Second stage Bio-chemical oxygen demand in waste water is also known as:

Explanation:

Biochemical oxygen demand (B.O.D.): It is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water or wastewater sample to break down organic material present in a given water or wastewater sample at certain temperature (20˚C) over a specific time period (5 days).

The carbonaceous stage (First stage): It represents that portion of oxygen demand involved in the conversion of organic carbon to carbon dioxide.

The nitrogenous stage (Second stage):It represents a combined carbonaceous plus nitrogenous demand, when organic nitrogen, ammonia, and nitrite are converted to nitrate.

Nitrogenous oxygen demand generally begins after 5th day.