Arsenic, Fluoride and Iron are major chemical contaminants that arise naturally in the groundwater systems of the Gangetic plains and affect huge populations in India and Bangladesh.
Groundwater has been extensively exploited in large areas of South Asia in the last twenty years or so, in response to the vulnerability of surface water to contamination by chemical and microbiological contaminants. The health problems related to surface water development are well documented. Surface water is more easily contaminated by microorganisms than groundwater. This occurs because the pathways for contamination are more direct and much quicker through surface runoff processes. Groundwater is particularly low in biological contamination because it is protected by the rock and sediments overlying the main aquifer. A lack of adequate sanitation compounds the problem. Infant mortality is a key indicator of the rate of water related disease and in South Asia this was (and often still is) extremely high. As a result a huge programme of groundwater development was pursued by UNICEF and the Public Health Engineering Department (PHED) in Bangladesh in the 1970’s. It was assumed that groundwater provided a safe and relatively inexpensive source of drinking water. To this day little resource assessment is conducted before a well is sunk.
However in the early 1990’s doctors in West Bengal, India, began to identify the first cases of arsenic induced skin lesions. Eventually the source of these lesions was identified. The source was shallow groundwater contaminated by naturally occurring inorganic arsenic. Only recently has the full extent of the problem been realised. Bangladesh and India face a huge public health challenge in addressing this issue. It is estimated that between 35 and 77 million people suffer from arsenic poisoning in Bangladesh alone.
One of the first tasks I had was to visit various water treatment plants that had been installed by contractors to the local PHED a year earlier. The plant consisted of a solar pumping unit (, with an adsorbent unit acting to remove the arsenic from the water supply. The water was then piped to a public tap stand. The plant had been designed and constructed by a contractor with a year’s operation and maintenance included in the contract. The village was in a fairly remote area of Bihar and the operation and maintenance of the plant had not been considered beyond the first year’s contract. A local man from the community had been trained at the start of the project in basic maintenance but that training did not extend to more technical aspects of the maintenance of the plant. As a result when the filter needed replacement the plant ceased to function. With the filter soiled and the tap stands damaged the community returned to their traditional, contaminated, handpump sources.
These experiences made me acutely aware of some of the key challenges in the WASH sector, challenges such as the selection and use of appropriate technology. How do we ensure the sustainability of the technologies and avoid the problem I witnessed with the handpump attachment units? One way is to involve the user at all stages of the process, from selection to installation to operation and maintenance, accepting however that some level of outside support is likely to remain necessary.
The contamination of groundwater by heavy metals in South Asia is a huge public health and environmental challenge. It is important to consider whether groundwater is the correct source in these communities with the knowledge we now have? If it is, there is a need for a thorough understanding of the processes leading to arsenic and fluoride contamination and the best way to develop groundwater in regions were these contaminants are a problem. This requires well trained hydrogeologists willing to cooperate with local communities and institutions to help them address this huge challenge.
For a good background reading on Arsenic in groundwater and strategies to reduce its impact see this link from UNICEF.