The self purification capacity of a river or stream depends on 6 main factors: temperature, hydrographic factors like velocity and surface area, the rate of re-aeration, the amount and type of organic matter present, the initial dissolved oxygen levels, and the types of microorganisms present. Faster moving streams with larger surface areas re-aerate more quickly, while streams with more biodegradable organic waste or lower initial dissolved oxygen levels have reduced self purification capacity. The presence of algae and bacteria can also increase re-aeration and help break down organic matter.

1. Factor affecting self purification
capacity of the river of stream

2. Self purification capacity of river or a
stream depends on following factor
• Temperature
• Hydrographic factor such as the velocity and surface
expanse of the river stream
• Rate of re-aeration
• Amount and type of organic matter
• Available initial Do
• Types of microorganism present.

3. Temperature

4. Hydrographic factor such as the velocity
and surface expanse of the river stream
• In a swiftly moving stream i.e. with high velocity the oxygen
is replenished quite rapidly (Sabrina et. al., 2014) .

5. • Rivers having large surface expanse will also have better
reaeration as large surface area is open to atmospheric
diffusion of oxygen.
....

6. Amount and type of organic matter
• If the Waste contains large amount of biodegradable matter its
oxygen demand would be very high.

7. Types of microorganisms present:
• If algae are present along with the bacteria re-aeration
would increase as algae carbon dioxide and gives out
oxygen.
Available Initial DO:
• Greater the concentration of DO at the time of
sewage discharge, the better and earlier the self
purification will occur.

8. THANK YOU
Any Questions???
SATYAM KUMAR CHAUDHARI
Roll. no. 45, CDES