Work out cod load instantly with clear inputs, formula shown and shareable results.
COD measures all chemically oxidisable matter and is always higher than BOD. The BOD to COD ratio indicates biodegradability: above 0.5 the effluent treats readily in a biological plant, 0.3-0.5 needs acclimatised biomass and longer sludge age, and below 0.3 biological treatment alone will not achieve consent.
COD load
Load (kg/day) = flow x COD / 1000
Biodegradability
BOD/COD ratio indicates the fraction amenable to biological treatment
COD and BOD limits are consent conditions. Persistent non-biodegradable load may require pretreatment at source under trade effluent controls.
COD takes two hours against five days for BOD, so it is the practical control parameter. A site-specific COD to BOD correlation is established and then COD is used for day-to-day monitoring.
Refractory organics, some solvents, surfactants and reduced inorganics such as sulphide and nitrite. A widening COD to BOD gap often signals an industrial discharge to the sewer.