The ability of vertical flow (VF) constructed wetland systems to treat high-strength (ca.300mgL of COd and ca. 300mgL
total-nitrogen) wastewater under tropical climatic conditions was studied during a 5-month period. Nine 0.8-m diameter experimental VF units (depth 0.6m) were used: three units were planted with Typha angustifolia L., another three
units were planted with Cyperus involucratus Rottb and three units were unplanted. Each set
of units were operated at hydraulic loading rates (HLRs) of 20, 50 and 80mmd . Cyperus produced more shoots and biomass than the Typha, which was probably stressed because of lack of water