satisfying the nutrient balance criteria for activated sludge process
to sustain aerobic metabolic activities. This implies that anaerobically
digested POME is suitable for activated sludge process without
the additional cost of adding nutrients into the system.
During the start-up period, it should be noted that there was
neither any addition of activated sludge into the SBR nor sludge
wastage from the system after the SBR was seeded. Throughout the
acclimatizing phase, the MLVSS concentration demonstrated
a steady rise from 4300 to 11,700 mg/L as shown in Fig. 1 a. The rise
in MLVSS concentration reflects the active growth of bacteria which
indicates the success of start-up. The bacteria consumed organic
matters and multiplied to form new cells. Fig. 1b illustrates the
percentages of COD and TSS removal during the start-up period. As
the feed COD increased stepwise, the removal efficiency of both
COD and TSS decreased gradually. However, both removal
percentages were relatively high albeit decreasing i.e. 91.7e97.7%
and 97.3e99.3%, respectively. On the other hand, the COD and TSS
removal efficiencies started to increase from the 20th day. This
signifies the microorganism were gradually adapting to the
increasingly high COD concentration of the influent. For most
industrial wastewaters, an acclimation period is necessary to
gradually expose the microbial community to potentially inhibitory
or toxic organic compounds. This allows the development of
appropriate enzyme producing genes that are essential to induce
biodegradation (Metcalf and Eddy, 2003). In this study, acclimation
was considered complete since the effluent COD and effluent TSS
were relatively constant after 28 days.