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Tag Archives: World Health Organization

A safe and clean water supply is becoming a scarce commodity in many parts of the world. With growing   population and rapid industrialization, the demand for water has increased dramatically. This in turns pushes the demand for energy and fossil fuels resulting in further increase in global warming. According to WHO (World Health organization) specifications, a clean and safe water should be free from pathogenic organism such as bacteria and virus, and also the TDS (Total dissolved solids) levels should be below 500ppm (parts per million). Unfortunately such quality water is not readily available from surface or ground water. The water stored in catchment area for supply of drinking water to cities requires certain chemical and biological treatments before it can meet WHO specification.

In many smaller cities especially in developing countries such treated drinking water is not available. NASA’s Gravity Recovery and Climate Experiment Satellite or GRACE orbiting earth in tandem, two satellites are able to measure the water storage on ground and below across the world. The NASA data shows that most of area in Northern India will be facing a severe shortage of water in the near future because farmers are pumping ground water   at an alarming rate. The ground water is getting depleted faster than it is being replenished. The water table has gone deeper and deeper and many of the pumps they used five to ten years ago cannot pump water anymore because the water levels have gone so deep. States like Punjab, supposed to be ‘wheat bowl of India’ are facing water shortage. Farmers who have used 100 feet bore well are now digging their bore well up to 900 feet. To make the situation worse, many of coal-fired power plants are licensed to meet the increasing power demand in India. Both quantity and quality of water has a direct impact on energy demand and global warming. The rainwater which replenished the ground aquifers are unable to match the water sucked by these pumps. About 114 million people living in Rajasthan, Punjab, and Haryana including the capital city of Delhi are facing water shortage.

The likely alternative for these states is to desalinate the seawater from the west coast of India and pump them all the way to Delhi, which are thousand of kilometers from the coast. The increasing economic growth of India has increased the demand for power, often based on coal. Power industry is one of the largest users of water. Plants located on coastal are able to use seawater for their ‘once through’ cooling system and for boilers. But the plants located inland have to use only surface water like rivers. They cannot use ‘once through’ system, but use a closed circuit cooling systems where they have to store large pool of hard water.

It is a vicious cycle. Water shortage increase the demand for power and power shortage increases the demand for water. Desalination is the only alternative but it is a very energy intensive and a costly solution. Changing climate, global warming, deforestation, and water shortage are ominous signs of Nature’s fury against human greediness.

When countries like Australia set up their largest desalination facilities, the country experiences the heaviest rains in decades with flash flooding in many parts, making politicians wonder whether their water management decisions are right. Unfortunately Science cannot solve our greediness only human beings can learn lessons from Nature and take right decisions.

 

 

Seawater is the largest source of Fresh water as well as the source of Hydrogen energy.However; Seawater cannot be used directly for these applications and it requires further treatment. Seawater has a number of dissolved salts and the TDS, total dissolved solids, of seawater is about 35,000ppm (parts per million).The commonly used industrial desalination process is by RO (reverse osmosis) as well as by multi flash distillation (MFD). Both these processes are energy intensive.RO process requires electrical energy and MFD requires thermal energy. Most of the countries in Pesian  Gulf use desalination process to convert seawater into drinking water as well as industrial water. These oil rich countries depend on the desalinated seawater as their main source of drinking water supply. In the desalination process by RO, the TDS level of seawater is reduced from 35,000ppm to 500ppm, meeting the WHO (World Health Organization) specifications for drinking purpose. The advantage with reverse osmosis process is it can remove even the smallest bacteria and virus, during the desalination. The water can further be disinfected by the injection of Chlorine before distributing for drinking purpose.

Majority of Desalination plants use RO process because it is economical. There is a worldwide shortage for safe Drinking water and more and more SWRO plants are coming up in various parts of the world. The technology of RO has advanced so much that the cost of desalinated seawater can compete with surface water in many parts of the world, especially in Gulf region where the energy cost is low. The rapid increase in population and industrial growth has created a greater demand for fresh water.

In conventional SWRO process, only 35-40% of fresh water is recovered and the balance 60-65% is discharged back into the sea as a highly saline brine, with TDS levels exceeding 65,000pm, almost double the salinity of seawater. Similarly most of the power plants located on sea coasts are using seawater for cooling purpose. In once through cooling system, the seawater is circulated into the power plant to condense steam in turbines and returned back to the sea. The temperature and salinity of the returning water into the sea is always higher than the intake water. Some oceanographers feel that such slow increase in salinity of seawater affects the temperature of the sea and the climate.

However, discharge of highly saline brine into the sea has become routine and EPA (Environmental and Pollution Authority) of various countries routinely approve such discharge, claiming it does not affect the marine life much. The environmental impact study conducted in one country is routinely followed by many countries and invariably conclude that such discharge has a very little or no impact to the environment. Human beings are concerned only with their environment and not with the Ocean environment where variety of marine species live. Our oceans have been heavily polluted from the time of industrial revolution by oil spills, toxic industrial effluent discharges, desalination and power plant discharges. The TDS levels of seawater in Gulf region has considerably increased in the past few decades. The TDS levels are about 50,000 ppm against conventional levels of 35,000PPM.The oceans are acidified by absorption of excess carbon dioxide from the atmosphere due to greenhouse gas emissions.

The power required to desalinate seawater is directly proportional to the osmotic pressure of seawater. The osmotic pressure increase as the TDS level increases, which in turn increases the energy consumption by desalination plants. A recent report from US government says that fresh water will become a serious issue after a decade and even wars may be waged between countries for the sake of fresh water. The human activities not only cause global warming but also changing the chemistry of our oceans. Steadily dwindling fish population is a clear sign of changing chemistry and biology of our oceans. In the absence of a proven scientific evidence to show that  human beings cause these changes in the ocean, we will carry on our business as usual until we reach a point of no return.

If you add salt to the water, it will not boil at 100C at 1 atmospheric pressure but slightly at a higher temperature. It is high school physics. When the salinity of the ocean increases from 35,000ppm to 50,000ppm, does it not affect the evaporation of the sea, which condenses into a cloud and come back as a rain? Does it mean there will be less precipitation in the future? Even if the ocean is under constant circulation, the overall salinity level keeps increasing.

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