Biochemical Oxygen Demand

All BOD values tested are within the range of typical values of BOD found in raw water sources, with the exception of Inlet C1 which is significantly lower.
However due to experimental errors the results obtained were not accurate to show a distinct pattern among the different sites tested.

DO vs BOD

The higher the BOD, the lower the DO present in the sample. This is caused by the organisms thriving in water, especially bacteria in polluted water such as the Grease Trap. And since the organisms in the waters require high amount of Oxygen for their activities, it results in the decrease of DO.

Given that the values of BOD are 4.75mg/L in average, it falls into the standard values of BOD of Raw Water source which is 3 to 15 mg/L.

BOD vs COD

There is no correlation between the BOD and COD of the different water collection points. Theoretically, as BOD concentration increases, COD concentration should increase as well. However, our results showed otherwise. The reasons could be that:

1. The COD and BOD values were too low and insignificant to show a strong relation between them.

2. Apart from the grease tap, the other water collection points were relatively low in organic matter that can be chemically oxidized and organic matter decomposable by bacteria. The grease tap contained chemicals with nitrogen/phosphorus compounds in them. These chemicals were mainly soaps, detergents and grease that resulted in the high COD reading.
These nitrogen/phosphorus compounds were later on channeled to plants which absorbed them reducing their concentration greatly in the inlet, outlet and ponds.

3. There had been human error in carrying out the BOD test resulting in inaccurate final values.

Hence, the correlation between COD and BOD values is non-existent and can be ignored in this project.