It is not possible to formulate the waste water content as each waste water has different organic contaminant components. As a measure of organic pollution in wastewater, the amount of oxygen consumed during biochemical oxidation is taken as basis. The BOD and COD values and whether the waste water is biologically refined can be clarified.

Microorganisms
Organic substance + O2 -----> CO2 + New Cell + Energy

High BOD for oxygen depletion in water potential. Oxidation of carbonaceous substances is the event of burning in water, dissolved oxygen in water is used during combustion. If the higher the amount of oxygen consumed, the higher the amount of organic matter in the water.

Biochemical oxidation is a slow process and the theoretical completion time is endless. Oxidation is 60-70% of ultimate BOD (BODu) for 5 days used for BOD test. During the measurement of BOD, factors such as ambient temperature and light should be considered. Algae that can breed during the measurement of BOD have negative effects on BOD5 values and cause false results.

Waiting for biochemical oxygen demand measurements. If algae concentration of amount high in wastewater, it can leads to poor first results. After a while, the dead algae increase the environmental BOD value. For this reason, measurement bottles should be kept in the dark during BOD design.