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Category Archives: water chemistry

There is so much discussion about Hydrogen as a source of clean energy because, it is the choice of Nature. Nature has provided us with fossil fuels which are Hydrocarbons, chemically represented by CxHy, Carbon and Hydrogen atoms. In the absence of Hydrogen in a Hydrocarbon, it is nothing but Carbon, which is an inert material. The Hydrocarbon gets its heating value only from the presence Hydrogen atom. The natural gas, now considered as the cleanest form of Hydrocarbon is represented by the chemical formula CH4, containing 25% Hydrogen by weight basis. It represents the largest Carbon to Hydrogen ratio at 1:4.This is the highest in any organic chemicals. In aromatic organic compounds such as Benzene, represented by C6H6, the Hydrogen content is only 7.69%.Even in Sugar which is an organic compound from Nature, represented chemically as C12H22O11 has only 8.27% Hydrogen. But Bioethanol, derived from sugar represented by C2H5OH has almost 13% Hydrogen.  Ethyl Alcohol known as ‘Bioethanol’ derived from sugar is blended with Gasoline (Hydrocarbon), for using as a fuel in cars in countries like Brazil. Brazil is the only country that does not depend on imported Gasoline for their cars. The same Bioethanol can also be derived from Corn starch. But the starch should first be converted into sugar before alcohol is derived; that is why it is more expensive to produce Bioethanol from starch than from cane sugar molasses. The climatic conditions of Brazil are more favorable for growing Cane sugar than corn.  Brazil is in a more advantageous position than North America, when it comes to Bioethanol. US is one of the largest consumer of Gasoline.US has imported 11.5 million barrels/day of oil in 2010.It has used 138.5 billion gallons of Gasoline (3.30billion barrels) in 2010) according to EIA. (US Energy Information Administration) It is estimated that Brazil’s sugar based Alcohol is 30% cheaper than US’s corn-based Alcohol. Brazil has successfully substituted Gasoline with locally produced alcohol .They also introduced ‘flexible fuel vehicles’ that can use various blends of Alcohol-Gasoline. Most of the Gasoline used in US has 10% Ethanol blend called E10 and E15, representing the percentage of Alcohol content in Gasoline. Brazil is the largest producers of Bioethanol in the world. Both Brazil and US account for 87.8% of Bioethanol production in the world in 2010 and 87.1% in 2011.Brazil is using Bioethanol blends of various proportions such as E20/E25/E100 (anhydrous alcohol) (Ref: Wikipedia). Almost all cars in Brazil use Bioethanol blended Gasoline and even 100% anhydrous Bioethanol are used for cars. Brazil has set an example as a ‘sustainable economy introducing alternative fuel’ to the rest of the world. The ‘bagasse’ from cane sugar is also used as a fuel as well in the production of ‘Biogas’, which helps Brazil to meet sustainability on renewable energy and greenhouse gas mitigation. The above example is a clear demonstration of sustainability because natural organic material such as sugar is the basic building block by which we can build our Sustainable clean energy of the future. The same Bioethnanol can easily be reformed for the production of Hydrogen gas to generate power and run Fuel cell cars. Many companies are trying to use chemicals such as metal Hydrides as a source of Hydrogen. For example, one company successfully demonstrated using Sodium Borohydride for Hydrogen production. Many companies are trying to find alternative sources of Hydrogen generation from water, including Photo-electrolysis using direct solar light and special photo catalyst materials. We know Nature produces sugar by using sun’s light, water and carbon dioxide from air by photosynthetic process. Can man duplicate this natural process and generate Hydrogen at the fraction of the cost by simply using water and sun’s light? The race is already on and only time can tell whether our pursuit for cheap and clean Hydrogen can become a commercial reality or just stay as an elusive dream.

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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