• • Achieved removal rates of 81.1% for COD, 98.1% for TN, 79.1% for TP, and 90.3% for TSS, meeting GB/T 18921-2019 standards for landscape water reuse, demonstrating practical viability for urban runoff treatment.
• • The alkali-modified straw zone was the primary removal unit, supporting the highest microbial richness (Proteobacteria 54.3%, Firmicutes 21.9%), which enhanced denitrification and hydrolysis-acidification, critical for TN and COD removal.
• • The system reduced PAH toxicity equivalent by 86.5%, with complete removal of BaP, DahA, BghiP, and IcdP in the straw zone, and removal rates of 49.1% for NaP and 59.2% for Acy via plants and biochar, indicating effective mitigation of carcinogenic risks.
• • Despite high hydraulic and pollutant loads and low temperatures causing slight performance declines, effluent remained compliant, underscoring system resilience for field applications.