Six identical reactors simulating VFCWs were divided into two
groups (Group A and B) in this study. Both groups are composed of
three duplicate reactors. The dimensions of the reactors are 1.5 m
(L) ×0.5 m (W) × 1.4 m (H). The reactors were filled with a coarse sand substrate to 120 cm in height. The d10and d50diameters of the
substrate are 0.25 mm and 0.60 mm, respectively. The uniformity
coefficient (Cu) of the substrate is 3.2 and the permeability coefficient is 1.27 × 10
−2cm s
−1
. Wastewater distribution systems were
installed at 10 cm below the surface level. Wastewater harvesting
systems were laid at 0.5 cm above the reactor bottoms, which were
40 cm below the distribution systems. Wastewater distribution and
harvesting systems were made of serrated PVC pipes of 20 mm in
diameter with holes for wastewater distribution/harvesting every
12.5 cm along the pipes. Each reactor has six wastewater and substrate sampling points at 0 cm, 10 cm, 20 cm, 40 cm, 60 cm and
80 cm below the wastewater distribution systems. The height of
the wastewater distribution systems is set to be 0 cm in this paper
hereafter. Phragmites australis were planted on top of the substrate
in the six reactors with a density of 4 stems·m−2