| Summary: | Amendments and modifications in conventional methods are continuously required to make wastewater treatment cost-effective, easy to handle, and eco-friendly. Given that, the present study aimed to investigate the efficacy of duckweed (Spirodela polyrhiza)-based multilayer floating constructed wetland (CW) with wood biochar (BC), as carbon stock in the support matrix for treatment of septage effluent. For that four different setups: S+BC+DW (sand + BC + duckweed), S+BC (sand + BC); S (sand); DW (duckweed) were prepared using PVC plastic columns (30 cm length × 11 cm Ø) filled with support matrix and changes in effluent parameters i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), ammonium N (NH4+-N), nitrate (NO3-N), phosphate (PO4−3), and sulphate (SO4−2) were monitored after each 24 h interval for 168 hr HRT. The maximum reduction in PO4−3, TN, NH4 +-N, BOD, COD, SO4−2 and NO3-N load was found to be 68.43 %, 64.29 %; 66.41 %, 81.87 %, 58.02 %, 60.48 %, and 64.45%, respectively in S+BC+DW setup. The performance of the studied CW setups was in the order: S+BC+DW> S+BC > S > DW. Phytoremediation assisted by BC-meditated adsorption and chemical oxidation could be the major mechanisms for septage effluent treatment in different CW setups. The results of the study could be beneficial for developing nature-based-low-cost septage treatment setups for rural areas under the decentralized wastewater treatment tools.
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