Environmental engineering Q3 Discuss the formal classificati

Environmental engineering

Q3 Discuss the formal classification of pollutants.

Solution

The simplest definition of pollutants is that it is the unwanted particle present in the environment, in any form, in so much concentration so as to adversely affect any of the existing species.

These pollutants can be classified based on several factors, some of which are discussed below:-

A. Depending upon their existence in nature

i) Quantitative pollutants: These are generally not present in the environment in a quantity that can adversely affect us rather they get accumulated in the environment due to various human activities. For example, the presence of CO₂ in our environment is necessary for the functioning of plants, however, it turns out to be a pollutant when it gets accumulated in the environment in abnormal quantity due to automobile exhaust, industries, etc.

ii) Qualitative pollutants: These are harmful even if present in small quantity in the environment, like Insecticides, etc.

B. Depending upon the form in which they persist after being released into the environment

  i) Primary pollutants: These are the pollutants that persist in the environment in the form in which they were released from the source. e.g. Ash, Smoke, etc.

ii) Secondary pollutants: These pollutants are formed after the primary pollutants chemically react with other constituents present in the atmosphere. e.g. Sulphur trioxide, Nitrogen dioxide, etc.

If a primary pollutant reacts to form another pollutant that is far more toxic than the primary pollutant itself, then it is called Synergism.

C.  From the ecosystem point of view, i.e., according to their natural disposal

i) Bio-degradable pollutants: These are the pollutants that degrade quickly by natural means or by engineered systems. Domestic sewage, heat and thermal pollution, etc. are kept in this group.

ii) Non-degradable pollutants: These pollutants either do not degrade at all or degrade at very very slow pace, in the natural environment. e.g. DDT, mercury salts, aluminum cans, etc.