Wednesday, March 30, 2011

Classification of contaminants

It is possible to classify the contaminants into three categories:
1.      Floating materials: Typical floating materials would be oils and grasses. They have been making the water unsightly; retard aquatic plant growth by blocking the sunlight and interfering with the natural reaeration; destroy the natural vegetation along the banks. 
2.      Suspended matter: A common example of suspended matter has been mineral tailings. Typically, mineral tailings from slime and sludge which smother purifying microorganisms and ruin fish spawning and breeding grounds. 
3.      Dissolved impurities: Typical dissolved substances would be acids, alkalies, and insecticides. In general, they have been making water undrinkable and destroy aquatic life. For example, phenols, even in very low concentrations provide a very objectionable taste and odor.
A major problem associated with water pollution has been the “biological oxygen demand”, or the BOD refers to the amount of oxygen required to biologically oxidize the water contaminants to carbon dioxide. The BOD is important in that the higher the BOD, the higher the organic content6 of the water, and the more dissolved oxygen which will be used to decompose these organics. A lack of dissolved oxygen in the water ways kills off desirable fish. The presence of organic substances can decrease the dissolved oxygen in another way. The organics, along with the nitrogen and phosphorus, primarily can serve as food for algae. These algae have been microscopic plants which live in water. The algae eventually die and decompose. In addition to producing a slimy scum and obnoxious odor, they require oxygen and hence can drastically decrease the dissolved oxygen supply as they decay.
Acid water system:
Another problem often experienced in natural water system due to industrial pollutants is a change in the pH of the water. Natural water now varies in pH from 4.0 to 9.5. Some of the acidification of the water occurs naturally. The pH of the water has a major effect on the type of fish and other aquatic plants species present. A recent study revels that about the pH was 30% more important than water temperature and 50% more important than dissolved oxygen.
Unpolluted vs. polluted water:
Strictly speaking, pollution has been any departure from purity. When environmental pollution has been the topic, the term has come to mean a departure from a normal, rather than from a pure state. Normal areas of use include:
1.      Recreation and aesthetics 
2.      Public water supply 
3.      Fish, other aquatic life, and wildlife
4.      Agriculture5.      Industry


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