Coal-based material as 3-D electrodes in continuous up-flow constructed wetland-microbial fuel cells

[Display omitted] •Constructed wetland-microbial fuel cell demonstrated appreciable performance.•Coal electrode-based system achieved a maximum power density of 44.25 mW/m3.•The maximum net energy recovery was 11.03 W.h/kg of substrate utilized.•Organic, surfactant, and PO43− removal of 82.71, 90, and 100 % achieved, respectively. The present investigation examined the feasibility of utilizing low-cost coal material as 3-D electrodes in a constructed wetland-microbial fuel cell (CW-MFC) system operated in continuous up-flow manner and by cultivating Canna Indica plants. Performance of two continuous up-flow CW-MFC-1 and CW-MFC-2, using cathode electrode thickness of 3 cm and 6 cm, respectively, and a radius of 7 cm, was compared. These CW-MFCs were operated under an optimal flow rate of 52 mL/h and a hydraulic retention time (HRT) of 42 h. The CW-MFC-2 achieved the highest chemical oxygen demand (COD) removal efficiency of 82.71 ± 1.80 %, while both CW-MFCs effectively removed 89.78 ± 0.59 % of sodium dodecyl sulphate (SDS) and ∼ 100 % of phosphate (PO43−). However, CW-MFC-1 showed the highesttotal Kjeldahl nitrogen removal (79.28 ± 1.08 %). The CW-MFC-1 achieved a maximum power density of 44.25 ± 2.83 mW/m3 and net energy recovery (NER) per unit mass of substrate utilization of 11.03 ± 0.71 W.h/(kg COD). In comparison, the CW-MFC-2 exhibited a maximum power density of 41.89 ± 1.66 mW/m3 and NER of 10.02 ± 0.40 W.h/(kg COD). Thus, coal with appropriate thickness can be used as an effective electrode material in CW-MFC for improved wastewater treatment and power harvesting.