Home >Documents >Arsenic in Bangladesh

Arsenic in Bangladesh

Date post:15-Nov-2014
View:117 times
Download:0 times
Share this document with a friend

Evidence Based Environmental Policy and Management 1: 1-? (2007)

Blue Gold: A Deadly GiftEvaluation of the removal of naturally occurring arsenic from groundwater in Bangladesh via a household filtration system based upon a composite iron matrix

Ame Alexandra PlantEnvironmental Studies, School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.

Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand


Evidence Based Environmental Policy and Management 1: 1-? (2007)

AbstractHigh concentrations of naturally occurring arsenic are found in the groundwater of Bangladesh. A wide range of technologies have been created to remove arsenic from drinking water. The SONO filtration system is a household level technology, and through coagulation, filtration and precipitation processes the arsenic is transformed from its potentially deadly soluble form into an insoluble solid that is exposed of as waste. The system is highly effective in its removal of arsenic and currently provides safe drinking water to millions. Such an achievement provides a small step in the direction of achieving the Millennium Development Goal of providing clean safe drinking water to a larger majority of the population. The system provides an affordable short term solution Keywords: Bangladesh, arsenic removal, household level, Filtration, Composite Iron Matrix, contamination, groundwater

Introduction Water, blue gold is finite, all the water that will ever be is, right now (National Geographic, 1993). The freshwater that we as the human race depend on amounts to 0.01% of all water on earth, illustarted below in figure 1 (Miller, 2005). With global trends set to see a human population of nine billion in 2050 the importance of water security is imminent (Crop Life International , 2004). The United Nations has addressed this threat in their Millennium Development Goals (MDGs) under goal seven, a difficult task in which they have stated it will require extraordinary efforts to achieve (United Nations, 2008).

Figure 1: The distribution of the World's water resources with emphasis on the distribution of fresh water. Source from (Lannoe, 2007)

A pressing issue of the global water crisis is concerned with water quality as it is the quality of water that determines its purpose (Department of the Environment: Water Heritage and the Arts, 2008). Many pollutants of both human and natural origin contaminate water undermining its quality (Miller, 2005). The effect on humans specifically can be devastating. The United Nations states that contaminated drinking water and poor sanitation kill 1.5 million children a year (United Nations, 2008). The contamination of water supplies via anthropogenic processes is generally

Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand


Evidence Based Environmental Policy and Management 1: 1-? (2007)

easy to rectify once the cause has been identified. Identifying contamination via natural processes on the other hand is much more difficult (Miller, 2005). One such problem is the contamination of water with arsenic. The effects on its consumers are horrific; acute poisoning results in diarrhea, vomiting, convulsions and blood in urine which may later be followed by coma or death. Chronic poisoning causes skin lesion, abnormal growth, and cancers. There is a great deal of concern about the later form of poisoning as it may take up to ten years before any symptoms are revealed (A. H Welch et al, 2003). This was the case for millions of people in Bangladesh. For years the people of Bangladesh had suffered epidemics of cholera, typhoid and dysentery as a result of drinking from pools and streams that where contaminated with harmful microbial pathogens (Baxter, 1998) During the 1970s UNICEF and the Government of Bangladesh encouraged its people to drink water from tube wells (Anwar, 2007). These tube wells accessed the abundant reservoirs of groundwater below their feet and promised high quality water. Regrettably the water contained the deadly poison arsenic (A. H Welch et al, 2003). By 1993 when the first symptoms of arsenic poisoning began to appear there were millions of tube wells throughout Bangladesh supplying water to around 90% of its population (BBC NEWS | Science/Nature | Water scarcity: A looming crisis?, 2004). The British Geological Survey was asked to test a proportion of these wells for arsenic contamination. The results indicated that approximately fifty percent of the tube wells tested were over the World Health Organization standard of ten parts per billion. In many cases the concentrations were greater than 200ppb (British Geological Survey). In addition hazardous concentrations of arsenic have been detected in forty seven of sixty four districts (SOES/DCH, 1998). The Government, UNICEF and others had to counteract their initial approach and encourage people not to drink from contaminated groundwater (Baxter, 1998). Millions of people are at risk from arsenic poisoning and the majority of those concerned are completely unaware of the daily hazard they face. Arsenic itself is colourless, odourless, and tasteless even in high concentrations requiring special chemical tests to detect its presence in drinking water (Lepkowski, 1999). Added to these problems are the socio-economic background of Bangladesh and the overwhelming dependence of its people on groundwater (DPHE/Danida, 1999). In view of the above factors there is an urgent need for a suitable treatment system for the removal of arsenic from groundwater. Socio-economic conditions of Bangladesh demand low-cost, easy to use, convenient, small treatment units that can be implemented in households and communities (Saha, 2001).Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand 3

Evidence Based Environmental Policy and Management 1: 1-? (2007)

A variety of technologies have been used for the removal of Arsenic from groundwater, including: 1. Co-precipitation with ferric chloride2. Absorptive filtration and exchange resins

3. Ion exchange 4. Membrane processes like reverse osmosis

High iron concentrations may decrease the effectiveness of the above technologies. As ferrous iron will be oxidized and form a ferric hydroxide coating upon surfaces, or in the case of number four above block the pores of membranes (Hering J. G, 1996) (McNiel, 1997) (Sorg, 1978). The Bucket Treatment Unit (BTU) developed by DPHE-Danida will be the focus of this literature based research report (Owen, 2001).

Aim The aim of this study is to evaluate the removal of naturally occurring arsenic from groundwater in Bangladesh via a household filtration system which is based upon a composite iron matrix. _____________________________________________________________

Objectives Answering this question necessitated breaking the task down into three information seeking objectives as follows: 1) What is the Bucket Treatment Unit and how does it operate? 2) Determine the arsenic removal capacity of the SONO filter 3) Determine the social aspects of the SONO filter: The management of spent material The manufacturing and distribution The social acceptability

Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand


Evidence Based Environmental Policy and Management 1: 1-? (2007)

Methods Each objective requires the same procedure of obtaining information when searching databases. Thus the methods of searching literature for information on each objective will be the same. ........................................................................................................................................Sample set and Procedure a) Search Databases

Search engines Google, Yahoo, AltaVista, and Ask.com (useful for acquiring basic information surrounding the objective) Google Scholar peer reviewed papers, thesis, books and abstracts from professional societies (useful for more reliable sources of information) Subject Gateways BUBL, Intute: Science, Education and Technology, Intute: Health and Life (academically reliable information.) Books Worldcat (access to electronic books) Databases science research.com, web of knowledge / web of science, water resources abstracts Journals Directory of Open Access Journals News Sources: EureaAlert, New Scientist, BBCi: Science and Nature (keep up-to-date on subject.

Before searching will ensure that the correct source has been chosen. To do so i will simply ask; does it have full text? Does it cover the right subject matter? Does it contain peer reviewed information? The next step in gathering information for each objective will involve being prompt. P-presentation: How is the information communicated? If pages are not clearly communicated then no more time will wasted upon them R-Relevance: information may not be relevant to my search due to; the geographical aspects, level (too basic or too specialized), emphasis. O-Objectivity: good information should be devoid of bias and be well balanced presenting information on both sides of an argument M-Method: research. the way information is produced; an opinion, research, reviews of

Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand


Evidence Based Environmental Policy and Management 1: 1-? (2007)

P-Provenance: who produced it where did it come from provides useful clues its reliability; authors, organisations. T-Timeless: The date of production/publish important indicator of reliability. Thus any information that does not have a date will not be considered for this report................................................................................................................................................... Sample set and Procedure b) Key Words Objective 1: Household, Filtration, System, Arsenic, Bangladesh Objective 2: Removal capacity, Arsenic, Bangladesh, Filtration, System, household Objective 3: Management, waste, material, manufacturing, distribution, social, cultural, acceptable, benefits, arsenic removal, Bangladesh, household


Sample set and Procedure C) Search Limits

Objective 1: Terminology has proven to hinder some searches as BTU is the simplest terminology the technology is known by and used throughout this study. The technology has various names. Very specific search provides a limited number of peer reviewed journals. Objective 2: Due to the specific nature of the report, the geographic location and socio-economic nature of the study area in addition to the fact that the technology was only created in 2001, there were very limited papers addressing the issue in focus. Objective 3: the barrier of language means that the peer reviewed literature sourced from Bangladesh is written by those who can afford an education; it is therefore difficult to truly state the social aspects of the SONO filter with certainty that what we read is correct................................................................................................................................................ Sample Set and Procedure D) Rational of limits

Objective 1: As the bucket treatment unit is fairly new technology and a specific topic all literature available was thoroughly researched.

Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand


Evidence Based Environmental Policy and Management 1: 1-? (2007)

Objective 2: The scarcity of the quantity of peer reviewed literature, although the few papers providing the in depth information needed where of high quality. Therefore all relevant information was thoroughly studied. Objective 3: Those who are educated are voices for their country and people, and are informers of the crisis in which they face daily. Other peer reviewed literature where compiled of author from less bias nations.E) Key Content

Objective 1: Structure and operation of the SONO filter system Objective 2: Effectiveness of SONO filter system in reducing arsenic concentrations Objective 3: Manufacture, distribution, management and social acceptability of SONO filter

F) Focus

Objective 1: Basic illustrations and descriptions of how the SONO filter operates Objective 2: Graphs and Tables from key sources illustrating how effective the SONO filter is at removing arsenic from ground water. Objective 3: Qualitative descriptions and illustrations of the social factors surrounding the SONO filter ResultsObjective 1: What is the Bucket Treatment Unit and how does it operate?

The BTU is a two-stage, pour-collect filtration system and was developed with Bangladeshi villagers in mind. The BTU consists of two 40-litre plastic buckets and illustrated below in figure 2. The top bucket is red in colour and contains the composite-iron matrix (CIM) in between two layers of sand. The bottom bucket is green in colour and has a simple sand and charcoal filter that cleans the water of iron and other impurities that may have drained from the first bucket (Figure 2) (A. Hussam, 2001) (Rasul, 2002).

Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand


Evidence Based Environmental Policy and Management 1: 1-? (2007)

Figure 2 A schematic representation of the Bucket Treatment Unit Source from (A. Hussam, 2001)

To produce clean drinking water groundwater is collected from a local well and poured into the upper red bucket which contains 32 kg of material. The water filters down through 10 kg of course river sand which are obtained from local river sediments and thoroughly washed before use. The course sand layer contains 95% SiO2 and acts as a filter oxidising soluble iron. The product of iron oxidation is the precipitate Fe(OH)3 (s) which is effectively trapped in the sand (A. Hussam, 2001). The course sand layer also provides mechanical stability by stabilising the flow of water. In addition this layer reduces the production of fine particles. This results in a low probability of the pores spaces between the sand grains clogging up, and a higher probability of the sand layer lasting for longer without compromising the quality of water (Mortoza, 2008). The water then passes through 5-10 kg of the composite iron matrix (CIM) which contains 92-94% Fe. The CIM is manufactured iron turnings obtaining from local industries. The turnings are washed and treated to enhance HFO formation. The CIM is the surface upon which ions of elements such as arsenic are captured and immobilized.Published by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand 8

Evidence Based Environmental Policy and Management 1: 1-? (2007)

Iron hydroxide has a remarkable capacity to capture ions of other elements. This is because of its molecular structure illustrated below in figure 3 which is full of gaps.

Figure 3: The molecular structure of iron (III) hydroxide, (the ball within the shaded green area is iron; blue = oxygen; white = hydrogen) note the openess of the structure. Source (Clark, 2003)

Effectively, hydrogen atoms are remote enough from iron and oxygen in the structure for them to produce localised positive charges at the surface of the mineral. Consequently negatively charged anions can attach to the surfaces of the iron hydroxide by adsoption. Iron (III) hydroxide therefore acts like a chemical mop (Pierce, 1982). The water then flows through a second layer of course sand (10kg) before being manually taped and piped through plastic tubing to the second green bucket (Wilkie, 1996) (A. Hussam, 2001). The water is filtered through a third layer of course sand (10 kg) which retains any iron leached from the first bucket. The following layer contains wood charcoal that is obtained from the firewood used for cooking. The charcoal absorbs any organic matter, and although passive to As this layer provides better tasting water. The water then flows through 9kg of fine sand derived from rivers and acts as a fine filtration system designed to catch ant residual particle. Finally the water passes through 3.5 kg of brick chips, obtained from local manufactures. The brick chips stabilise water flow before being manually tapped into any container below (A. Hussam, 2001) (Yuan, 2006) (Raven, 1998). The structure itself consists of two 40 litre buckets made of food-grade high density polypropylene buckets. These buckets are produced by local plastic modelling industries and are fitted with a top cover to reduce further contamination and are moulded with outlets for the flow control taps. The flow controllers are made ofPublished by the School of Geography Environment and Earth Science Victoria University of Wellington, New Zealand 9

Evidence Based Environmental Policy and Management 1: 1-? (2007)

either moulded plastics or metal taps and control the flow of water through the system. Lastly a metallic filter stand made by local welders provides support for the buckets and completes the Bucket Treatment Unit (A. Hussam, 2001).

Objective 2: Determine the arsenic removal capacity of the unit

The BTU was tested with contaminated groundwater by Hussan and Munir from six different tube wells in six different households; Fatic, Caurtpara, Zia, Alampur, Kaliskhnpur and Juniadah (A. Hussam, 2001). The CIM removed the inorganic arsenic through a series of possible reactions which are visible in appendix D for reference. The results indicate that arsenic concentrations ranging from 32-2423 ug/L where entered in to the filtration system. The potable water that had been filtrated on the other hand only contained between

Popular Tags:

Click here to load reader

Reader Image
Embed Size (px)