3.3. Waste degradation and settlement
Waste settlement is an important indicator of the degree of
waste stabilization. The reduction of waste mass could be reflected
by the increase of waste settlement, which has been explained by
first order reaction kinetics (Hettiarachchi et al., 2003). Fig. 4
shows the settlement of each bioreactor. As presented in Fig. 4,
the initial settlement variation was about 5–8% for the first week
in all bioreactors. Settlement continued as waste degraded in C1
and C2. The highest degree of settlement was achieved in C2. By
the end of the experiment, the settlement of A1, C1, and C2 was
10%, 15%, and 22%, respectively.
The VS values of waste samples from each bioreactor was presented
in Fig. 5(a). Compared to the initial VS of fresh waste
(64%), the VS of waste in A1 was 59% after 300-day operation,