Effect of Dissolved Oxygen Concentration on BOD Decay

The Biochemical Oxygen Demand (BOD) is a quantity of the dissolved oxygen being
utilized bythe aquatic microorganisms in metabolizing the organic matter, oxidize
reduced nitrogen, andoxidize reduced minerals suchas ferrous iron. BODis alsoan
indirect measure ofthe substrate itself.
Forthisproject, the main objective is to identify the relationship between BOD decay
and the dissolved oxygen concentration. Dissolved oxygen concentration is oneof the
major factors affecting the BOD decay.
Basically, the scope of study for this projectis to relate the dissolved oxygen
concentration term into the BODdecayrate models, either in the First Order or
Second Order Model and then relate the effect ofthe order ofthe models itself to the
BOD decay rate.
The methods used in this project are to apply the models into a software application to
see the graphical presentation oftheBODdecay rate for the model. Thisis done by
assuming the First-Order BODdecay rate constant or kj according to other
researchers' works and journals and then applied into the models whichfurther
integrated into themass transport equation. From themathematical approach and
computer modeling works, the main findings of the project is thatwhen the dissolved
oxygen concentration is increased, the rate ofBOD decay will increase butthisonly
come up until certain value of dissolved oxygen concentration due to the saturation
factor ofthe oxygen. This applies to both models that are used in this project. It is also
found that the Second-Order Model exhibit a bit faster reaction than the First-Order
Model but this difference only applies in the earlier stage of the decaying. Other than
that, there are no significant differences between First-Order Model and Second-
Order Model.
In conclusion, theBOD decay rate increases as the dissolved oxygen concentration
increases until the saturation point ofthe oxygen and the Second-Order Model decay
rate is slower in theBODremoval comparing to the First-Order Model butthis does
not mean that First-Order Model is better than the Second Order Model but only
highlighting the importance ofdifferent approaches by researchers in interpreting the
BOD decay in order toobtain more accurate interpretation ofthe BOD decay rate in
water.