LAUSR

Abstract The conventional Bio-Rack Wetland System (CBRWS) is a comparatively a novel technique for treating wastewater. It has potential to overcome clogging problem in constructed wetlands. Modifications are possible to enhance treatment potential of CBRWS with relatively lower cost. In the present study, modifications were implemented by planting multispecies (Canna indica and Typha angustata) vegetation in bio-racks made up of discarded non-perforated plastic water bottles in which plug-flow was induced through baffling. The performance of CBRWS and Modified BRWS (MBRWS) was evaluated for the removal of dissolved organics (Carbon and Nitrogen) from domestic wastewater. CBRWS and MBRWS were operated in sequential continuous [1.5 h, 4–24 h (in multiples of 4) HRT] and MBRWS in continuous (4, 12 and 24 h HRT) mode. The systems were operated at Organic Loading Rate (OLR) of 0.25–3 kg COD/m3 d. The removal efficiency of MBRWS was more than CBRWS by “4–9%, 4–13% and 3–16%” for “COD, BOD3 and TKN”, respectively. Dissolved oxygen level was also increased by 0.6–1 mg/L in MBRWS at all HRTs. The contribution of baffling used to induce plugflow conditions in MBRWS was found to be more significant than the use of multispecies vegetation for the removal of dissolved organics. The study demonstrated potential of MBRWS to maintain better aerobic conditions and treat wastewater at lower HRTs.