DESALINATION AND TREATMENT OF MUNICIPAL WATER VIA SOLAR ENERGY
Apr 28 - May 11, 2008
Oceans account for approximately 97.4 percent of the world's water, another 2 percent is caught in ice caps and glaciers. Leaving out saline ground water and inland saline seas from the remainder, some 0.5 percent of the earth's water is directly suitable for human and livestock consumption and fit for agricultural and industrial use. Over the last few decades desalination technologies have been used increasingly throughout the world to produce drinking water from brackish ground water and sea water to increase the quality of available supply of fresh water for drinking as well as for industrial and agricultural purposes, and to treat industrial and municipal waste water prior to discharge or re-use. Humans cannot drink saline water. But saline water can be transformed into fresh water, which every living being needs every day. The process is called "desalination" and it is being used more and more around the world to provide people with neat and clean fresh water.
Desalination/distillation is one of the ancient water treatment method and it is still a popular mode of treatment throughout the world. In the past many civilizations used this process on their ships to convert sea-water into drinking water. Now-a-days desalination plants are used to convert sea-water to drinking water on ships and in many arid regions in the world and to treat water in other areas containing natural and unnatural contaminants. Desalination is a wonderful water treatment technology that completely reduces the wide range of drinking water contaminants.
Natural process of desalination: Nature guides us for adopting the desalination process that is in vogue in nature itself. In nature this basic process is responsible for the hydraulic cycle. The sun causes to evaporate water from the surface sources, including lakes, oceans and streams. Water vapors eventually come in contact with cooler areas, where they re-condense to form dew drops or rain. This process can be initiated artificially and at a more rapid speed than the natural process, using alternative sources of heating and cooling.
ISRAEL AND OTHER M.E. COUNTRIES USING WATER DESALINATION PLANTS:
A first plant for annual desalination of 100 million cubic meters is under construction in Israel. It will operate by the Reverse Osmosis technology at the lowest price ever reached for a desalination process that is less than 50 cents per cubic meter. The Alternate Method is Low Temperature Desalination, which may prove advantageous under different conditions, especially when the plant is beside the power plant and excess water heat can be utilized. Israel is a pioneer of desalination of water technology in the world and is recycling and purifying municipal waste water for irrigation. A record 70 percent of municipal waste water is being reclaimed and used for agriculture in that country.
Kuwait in the Arab world was the first state to adopt sea-water desalination, linking the electricity generation to desalination. This co-generation resulted in minimizing the cost of both energy generation and desalination of water. The desalinated water production in Kuwait started as early as in 1957 when 3.1 million cubic meters desalinated water was produced per year. By 1987 it rose to 184 million cubic meters per year.
In Qatar an intensive programme for desalination of brackish water was launched, which was expected to supply 150 million cubic meter of water pear year by 2000. This would cater to one third of the total demand while the rest would be supplied from ground water sources, which are mostly brackish.
Saudi Arabia entered the desalinated water field at a much later stage and its first desalination plant was commissioned in 1970. It has, however, gone in for a grand programme on both the Red Sea and Gulf Coasts. Thirty desalination plants had been installed by the end of year 1980. The total production of desalinated water is estimated to be 216 million cubic meters (572 million US gallons) per day including the facility at Al-Jubail, producing one million cubic meter water per day, which is currently the world's largest distillation plant. This desalinated water is used both for drinking and irrigation purposes.
There is, however, increasing governments" concern about the production cost of desalinated water, especially in Kuwait. Efforts are being made to ensure that water use is as efficient as possible.
DESALINATION PLANTS IN PAKISTAN:
The Nice Link Trust has established 8 solar desalination plants at Ibrahim Haidry and Rehri for the purification of municipal water for potable use. It has been sponsored by the Federal Republic of Germany and is meant for the people living in the coastal areas, who have presently no access to drinkable water. The project is being funded with $21 million by Asian Development Bank (ADB) for water treatment for coastal areas of Sindh, especially Thatta and Badin. Thar, Nara and other vast areas have extremely poor quality of water, which is unfit for drinking, particularly because of high fluoride in ground water in some areas of Tharparker. Similarly, there is highly brackish water in the Makran coastal zone and several other areas in Balochistan, which is unfit for human consumption. However, experts feel that inexpensive drinking water can be supplied to the communities living in the far-flung regions by installing desalinating plants at strategically suitable locations to be operated by solar energy. If this project proves successful, it can be replicated in other coastal areas with scarcity of drinking and irrigation water.
About 28 percent of the area in Sindh has fresh ground water suitable for irrigation. This fresh ground water can only be availed at a depth of 20-25 meters. It is, however, a cause of great worry and concern that the ground water table is rapidly receding at a speed of 10 meters per annum. The per capita fresh water availability, which was 5600 cubic meters, has dropped to 1000 cubic meters, which comes to five fold reduction.
FACTORS RESPONSIBLE FOR MAKING OUR WATER RESOURCES SALINE AND BRACKISH:
The quality and quantum of ground water and surface water have reached an alarming situation. Indiscriminate and almost unabated disposal of untreated municipal and industrial waste water, excessive use of fertilizers, chemicals, insecticides and herbicides in agriculture have polluted water in our rivers, canals and tube-wells.
DESALINATION OF BRACKISH WATER:
If solar power is made available for desalination of sea-water or other brackish water, we can not only overcome the shortage of drinking water in the remotest areas of the country like the barren lands and deserts of Balochistan and Sindh but can also use excess water for irrigation. This can be made possible by pumping sea-water of these far flung areas and after treating it by means of desalination plants operated by solar energy can be pumped to coastal villages and other areas to be used as drinking water. Alternatively sea water can be desalinated near coastal areas and the water that remains untreated can be pumped back into the sea and treated water supplied to towns and villages with the help of pumping stations. Treated water can be carried and transported through underground pipeline to the areas where it is needed to be used as is being done in Saudi Arabia. It would be worthwhile to mention that we have got sufficient expertise in Pakistan in SNGPL and SSGC, our two major gas companies, for laying bigger diameter pipeline underground without involving foreign companies.
FIRST COMMERCIAL VENTURE FOR SEA-WATER TREATMENT AT GWADAR SITE:
It is heartening to note that Karachi Nuclear Power Plant (KANUPP) completed its first commercial project of sea-water reverse osmosis Desalination Plant, in which KANUPP provided consultancy and supervision to Gwadar Port Authority. The installation of the plant has been done by M/s. Imperial Electric Company (Pvt) Limited on 14th January, 2005 and commissioning was carried out under the supervision of KNPP experts. It is said that this plant was designed and manufactured by PCSIR. That is inspiring and the government should encourage local expertise for the sake of cost control and to boost our own expertise while availing foreign desalination expertise.
It is a great challenge for the incoming government to provide neat and clean drinking water to its bulging population besides supplying adequate irrigation water for agriculture sector. It is hoped that the new set-up would not fail to end the deprivations of the massive resource-less and poverty afflicted population in this regard.