Organic micro-pollutant removals from landfill leachate in horizontal subsurface flow constructed wetland operated in the tropical climate

The removals of organic micro-pollutants (OMPs) including phenolic compounds and phthalic acid esters from landfill leachate in horizontal subsurface flow constructed wetland (CW) with Typha sp. were investigated over 3 years under no plant harvesting condition. The mass removal efficiencies of OMPs were found increasing with operation time and averaged at 58-73% as CW media became matured. Highest removals (73%) were observed for hydrophilic compounds (DEP and DBP) followed by moderate hydrophobic compounds (2,6-DTBP and BHT) whereas more hydrophobic compound (DEHP) was lowest removed (58%). Higher OMP removals were observed in the summer season when their influent concentrations became elevated. Hydrophilic DEP and DBP compounds were mainly removed through biodegradation. DEHP was initially removed through adsorption but subsequently biodegraded in the long-term therefore its accumulation in media was kept at low level, i.e. 10% of maximum adsorption capacity during 3 years operation. Microbial community analyses reveal the presence of Sphingomonas sp. and Rhodococcus sp. as predominant microorganisms responsible for the biodegradation of OMPs. This study shows an evidence for sustainable application of CW to the treatment of landfill leachate containing OMPs in the tropical climate.