It can be observed that BOD removal efficiency followed a similar pattern to that of
COD removal efficiency. An increase in both the COD and BOD removals was obtained when the MLSS concentration increased from 18,000 to 27,000 mg/L at an OLR of 2.5 and 3.5 g COD/(L day).Further increase in MLSS concentration had resulted in a drastic
decrease in COD and BOD removals.