attributed to the degradation of primary sludge within each
tank, which converts to CODtot and CODdis.
The results indicate that the COD removal performance
of the three reactors was different in each operation phase.
As a whole, the removal efficiencies for CODtot of R1 and
R2 were improved by approximately 10–20% compared
with that of the conventional tank R3. The accumulated
removal efficiency of CODtot in R1 remained higher than
50% although the HRT decreased from 36 h in P1 to 12 h in
P3 and the individual removal efficiency of CODtot in the
first compartment in R1 increased from 21% in P1 to 53%
in P3. This indicated that the anaerobic sludge was being
stabilized with the increasing period of reactor operation,
despite the reduction inHRT from36 to 12 h. The individual
removal efficiency of CODtot in the first compartment of
all the three reactors was similar, however the removal of
CODtot in the second and the third compartments of R1 was
always higher than the corresponding values in R2 and R3.