The source for most of the domestic and industrial water the world over, is groundwater obtained through wells or springs. In its natural state, groundwater can usually be used without purification. But the contamination levels in India are very high, making purification of groundwater inevitable.
With population of over a billion, India is a major user of groundwater. Currently, the annual extraction of ground water in India is estimated to be about 210bcm (billion cubic metres), the highest in the world. India is also the world’s the biggest user of groundwater for irrigation. There is significant use of groundwater in almost all parts of the country except in Orissa, Assam, Bihar, Chattisgarh, Jharkhand and Jammu and Kashmir. Another more worrying dimension that has emerged in the past two decades, is a direct link between industrial, agricultural and household activities, and contamination of groundwater.
Contamination of the water table is caused mainly through dissolution of two broad classes of chemicals:
1. inorganic minerals, salts, and metals
2. synthetic organic compounds
Most inorganic compounds are harmless at the concentrations commonly found in unpolluted groundwater, and some, such as potassium, magnesium, and calcium, are even beneficial to human health. Others, such as arsenic, barium, or mercury, can occur naturally in concentrations that are considered harmful. Human activities are another source of inorganic substances in groundwater. Bacteria, viruses, or parasites can seep into the groundwater from sources such as septic systems, leaky sewer lines, barnyards, or fields spread with manure.
Organic compounds are chemicals containing carbon and other elements such as hydrogen, nitrogen, or chlorine. Many occur in nature, and many others are manufactured for a wide range of purposes, including cleaning fluids, wood preservatives, and pesticides. The production of synthetic organic compounds has increased more than 10-fold in the past 40 years, and some of these chemicals have become significant groundwater contaminants.
Studies estimate that nearly 59% of all districts in India have problems related to either the quantitative availability or quality of groundwater. Out of the 593 districts in India from which data is available, several have problems due to high fluoride content (203 districts), iron content (206 districts), salinity (137 districts), nitrate content (109 districts) and arsenic content (35 districts) in their ground water sources. Biological contamination causing intestinal disorders are present throughout the country.
Even as concrete policy changes and governmental intervention are the need of the hour, far-sighted and environmentally aware companies have been dedicated to providing water purifying technologies for years now.
There are two distinct separation technologies – ion exchange resins and Reverse Osmosis (RO) membrane elements – which can be either used separately or together to bring ground water to safe levels.
Synthetic ion exchange resins are polymers that are capable of exchanging particular ions within the polymer with ions in a solution that is passed through them. They are used either to soften the water or to remove the mineral content altogether, but also for various other applications including separating out some elements. Water purification using this method is environmentally friendly because it deals with substances already occurring in water. The long life of resins and low maintenance of the purification equipment makes this a very attractive method.
Reverse osmosis (RO) is a membrane-technology filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent passes to the other side.
The situation with groundwater being the way it is, using water straight from the source is no longer an option. What really is a matter of choice, is the type of purification system one would use.Prakash Shanmugam Head of Liquid Purification Technologies BU Lanxess