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Municipal Water Treatment

Water Treatment

“Water is life”. It is a unique natural resource among all sources available on earth. No life form can be sustained without water on the planet. It is essential for all the important activities like food production, industries like energy, production and manufacturing, although water is nature’s most wonderful and abundant compound but only less than 1% of the world’s water resources are available for ready use. Hence it is required to use it carefully and economically. It plays an important role in economic development and the general well being of the country.

HUMAN CONSUMPTION/DRINKING WATER:

NATURAL/SURFACE WATER TREATMENT:

Out of all the water available on the Earth, 97 % of water is saline and is in oceans, 3% of water is freshwater available in rivers, streams and glaciers. There is enough freshwater available on the planet for current population of the world but it is distributed unevenly.

Water resources including rivers, lakes or fresh water wetlands are known as surface water resources. Precipitation is the natural recharging source for the surface water resources and it also maintain the hydrological cycle. Rivers are the major source of water in India.

With growing populations and an overall increase in living standards, not only is the overall demand for freshwater pushing limits (one third of world now lives in areas of “water stress”) but increasing pollution from urban, industrial and agricultural sources is making available resources either unusable or – if there is no alternative – dangerous to health. Almost 5 million deaths in the developing world annually are due to water related diseases, much of this being preventable with adequate supplies of safe water. Surface water typically contains a high suspended solids content, bacteria, algae, organic matter, creating bad taste and odour. Hence require suitable and sustainable treatment

Two processes are commonly used to treat surface water:

  • Conventional treatment including clarification (coagulation/flocculation, sedimentation or dissolved air flotation), sand filtration, activated carbon adsorption and disinfection.
  • Advanced treatment based on ultrafiltration technology.

Ground Water Treatment

Water sources like subsurface water or water within aquifers are known as ground water resources. Ground water resource recharge from the precipitation mostly in the monsoon seasons in India. Canal irrigation and other form of irrigation systems also contribute to the recharging of the ground water.

Ground water occurrence in the country is highly uneven due to diversified geological formations with considerable litho-logical and chronological variations, complex tectonic frame work and also climatological variations. Approximate domestic requirements in rural areas and over 50% of requirements of urban and industrial uses in the country In general, greater part of the country, ground water is of good quality and suitable for drinking, agricultural or industrial purposes. Ground water in shallow aquifers is generally suitable for use for different purposes and is mainly of Calcium Bicarbonate and Mixed type. However, other types of water are also available including Sodium-Chloride water. The quality in deeper aquifers also varies from place to place and is generally found suitable for common uses.

There is salinity problem in the coastal tracts and high incidence of fluoride, Arsenic, Iron & heavy metals etc in isolated pockets have also been reported. The distributions of various constituents present in ground water in different parts of the country.

There are many different groundwater remediation methods, but they all have the same goal: clean polluted water. Commonly following methods adopted for Ground Water Treatment .
  • Chemical – Carbon absorption, ion exchange, chemical precipitation, and oxidation are all ways to achieve clean groundwater by way of chemical remediation
  • Physical - In many ways this is the most basic of these groundwater remediation methods. Using air to strip water clean, or air sparging is one such way. By far the most common though is called pump and treat, and actually utilizes multiple techniques. True to its name, this process involves physically removing the water from the ground and treating it by way of biological or chemical means.

Sea Water Treatment/Desalination

Less than 3% of the world’s water is fresh – the rest is seawater and undrinkable. Of this 3% over 2.5% is frozen, locked up in Antarctica, the Arctic and glaciers, and not available to man. Thus humanity must rely on this 0.5% for all of man’s and ecosystem’s fresh water needs.

Sea water contains many impurities in other word sea water may be considered as an aqueous solution containing a variety of dissolved solids and gases. Best method of removal of impurities would be evaporation.

Most commonly used technique for Sea Water Desalination
  • Distillation
  • Multi-stage flash distillation (MSF)
  • Multiple-effect distillation (MED|ME)
  • Vapor-compression (VC)
  • Electrodialysis reversal (EDR)
  • Reverse osmosis (RO)
  • Nanofiltration (NF)
  • Membrane distillation (MD)