indicating little biodegradable waste was decomposed during the
experiment. Due to the top layer aeration, the VS greatly decreased
in hybrid bioreactors. The VS values of waste samples from the top
layers (29% in C1, 15% in C2) were lower than those from the bottom
layers (33% in C1, 36% in C2). As expected, high aeration frequency
caused more waste biodegradation in the top layer of C2,
resulting in lower VS value than that of C1. Fig. 5(b) shows the picture
of all reactors after the thermal insulation cover was removed.
It was observed that considerable amounts of waste in C1 and C2
turned its color to black, indicating reduced conditions, while the
waste in A1 remained its original color.