Enhanced removal of nutrients and coliforms from domestic wastewater in cattle dung biochar-packed Colocasia esculenta-based vertical subsurface flow constructed wetland

Abstract The efficiency of Colocasia as well as cattle dung biochar addition in a constructed wetland, is not well documented in published literature. In this study, Colocasia esculenta-based vertical subsurface flow constructed wetland (VSSFCW) packed with heterogonous gravels and cattle dung biochar was established to examine the removal of nitrate (NO3-N), ammonium N (NH4+-N), sulfate (SO4−2), phosphate (PO4-3), chemical oxygen demand (COD), total N (TN), and total coliforms from domestic wastewater. To achieve the goal, three setups of VSSFCWs; SB (medium + biochar (10 % v/v)); SBP (medium + biochar + Colocasia); SP (medium + Colocasia) were established and wastewater characteristics (pH, DO, NO3-N, NH4+-N, TN, SO4−2, PO4-3, COD, and total coliforms) were monitored after each 24 h interval for 40 d after 70 d of initial acclimatization of the setups. SBP showed the highest average removal efficiency for COD (92.6 %), NO3-N (81.7 %), NH4+-N (81.2 %), SO4−2 (85.4 %), PO4-3 (69.5 %), total coliforms (97 %) than SB and SP during of the 40 d treatment period. Plant uptake rate was also measured and biochar amended VSSFCW showed the highest values of leaf area, biomass growth (2.58–3.44-folds). N-uptake (36.81 g N m−2), and P-uptake rate (12.3 g P m−2) than SP setup. The treated domestic wastewater by biochar amended VSSFCWs compliance with the limit set by the national pollution monitoring agency of India. Role of aeration and varying wastewater strength (especially COD load) in the performance of Colocasia-based CWs’ could be undertaken as a research problem for future studies to develop an efficient engineered wetland system for on-site wastewater treatment.