One of the key challenges in landfill leachate management is the prevention of environmental pollution
by the overflow of untreated leachate. To evaluate the feasibility of constructed wetlands (CWs) for the
treatment of waste landfill leachate in tropical regions, water reduction and pollutant removal by a CW
subjected to different flow patterns (i.e., horizontal subsurface flow (HSSF) and free water surface (FWS))
were examined in both rainy and dry seasons in Thailand. A pilot-scale CW planted with cattail was
installed at a landfill site in Thailand. With HSSF, the CW substantially removed pollutants from the land-
fill leachate without the need to harvest plants, whereas with FWS, it only slightly removed pollutants.
Under both flow patterns, the CW significantly reduced the leachate volume to a greater extent than surface
evaporation, which is regarded as an effect of the storage pond. Additionally, water reduction
occurred regardless of season and precipitation, within the range 0–9 mm d1
. In the case of low feeding
frequency, water reduction by the CW with HSSF was lower than that with FWS. However, high feeding
frequency improved water reduction by the CW with HSSF and resulted in a similar reduction to that
observed with FWS, which exhibited maximum evapotranspiration. In terms of water reduction, with
both HSSF in conjunction with high frequency feeding and FWS, the CW provided a high degree of evapotranspiration.
However, pollutant removal efficiencies with HSSF were higher than for FWS. The present
study suggested that CWs with HSSF and high frequency feeding could be useful for the prevention of
uncontrollable dispersion of polluted leachate in the tropical climate zone.