Safe water and sanitation needs priority attention atleast in a developing third world country like ours since most of the prevalent health problems in these areas like diarrhoea, dysentery, cholera, can be traced to them. With rapid industrialiation and urbanisation the need for centrally managed water supply systems has become necessary to ensure a safe water supply.
All fresh water contains dissolved materials such as phosphates, gases such as oxygen and organic compounds besides suspended particulate material such as silt and microorganisms. The quantities of each vary greatly from one area to another but there exists a delicate balance between them. A dramatic increase in any one of them can, however, lead to 'aquatic chaos' in which the whole ecology of a water body is upset. Then the water becomes unfit for human consumption, and some or all-forms of aquatic life are killed. Both these effects are becoming increasingly common.
To be potable, water should also be safe. Nature has its own way of purifying and storing water. Rain water, though comparatively pure, collects solid and. gaseous matter and can become impure. This water after passing through layers of silt, clay, fine pebbles and large stone boulders gets collected in underground tunnels as ground water. This is how clean safe ground water is stored by nature.
But since ground water cannot solve the requirements in big cities and urban settlements, ways of purifying fresh water from surface water bodies like rivers and supplying this water have been devised. Most large cities use surface water sources.
Large Scale Purification of Water
The urban water supply programmes required large scale purification of water. The methods usu~lly employed include:
1) Sedimentation by storage : Water is collected from the source either in natural or artificial Reservoirs. The process of storage itself allows considerable purification:
- 90% of suspended impurities settle down in 24 hours.
- the anaerobic organisms oxidize the organic matter in the water
- the pathogenic organisms gradually reduce in number even upto 90% during storage of 5 to 7 days. Longer storage may allow growth of plants like algae.
2) Filtration : This is the second stage in purification of water where 98 to 99% of disease-causing organisms along with other impurities get removed. Two types of filters are used : i) Biological or slow sand filters and ii) Mechanical or rapid sand filters.
Water Quality Standards
Water quality standards have been formulated for urban water supply bodies because this would help to minimize all known health hazards.
The standards for drinking water take into account the following constituents in determining the quality:
- Microbiological pollutants : bacteria, viruses etc. :
- Toxic substances : arsenic, cadmium, cyanide, lead, mercury, selenium etc.:
- Specific substances affecting health : fluorides, nitrates, polynuclear aromatic hydrocarbons;
- Acceptability of water colour, odour, hardness and taste of water;
- Radio-active substances.
No matter how it is accomplished, keeping water pure enough to be usable has become expensive. Clean water in the future will undoubtedly account for a large percentage of tax payer's money and will also add to the cost of products from industry, but the investment in clean water contributes greatly to public health. Clean water is a people's issue. People must make certain that those elected to political positions understand the importance of the water problem and then keep constant watch to be sure that appropriate actions are taken.
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