Archive for July, 2010


Arsenic in groundwater- West Bengal

Arsenic in groundwater is becoming a difficult problem in many parts of the country. This problem is acute in West Bengal and is spreading to other parts of the country with awareness to quality of drinking water is growing.

Take the case of West Bengal. In 1959, minor-irrigation projects were started in the state in collaboration with the Exploratory Tube-well Organization of the Union government. As per the 2001 census, there are about 5, 50,000- tube wells in the state; 64 per cent of 54640 square kilometres of cultivable land in the state is under irrigation — by tube wells that tap groundwater. Irrigated farming has supported millions of people, but that has a horrible spin off: arsenic levels have risen in the shallow aquifers of West Bengal. But how did irrigation lead to such pollution? The water used for farming had high levels of arsenic and the arsenic accumulated in the roots of rice plants — its levels are reported to be as high as 169 parts per million. When these roots were ploughed back into the soil, during subsequent irrigation arsenic released from roots found their way to the shallow aquifers. The paddy stem, leaves, the grain and the husk have arsenic concentration far above the level prescribed by the World Health Organization. All these parts are consumed by man and animals!! Now even the kitchen vegetables also registered arsenic levels above the prescribed limit.  Now arsenic has entered the food chain in West Bengal. This development began a couple of decades ago and is continuing unabated. Groundwater irrigation was envisaged as a panacea for food shortage, it has polluted drinking water and killed many. The Water Investigation and Development Department, which oversees water quality has completely ignored the problem. And preliminary studies indicate that the rot is spreading to parts of Northeast India.

What can be done?

            There are several technologies to remove arsenic from drinking water  — some of these are reverse osmosis, precipitation and flocculation and solar oxidation. But these are costly and unfeasible to implement and practice by the rural population.

            Providing safe drinking water to rural communities is an integrated effort, which requires engaging skills of hydrologists, engineers, medical experts and non-governmental organisations. These specialists should be involved in identifying the areas affected by arsenic and in collecting data about the extent of the problem. Once this is done, the affected basins should be mapped and permanent observation basins identified. This will not only create a good data bank on individual basins but also trained personnel who can be consulted to oversee the problem in future.

            Tackling the arsenic problem also requires changing people’s mindsets. Since the chemical does not affect humans overnight, there is always a tendency to procrastinate on solutions. The state groundwater organisations and public health departments should take the help pf grassroots bodies in raising people’s awareness in the affected areas.   

Over the long-term

But these are all short-term solutions. There is no viable long-term panacea except harnessing surface water to mitigate both drinking water and arsenic problems. The large volumes of surface water that gets discharged into the seas every year can easily be used for these purposes. For example, the government of Meghalaya has created an excellent lake to store surface water; this reservoir supplies water to communities in Shillong. Facilities to create such water bodies exist in all the northeast states. Besides, the entire region has a good water drainage system; interlinking them scientifically could provide water for irrigation as well as for drinking.  The microbial problem associated with surface water sources can easily be tackled compared to removal of arsenic in groundwater. Of course, interlinking has political problems which can be solved. This is much easier than saving millions from arsenic related diseases. Making the project completely transparent would take care of the problem to a great extent: the data generated should be made available in the public domain. Academic institutions and the state public works departments should collaborate in the endeavour.



Geothermal heat pumps (GHP) are environmentally benign and represent a large potential for reduction of CO2 emission. The CO2 emission rates depend on the energy efficiency of the equipment as well as the fuel mix and the efficiency of electricity generation.

 The heat pump needs auxiliary power to accomplish the temperature rise needed in the system. This power, if supplied by renewable energy source like geothermal, then the amount of CO2 emission will be near zero. On the other hand if energy supply is from fossil fuels, then there will be CO2 emission but the amount of CO2 emitted will be lower by several factors compared to conventional energy source used for space heating and cooling.      

The average CO2 emission associated with generation of electricity is estimated to be 0.953 kg CO2/kWh ( coal based power plants) while geothermal power plants emit  0.893 kg CO2/MWhr. Electrically driven heat pump reduces the CO2 emission by 45% compared with an oil fired boiler and 33% compared with a gas fired boiler. The total CO2 reduction potential of heat pumps has been estimated to be 1.2 billion tonnes per year or about 6% of the global emission.

 In India, 33 % of electricity  ( coal based power) is utilized by the building sector (commercial and domestic ). A major amount is spent for space cooling, refrigeration and hot water supply. This amounts to emission of 234 x 109 kg CO2. If India utilizes  G H Ps (low enthalpy geothermal sources), so much of CO2  emission can be reduced.


Geothermal and Food Processing Industry

“One of India’s proudest accomplishments has been achieving self-sufficiency in food production and that the country produces a wide variety of agricultural products at prices that are at or below world values in most cases”- states the office of the agricultural affairs of the United States Department of Agriculture (USDA). This is true and India can capture the world market if it utilizes the available geothermal resources for increasing the shelf life of these vegetables and earn huge foreign exchange. The dehydrated agricultural products are expensive since their price is linked to the thermal power cost generated from fossil fuels.  The cost can be curt drastically if geothermal resource is used for such purposes.  In the entire Europe, Latin American Countries and USA,  dehydration of agricultural produce is a multi-million dollar business. For more details on how India an gain …… the attached article in GeoHeat Bull 2001


Earth Scientist’s role in Society

In a single sentence of a speech to the Royal Society, in London, in 1988, Margaret Thatcher succinctly connected science to the creation  of social wealth when she said: “the value of Faraday’s work today must be higher than the capitalization of all the shares on the stock exchange.” Add a few other examples of the work of scientists that has transformed society, such as the Green Revolution in world agriculture, the transistor revolution that opened closed societies to change and the biomedical revolution set off by molecular biology, and the benefits of science to society take on real meaning. The Earth sciences have a unique role in this regard, which was underscored by the twentieth-century US historian Will Durant when he is said to have cautioned: “Civilization exists by geological consent, subject to change without notice.” Today, Durant might add a few new vulnerabilities faced by civilization, which I comment on later in this article…………………..Earth scientists should be proud of the contributions to society they are making in the course of applying and advancing their science. The wider application of old knowledge still serves many purposes, including lessening the destruction of natural disasters. The latest challenge is to apply the new understanding of our planet that has been uncovered by research to halt and reverse the environmental damage inflicted by humankind.  In  ‘Nature’  January 2008 by Frank Press, President emeritus of the US National Academy of Sciences and Institute Professor emeritus, Massachusetts Institute of Technology.