In this treatment, water passed once through the biofilter with
residence time of one day. All biofilters received 3 L wastewater
on the first day of operation. The following day, and on subsequent
days, water was drained from the flood/drain biofilters over
a period of approximately 10 min and discarded. Fresh wastewater
was then added to the supply tank of all six biofilters and allowed
to flow under gravity into the biofilters over a period of 4 h. As the
supply tanks emptied they refilled the flood/drain cells and displaced
the old water from the submerged cells (see Fig. 1). Water
displaced from the submerged wetlands was discarded. Each week
for 9 weeks during treatment 1, water samples were taken for analysis
from the inlet water (in the supply tank) on day 6 and the outlet
water of all biofilters on day 7