Arsenic In Ground Water Of Terai Region Of Nepal, Its Effect And Mitigation Measures Adopted

Arsenic in Ground Water of Terai Region of Nepal, its effect and Mitigation measures adopted. By Preetam Pandey B.E (Civil)

Submitted to Dr. Chhattra Mani Sharma, Instructor Natural Resource Management, Department of Human and Natural Resource Studies in Partial Fulfillment of the Requirements for the Degree of I Semester

MASTER OF ARTS in Human and Natural Resources Studies at the

KATHMANDU UNIVERSITY SCHOOL OF ARTS JULY 2009

Arsenic in Ground Water of Terai Region of Nepal, its effect and Mitigation measures adopted. By Preetam Pandey

Abstract This paper focuses on the effects in human health due to arsenic contamination in drinking water. Some mitigation measures which are commonly applied in the rural areas of Terai region of Nepal are discussed. Key words: Contamination, tubewell, gagris, handpumps.

Introduction Groundwater Arsenic problem (Arinita, 2006) in Nepal is a relatively new issue. The first study on arsenic contamination was conducted in Eastern Terai region of Nepal by the Department of Water Supply and Sanitation (DWSS) in 1999, indicated the possibility for arsenic contamination in groundwater of Terai (DWSS/WHO, 1999). Since then, the governmental and non-governmental organizations and some researchers tested several thousand tubewell water samples to identify arsenic contamination level and found that 7.4% of the tubewells had arsenic concentration more than maximum permissible limit of Nepal (0.05 mg/L) (NASC1/ENPHO2, 2004). The updated database of 512,840 tubewells so far tested for arsenic levels as of May 2006 in 20 Terai districts reported 11.5% water samples to exceed the WHO guideline value of 0.01 mg/L and 2.4% samples above the Nepal Standard of 0.05 mg/L (NASC/DWSS/UNICEF, 2006). In Nawalparasi, Bara, Parsa, Rautahat, Rupandehi and Kapilbastu districts, tubewells exceeding 0.01 mg/L of arsenic varied from 8.3% to 25.8%, while it was 2.3% to 12.1% for 0.05 mg/L of arsenic. 1 2

NASC- National Arsenic Steering Committee ENPHO- Environment and Public Health Program

Nepal though increased water supply coverage substantially over the past two decades but is still facing problems related to drinking water. Eighty-one percent of Nepal’s population now has access to either piped municipal water supplies or tubewell water sources (Adamsen, 2002). These high levels of coverage do not necessarily ensure the provision of safe water in Nepal. Municipal water supplies are rarely chlorinated to adequate levels and bacterial contamination in tap water is common. Widespread bacterial contamination problems have also been identified in all kind of water supply systems in rural areas of Nepal. These water quality problems are frequently exacerbated by unsafe water storage practices in both urban and rural regions of the country (R.R.Shrestha, 2003). The sanitation situation in Nepal is even more troubling. As a result of the failure to provide safe water and adequate sanitation, the effects of waterborne disease weigh high. Regular out breaks of water borne epidemics, increasing number of patient being admitted to hospitals, high infant mortality rate are some of the consequences. In addition to microbiological quality, public health impact due to ingestion of arsenic contaminated water has also been reported in Terai belt of the country. It has been estimated more than 3 million people in the country are at risk due to arsenic in drinking water (R. R. Shrestha et. Al, 2002).

Fig: Arsenic Affected 20 Terai District

Reference: ENPHO, Kathmandu

Arsenic in drinking-water in Terai Region of Nepal is attracting much attention for a number of reasons. It is a problem to the population, including concerned professionals. There are millions of people who are affected by drinking arsenic-rich water and fear for future adverse health effects as a result of water already consumed. It was followed by a mass scale arsenic contamination investigation by Nepal Red Cross Society with the Technical assistance of Environment and Public Health Organization (ENPHO) and financial assistance of Japanese Red Cross Society. Later other rural water supply agencies like FINNIDA, NEWAH and Department of Water Supply and Sewerage (DWSS/UNICEF) started testing its tube wells in its project areas of Terai region. In total, out of the 20,240 tube wells tested till date in Nepal, 1550 (about 8%) tube wells has arsenic concentration above Nepal Interim Standard (50ppb) while 5881 (29%) tube wells exceeds the WHO standard (Study conducted by NRCS/ENPHO, FINNIDA, DWSS, RWSSFDB, RWSSSP/DIDC, DEO, Plan).

Causes of Arsenic Contamination in Groundwater The causes of arsenic contamination in ground water are still not known clearly. Theories show that rocks rich in arsenic were eroded from the Himalayas and other high lying source areas through flood and soil erosions. Arsenic is widely distributed throughout the earth's crust and is introduced into water through the dissolution of minerals and ores, and concentrations in groundwater in some areas are elevated as a result of erosion from local rocks. Industrial effluents also contribute arsenic to water in some areas. However, three factors are supposed for groundwater arsenic contamination in the terai region of Nepal.  Arsenic present in the aquifers sediments  Arsenic released from the sediments to the groundwater  Arsenic flushed away in the natural groundwater circulation. Due to heavy groundwater extraction and fluctuation of water tables from pre-monsoon and post monsoon and also due to thousands of bore holes, the groundwater aquifer is aerated. This can oxidize arsenic bearing sulfide minerals like arsenopyrite (FeAsS) and

pyrite (FeS2). This oxidation process release arsenic into underground water (Clark & Whitney, 2001).

Acceptable Level of Arsenic in Drinking Water The total daily intake of Arsenic by the general population is usually less than 0.2 mg/day (Shrestha & Arinita, 2005). The WHO had issued a ‘Guideline Value’ for arsenic in drinking water at 50 ppb or 0.05mg/L and many countries have kept this as the national standard or as an interim target. According to the last edition of the WHO Guidelines for Drinking-Water Quality (1993): 

Inorganic arsenic is a documented human carcinogen.



0.01 mg/L was established as a provisional guideline value for arsenic.



Based on health criteria, the guideline value for arsenic in drinking-water would be less than 0.01mg/L.



Because the guideline value is restricted by measurement limitations, and 0.01 mg/L is the realistic limit to measurement, this is termed a provisional guideline value.

Effects of Arsenic in Human health Symptoms of Arsenic toxicity can be observed within 2 to 10 years of exposure(WHO). However it depends upon the dietary and metabolism factor of individual. Chronic exposure to low concentrations of arsenic is of primary interest when the health significance of arsenic in drinking water is evaluated. According to WHO the following are the effects of Arsenic in human health 

Chronic arsenic poisoning, as occurs after long-term exposure through drinkingwater is very different to acute poisoning. Immediate symptoms on an acute poisoning typically include vomiting, oesophageal and abdominal pain, and bloody "rice water" diarrhea.



The symptoms and signs that arsenic causes, appear to differ between individuals, population groups and geographic areas. Thus, there is no universal definition of the disease caused by arsenic. This complicates the assessment of the burden on health of arsenic. Similarly, there is no method to identify those cases of internal cancer that are caused by arsenic from cancers induced by other factors.



Long-term exposure to arsenic via drinking-water causes cancer of the skin, lungs, urinary bladder, and kidney, as well as other skin changes such as pigmentation changes and thickening (hyperkeratosis).



Increased risks of lung and bladder cancer and of arsenic-associated skin lesions have been observed at drinking-water arsenic concentrations of less than 0.05 mg/L.



Following long-term exposure, the first changes are usually observed in the skin: pigmentation changes, and then hyperkeratosis. Cancer is a late phenomenon, and usually takes more than 10 years to develop.

Symptom of Arsenic Contamination.

Mitigation Measures It is now obvious that only by increasing the water supply coverage the public health status cannot be improved unless there is safe water to drink. To over come the problem of arsenic contamination in groundwater of Terai region of Nepal the following methods are adopted.

1. Switching to safe and Deep wells. As part of the long term alternatives dug wells, gravity fed water supply system are considered. In dug wells two or three hand pumps are attached and the opening is sealed but with some ventilation to avoid cross contamination. There is proper drainage system and platform to avoid leaching of contaminated water (Tuinhof, 2004). These dug wells has not only solved the problem of arsenic in the area, but people are happy to use their traditional water source as they find dug wells as one of the reliable water source in the village (Maskey, 2006).

F Fig: Well not in good condition. Source: ENPHO, Kathmandu

Fig: Well improved well/ Deep well.

2. Water treatment by different types of filters. a. Two Gagri System b. Three Gagri System c. Improved Biosand Filters d. Kanchan Arsenic Filter

a.

Two Gagri System with chemical powder:

The system consists of two vessels made of clay. A highly porous filter candle/ terrafil disc is fit at the upper Gagri. Water is collected in the lower or second Gagri. This system uses a chemical powder, a combination of three different chemicals: Ferric Chloride, Sodium Hypochloride and Charcoal, which act together as coagulant, oxidant and absorbent. One pouch of this powder removes arsenic from 20-liter of water. The basic principle of this chemical is that it oxidizes Arsenic III to Arsenic V followed by coagulation and co-precipitation. This powder is dissolved in 20liters of water and stirred intermittently for half an hour. Then the water passed through the first Gagri which contains the filter and collected in the second Gagri. Aside from removing arsenic it also removes iron, disease causing bacteria, turbidity and odor.

Photo: 2 Kulsi system (Source: ENPHO)

b.

Three Gagri System

This system does not use any chemicals for arsenic removal but uses locally available material like sand, brick and charcoal. The first upper most Gagri consists of brick chips iron nails and coarse sand while the second Gagri consists of brick chips, charcoal and fine sand (Shrestha, 2003). Water containing Arsenic is poured through first container, which passes through the second Gagri and gets collected to the third. The natural filtration process removes arsenic iron and other unnecessary chemicals. This also uses the principle of absorption, oxidation and filtration (Tabbal, 2003). Efficiency test conducted for this filter showed that there is very high level of arsenic removal upto 95%. Since this filter were provided to the households consuming arsenic contaminated water up to 350 ppb, the removal rate tested by the ENPHO arsenic field test kit showed almost zero concentration in most of the treated water. Socially, this filter is accepted by the community, as it does not use any chemical and the material used is readily available in their locality. Household themselves can maintain this filter thus they are very satisfied. households drinking water from NRCS, RWSSSP and DWSS tube wells.

Photo: Three Gagri System (Source: RK Malla)

This system may cost up to Rs.500-700, however, if the household provides some part of the filter like stand and gagris which are the major component of the system the cost may reduce drastically.

c.

Improved Bio-sand Filter

Bio-sand Filters that are being used around the world to remove both physio-chemical and bacteriological contamination is now also being tested for arsenic removal. This filter has been introduced in the Terai region previously for removal of iron and bacteriological contamination (Shrestha, 2003). Since this filter system is durable and considering the iron removal efficiency, it is expected that it will also remove arsenic with some modifications. The newly improved bio-sand filter has a tray above the biological layer where iron nails are kept (Tabbal, 2003). This filter uses the process of aeration, absorption and filtration. This system removes iron, arsenic as well as bacterial contamination without using any chemicals. As this system has high flow rate of 30 lt per day this has been of high demand in

Photo: Bio Sand Filter (Source: Kalawati Pokharel).

the communities not only for arsenic removal but also due to the flow rate that serves the household with ample water per day. Efficiency tests shows that this filter removes more than 95% arsenic on an average and 99% in most of the cases (Malla, 2006). So far the filter has removed arsenic from 580 ppb to 20ppb which is quite impressive (Arinita, 2006).

d.

Kanchan Arsenic Filter

The Arsenic Kanchan Filter is a built on the platform of a slow sand filter, modified to include arsenic removal capability. Slow sand filters were developed in the 1820s in Scotland by Robert Thom and in England by James Simpson and became successfully established in Europe by the end of the 19th century (Tabbal, 2003). The Arsenic Kanchan Filter combines both these concepts – slow sand and an intermittent household-scale system with the innovation of a diffuser basin containing iron nails for arsenic removal. This KAF is constructed of simple materials available in the local markets of Nepal. These materials include plastic containers, PVC pipes, iron nails, brick, sand, and gravel. The construction of the filter can be carried out by locally trained technicians using simple tools such as wrenches and hammers. The figure below shows the components of the Kanchan Arsenic Filter (KAF). In the KAF, arsenic is removed by adsorption onto the surface of rusted iron nails (i.e. ferric hydroxide). Pathogens such as bacteria are removed mostly by physical straining provided by the fine sand layer, by attachment to previously removed particles, and, to a less degree, by biological predation occurring in the top few centimeters of the sand. Over the course of the project, four different versions (concrete square, concrete round, Hilltake plastic, Gem505 plastic) of the KAF have been designed, each representing an improvement in performance and cost.

Source: Kalawati Pokharel

Activities Undertaking for Arsenic Mitigation in Terai (Nepal) As earlier mentioned Arsenic problem in Nepal is relatively new issue. Different agencies has worked out for the identification of problems due to the arsenic contamination, however some have also started mitigation programs in some of the affected areas.    

For better coordination among the concerned agencies related to the water supply GoN has already constituted NASC. Experience sharing workshop with professional of Bangladesh and West Bengal has been a regular process of GoN. A standard set of information, education and communication materials has been developed by NASC. ENPHO, FINNIDA, MIT3, NEWAH4 have undertaken arsenic testing program in their limited areas. These agencies have worked out for some arsenic removal plant. These agencies are continuously supporting and have been conducting awareness programs in their working areas.

Conclusion and Recommendations All arsenic mitigation have their own advantages and limitations depending on various conditions. The alternatives provided will be an asset to affected household if they could get arsenic free water when needed.

Acknowledgement The author would like to thank Mr. Basanta Adhikari & Mr. Bishnu Pokharel of NEWAH and Mrs. Kalawati Pokharel of RVWRMP (FINNIDA) for their support for providing photographs, journals, data and information.

3 4

MIT- Massachusetts Institute of Technology NEWAH- Nepal Water for Health

References Adamsen, K. R & Pokharel, A. (2002) “The Arsenic Contamination of the Drinking Water in Nepal.” NEWAH, Kathmandu, Nepal Clark, D & Whitney, J.W, (2001), Options for Hydrological Investigations of Arsenic Occurance in Ground Water in Nepal; UNICEF, Nepal/ National Arsenic Steering Committee of Nepal, U.S Embassy, Kathmandu Maskey, A. (2006), “Arsenic Mitigation Initiatives in Nepal.” Kathamandu, Nepal Maskey, A. (2001) “Arsenic Contamination”. ENPHO 10th Anniversary Report, page 40-41. Malla, R.K. (2006), Arsenic Mitigation Strategies and Progress in Nepal, National Arsenic Steering Committee (NASC), Kathmandu, Nepal NASC/ENPHO. (2004). The State of Arsenic in Nepal – 2003. Nepal Arsenic Steering Committee/Environment and Public Health Organization, Kathmandu, Nepal. January 2004. Reczynski, W, Dynamics of Arsenic-Containing Compounds' Sorption on Sediments, AGH University of Science and Technology, Faculty of Material Science and Ceramics, Department of Analytical Chemistry, Poland Shrestha, R. R et al. (2003), Groundwater Arsenic Contamination, Its Health Impact and Mitigation Program in Nepal. ENPHO, Kathmandu, Nepal, page 185 – 200. Shrestha R, R: Maskey, A. (2005), Groundwater Arsenic Contamination in terai Region of Nepal & Its Mitigation. ENPHO, Kathmandu, Nepal Tuinhof, A. (2004) “Approach to Mitigation of Groundwater Arsenic Contamination Including New Groundwater Legislation.” The World Bank, Nepal Tabbal, G. (2003), “Technical and Social Evaluation of Three Arsenic Removal technologies in Nepal.” McGraw Hill University, Submitted to the Department of Civil & Environmental Engineering for partial fulfillment of the requirements for the degree of Master of Engineering in Civil and Environmental Engineering WHO, “United Nations Synthesis Report on Arsenic in Drinking Water.” Available: http://www.who.int/water_sanitation_health/dwq/arsenic3/en/