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Water Problems And Solutions!

Updated on June 29, 2013
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Major part of world consists of water. About 70% of the earth's surface is covered in water. But water also exists in the form of vapour and groundwater.

The total water supply of the world is 1.400.000.000 km3. (A m3 of water equals1,000 litres.)
Each year, 119.000 km3 of water precipitates on land and 74.200 km3 evaporates into the atmosphere, by transpiration from soil and vegetation. On ocean and sea surface 450.000 km3 of water falls every year and 502.800 km3 evaporates. Of the freshwater on Earth, about 2.200 km3 flows into the ground.

Water is the major component of human’s body. Almost in every organism, nutrients and other enzymes are transported with the help of water. Human body consists of 66% of water.(source- water quantity FQA)

Source

Shortage of Water

Earth is largely covered with water and yet many countries are increasingly facing shortage of water, especially potable water. To cite a current example, all the countries in the Mekong River basin are presently facing water shortages. (Source - Straits Times)

Shortage is caused by many factors. The quantum of rainfall an area receives is basically determined by its geographical location, topography and terrain. Rainfall and topographical aspects also impact the availability of ground water resources. As such, while some countries are naturally endowed with ample fresh water resources, there are others with limited or very little water. Water availability has been generally dwindling in most of the countries due to industrialisation, disposal of industrial and chemical waste into water bodies, traditional systems of flood irrigation along with heavy fertiliser usage, failure to recycle water, lack of water harvesting, over-use, construction of too many dams and so on. Changing weather patterns affecting rainfall patterns and frequent droughts are other causes.

With global warming causing drastic weather changes, conservation, augmentation and proper utilisation of water, especially potable water, has become very critical to support the growing world population across the globe. Countries with lesser access to fresh water resources are still more vulnerable. They have to leverage technology to sustain water supply through recycling and desalination.

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National Taps

Singapore has limited water resources, but requires over 1 million cubic meters of water per day to ensure supplies to its 4.9 million people. By ensuring proper catchment, 50% of the water supply requirements are met out of rainfall. It is recognised as the first national tap by the Public Utilities Board of Singapore. (Source – Tuas Seawater Desalination Plant)

The second tap is import from Malaysia; this source is likely to be politically vulnerable. Singapore has relied on importation from Malaysia to supply half of the water consumption in Singapore. As of 2009, imported water had been reduced to 40% of total consumption. The two water agreements that supply Singapore this water are going to expire by 2011 and 2061 respectively. This led to controversies and disputes amongst the two countries mainly about the price of the water. Hence, the government of Singapore has decided to increase self-sufficiency in its water supply.

NEWater is the brand name given to reclaimed water produced by Singapore's public utilities. It is treated waste water (sewage) that has been purified using dual-membrane and ultraviolet technologies.

There are four NEWater factories, located at the Bedok, Kranji, and Seletar, and Ulu Pandan Water Reclamation Plants, produces about 32 million US gallons per day (1.4 m³/s). These plants can supply 15 % of Singapore's water needs.

The fifth NEWater plant opened at Changi. With a capacity of 50 million gallons per day, NEWater is currently able to meet 30% of Singapore's water requirements through recycling. (Source - wekipedia)

Singapore has also started several campaigns to ask people to conserve water. They aim to reduce consumption from 161 litres per day per person to 155 litres and gave tips includeing spending one minute less in the shower.

Desalination Process

The plant design uses an open seawater intake structure. It has two separate inlets equipped with mechanical screens. Growth inhibitors reduce the potential for marine growth around the screens, pipes and other structures.

The plant design uses an open seawater intake structure. It has two separate inlets equipped with mechanical screens. Growth inhibitors reduce the potential for marine growth around the screens, pipes and other structures.

Chemical de-chlorination takes place both upstream and downstream of the filters leading to the RO plant. Further downstream adjustments of pH balance are possible. Dissolved air flotation (DAF) removes oil, grease and suspended solids from the flow, which then passes through primary gravity sand filters (GSF) and secondary pressure sand filtration (PSF) before entering the plant’s reverse osmosis (RO) treatment train.

The RO treatment train at Tuas employs two passes - first for removal of dissolved solids (salts) and second to reduce boron levels. Water is treated before release to the water supply grid. Lime is used to correct pH level and improve the taste. Chlorine or ammonia is used for final disinfection. Chemical dosing ends with addition of fluoride. Energy recovery is ensured through a Pelton wheel and pressure exchange type Energy Recovery System.

The by-product, viz. brine stream is discharged to the sea via submerged outlets. At 4.1kWh/m3, the plant is one the most energy efficient, which keeps the production cost the lowest in the world.

Source

Desalination And Problems

Desalinating water is expensive. High capital costs, energy requirements, challenges in transporting or piping desalinated seawater to distant locales in large countries and marine and air pollution are some of the key concerns in producing desalinated water. However, for cities on the coast or island nations, desalination is being increasingly viewed as an untapped and unlimited water source.

Water intake from the sea to desalination plants, especially when co-located with power plants damages fishes, plankton and other marine life. Beach wells and other alternatives can reduce the harm, but increase energy usage and costs. Output is also impacted. Other environmental concerns include air pollution and greenhouse gas emissions from the power plants that provide electricity or thermal energy to the desalination plants.

The brine left behind is a highly concentrated, extremely saline waste and is often disposed of into the ocean. The benthic community may not withstand such extreme variations in salinity. Many filter-feeding animals are destroyed by osmotic pressure when such water is returned to the ocean. As the concentrated brine is denser than the surrounding sea water, it sinks and remains at sea bed long enough to damage the ecosystems. While careful discharge into the oceans can minimize this problem, inland disposal of brine can ruin fresh water supplies such as ponds, rivers and aquifers.

Desalination is viewed as the first option for increasing supply of drinking water. New technologies such as forward osmosis, solar desalination, geothermal desalination, nanotubes membranesand so on are being developed for water filtration. These may produce a water desalination process that would require substantially less energy than reverse osmosis.Fresh water can also be produced by freezing seawater. Low Temperature Thermal Desalination (LTTD) is another technology in use in India to desalinate water in an energy efficient manner.

Desalination water is a major source of potable water in the entire Middle East and many other water deficient areas. As countries such as Saudi Arabia and UAE have very scanty rainfall, potable water is mainly obtained by desalinating sea water.

As Singapore has shown, cost effective desalination of sea water is feasible. Proper design has also minimised damage to marine life or global environment. Large-scale desalination is normally very expensive. Several methods are available for desalinating water. The world's largest desalination plant in Jebel Ali in the UAE uses multi-satge flash distillation to produce 300 million cubic meters of water per year. It has traditionally been the leading desalination method, but most new facilities use energy efficient reverse osmosis technology.

The water tap of desalination is ideally suited to Singapore. Given lack of fresh water resources, there is a limit to which rainfall or recycled water can meet its requirements. Commercial import of bulk water from neighbouring countries is feasible but does not make political or strategic sense. USA has been importing water from Canada using very large carries, but the geopolitical situation in Asia is different. Singapore can easily import water from Malaysia by pipelines, but that would keep Singapore vulnerable to political decisions made in Malaysia. As such, Singapore needs to expand water supply options such as installation of rainwater tanks, storm water harvesting infrastructre and recycling of urban runoffs and waster water. Keeping in view its technological lead, Singapore can also develop new filtration techniques to reduce desalination costs and minimise environmental damages and share the same with other water scarce nations.

Reverse Osmosis

As we all know, osmosis is the diffusion of water or any other liquid through a semi-permeable membrane, which is permeable to the solvent, but not to the solute. The membrane separating two solutions of different concentrations normally allows the solvent from the less-concentrated (hypotonic) solution to diffuse to the more-concentrated (hypertonic) solution. By increasing the pressure on the hypertonic solution, relative to the hypotonic, osmosis can be controlled. Reverse osmosis (RO) of sea water is based on this principle. Sea water is kept on the pressurized side of the membrane and the pure solvent (water) is allowed to pass to the other side. This is the reverse of the normal osmosis process.

The membrane is designed to allow only water to pass through. A high pressure is exerted on the high concentration side of the membrane, usually 40–70 bar (600–1000 psi) for seawater, to overcome the natural osmotic pressure, which is around 24 bar (350 psi).

Do you think New Water is safe to drink?

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    • teflindo profile image

      Wayne Duplessis 

      2 years ago from Surabaya, East Java, Indonesia

      An important discussuon that needs to happen publically. Hope articles such as yours push these ideas to the fore.

      Regards, Wayne

    • profile imageAUTHOR

      Bharat 

      5 years ago from Singapore

      Thank you. I will try to bring in more of these :)

    • susi10 profile image

      Susan W 

      5 years ago from The British Isles, Europe

      This is an interesting article and provides in-depth information about water. I will definitely be reading more of your work.

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