Although the COD and BOD removal efficiencies of the system
declined with increased OLR, the system was capable of removing
more substrate at higher loadings and the resulting effluent BOD
were still well below the discharge standard (100 mg/L). Typical
OLRs for high rate and conventional activated sludge systems vary
from 0.5 to 5 kg COD/m3 day and from 0.25 to 0.5 kg COD/m3 day,
respectively (Forster, 2003). In this study, more than 93% of COD
and 95% of BOD could be removed for OLR up to 6.5 kg COD/m3 day
and 0.62 kg BOD/m3 day, which signifies that the SBR is highly
effective and excels the conventional activated sludge systems. The
optimum OLR which give the highest COD and BOD removal effi-
ciencies are found to be 3.1 kg COD/m3 day and 0.29 kg BOD/
m3 day, with treated effluent COD and BOD values of 626 mg/L and
18 mg/L, respectively