The environment is something you are very familiar with. It consists of the air, water, land, and all the conditions that surround living organisms. It can be living or non-living things. It is the sum total of everything around us.

The pollutants (substances that damage the environment) can be classified into two basic groups:

(a) Non-degradable Pollutants:

These are not broken down by the natural processes like the action of microbes. Most of these Mutants get accumulated in the environment and also get biologically magnified as these move along the food chains in an under the composed state. These may also react with other compounds in the environment to produce toxins.

These can be further subdivided into two more classes:

(i) Waste:

E.g. glass, plastic, phenolic, aluminum cans etc.

(ii) Poisons:

E.g. radioactive substances, pesticides, smog gases, heavy metals like mercury, etc.

(b) Degradable pollutants or Biodegradable Pollutants:

These are natural organic substances which can be decomposed, removed or consumed either by natural processes like biological or microbial action or by some artificial systems, like sewage treatment plants.

The degradable pollutants can be further subdivided into two categories:

(i) Rapidly degradable or non-persistent pollutant:

The degradation of these pollutants is a very faster process. For example, the decomposition of sewage and wastes of animals and plants is a faster process. The domestic sewage can be rapidly decomposed by natural processes. However, the problems become complicated when the input into environment get exceeded of the decomposition or dispersal capacity.

(ii) Slowly degradable or persistent pollutant:

The degradation of these pollutants is a very slower process. It seems as if the amount of pollutant remains unchanged with time. For example, degradation of synthetic compounds and radioactive elements like Iodine 137, takes a longer period of time.