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Objective. Pollution and pollution control. Classification of Pollutants
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Objective
Ø To study the use of Bioremediation techniques applied to remove, degrade or detoxify pollution in environmental media, including soil, water and air.
It is now clear that many past and present industrial products and processes can be seen as environmentally unfriendly and are major sources of pollution. Historically, civil engineering or, more specifically, sanitary engineering, dealt mechanistically with such socially important areas as drinking water, catchment and treatment, waste water (domestic and industrial), solid wastes and industrial off-gases. The bio-component of all these processes was largely ignored. While biotechnological processes have always been part of these industrial activities, they are now increasingly being viewed in an overall environmental context.
The duration of the contamination is regarded to be because of their difficult biodegradability. The trend of environmental pollution is so fast and vast that the detectable rates of contamination are even encountered in the farthest ocean waters. Based on the estimations made by the Environmental Protection Agency only around 10 % of all wastes were safely disposed off.
Pollution and pollution control
According to National Academy of Science, USA 1966:
Pollution is “an undesirable change in physical, chemical and biological characteristics of water, air and soil that may affect human, animal or plant life, industry progress, living conditions and cultural assets”.
In essence, pollution is the introduction of substances into the environment which, by virtue of their characteristics, persistence or the quantities involved, are likely to be damaging to the health of humans, other animals and plants, or otherwise compromise that environment’s ability to sustain life. It should be obvious that this is an expressly inclusive definition, encompassing not simply the obviously toxic or noxious substances, but also other materials, which can have a polluting effect under certain circumstances.
A pollutant may be defined as, “anything, living or non-living or any physical agent (e. g. heat, sound etc. ) that in its excess makes any part of the environment undesirable.
Classification of Pollutants
The diverse nature of potential pollutants makes their systematization difficult in absolute terms; it is possible to produce functional classifications based on various characteristics.
The nature and concentration of a pollutant determine the severity of its detrimental effects on human health.
From an ecological perspective, pollutants can be classified as degradable, slowly degradable and non-degradable. The Degradable or called as non-persistent pollutants can be rapidly broken down by natural process. For example domestic sewage, discarded vegetables, slowly-degradable or persistent pollutants are pollutants that exist in the environment for many years in a stable condition and take decades or longer to degrade.
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On the basis of existence in nature
a) Quantitative Pollutants- The substances that are already present in the environment, but are termed as pollutants when their concentration (quantity) increases in the environment. eg. CO2 is present in the environment in greater quantity than normal and is hence termed as a quantitative pollutant.
b) Qualitative Pollutant- The substances, which are not normally present in the environment and are, added by human beings and are pollutants by nature. Eg. insecticides, pesticides.
On the basis of the form in which they persist
a) Primary Pollutants- The substances which are directly emitted from the source and remain in that form are termed as primary pollutants eg, smoke, fumes, ash, dust, nitric oxide and sulphur dioxide
b) Secondary pollutants- The substances which are formed by chemical reaction between the primary pollutants and constituents of the environment (i. e. those which are already present in the environment) eg smog, ozone, sulphur trioxide, nitrogen dioxide.
Classification can also be based on the chemical or physical nature of the substance, its source (Table 1), the environmental pathway used, the target organism affected or simply its gross effect. Figure 2 shows one possible example of such a categorization system.
Fig. 2. Pollution classification.
Table 1. Some examples of pollution classification considering the source of pollution.
| Type of Industries | Type of Pollution |
| Manufacture of chemicals, pesticides, medicines | Water pollution, air pollution |
| Manufacture of gases | Air pollution |
| Transport vehicle manufacturing | Solid wastes, noise pollution, air pollution |
| Forest dependent industries | Air pollution, solid wastes and sound pollution |
| Food industries | Water pollution, air pollution, food pollution |
| Sugar industry | Water pollution, air pollution, solid wastes |
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