The CW system included four rectangular treatment cells, each
measuring 2.14mlong, 0.76mwide and 0.61mdeep, with a surface
area of approx. 1.63m2 and a total volume of 992 L. A diagrammatic representation of cell dimension and experimental layout is
shown in Fig. 1. The cells were lined with low-density polyethylene
(LDPE) sheets to avoid any loss from the cells and filled with layers
of gravel of two different sizes (approximately 2.5cm and 1.5cm
diameter) to a depth of 0.61 m, with an effective 30% pore space.
The arrangement of the inlet and outlet pipes and for the distribution
of the wastewater within the cell was similar to that described
in the previous study (Ghosh and Gopal, 2007). The wastewater
tanks were connected to the inlet pipe of the cells with ball valves
to hydraulically maintain pre-determined inflow rate in the cells.
Young sprouts of T. angustata were planted equidistantly at
20cm interval in all the treatment cells. Dead shoots were replaced
with the new ones randomly until the growth stabilized in the
gravel bed. The plants were allowed to grow and multiply to form a
dense stand in the cells over a four months period from April to July
2006, with periodic application of wastewater as a source of nutrients
for the plants, before the selected inflow rates of wastewaters
were introduced.