Tuesday, 18 October 2005

Serving Human Needs-Nuclear Technology for clean drinking water

Clean drinking water
In the last century human population trebled, but fresh water consumption was six folded. Without efficient water resources development, management and use, half of the world’s population will be living in water stress region with competition from agricultural, industrial and domestic use. This is what World Water Vision unit of the World Water Council warns. Forty years ago human population was three billion; today it is over six billion. By 2050 it is expected to hit 9 billion. But the availability of water to meet the growing demands remains unchanged. Without water we cannot survive more than three days. As of now one out of five people on the planet earth does not have access to safe drinking water. Every year more than three million people die of waterborne diseases of
which two million are young children. A blue circle appeared to be mostly covered with water as visualized from outer space, the earth is in fact two third filled with water. However over 95% of earth’s water is salty or brackish. Of the remaining 3% about seventy five percent is locked in ice caps and glaciers. In fact the inventory of fresh/
clean water available for human use is less than one tenth of one percent of all water on the earth. No wonder the Ancient Mariner Lamented “ water, water every where nor any drop to drink.”


Bangladesh Scenario
Against the backdrop of such global scenario, the water situation in Bangladesh is very alarming. A land of rivers, tributaries and covered by Ganges-Bramaputra-Meghna delta which is one of the largest delta in the world, the country is facing an unforeseen tragedy with a clean source of water for avoiding water borne infection. Up until early 70’s most of the rural population got its drinking water from surface ponds and nearly quarter of a million children died each year from waterborne diseases. Then ground water became a major source of drinking water. The provision of tube well water accounting for 97% of drinking water of rural population resulted in significantly reducing high incidence of diarrheal diseases. However, paradoxically the same wells that saved so many lives
now pose a serious threat due to unforeseen hazard of arsenic. A survey of well waters (n=3534) from throughout Bangladesh has shown that water from 27% of the shallow tube wells i.e. wells less than 150m deep, exceeded the Bangladesh standard for arsenic in drinking water (50 µg/L), while 46% exceeded the WHO guideline value (10 µg/L). Figures for deep tube wells (greater than 150 m) are 1% and 5% respectively. Since it is believed that there are a total of 6-11 million tube wells in Bangladesh mostly exploiting the depth range 10-50m, some 1.5-2.5 million wells are estimated to be contaminated with arsenic according to Bangladesh standard. About 35 million people are believed to be exposed to arsenic concentration in drinking water exceeding 50µg/L and about 57 million people exposed to concentration exceeding 10µg/L.
A global Problem.
The situation is not unique to Bangladesh the presence of arsenic in drinking water is a world-wide problem causing a wide range of health effects. Millions of people in Argentina, Mexico, Taiwan, India, Mongolia, Hungary and Rumania are exposed to drinking water containing much higher levels of arsenic than WHO guideline. Arsenic is a natural element. It is also a poison. Only about 125 gm is enough to kill a person in a single dose. Arsenic is also hazardous if ingested in drinking water above the safe limit. It takes from 2-15 years to develop arsenicosis.

Origin of Arsenic.
Earth crust contains arsenic to the extent of 1.5-1 mg/kg in the form of minerals. Natural leakage from arsenic-rich minerals may cause contamination of soil and ground water. The arsenic is of natural origin and is believed to be released to ground water as a result of a number of mechanisms which are poorly understood. This release appears to be associated with the burial of fresh sediments and the generation of anaerobic (oxygen deficient) ground water conditions. It probably occurred thousands of years ago. The arsenic is thought to be desorbed and dissolved from iron oxides that earlier scavenged the arsenic from river water during their transport as part of normal sediment load. This is called iron oxide reduction hypothesis. Natural variation in the amount of ironoxide at the time of sediment burial may be a key factor in controlling distribution of high arsenic in ground water. From a world wide perspective, drinking water derived from aquifers showing similar characteristics to those of the Bengal Basin should be considered “at risk” and need to be systematically tested for arsenic.

Deeper the better.
Deep groundwater (>150 m deep) where available appear to offer a long-term source of clean drinking water. Experience gained so far indicates that the great majority of these would not only pass current Bangladesh standard for arsenic but would pass all other existing national and international guidelines. As such nationwide availability needs to be established in terms of quality, quantity and sustainability. The possible impact of large-scale extraction of irrigation water on the deep aquifer also needs to be considered.

Nuclear techniques in search of ground water resource
A groundwater system can be a complex and unknown maze hidden deep beneath the surface of the earth. When hydrologists find such a source they need to know its quality, quantity and if there is a water supply renewing it. Otherwise, it will be like fossil fuel which once used is not replenished. The traditional tools to answer those questions are very slow and also not available in most of the developing countries. Isotope hydrology, i.e. the use of heavy isotopes along with other hydrological and geo-chemical methods, have been successfully used to better understand ground water occurrence flow and quality problem. Isotope techniques have been successfully used for groundwater assessment, monitoring of water flow, contamination of water resources improved groundwater utilization and overall water resource management in different regions of Africa and West Asia. In India isotope techniques have been successfully applied for understanding groundwater recharge process in the arid zone. In Ethiopia integration of isotopic techniques into hydrological practices has resulted in successful groundwater
resource assessment and management. In Algeria isotopic studies showed differential recharge between the aquifers thus leading to strategic water resource management.
In Bangladesh a IAEA-TC pilot project on groundwater resource investigation was executed during 1999-2000 year cycle in collaboration with BAEC and the end user Bangladesh Water Development Board. The main objective was to obtain the baseline data on isotope in different aquifers for age dating and related geo-chemistry.
The findings of that research pilot project demands further study in groundwater pollution, especially arsenic using isotope technique for tapping arsenic free deep aquifer in Bangladesh.
As has been mentioned earlier millions of people in Bangladesh are facing the major public health crisis due to arsenic contamination in the groundwater aquifer, which is the primary source of drinking water. The World Bank is leading the Bangladesh Arsenic Mitigation and Water Supply Project (BAMWSP) to assist the Government of Bangladesh for providing safe drinking water options. But, reliable criteria are not available to evaluate the long-term consequences of the mitigation option. With a view to developing the alternate solution for mitigation option, the follow-up of the previous Pilot TC project on groundwater arsenic contamination is being undertaken by IAEA and BAEC in collaboration with the end users Bangladesh Water Development Board and
Geological Survey of Bangladesh.
Isotope techniques provide invaluable information on the sources, movement and quantity of water in different environments, including rivers and lakes. They are particularly effective in investigating water reserves below the earth’s surface, or groundwater. Isotope hydrology provides insights into water’s character and helps to build the foundations for rational utilization of this valuable resource.
Some observations
Without a few exceptions, ground water from the deep aquifer seems to be arsenic free. There is no reason to believe that deep aquifer will not be contaminated or remain free of contamination. Proper care must be taken during construction to isolate upper and lower aquifer. The efficient exploitation of ground water requires detailed investigation on the quality and quantity of ground water. It is prudent to integrate isotope techniques in hydrogeologic characterization and study of ground water exploration for sustainable clean drinking water supply.
It is believed that the nuclear analytical and isotope hydrology techniques can make more important contributions in this problem. The hydrogeology of the contaminated shallow aquifers and presently uncontaminated deeper aquifers can be investigated using isotopic techniques to identify alternative source of non-contaminated ground water in deeper aquifers. Currently favored mechanisms of arsenic mobilization are inconsistent with isotope data.
The most likely process of arsenic mobilization may involve description from the sediments as a result of continuing recharge of fresh, arsenic free water in the shallow aquifers.
Rio ’92 and freshwater
At the Rio Conference on environment and development, 1992, governments adopted Agenda 21, committing themselves to strive towards a fair and more sustainable development for all people, present and future.
Recognizing the importance of freshwater in social and economic activities, Chapter 18 of Agenda 21 called for action to protect the quality and supply of freshwater resources with following principles.
l Freshwater resources are essential and indispensable part of terrestrial ecosystems.
l Water is needed in all aspects of life. The currently poor and deteriorating state of water resources in many parts of the world demand integrated water resources planning and management. Trans-boundary water resources and their use are of great importance to States sharing river systems.
From Rio to Johansberg
The World Summit on Sustainable Development will be held in Johannesburg in September 2002 to review the progress made in addressing the underlying issues that influence sustainable development including water. The year 2002 mark not only the 10 year anniversary of that landmark event, but also this year the World Summit on Sustainable Development will be held at Johanesberg in September Water and development are intrinsically linked. Once viewed as an infinitely renewable and bountiful resource, water today defines and confines development aspirations?human, social, and economic in many parts of the world.
World Water Day
The UN General Assembly resolved to observe World Water Day on March 22 following the recommendations of Rio de Janeiro. World Water Day 2002 is an important step to reflect on water and development issues, at all levels national, regional and global to recognize successes and challenges, and to strengthen the international collaboration in water related issues.
Conclusion :
One of the key methods of unlocking the water code in nature is isotope hydrology by which we can get a clear picture of underground water source, its age, movement, reactivity, pollution all of which are important to make efficient use of water. It is recognized that one of the main reasons for current and emerging water shortages is
often found in inadequate water resources management. The sustainable development of water resources hinges on sound and holistic approaches of water resources management, such as integrated water resources development and demand-side management. The collection of hydrological, meteorological, hydro-geological, ecological and socio-economic information for water resources assessment and monitoring is essential for informed decisionmaking.
Despite innovative information technologies, data collection at the field level remains crucial for sound
and accurate water resource management and assessment. Unfortunately, this is often disregarded. Financial constraints have reduced the ability of public service institutions in charge of water resources to collect data at the field level in many developing countries. In many cases there has been a decline in the quantity and quality of information on water resources, and their uses. The techniques of isotope hydrology, play a crucial role in the data collection efforts to better understand freshwater systems in order to be able to manage them in a sustainable manner.

No comments:

Post a Comment