Index >> Water Microbiology >> Polluted Water

Polluted Water

In polluted waters, there are large amounts of organic matter from sewage, feces and industrial complex. The microbes are usually heterotrophic. The digestion of organic matter by these organisms is incomplete, due to which there accumulate acids, bases, alcohols and various gases.

The major type of bacteria are coliform bacteria the Gram-negative nonsporeforming bacilli usually found in the intestine. This group includes E. coli and species of Enterabacter. They ferment lactose to acid and gas. Noncoliform bacteria Streptococcus, Proteus and Pseudomonas are also present.

Under some conditions, the polluting organisms multiply rapidly and consume most of the available oxygen. For instance, nutrients enter the river from sources like sewage treatment plants or urban suburban runoff.

They produce gases. One gas, H2S combines with lead or iron to give a precipitate which makes the mud black and the water poisonous.
Due to complete depletion of oxygen, the suspended bacteria die in their own waste products. There is hardly any life in water at this stage. The gas bubbles from the anaerobes in the mud break the surface. Such processes lead to death of a river.