Biochemical oxygen demand is just a measurement of consumed oxygen by aquatic organism to decompose organic matter. whereas chemical oxygen demand is the requirement of dissolved oxygen for oxidation of both organic and inorganic constituents. hope it's clear to u now:)

Biochemical Oxygen Demand (BOD) vs. Chemical Oxygen Demand (COD)

Definition:
- Biochemical Oxygen Demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample.
- Chemical Oxygen Demand (COD) is the measure of oxygen required to oxidize all organic and inorganic matter in a water sample through chemical processes.

Difference in Measurement:
- BOD is a measure of the amount of oxygen consumed by bacteria and other microorganisms during the decomposition of organic matter, giving an indication of the level of organic pollution in water.
- COD, on the other hand, measures the amount of oxygen needed to chemically oxidize both organic and inorganic compounds present in the water sample, providing a broader assessment of overall water quality.

Time Frame:
- BOD typically takes 5 days to determine the oxygen demand, as it relies on the biological activity of microorganisms.
- COD results are obtained much faster, usually within a few hours, as it involves chemical reactions rather than biological processes.

Application:
- BOD is often used to assess the organic pollution in wastewater and surface water, especially in environmental monitoring and treatment plant design.
- COD is commonly used in industrial wastewater treatment, as it provides a quick assessment of the amount of pollutants present in the water.