The operational modes included batch-loaded and continuously
loaded systems. The comparison was made during two periods
during which wastewater and environmental conditions were
identical. The experiment operated in batch load was carried out
from April to June 2010, while the continuous mode experiment
was conducted from September to November 2010. Water depth
was maintained at 5 cm below gravel surface, and in the batch
mode the hydraulic application rate was maintained at 2.8 cm/day
for a 4-day retention time. Artificialwastewaterwas rapidly filled in
each bed, sampled at 2- and 4-day intervals, and then drained
completely every 4 days and filled again. In contrast, the continuous
loading method was operated at different retention times (2 days
and 4 days) with hydraulic application rates of 5.6 cm/day and
2.8 cm/day, respectively. Holding tanks of 150 L capacity served as
the reservoir for the source wastewater. Continuous loading was
accomplished by using a six-channel peristaltic pump. Each
channel was adjusted to a flow rate of 12.5 ml/min resulting in
retention times of 4-days, and 25 ml/min resulting in retention
times of 2-days.