This indicates that each compartment in R1 operated most
effectively.
The removal efficiency ofCODtot in R2 fluctuated somewhat
with the change of the HRT, decreasing from 55% in
P1 (HRT 36 h), to 40% in P2 (HRT 24 h) and increasing
to 59% P3 (HRT 12 h). While the value in the first compartment
in R2 stably increased from 31% in P1 to 57%
in P3, which was higher than the values of compartment
one during each phase in tanks R1 and R3. In addition,
the individual removal efficiency of CODdis decreased from
40% in the first compartment to 3% in the third compartment
in R2 during P3, compared to a gradual increase in
P1 and P2. It is likely that this was caused by the retaining
effect of the YDT carrier being weakened with the increasing
horizontal flow velocity from P1 to P3, and that the
solids added in the experiment were carried with the flow
of wastewater to the next compartment in tank R2.