Rapid treatment of textile wastewater using a Phragmites-derived biochar-amended hybrid constructed wetland

Constructed wetlands (CWs) offer a nature-based alternative for industrial wastewater management, yet extended treatment periods often limit their practical deployment. The present work evaluates a mesocosm-scale vertical-horizontal hybrid CW amended with Phragmites-derived biochar for rapid treatment of textile wastewater over a five-day period. The system delivered 90.03% removal of chemical oxygen demand, with notable reductions in ammonium (85%), color (83.47%), chloride (80%), and fluoride (69%), while arsenic and cadmium were reduced to below ICP-MS detection limits (>99% removal). FTIR spectra of treated wastewater showed diminished intensities of O-H, CO, C-O, and N-H functional groups, reflecting the attenuation of dye-related functional groups through combined adsorption and transformation processes. Physiological and biochemical responses of P. karka indicated sustained metabolic activity and enhanced antioxidant defense, while metal accumulation patterns (BCF >1 for Ni, Cu, Zn, Cd, and Pb) confirmed strong phytoremediation potential. Post-treatment biochar analyses revealed preserved mineralogical features and functional groups, indicating structural stability and potential for future reuse, although regeneration and reuse were not evaluated in the present study. Collectively, the results demonstrate that integrating biochar and P. karka into hybrid CWs can accelerate pollutant attenuation through complementary adsorption, plant uptake, and associated biological processes. Although short-term performance over a limited treatment duration is promising, longer operational periods and field-scale assessments are needed to determine system resilience and long-term treatment viability.