Palatable clean drinking water is becoming scarce in the present day world. Water table is decreasing day by day and the river water, even after treatment on a community basis, contains many contaminants. The levels of many pollutants like selenium, chromium, cadmium and arsenic have increased in water to dangerous levels. A long-term consumption of these pollutants may damage kidneys, liver and our nervous system. These also could lead to deadly diseases like cancer.
Off late we have different kinds of purifiers available in the market which are available at a very wide range of prices. These purifiers are associated with their own disadvantages, like, some of them consume energy in the form of electricity, some are made up of non biodegradable materials, some are very costly etc.
Some plants have been proved to be excellent for water purification. Plants like the Prickly pear cactus (Opuntia ficus-indica) or Moringa (Moringa oleifera) have the capacity to purify water. The Prickly pear cactus was used for water purification by Mexican communities long back during the 19th-century. As man marched ahead on the roads of civilization these facts were forgotten by him. He started his hunt for high technology methods of water purification.
A group of scientists from the University of South Florida in Tampa rediscovered the natural method of water purification using prickly pear cactus in 2010.
Norma Alcantar and her colleagues have used sophisticated microscopic analysis to prove the effects of cactus on dirty water.
Mucilage is glue like gummy substance secreted by plants which acts as a flocculant in water. It can precipitate substances into flakes and hence can remove substances like heavy metals (selenium, chromium, cadmium and arsenic) and even bacteria from water [1]. This thick gum is used by the plant to store water. When this magical mucilage is added to water, it sticks to the sediment particles and bacteria, which later drops down to the bottom of the water samples. According to Alcantar 98% of added bacteria, Bacillus cereus, was removed from the water sample. However, experiments are yet to be carried in natural water.
Apart from cactus there are some other plants also which help in water purification.
- Drumstick (Moringa Oleifera) – It is a drought resistant tree which can grow on a large number of poor soils including barren land. The seeds of this tree have coagulant properties and can purify turbid contaminated water. The seeds have to be crushed and the paste has to be mixed with water. The water has to be left undisturbed for an hour. The paste coagulates suspended impurities like bacteria, dirt etc and make water ready for domestic consumption. Dust and bacteria settle down which can be later be separated from pure water lying on the top. The protein component of these seeds acts as polyelectrolyte which can cross-link with charged particles.
- Nirmali (Strychnos potatorum) – The seeds of this plant are commonly used to clean water in India.
- Tulasi (Ocimum sanctum) – It is a famous medicinal plant and finds a widespread application in India. The seeds of this plant are also known for their water purification properties. However these seeds can purify water up to a certain extent and make it palatable for domestic purposes.
Many rural and underdeveloped countries have no access to the conventional water purification devices due to which people dwelling there are forced to drink contaminated water. Cactus plant and other plant products can be grown at many places at a lower cost. These plants can serve as a natural and renewable material for water filtration and at the same time save the lives of many people. It is a cost-effective alternative and also saves a lot of energy.
Reference:
Buttice AL, Alcantar NA et al. Removal of sediment and bacteria from water using green chemistry. Environ Sci Technol. 2010 May 1;44(9):3514-9.
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