The Hindu : How safe is our water?

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Sunday, Aug 24, 2003

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How safe is our water?

Groundwater is easily polluted and restoring its quality is impossibly expensive, writes N. Gopal Raj.

The falling water table has only added to the problem.

A FEW months ago, it was the issue of pesticide residues in bottled water. Now there are similar concerns over the bottled soft drinks, Coke and Pepsi. There have been reports, too, of high levels of cadmium, a toxic heavy metal, in the waste sludge produced at the Coca-Cola bottling plants in Kerala and West Bengal.

There is an important common thread running through all these incidents: groundwater. These incidents may be just the latest alarm signals about how badly India's groundwater is getting polluted. Bottled water and soft drinks are largely consumed by the more affluent. Groundwater, on the other hand, meets the needs of 60 per cent of India's households. So the quality of groundwater can potentially affect over 100 million households, rich and poor, urbanites and villagers alike.

Contrary to what is often believed, groundwater is easily polluted. There are so many possible pollutants, both industrial and agricultural. The polluters, likewise, can be countless, from individual farmers and households to small garage-scale entrepreneurs and large industrial operations. Once polluted, restoring the quality of groundwater is impossibly expensive even when technically feasible. Filtering and other ways of removing or at least reducing the levels of pollutants when pumping out water is also costly and viable only for industrial scale operations. Even monitoring groundwater quality poses huge problems.

Payal Sampat, in her paper titled "Deep Trouble: The Hidden Threat of Groundwater Pollution", published by the Washington, D.C.-based Worldwatch Institute , writes graphically about the seriousness of the issue: "We are now learning that the water buried beneath our feet is not only susceptible to pollution, it is in many ways more vulnerable than water above ground... Because it is underground and slow moving, groundwater stores pollutants far longer than, say, rivers or air do. Hence, the very characteristic that makes aquifers ideal reservoirs of freshwater — their ability to accumulate and retain liquid for longer periods of time — also enables them to become long-term sinks for contaminants. It's true that some aquifers recycle water back to the environment fairly quickly. But the average length of time groundwater remains in an aquifer is 1,400 years, as opposed to just 16 days for river water. Some aquifers contain water that fell as rain as much as 30 millennia ago. So instead of being flushed out to the sea, or becoming diluted with constant additions of freshwater, as rivers, lakes, and streams are, aquifers continue to accumulate pollutants, decade after decade — thus steadily diminishing the amount of clean water they can yield for human use."

Groundwater pollution has become such a problem principally because of the nature and widespread use of modern chemicals. In addition, modern lifestyles demand the use of natural resources such as coal, petroleum and minerals on an unprecedented scale, with resultant costs in terms of pollution. From the start of the industrial revolution, smoke-belching factories have epitomised pollution and human degradation of the environment. So pollution control measures have been strongly enforced in the industrial sector. But it is necessary to recognise that agriculture too can be a major polluter of groundwater.

Globally, agriculture is the biggest consumer of water. In India, agriculture consumes about 90 per cent of the water (groundwater as well as surface water sources), compared to about three per cent for domestic use and less than five per cent by industry. The number of diesel and electric pumpsets has increased over 200 fold since 1950 and is currently estimated to number around 20 million. Groundwater is used for over half the irrigated area of the country. About half the water withdrawn for agriculture is returned soon afterwards, either seeping back into the ground or flowing to the rivers. These returning waters, however, can be laden with chemicals. With large areas under cultivation and these chemicals applied year after year, pollution can steadily build up in the underground aquifers.

Take for, instance, the use of chemical fertilizers. By 1991, India's fertilizer use per hectare was 60 per cent higher than in the United States, according to an FAO-sponsored publication. Excessive application of nitrogenous fertilizer, as well as organic waste and sewage, has been implicated in the nitrate pollution of groundwater. High nitrate levels are possibly the most widespread contamination of groundwater globally and can lead to health problems such as the `blue baby syndrome.' India uses over 11 million tonnes of nitrogenous fertilizer annually.

Even in the early 1990s, the agriculturally advanced States of Punjab and Haryana, where fertilizer is intensively used, had wells with nitrate levels well above the safe limits prescribed by the World Health Organisation (WHO). A few years ago, the Central Ground Water Board (CGWB) found that water from wells in over 300 sites scattered across Gujarat too had high nitrate levels. In 1997, Ashok Keshari of IIT Delhi found nitrate levels in the groundwater at many places in Varanasi and in Jaunpur town (close to Varanasi) that were several times higher than the WHO norm. In a published paper, he blamed the utilisation of sewage effluents for agriculture, leakage from sewerage systems, septic tanks and natural drains carrying municipal wastes, and application of fertilizers. Now wells with high nitrate levels were being found in the Faridabad area near Delhi, Dr. Keshari told The Hindu. Recently, the environment magazine, Down to Earth, reported that the CGWB had found high nitrate levels in the groundwater used in Bangalore and in many villages in Karnataka. In north Bangalore, the nitrate concentration was said to have doubled in a year.

The cadmium found in the sludge from the Coca-Cola bottling plants in Kerala and West Bengal too could have had its origins in the chemical fertilizer used. Phosphatic fertilizers are produced from phosphate rocks which vary in cadmium content from less than one to over 100mg/kg. Cadmium in phosphate fertilizer is of particular concern because its absorption by food plants provides the main exposure route for humans, according to Valerie Thomas of the Princeton University, U.S. But as the experience of the Rhine basin in Europe shows, cadmium can also be released into the air by the burning of coal and oil as well as other industrial activity, and then get deposited in the soil. Tight emission controls help reduce the cadmium load. Ever since the first synthetic pesticides were introduced in the 1940s, these chemicals have become an integral part of modern intensive farming practices. In India, pesticide use has doubled in the past three decades. Many of these chemicals are toxic to humans, and America and Europe set limits on the maximum pesticide residues permissible in foods. When applied to plants and the soil, these often harmful chemicals can readily leach into groundwater. Worse, they can persist in the groundwater long after the chemical has been banned. DDT is still found in groundwater in the U.S., three decades after it was banned there. Even when more short-lived pesticides are used, the environment of the aquifer can slow their breakdown. Scientists have found that the herbicide alachor, whose concentration halves in 20 days in the soil, can take up to four years to reach similar levels in groundwater. Moreover, the products created by the breakdown of some pesticides can be just as toxic.

In India, there have been reports of high levels of DDT in groundwater. The March issue of Down to Earth pointed out that several pesticides banned in many Western nations can still be sold in India. Pesticide residues in bottled water and soft drinks are likely to be yet another indication that the groundwater is contaminated. The Union Government has taken steps to regulate pesticide residues in bottled water and, in the wake of the latest controversy, has said in Parliament that it was considering making these standards applicable to soft drinks as well. Even though such regulatory measures are essential, they are nevertheless only treating the symptoms and not the root cause — - the presence of pesticide residues in source water, observes the New Delhi-based Centre for Science and Environment (CSE), which has played a leading role in reporting the pesticide residues in these products. Pesticides are constantly seeping into groundwater as well as surface water due to the porosity of laws that govern the use of these toxic chemicals, it points out.

Pollutants are present in the groundwater, not just in colas.

Sometimes, just excessive drawing of groundwater, which is already a major problem in many parts of India, can create and worsen pollution. One obvious example is of seawater incursion into depleted aquifers near the sea. These aquifers would normally drain into the sea. But when they are depleted, the flow reverses and seawater seeps into the aquifers. Just two per cent seawater entering an aquifer is sufficient to make the groundwater too salty to drink or use for irrigation.

Large-scale drawing of groundwater can create more serious hazards. The arsenic contamination of groundwater in West Bengal and neighbouring Bangladesh has affected millions and has been called the largest mass poisoning in history. Some research publications have suggested that the massive withdrawal of groundwater for irrigation could have played a part in releasing arsenic from the sediments which hold it. Now there are reports of arsenic-contaminated groundwater in parts of Bihar and Uttar Pradesh served by the Ganga, as well as in Chandigarh and parts of Haryana.

Moreover, such depletion of groundwater increases the flow within the aquifers, points out Dr. Keshari. This, in turn, can accelerate the breakdown of sediments, thereby releasing polluting chemicals, as well as spread the pollution faster through the aquifer and other linked water channels. Such mechanisms could have aggravated the fluoride contamination of groundwater that is now being reported from different parts of the country, from Rajasthan and Gujarat to the Gangetic plains and the Deccan Plateau. As with the arsenic contamination, fluoride contamination too occurs through a natural process in which fluoride bearing rocks crumble and break down. But the process can speeded up if the chemistry of the aquifer is disturbed. Industry, user of minerals, metals and fossil carbon fuels, as well as the primary producer of chemicals on a colossal scale, is a major source of pollution. Toxic chemicals in the industries' liquid effluents, solid wastes and even their atmospheric releases can ultimately find their way to the groundwater and rivers, causing untold damage. Some 4.4 million tonnes of hazardous wastes are being generated by 13,011 units spread over 373 districts of the country, according to the latest annual report of the Union Ministry of Environment and Forests. Just three States — Maharashtra, Gujarat and Tamil Nadu — account for over 63 per cent of the total hazardous wastes generated in the country.

The Hazardous Wastes (Management and Handling) Rules of 1989 were intended to plug loopholes in the way industries handle their toxic waste. But these Rules have not yet been seriously implemented nationwide, points out Ramesh Ramaswamy, a Bangalore-based consultant industrial ecologist. Proper sanitary landfills, which can handle the toxic wastes produced by industries, have still to be set up. As a result, these dangerous wastes continue to be disposed of haphazardly. "There are only 2 or 3 such landfills in Gujarat and Maharashtra and even these are reported to be inadequate," he says. The system for collecting and handling municipal waste and sewage, which too can contain toxic material, is also inadequate.

Households too can add to the pollution. The Ministry of Environment and Forests estimates that 22,900 million litres a day (mld) of domestic wastewater is generated from urban centres, almost twice as much as the 13,000 mld of industrial wastewater. The treatment capacity available for domestic wastewater is only for 6,000 mld and for industrial wastewater 8,000 mld, according to the Ministry. Nor, according to experts, is there a proper system in India for handling municipal solid wastes. An added problem in India is that the small and unorganised sector industries dump their wastes into the sewage and municipal refuse system, making them more toxic and dangerous.

At a time when the sustainability of India's groundwater is already under strain from excessive withdrawal, pollution from industry, agriculture and households jeopardises what remains. Even the scattered reports of groundwater pollution from different parts of the country are alarming. If action to reduce pollution on all fronts is not initiated rapidly, the source of water for the majority of Indians will rapidly dwindle. A crisis is in the making.

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