Abstract:

The potential of using constructed wetlands as a cheaper and yet effective alternative method
for treating domestic wastewater in tropical environments was investigated in this study from
May 1996 - April 1999. The major aim was to determine their technical viability with respect
to treatment performance under different operating conditions and the economic
competitiveness of the technology in Uganda and within the region. A pilot constructed
wetland design, based on horizontal flow criteria and receiving pre-settled sewage from the
Jinja Kirinya Sewage anaerobic lagoons was used in the study. The wetland had a total
surface area of 320 m2
, which was sub-divided into eight individual units. Four of the units
were planted with Cyperus papyrus floating without a substratum base and two with
Phragmites mauritianus anchored on a substratum base. Two units were used as controls, one
of them had a substratum base of similar volume as the planted ones. The wetlands were
operated over three consecutive phases. In the initial phase, all planted units remained intact
but in the 2nd
phase, plant biomass was removed from a quarter of the area of the two
Cyperus papyrus and one Phragmites mauritianus wetland units. In the last phase, two
wetland units of each plant type and one control (open) were joined in series; two other
papyrus wetland units with smaller areas of alternating planted and unplanted sections were
joined in series.