Eutrophication - Effect on Water Bodies

Moderate quantities of sewage decay naturally in a water body and water gets purified after some time. But the problem arises when the volume and concentration of sewage dumped increases beyond and recovering capacity of the water body. In general the following events take place in nutrient-rich water body.

• Good nutrition helps in the excessive growth of algae-characterised by algal bloom.
• The DO of water decreases as the demand for oxygen exceeds production by photosynthesis and reaeration, a few species of fish die.
• Algae die and aerobic bacterial growth begins on decayed matter.
• This leads to deoxygenation of water and consequently more aquatic species die.
• Anaerobic bacteria take over and release methane and other gases giving a foul smell.