Nitrogen removal from high-ammonia wastewater using vegetated biofiltration systems: Insights from 18-month mesocosm study

. Seven plant species, two system designs (standard nitrification-denitrification and anammox-favouring), and varied hydraulic regimes were tested. Results showed average total nitrogen removal of 31.5 ± 15.8%, with consistent COD (>80%) and orthophosphate (>85%) removal. While vegetation effects were limited overall, Cyperus alternifolius and Canna indica enhanced nitrogen removal under specific conditions. Alternate-day dosing and lower dosing volumes improved performance through enhanced retention time and oxygen availability, while extended drying periods (20 days) impaired removal. Anammox-favouring columns achieved comparable nitrogen removal with reduced footprint. Findings demonstrate VBS viability as low-energy polishing systems and provide design optimization guidance for decentralized wastewater treatment applications.