Typical values for the F/M ratio in conventional activated sludge
system range from 0.2 to 0.4 g BOD/g MLVSS.d (Woodside
and Kocurek, 1997). The F/M ratios of 0.06e0.18 g COD/g MLVSS.
d (corresponding to 0.006e0.018 g BOD/g MLVSS.d) applied in this
experiment are low due to the relatively high MLSS and MLVSS
level maintained in the SBR as compared to other activated sludge
system which are normally operated with MLSS level of
500e5000 mg/L (Leslie Grady et al., 1999). Due to the relatively
high TSS and COD concentration of the influent, high MLVSS
concentration are operated in the SBR to ensure the bacterial
population is adequate to degrade the organic matter efficiently.
The combinations of high biomass concentration and complete
retention of solids allow the process to be operated at low F/M ratio