of the aquifers are unconfined and they run more risk of contamination. Only in the southern part of West Bengal and Bangladesh thick clay barriers are present and may be used for deep tube-wells taking all precautions during tube-wells installation, artificial changes etc. Even for irrigation, we are digging deep tube-wells. Recently, a veteran geologist has in an article captioned against such reckless use of deeper aquifers and has cited its disastrous consequences. It must be realized that water held in recent rainfall does not replenish this resource. Recent isotope studies carried out in Rajasthn-India indicated that such water could be 600 to 10,000 years old.

A few samples of tube well water were collected from a village, Chapil of Dhamrai Police station, in the district of Dhaka (about 30 miles north of Dhaka city). The levels of arsenic and other trace metals were measured by Inductively Coupled Plasma Mass Spectrometry (ICPMS) method. These results and an attempt of arsenic removal from a standard solution will be discussed.

This presentation will begin by reviewing the range of proposed remediation technologies for treating arsenic-contaminated wells in Bangladesh. The general categories of heavy metal removal by coagulation /filtration, sorption and membrane techniques will be covered. Special emphasis will be on those technologies highlighted in recent international arsenic conferences in Dhaka (February and December, 1998) and San Diego (July, 1998) and on suggested technologies put forward by WHO, the University Connecticut (Nikos Nikolaidis), Bengal Engineering College, and the Council of Scientific and Industrial Research (India). A newly proposed option which substitutes the natural polymer chitosan for metal salts, will be discussed. Next, we will examine these technologies in terms of available information on treatment performance and costs. Third, this presentation will consider the accessibility of these technologies to community and women's groups, in terms of their appropriateness, simplicity, transferability, use of local skills and resources, cultural sensitivity. This examination leads to a conclusion that innovative coagulation/sedimentation/filtration approaches are among the best treatment options in terms of the three criteria: performance, cost, and appropriateness.

The U.N. Earth Summit (1992) and the U.N. Beijing's Women's Conference (1995) have acknowledged women's intimate connection to water. All over the world, and including Bangladesh, women collect and carry water for their families, use water for cooking and cleaning and for growing food. Community and women's groups will be the front-line users of arsenic treatment technologies in Bangladesh. Thus, this paper will also examine the relationship between the technologies and the users of these technologies. Brief case studies of technology transfer and skills development training with peasant women's groups in Myanmar, Nepal and India will be included.

In many affected areas of West Bengal and Bangladesh, villagers do not have access to any secondary source of arsenic-free water. Surface water treatment and subsequent distribution of treated water in such remote areas will be extremely complex and costwise prohibitive. Installing operationally simple low-cost arsenic removal units at the existing wells is practically the only way-out to ensure a supply of safe drinking water. To this end, through a grant from Water For People (WFP) in Denver, CO, to Bengal Engineering College in Howrah, WestBengal, four well-head arsenic removal units have installed in villages of North 24 parganas during 1997 and 1998.

All of them are running quite satisfactorily and providing arsenic free water to hundreds of villagers. The key features of these units can be summarized as follows:

• The entire operation is manual and does not require any electricity. The arsenic removal columns are installed at the exising tube wells with hand pumps.

• Activated aluminia which selectively removes dissolved arsenic from groundwater without changing the water's composition otherwise is the primary adsorbent in these columns. Activated aluminia is readily available from a company in Durgapur, West Bengal. The entire unit is fabricated and installed using indigenous materials only.

• The arsenic-removal unit does not warrant any chemical addition or continuous monitoring. All one needs to do is to open a valve, operate the hand pump and then collect arsenic-free water in a bucket or a vessel.

The regeneration process has been standardized and these units are currently being operated and maintained by villagers through a committee. Each unit has the capacity to serve two to three hundred households. With a moderate amount of planning, such well-head units can be installed in villages of Bangladesh without any major difficulty. More specific aspects of these easy-to-operate arsenic removal units will be presented.

Concerns about the health risks associated with arsenic in drinking water from natural and anthropomorphic sources and the need to remove arsenic from landfill-leachate contaminated groundwater has led to the development of a simplistic and cost effective method for removing arsenic from drinking water. The Arsenic Remediation Technology (AsRT) uses common materials, zero-valent iron and sand, to remove arsenic to levels below 1 ppb. After completing successful laboratory scale tests at the University of Connecticut, a two-year pilot demonstration was conducted at the Winthrop Superfund Site in Maine. Nine months of operation has resulted in lowering the influent As(III) concentration from about 350 ppb to less than 1 ppb in the groundwater. AsRT does not appear to be affected by the 500 ppm of sulfate in the water being processed.

The field tests were designed to not only confirm the ability of AsRT to handle actual arsenic-contaminated groundwater, but also to generate design information that is needed for sizing. The AsRT field tests consist of a set of columns filled with the zero-valent iron and sand mixture through which the influent containing arsenic from an existing extraction well is passed. The affect of flow velocity, and hydraulic detention times were also studied and indicate that a 90% removal efficiency was achieved for a detention times less than 5 minutes. The field columns have treated over 20,000 pore volumes and are estimated to continue for another 20,000 more. The AsRT pilot is designed to treat 26 Liters for each gram of zero-valent iron. With zero-valent iron currently priced at $350 per ton, this method may prove to be a cost-effective alternative to combat a growing global problem. The considerations for a point-of-use filter and the bearing of the AsRT pilot data on that problem will be discussed.

Bijoypur clay from Mymensingh and processed cellulosic materials like delignified jute, bleached sawdust and pulped newspaper were found to adsorb both As(III) and As(V) in solutions acidified with vinegar or hydrochloric acid. Adsorption studies were carried out in batch and column type experiments using synthetic and source waters. Iron(III) hydroxide coated newspaper pulp in lab-scale, adsorption filters coagulated arsenic most. The material showed potential for use in small scale home treatment units. Workable exposure length flow, rate and extractant volume demonstrated arsenic removal at least to or even below the maximum contaminant level of 50 ppb. The sludge was regenerated by sodium hydroxide elution.
 
 
 
 
 

(Prior to earning his doctorate, Timir Hore carried out many complex hydrogeological investigations including the development of a massive universe of groundwater data collected in and around the Callcutta area. Since 1986, Dr. Hore has implemented numerous and extensive goundwater investigations and remedial programs in New Jersey and Pennsylvania and elsewhere in the USA. He is currently Principal Hydrogeologist with C&H Environmental Inc., in New Jersey).

Arsenic has been identified as a contaminant. in concentrations above any safe drinking-water

standard, in the groundwater underlying part of West Bengal, particularly around Greater

Calcutta, and much of the Peoples Republic of Bangladesh. The persistence of soluble compounds of this metal in groundwater has become a truly serious public-health problem, since the indigenous populations drink and cook with the arsenic-contaminated water, and use it for other routine domestic purposes.It has been known that the water table throughout Bengal and Bangladesh has been dropping steadily for some years, due largely to over-pumping. Furthermore, the resource represented by the Ganges river, the Brahmaputra (also called Jamuna) river, and the great delta which is formed by the merging of the two rivers, is also known to be stressed by overuse.

Unsafe concentrations of arsenic have long been known to be present in the groundwater at scattered sites in the region, but the appearance of unsafe concentrations of arsenic in the groundwater over an extensive area of the region is a relatively recent phenomenon The root cause appears to be over-pumping, and the lowering of the water table which has resulted. As the water table drops in areas not previously affected by the contamination, water from neighboring areas which are affected by the contamination can migrate literally from higher to lower levels. Such migration is facilitated by well construction which does not embody double casing and other means for preventing movement of water from upper strata to lower strata.

During a visit to Calcutta from mid-December 1998 to mid-January 1999, the author of this note discussed this growing problem with a variety of professionals - university professors, chemists, microbiologists, geologists, and hydrological and hydrogeological professionals, active and retired, in and out of government. We discussed methods of data gathering, modes of investigation, and most intensely, their views on how to handle this alarming threat to public health.One overarching truth became clear in the course of these informal discussions. Professionals of great competence working in different scientific disciplines, each viewing the situation from a unique point of view conditioned by his unique background, can accomplish little without coordination and exchange of information. The problem cannot even be properly described until a systematic investigation is undertaken involving the sampling of all existing water-supply wells. Well logs are not now available for all existing wells, and where available do not always provide needed useful data. Well construction conforms to no standard: some wells are believed to have been drilled through multiple water-bearing strata without proper isolation or protection; little attention is ordinarily devoted to well design adequate to protect uncontaminated water-bearing strata from contaminated strata. The problem presented by the wells which drilled through multiple strata is especially serious, since groundwater samples from such wells are at best ambiguous: if there is arsenic in the water, from which aquifer or aquifers did it enter?

Further, the soil, geology and hydrogeology of the present area of concern have been delineated and mapped only in terms of broad stratigraphy. Several of the known water-bearing horizons underlying the region may not present much in the way of groundwater supply, but may be quite effective in producing arsenic contamination. Groundwater flow direction by survey of the groundwater elevations in each individual aquifer has not been determined. There is no hydrogeolo-ical model of the region. And, not surprisingly considering these lacks, no systematic effort has been undertaken to prevent vertical or horizontal migration of contaminants such as arsenic and its soluble compounds from one aquifer to another.

It should be noted that arsenic is not the only contaminant putting the regional supply of potable water at hazard. There are other serious contaminants, both organic and inorganic. The effect of arsenic is dramatic and quickly observable in the human population; other contaminants which have been found in the regional groundwater kill slowly, with effects that may be irreversible when finally identified.

The geologists and hydrologists with whom the author discussed this regional problem were agreed [1] that no additional well drilling should be undertaken in the region without prior study and approval by a qualified hydrogeologist. [2] That before any drinking water well is installed, the integrity of the site soils, the nature of the aquifer soils, and the characteristics of the water in the target aquifer, should all be analyzed. [3] That if any contamination is detected in any water-bearing stratum during drilling, construction of the well should be stopped immediately, and only continued if double-case protection is feasible to prevent vertical migration of the contaminant. [4] If the well conduit passes through water-bearing stata above the target aquifer, the case should be sealed with a bentonite/cement slurry; and [5] the upper 4'-6' of all well tubes should be sealed with bentonite/cement mix to prevent movement of contaminants from the surface along the pipe into the subsurface soils.

Above all, there was complete agreement that the time to attack the problem was now, and that the attack on the problem required first of all the development of reliable data. Such a database must provide information on the regional groundwater characteristics both horizontal and vertical. To be reliable, it must be gathered by an objective scientific organization of recognized competence in the related disciplines. Individuals or organizations with narrow focus and self-serving concerns cannot seriously address this problem, and funds given to such individuals or organizations are not likely to produce meaningful results. Groundwater systems in the delta and adjacent are complex, and solid investigation by knowledgeable scientific minds will be required to identify and delineate the contaminant plume or plumes, determine movement of such plumes, and develop effective programs for remediation or correction of the problem.

Furthermore, the consensus among these professionals was that the governments of West Bengal and Bangladesh should begin to enforce beneficial control in this matter quickly. Strict laws and regulations strictly enforced are needed. Arsenic compounds were at first detected in only a few areas but now the problem has spread and serious groundwater impacts are being experienced. Without the intervention of the government and the cooperation of the relevant scientific disciplines, the seriousness of the problem will rapidly spread. The old-fashioned approach of the wildcatter, that common sense is adequate to the purpose, is ineffective respect to this problem.

Professor and Head, Dept. of Community Medicine, NIPSOM, Mohakhali, Dhaka-1212
Associate Professor, Dept. of Occupational and Environmental Health, NIPSOM, Mohakhali, Dhaka-1212
Assistant Professor, Dept. of Occupational and Environmental Health, NIPSOM, Mohakhali, Dhaka-1212
Medical Officer, Leprosy Hospital Mohakhali, Dhaka-1212
Lecturer, Dept. of Community Medicine, Feni Medical College, Feni
Medical Officer, Dept. of Occupational and Environmental Health, NIPSOM, Mohakhli, Dhaka-1212
Professor, Dept of Parasitology, NIPSOM, Mohakhali, Dhaka-1212

Objective: Explore the pattern of health effects due to arsenic contamination of ground water and evaluate the chronic arsenicosis management regimen currently being practiced in Bangladesh.

Methodology: This paper has been prepared on the basis of fact finding surveys conducted purposively from 1994 to 1998 and record of patients available at Department of Occupational and Environmental Health (DOEH), NIPSOM. The surveys were carried out in villages on receiving information from the locality about the presence of groundwater contamination by arsenic and/or presence of suspected patients. Evaluation of the chronic arsenicosis management regimen currently being practiced was carried out on 43 patients in a village that is being monitored by DOEH.

Results: Arsenic contamination of ground water has been identified in 52 districts, and a total 6000 cases located in 170 villages of 72 thanas of 37 districts have been identified. The most common presentations are melanosis (93.5%), Keratosis (68.3%), leukomelanosis (39.1%) and hyperkeratosis (37.6%). A few obvious skin cancer patients have been detected. The clinical manifestations were categorized in three stages and most of the patients were found in the first and second stages. Cases in initial and second stages showed improvement on intake of Vitamins A, E, & C, and keratolytic agent (where applicable) along with withdrawal of further intake of contaminated water.

Conclusion: Toxic effects arising from arsenic contamination of groundwater is a new and emerging public health problem in Bangladesh. An estimated 50 million people are at risk of developing arsenicosis. The commonest clinical manifestations are melanosis and keratosis. Vitamins A, E, & C, and keratolytic agent (where applicable) along with withdrawal of further intake of the contaminated water appears to have a role in the management of the patients.

There are over three million shallow tubewells in Bangladesh providing over eighty percent of drinking water to people. Water from a large number of these tubewells are contaminated by Arsenic. In some areas the contamination has exceeded the safe limit by over 50 times. Skin and internal diseases have been observed among thousands of people and several deaths have been reported. More important here is to note that Arsenic really affects the whole body causing respiratory problem and even cancer to the affected people. Studies also claim that Arsenic affects children's intelligence.

The arsenic research group of BCSIR undertook survey work in different districts of Bangladesh and could detect up to 2.7 ppm of Arsenic (54 times over safe limit). No apparent connection between depth of the tubewells and arsenic content could be observed. Surface water and water from deep tubewells was found to contain arsenic below safe limit.

A mitigation technology which consists in adding a floc forming composition to the contaminated water followed by filtration through a specially formulated filter bed has been developed for removal of this soluble Arsenic from tubewell water. The amount of floc forming composition depends on the quantity of Arsenic present in water. About 30 minutes is required for adsorption of arsenic on the floc. Water containing up to 2.7 ppm arsenic could be purified below safe limit set by WHO.

The flow rate is approximately 6 litres per hour. The cost of a filter for filtering up to 6000 litres of water is about Tk. 300/=($6.0) only. Cost of floc forming composition for a litre of water (with 1.0 ppm arsenic) comes to about Tk. 0.20 only.

The materials required for the preparation of floc forming composition and the filter are all available locally. Considering the flow rate, low adsorption period and above all low cost, the technology seems to be suitable for the rural poor people of Bangladesh.

One response to arsenic-contaminated groundwaters in Bangladesh is to identify and use alternate drinking water supplies. Surface waters such as rivers and ponds will typically require sediment filtration and biological-disinfection before they can be used for this purpose. A PV-powered 160-Watt system built around a low-cost UV disinfection unit was successfully demonstrated in Dhaka in February 1999, at the request of the US Dept. of Energy. The system was set up in one day, uses physical and activated carbon filtration followed by UV disinfection, and provides up to 21,000 liters per day. The same UV unit ("UV Waterworks") can be part of a range of treatment system configurations, built to address specific site conditions. These systems can be operated in rural or urban locations as water vending stations for micro-enterprise efforts, or as freely distributed public health measures.
 

Arsenic contamination of ground water and its adverse effect on health has now been established as a public health problem. In order to measure the magnitude of the problem Dhaka Community Hospital, along with School of Environmental Studies, conducted a country wide cross sectional survey. We collected and analyzed 1045 ground water samples from all the districts of Bangladesh using FI- HG- AAS methods. Out of these samples 45.36% contained arsenic more than 0.05 mg/l in 41 districts, the maximum permissible limit of arsenic in drinking water for Bangladesh as recommended by World Health Organization. Total population of these 41 districts is 76. 9 million, a large portion of whom were found to drink arsenic contaminated water. We examined randomly selected 7588 people from 23 districts who were drinking arsenic contaminated water and found 33% of this population showing arsenical skin lesions. Since latent period for arsenicosis is quite longer, the disease burden we are experiencing now is the tip of the iceberg. A concerted effort is required to combat the future burden due to arsenic.

The problem of arseniferous groundwater in the Bengal Delta Plains (BDP) has emerged as one of the major global issues which needs immediate attention (Bagia and Kaiser, 1996; Bhattacharya et. al. 1997, 1998; ACIC, 1999). The problem is spread over a wide geographical area both in West Bengal and in Bangladesh. Groundwater development has increased alarmingly over the past three decades to sustain the need for water for irrigation as well as providing safe drinking water supply. Unfortunately, the consumption of groundwater during this period has resulted in acute environmental health disaster in the entire region (Mandal et al. 1996; Dhar et al. 1997). The provision of safe drinking water to a vast cross section of population in West Bengal and Bangladesh has become an issue of great concern. There is almost no possibility to refrain people from drinking well water or stop the practice of wetland cultivation. Simultaneously, there is no possibility to arrange alternate drinking water supply through community water treatment systems for the rural and semi-urban population. The choice of any remedial technique must therefore be low-cost and affordable by the rural population that should comply with the existing framework of groundwater use as well as the land use pattern in the region. Moreover, the techniques of groundwater amendment may vary depending on the short term and long term perspectives.

In terms of the low-cost remediation techniques for safe drinking water supply, three major options are: i) Auto-attenuation, ii) Use of geological material as natural adsorbents for arsenic viz. laterite or Fe-rich oxisols-, and iii) Artificial) recharge or more specifically reinfiltration of groundwater to the aquifers following aeration. The present paper discusses the possibilities of each of these remedial techniques and their possible applications in the affected segments of the Bengal Delta Plains.

Auto-attenuation is one of the most convenient method to remediate the groundwater. The principle is simple, which needs collection of groundwater from the wells and let it stand for a specific period of time. Since most groundwater from the Holocene alluvial aquifers in the BDP have high concentration of dissolved iron, they are readily oxidized and form ferric precipitates in the containers. The auto-oxidation of Fe²⁺ to Fe³⁺ generates favorable substrate with surface reactive sites for the adsorption of both uncharged AS³⁺, as well as anionic As⁵⁺ species. Our recent observations on the Bangladesh groundwater samples, filtered and acidified after collection in-situ from two adjacent wells from Harian village in Rajshahi District have indicated an initial Fe and As concentrations of 9-9.5 mg/L and 92-120 m g/L respectively. Filtered, unacidified samples from the same wells were analyzed after a residence time of 15 days following refiltration and acidification. The analyzed concentrations for Fe and As were found to be in the range of 53-47 m g/L and 23-36 m g/L respectively. A similar set of water samples from different depths at Ujalpur in Meherpur District however revealed contrasting results. Shallow groundwater from a depth of 30 m with initial Fe and As concentration levels of 9.2 mg/L and 104 m g/L respectively were reduced to 20 m g/L Fe end As after a gestation period of 15 days. Groundwater from the deeper aquifer (90 m) with low initial Fe concentration (2.7 mg/L) and As concentration of 86 m g/L indicated no remarkable change in the arsenic concentration (80 m g/L) even though Fe concentration was reduced to 13 m g/L. The differential behavior is related to the variations in the hydrochemical characteristics, particularly the redox conditions of the groundwater (Eh = -0.4V). On the basis of these observations it can be suggested that auto-attenuation needs to be investigated further as a method for the amendment of high As groundwater.

Laterite has been tested as an adsorbent and proved to be a promising low-cost remedial technique to safeguard drinking water (Larsson and Leiss, 1997; Larsson et al. 1998). Laterite is a red colored vesicular clayey residuum occurring abundantly in the tropical regions. The major components in laterite are hydrous oxides of iron- and aluminum, with minor proportions of manganese and titanium. Laterite is an acidic soil with a typical pH between 4-5. Both hydrous iron and aluminum oxide components in laterite have a PH_zpe at 8.5-8.6 (Anderson et at 1975: Kinniburgh et al. 1976). Under natural conditions they are characterized by net positive surface charge, and thus have the capacity to adsorb several anionic contaminants at wide pH range (Pierce & Moore, 1982; Wilkie & Hering,1996). Laterite could either be used in a filter column or directly mixed with water in the water vessel where the soil particles would act as adsorbent during sedimentation. The results of the adsorption batch experiments on high-As groundwater from village Ghetugachi, Chakdaha in Nadia district in West Bengal indicate that laterite is an effective filter medium, notably for those in which the arsenate dominates over the arsesnite. The adsorption experiments performed on the water indicated considerable decrease in arsenic concentration after treatment with laterite. The efficiency varied between 50-90 % for 5 g of added laterite per 100 ml water under an equilibration period of 20 minutes. The maximum effective adsorption was achieved during the first 10 minutes and remained more or less constant with time. The fine grained laterite indicated highest adsorption due to available reactive surface area. Amendment of laterite by treating with 0.01 M HNO₃ increased in the adsorption capacity of the laterite due to an increased specific surface area.

Artificial recharge has been used to augment the groundwater availability. It has also been used to improve the groundwater quality to a limited extent in Finland and in Sweden to remove iron from the groundwater. Tests have been made in Denmark to remove nitrate from groundwater by recharge through straw beds supplying organic matter for denitrification. Groundwater recharge has been used in India to decrease the fluoride content of groundwater. Evidences met within the Bengal Delta Plain reveal that the arsenic in groundwater is mobilized from an adsorbed pool of arsenic in the ferric precipitates through reductive dissolution. The aim must then be to lift the redox-state from the ferric/ferrous level to a higher level by introducing another electron-acceptor than ferric iron. There are essentially two choices, oxygen or nitrate. Oxygen has a limited solubility at the high ambient temperature met with in the area. Furthermore if pond recharge is used, algal growth and subsequent degradation may consume the oxygen rather fast. In well recharge, clogging by ferric precipitates may pose a problem. Denitrificaton requires three conditions, the presence of nitrate, anaerobic conditions and a degradable organic matter (Jacks et at. 1999). Nitrate can be added and anaerobic conditions are already prevailing in the aquifers, manifested in the almost ubiquitous presence of dissolved iron in the groundwater. The key factor is the degree of degradability of the organic matter. The organic matter must be 'chewable' for the denitrifiers. It may not be a disadvantage if the organic matter is a bit refractory as that would imply that the effect of recharge will be rather soft along the water pathways avoiding local clogging with ferric precipitates. Ferrous iron in the blue clay layers sandwiched with in the post-glacial aquifers can chemically reduce nitrate in the Danish groundwater environment.

An indication whether nitrate could be used as an oxidant could be obtained by analysis of the ¹⁵N¹⁴N ratio in the traces of nitrate occurring in the groundwater. Denitrification discriminates¹⁵N and causes accumulation of the isotope in the residual nitrate. The applicability of using nitrate as oxidant should then be tested in batch tests with sediment samples, preferably non-oxidized, cored material. In the field the recharge proposal could first be tested in areas where the upper aquifer is unconfined so that recharge ditches or ponds could be used. Well recharge requires far more knowledge about the hydraulics the groundwater flow and is expensive. Rather simple and reliable recharge wells have been designed by Vivekananda Research and Training Institute in Gujarat in India (Raju & Ferroukhi 1996). They are based on sand-filtration before the entry into the recharge well and have been in use for 8 years up till now. If groundwater recharge is a viable solution, the in situ oxidation of ferrous iron offers the advantage that large amounts of ferric sludge is avoided.

References

ACIC (1999) West Bengal and Bangladeshd: Arsenic Crisis Information Center. URL: http://bicn.com.acid

Anderson M.A., Ferguson J.F. & Gavis J. (1976) Arsenate adsorption on amorphous aluminum hydroxide. J. Colloid Interface Sci. 64: 391-399.

Bagia P., and Kaiser J. (1996) India's spreading health crisis draws global arsenic experts. Science 274: 174-175.

Bhattacharya, P., Chatterjee, D. and Jacks, G (1997). Occurrence of arsenic contaminated groundwater in alluvial aquifers from Delta Plains, Eastern India: Options for safe drinking water supple. Int. J. Water Res. Management 13(1): 79-92

Bhattacharya, P., Larsson M., Leiss, A., Jacks G., Sracek, A. and Chatterjee, D. (1998). Genesis of arseniferous groundwater in the alluvial aquifers of the Bengal Delta Plains and strategies for low cost remediation. Abstract Volume. International Conference on Arsenic Pollution in the Bengladesh: Causes, Effects and Remedies, Dhaka, Bangladesh, p.120-123.

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Kinniburgh DG, Jackson ML and Syers JK (1976). Adsorption of alkaline earth, transition and heavy metals by hydrous oxide gels of iron and aluminum. Soil Sci. Soc. Am. J. 40: 796-799.

Larsson M, Leiss A. Bhattacharya P, Jacks G and Chatterjee D (1998). High-arsenic groundwater is West Bengal, India: Test of laterite as a filter media. Nordic Society of Clay Research, Meddelande 12: 12-14.

Mandal BK, Roy Chowdhury T, Samanta G, Basu GK, Chowdhury PP, Chanda CR, Lodh D, Karan NK, Dhar RK, Tamili DK, Das D, Saha KC and Chakraborti D (1996). Arsenic in groundwater in seven districts of West Bengal, India. The biggest arsenic calamity in the world. Current Science 70(11): 976-986.

Pierce ML and Moore CB (1982). Adsorption of arsenite and arsenate on amorphous iron hydroxide. Water Res. 16: 1247-1253.

Raju KCB and Ferroukhi L (1996). Water harvesting in coastal areas. In: J. Pickford et al (eds) Proceedings of the 22^nd WEDC Conference, Reaching the Unreached: Challenges for the 21^st Century, New Delhi, 201-204.

Wilde JA and Hering JG (1996): Adsorption of arsenic onto hydrous ferric oxide: effects of adsorbate-adsorbent ratios and co-occurring solutes. Colloids Surfaces A107, 97-107.

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