Newly developed baffled subsurface-flow constructed wetland for the enhancement of nitrogen removal

► Baffled subsurface-flow constructed wetland for nitrogen removal enhancement. ► Enhancement of aerobic and anoxic/anaerobic conditions in baffled wetland unit. ► Better performance of baffled unit in NH4+-N removal due to longer pathway. ► Complete oxidized nitrogen removal due to release of COD from rice husk media. The objectives of this study are to compare the performance of newly developed baffled and conventional horizontal subsurface-flow (HSF) constructed wetlands in the removal of nitrogen at the hydraulic retention times (HRT) of 2, 3 and 5days and to evaluate the potential of rice husk as wetland media for wastewater treatment. The results show that the planted baffled unit achieved 74%, 84% and 99% ammonia nitrogen (NH4+-N) removal versus 55%, 70% and 96% for the conventional unit at HRT of 2, 3 and 5days, respectively. The better performance of the baffled unit was explained by the longer pathway due to the up-flow and down-flow conditions sequentially thus allowing more contact of the wastewater with the rhizomes and micro-aerobic zones. Near complete total oxidized nitrogen was observed due to the use of rice husk as wetland media which provided the COD as the electron donor in the denitrification process.