All papers are checked via
|← Manipulation of Time and Space||Robotic Surgery →|
Fresh water contains extremely low salt concentration usually below 1,000 milligrams per litre of dissolved solids. The earth’s water supply is approximately 97 percent that is found in the ocean but it contains minerals; the remaining 3 percent is fresh water found in continental and mountain glaciers, lakes, streams, marshes and underground. Fresh water is vital for living creatures and specifically humans who must replace 2.4 litres of water a day. Humans also use water for other essential activities like agriculture, in the industries and power generation.
This is the reason why fresh water is currently said to be under the risk and is becoming scarce with the dawn of every new day. Experts state that in the next two decades water demands will rise to levels that will leave about 54 countries suffering from a shortage of water fit for human consumption. The figures currently show that at least 31 countries are facing water shortage. Among them are Ethiopia, India, Kenya, Nigeria and Peru. Countries have been formulating techniques that are geared towards alleviating the looming crisis around the globe and specifically arid areas. Some of these techniques include desalination and rain water harvesting.
Desalination is termed as a process that purifies water by bringing down the salt levels in the water as well as other minerals from saline water. This process converts salty water to fresh one to make it suitable for human consumption.
This is a process that can be used to supply water to arid areas where the ground water is deficient. The process does not rely on rain water, for instance the one found in Jebe Ali in the United Arab Emirates and the United States of America located in Tampa Bay, Florida.
If to observe global statistics, we can see that among other over 15,000 desalination plants (International Desalination Association 2009) these plants have been producing millions of cubic metres of water that have supplemented limited fresh water supply in these locations.
There are a number of desalination techniques around the globe that include:
a. Forward Osmosis Desalination
Forward osmosis desalination is a technique that is still in its research and development stage. However, it is able to produce large amounts of fresh water from the sea.
The technique is cost-effective since it does not require hugely expensive equipment to carry out the purification process. The technique uses polymer membrane to break up the minerals from the liquid being treated.
A concentrated solution that possesses high osmotic pressure like an ammonia carbon dioxide is used to draw seawater through the membrane. The membrane prevents the passage of solids. The draw solution is then pumped into another tank while the residual fresh water is left in a different tank. The fresh water is then pumped away for post-processing and storage for future use.
b. Reverse Osmosis Desalination
Reverse osmosis has been used to sanitize water for human consumption and irrigation in agriculture. This technique uses a polymer matrix semi-permeable membrane that prohibits the salt and other particles from passing into the water.
The process allows flow of sea water through the wells that are sunk into the sand; therefore, the water is filtered before entering the desalination plant. The desalination plant then turns the seawater into clean water by use of reverse osmosis technology along a new innovation of energy recovery to drive the pressurizing seawater pumps.
c. Fast Flow through Carbon Nanotubes Desalination Technique
This technique is also being tested in its development stages and has proved to save energy and the cost of desalination. The technique is likely to replace the use of the conventional membranes in desalination of ocean water.
The technique uses carbon nanotubes which are made of roller sheets of carbon atoms. The flow of water through the ultra smooth bore of the tubes leads to a reduction in the pressure of water with the help of the nanotube membrane. The membrane has a silicon wafer chip that contains a carbon catalyst to produce the carbon nanotubes, which are formed vertically and are packed together.
d. Biomimetics and Desalination
This technique uses the concept of living cells that have tiny water tubes which take in water and leave out dissolved solids that include salt and other minerals. The concept is borrowed from reeds which grow in salty waters but can separate fresh waters from the rest of the solids.
2. RAIN WATER HARVESTING
In the last two decades farmers in India alone are increasingly tapping the available groundwater. Millions of wells have been dug in India, groundwater levels have therefore plunged in many areas because of excessive pumping. By 2025, per capita water availability in India could fall below 1,000 m3 (Shahriar M. Wahid, 2008).
Among many other situations it has left water levels in most arid areas stressed, however, arid areas sometimes experience plenty of rain which flows freely to waste or feed either lakes or oceans. After the pouring rains have fallen, the residents of these arid areas are left with the fresh water for their consumption or irrigation.
This can be clearly showed in the desert state of Rajasthan, India. Rajasthan is an arid land as it has experienced 40 droughts during the last five decades. The groundwater has receded to 300 – 400 feet in depth due to overexploitation and the dryness of the dug wells. About 30 percent of the hand pumps have gone dry but the situation is gradually changing due to the water harvesting initiative.
The use of water harvesting is the technique that can help alleviate this problem of fresh water deficiency in the arid areas in the entire world. The techniques have been used in Africa, Brazil, Argentina and Paraguay among other drought hit areas at highly successful levels.
The technique is cheap and easy to maintain as compared to the earlier discussed desalination technique. Rain water harvesting can be applied in both small and large scales. It can be applied through the use of drums and tanks at household levels while in the same time huge dams can be sunk to hold flowing water.
COMPONENTS OF HARVESTING SYSTEM
There are three main components of a rainfall harvesting facility that include a collecting area, a transference system and a storage area. Once the flowing water is harvested, it is then transferred to a storage place where it can be purified for human consumption or channeled to relevant locations.
Water scarcity in arid and semi-arid areas can be mitigated with the right application of modern techniques. On the one hand, taking into consideration 97 percent of the Earth’s water containing minerals, these techniques can be utilized to increase the availability of fresh water in arid areas as well as the rest of the world. On the other hand, the use of rainfall harvesting has been applied in many locations successfully. The same should be introduced in those areas that have receding water levels. Since unusually heavy rains are experienced occasionally in these areas, the flowing water should be trapped and stored for human use.