AIMS OF THE PROJECT
It is nearing almost a decade since arsenic poisoning known in Bangladesh. Deaths, arsenic related diseases and potential chronic arsenic suffering are rapidly increasing day by day. Researchers estimate that 18 million to 76 million people are at risk in Bangladesh (Tampa Bay Business Journal, 1998).Millions of the poor villagers are kept in dark without getting any proper assistance. The Daily Star (17.2.99) reports that villagers complain that various teams of experts from home and abroad have been visiting their localities, but they are busy only collecting data and sample and taking interviews of the victims. No measure was there to effectively help the people about how could they save themselves from this problem, they complained. Dr. Allan H. Smith, an epidemiologist at the University of California at Berkeley reports after visit to Bangladesh, "We know what causes the damage and we know what to do about - provide safe water, we just need to do it." Aftermath of recent severe flood the presence of arsenic in the ground water has all but been forgotten. Sylvia Mortoza (1998) comments that arsenic contamination of ground water is seen by many as an opportunity to get rich and now looked upon by man as God-sent gift or bonanza, or at best a chance to prove a theory or sell a ready-made remedy. Recently a huge arsenic removable techniques are offered in the internet, such as, "You don't have a lot of opportunities in one lifetime to make a significant impact on the world and make money at the same time"( R. Papadopoulos, Chairman and CEO of Project Earth, Tampa Bay Business Journal, Nov. 30, 1998).
There is already arsenic menace, which has opened a new market. Prof. Khorasani (1998) proposed for a U.S . Technology that will cost about 20 million US dollars. But to remove arsenic by sunlight method costs almost nothing and can be carried out all over Bangladesh without relying foreign technology and the same amount can be spent for the improvement of living conditions of landless farmers or poor.
The method is simple and some relief can be obtained on arsenic contaminated drinking water, sulphate reduction and remove water-borne pathogen in Bangladesh.
But cheaper solution that would take trouble to go among the people and teach them the simple technology that does not create enough money to made and does not attract NGOs and government agencies. .
The principal goal of this project is to introduce least cost-effective, efficient and appropriate method of water purification, arsenic removable, health and disposal in the light of adaptability and easy reproducibility within Bangladesh environment. In fine, the goals are:
- Formation of village committees who will be trained to look after water purification and disposal units, health and environmental aspects.
- Water purification from 1000 tube wells (1000) families contaminated with arsenic/enteric bacteria, coliform bacteria by using sunlight, air and earthen pot;
- Introducing inexpensive sand filterer using local clay pot, sand (and charcoal, if water is contaminated with pesticides, etc.).
- Cleaning , maintenance and self production of sand filterer.
- Innovating clay potters to introduce optimal water containers and sand filterers.
- Disposal of arsenic precipitates in cow-dung pits.
- If tube well near water pond is arsenic free or low arsenic, advise to shift other tube wells to this site
- Construction of water tank that obtain sunlight and passed through sand filterer for school children (500-800) .
- Cultural and social meetings for transfer of knowledge.
AREA OF THE PROJECT
British Geological survey (1998) has compiled nation-wide distribution of arsenic in ground water at union level on computer and geo-coded to thana level that indicate that south-west region is extensively contaminated. The most intensely contaminated areas are found along the Lower Meghna in the greater districts of Comilla, Noakhali and Faridpur.
The older Ganges aquifer (GI) is thinly bedded and fine grained strata contains most of the contaminated wells. Highly contaminated wells occur beneath the older Ganges floodplain, whereas Alluvium Sand more thickly bedded G2 aquifer that has been deposited within the last 15,000 years are virtually free of arsenic. The sediment deposit since millions of years in Bangladesh is channel deposits (coarse grained), as braided or meandering rivers with gradually fining sequence in levee slope or crevasse splay deposits and finer over-bank deposits and deposits in natural depressions and different depositional units in the lower delta regime which further characterised by seasonal variations and fluctuations of sea level under highly complex processes. Arsenic reacts with soil components, where the predominant reaction is adsorption and reaction reaction with hydrous iron and aluminium oxides which coat soil particles. Heavier soils with higher clay content and hydrous oxide content adsorb more arsenic than lighter sandier soils with low clay content. Author(1999) found along Kumar River, Faridpur that arsenic content along back-swamp (Holocene) river deposit contains a high arsenic content in groundwave, where as sandbar (mid-channel, pointbar ) almost the absence of arsenic content in ground water. Aim is that to identify such sand bar deposits and advise to use water from these units.
Department of Public Health and Engineering and Safiullah (!998), DCH and British Geological Survey (1998) carried out extensive water analysis in Faridpur shows more than 29 percent of wells between 10-100 meter are contaminated (above 0.05mg/l arsenic). A very high percentage of contaminated wells are expected, if WHO standard is considered. The present project aims to produce 1000 water purification units, sand filterer, disposal and education & management for very low income families of different Thanas of Faridpur that are worst affected by arsenic contamination. Besides 50 water purification units for about 800 school children will be constructed. The area is known, where experimental studies for "sunlight , air and clay pot" method of removing arsenic was successfully carried out in January/February 1999.
OPEN DUG HOLES
Immediate emphasise will be given for open dug hole in bangla "Kua" or "Indira" protecting biological contamination. These Kuas are arsenic free, as light, air and filtration within oxidizing condition keep water arsenic free. Water from the open dug hole can be improved through protection (keep it clean) and bacteria can be removed through solar radiation (without cost) or through boiling. A simple filterer produced and maintained by the villagers cannot cost more than 100 Taka (2 US Dollars). Water collection can be further improved through hand pumps and filter Water from the open dug hole can be improved through protection (keep it clean) and bacteria can be removed through solar radiation (without cost) or through boiling. A simple filterer produced and maintained by the villagers cannot cost more than 100 Taka.
"Open dug hole" or bangla Kua or Indira does not contain arsenic. At Alipur, Faridpur I found an open dug hole "Kua" and a tube well where water from the tube well contained 0.50mg/L arsenic (WHO standard 0.01mg/l) and water from "Kua" did not contain any arsenic. But this open dug hole has vanished from Bangladesh through UNICEF and other agencies.
1. Filling checklist
2. 50 litre arsenic contaminated water from tube-well put in a clay pot
3. Sample for laboratory and field analysis for arsenic, iron
4. Water put in the sun and added iron, if water constitute low in iron
5. Water is kept for 6-8 hours, alum added, if necessary
6. Water is poured carefully over sand filterer keeping coagulation sludge at the bottom for disposal.
7. Water analysis after filtration;
8. After filtration water is ready for drinking and cooking purposes.
9. If filtration slows down, it is cleaned, by gently passing water from the bottom to top and water sludge containing iron and arsenic, transfer to the disposal unit.
APPROPRIATE METHOD FOR BANGLADESH
Sunlight Air Method
While going through many literature author found astonishingly simple arsenic removable method practised by the arsenic miners in Australia. Researchers in Australia developed simple method to remove arsenic from contaminated drinking water or mining waste using just sunlight and air (Young, 1996). The ultraviolet radiation in sunlight helps the dissolved oxygen to oxidise the arsenic to the less toxic form, which can then be precipitated (iron arsenate) and removed. In the mid 80's Roberts, Kris D. treated arsenic contaminated water SE north Dakota by a very old technology for removing iron and manganese from potable water through wood plate aeration tower feeding sand filterer. Arsenic co-precipitates with iron and manganese, where arsenic concentration from 40-90 µg/l reduced to 10-20 µg/l (ND, Department Health, USA, 19.06.98)
The ability of iron oxides and hydroxides to absorb arsenic and heavy metals is well known.. Under oxidising conditions amorphous arsenic reacts with ferric Oxy-hydroxide to be precipitated in the bottom. As dissolved iron is oxidised it precipitates as iron Oxy-hydroxide, which scavenges arsenic from solution. Inorganic arsenic contaminated water, spiked with equivalent sulphate concentrations passes through an ferruginous sand fillings/sand "filterer". This results in removing most of the arsenic from the solution. The chemical process that takes place is as follows: Elemental iron will oxidise to ferrous iron (Fe(II)). If there is oxygen present in solution (aerobic), it will be consumed according to the reaction:
2Feo + O2 + 4H+ = 2Fe+2 + 2H2
This reaction will utilise all oxygen in solution and it will cause a temporal reduction in the pH of the solution. When the solution becomes anaerobic, iron oxidation will be coupled with the hydrolysis of the water. When this occurs, the sulphate and arsenate reduction is as follows:
Feo = Fe+2 + 2e- Iron Oxidation
Fe+2= Fe+3 + e- Iron Oxidation
8e- + 9H+ + SO4-2 = HS- + 4H2O
2e- + 2H+ = H2(g) Hydrolysis of water
2e- + 4H+ + HAsO4-2= H2O + H3AsO3
Further on, the products of these reactions can form precipitates that would include the formation of Fe(OH)3, FeAsO4, FeAsS and the like. Inorganic arsenic species could also be removed from the solution through the formation of co-precipitates, mixed precipitates and by adsorbing onto the ferric hydroxide solids.
REMOVEBLE OF SULPHATE
Removal of sulphate is also very important. The application of uncontrolled chemical fertiliser has increased sulphate concentration in many areas. Sulphate is a substance that occurs naturally in drinking water. Health concerns regarding sulphate in drinking water have been raised because of reports that diarrhoea may be associated with the ingestion of water containing high levels of sulphate. Of particular concern are groups within the general population that may be at greater risk from the laxative effects of sulphate when they experience an abrupt change from drinking water with low sulphate concentrations to drinking water with high sulphate concentrations. One potentially sensitive population is infants receiving their first bottles containing tap water, either as water alone or as formula mixed with water. Other groups of people who could potentially be adversely affected by water with high sulphate concentrations include transient populations (i.e., tourists, hunters, students, and other temporary visitors) and people moving from areas with low sulphate concentrations in drinking water into areas with high concentrations.
On July 19, 1979 (44 FR 42195) EPA published a secondary maximum contaminant level (SMCL) for sulphate in drinking water of 250 milligrams per litre (mg/L), based on aesthetic effects (i.e., taste and odour). The World Health Organisation's (WHO) recommended sulphate guideline is 400 mg/L, which is based on taste.
REMOVEBLE OF WATER-BORNE PATHOGENS
UV Des-infection system:
Illnesses very commonly occur in Bangladesh caused by pathogens commonly transmitted by water include typhoid, cholera, dy-sentry, hepatitis, giardiases, polio, legionaries disease, and several gastrointenstital and influenza-like illnesses. There are many cost expensive methods to eliminate water-born pathogens. An alternative to UV Des-infection is solar radiation. Oydeyemi, O. (1999) , Brace Research Institute focused solar radiation as an alternative to UV radiation can be applied to combat water related and water borne diseases. Since ancient times in Bangladesh our ancestors knew the benefits of water kept under sun, before taking the bath of new-born babies. Accra et al. (1984) experimentally showed the following results:
· 99.9 per cent of coliform bacteria were killed after 95 minutes of exposure to sunlight, but it took 630 minutes to achieve the same level of destruction under room lighting.
· Under direct sunlight 99 per cent kill of total bacteria was achieved in 300 minutes compared to 850 minutes under room conditions.
· Under sunlight achieved complete destruction of enteric bacteria as follows :
- Pseudomonas aeruginosa 15 minutes
- Salmonella flexneri 30 minutes
- S. typhi and S. enteritis 60 minutes
- Escherichia coli 75 minutes
- S.paratyphi B 90 minutes
- Aspergillus niger 3 hours
- A. flavus 3 hours
- Candida and Geotrichum spp. 3 hours
- Penicillin suspension 6-8 hours of exposure.
The use of sand filtration to improve water quality is not a new concept. Slow sand filtration has been used for decades to treat wastewater and purify drinking water in many parts of the globe. Sand filtration has been proved to be both an economical and effective option for removing pollutants. Designers are constantly refining the basic sand filterer to increase the level of consistency of nutrient and bacterial removal. A popular approach has been to add an additional organic layer to the filterer bed to increase pollutant removal capability. A series of organic media have been used including a top layer of grass/soil, grass/peat or compost, a middle layer of peat, activated carbon, and even zeolites. Another option to improve sand filterer performance is to create a permanently saturated, anaerobic zone at the bottom of the filterer bed. Conditions in this zone are favourable for de-nitrification, which might substantially improve the rate of nitrate removal. Performance and monitoring data for sand filterers from Texas, Delaware, Florida, Virginia, the district of Columbia, and Washington in the USA suggest that are very effective in removing particulate pollutants such as total suspended solids, heavy metals, organic carbon, and organic nitrogen..
Regular maintenance is an essential component of the operation of a sand filterer. At least once a year each filterer should be verified as most filterers exhibit diminished capacity after a few years due to surface clogging by organic matter, fine silts, hydrocarbons, and algae matter. Operation of sand filterer requires replacement of the surface sand layer on a relatively frequent basis.
Design Variations of the Sand filterer
The versatility of the sand filterer is reflected in the numerous design variations that have been developed to address many different climatic and development conditions. Nearly a dozen variants of the basic sand filterer design are currently in use, and engineers and practitioners continue to create more. A simple sand filterer in a clay pot for 20 litre water has been introduced to remove arsenic and other contaminants.
Disposal of the arsenic-contaminated coagulation sludge from the C/F and LS technologies may be a concern. For large treatment plants, a large body of water would likely be needed to discharge the contaminated brine stream from the RO/NF technologies. Inland treatment plants would possibly need either some pre-treatment prior to discharge or would need to discharge to the sanitary sewer due to the increase in salinity. Discharge to sanitary sewers may require pre-treatment to remove high arsenic levels. The waste stream produced by IE/AA technologies is a highly concentrated brine with high TDS. These brine streams may required some pre-treatment prior to discharge to either a receiving body of water or the sanitary sewer.
Low Cost Tech:
Regeneration of AA columns results in a toxic waste containing very high concentration of soluble arsenic. The effluent of acid rinses is mixed with the caustic rinses and this mixed arsenic waste can then be disposed on a prepared bed of cow-dung in a shallow hole dug in earth. The micro-organisms in cow-dung transform the arsenic to gaseous arsine and arsenic is thus released into the surrounding air.
EXPERIMENTAL STUDY - SUNLIGHT AIR AND CLAY POT METHOD
During January and February 1999 in-collaboration with Bangladesh Geological Survey worst arsenic affected areas of Commilla and Faridpur
An experimental study has been carried out from January to till today (18.02.98) to test whether the simple method of oxidation and removable can eliminate arsenic from contaminated drinking water in Bangladesh by transforming toxic As+3 to As+5 under artificially producing abiotic oxidation environment. Dieter (1987) reports that arsenic content can be reduced to 10µg/l (Allowable Standard 50µg/l) through precipitation of iron-arsenate. Ahmed and Nickson (1997) showed that significant reduction of arsenic was detected in Bangladesh with the removal of iron.
Contaminated water can be put in troughs dug (like small swimming pool) and lined with plastic can hold cooking and drinking needs of 100 families every day. Using sunlight alone, the oxidisation process can take a few hours, but for lightly contaminated drinking water, it takes only a few minutes. For more contaminated water (mining sludge), UV lamps similar to those currently used to disinfect water can modified to speed up the process (Young, 1996).
Arsenic contaminated waters were collected from Comilla and Faridpur districts tube-wells depths vary from 45 feet to 150 feet during January and February 1999 and successfully eliminated arsenic by simple sunlight, air, clay pot and simple sand filterer method.. Extremely contaminated waters where deaths occurred has been obtained from Faridpur. About 67 samples of various locations have been tested at various location.
i) Arsenic content before treatment: above 1.7 mg/litre(Bangladesh allowable standard 0.05 mg/litre)
ii)After clay pot and sun treatment: 0.1mg/litre (twice the amount to allowable standard)
iii) After clay pot and sun treatment + Alum (Fitkari): 0.05 (allowable standard)
iv)After Sand-filterer : almost absent
Added ferrous iron to contaminated water (1.7 mg/litre) and kept openly inside a room in a transparent plastic jar:
Result after 8 hours --- arsenic almost absent
After filterer: almost absent.
Sand filterer (Bangla- Chakni)
Our project experiences show more effective and pragmatic project (October 2003):PROJECT REPORT AUGUST 2003
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Arsenic Removal Program