per kgVS than C2 with high aeration frequency (4 times per day).
So, the use of frequent aeration is not recommended, if landfill
operators aim to maximize methane recovery from MSW.
The use of higher aeration frequency in the hybrid bioreactor
enhanced the rate and the magnitude of settlement (15% in C1
and 25% in C2). Comparing the VS values of aerated layers in C1
and C2, the lower VS content in the upper layer of C2 supported
that MSW could stabilize faster with the higher frequency of aeration.
The greater settlement coincided with the greater loss of VS.
During the aerobic–anaerobic transition phase, adverse effects
of leachate recirculation on methane production rate was observed
in this study. Stopping aeration led a sudden increase of leachate
VFA levels (from 8200 mg/L to 16,000 mg/L in C2) that could be
above the VFA toxic level for methanogens. It is suggested that leachate
recirculation need to be performed with monitoring the level
VFA concentration to avoid the inhibition for methanogens.