Flow-configuration effects on pollutant removal and plant physiological responses in <i>Phragmites karka</i> –planted hybrid constructed wetlands treating textile wastewater

Constructed wetlands offer an eco-friendly, phytoremediation-based solution for managing industrial effluents. Hybrid constructed wetlands are gaining attention for improved pollutant removal, yet the role of flow configuration remains insufficiently explored. This study compares two hybrid vertical-horizontal flow and horizontal-vertical flow constructed wetlands for treating textile wastewater under identical operational conditions. Performance was evaluated based on pollutant removal and the physiological responses of <i>Phragmites karka</i>. The vertical-horizontal flow to horizontal-vertical flow system showed higher removal efficiencies for chemical oxygen demand (85.07%), color (60.6%), chloride (69.66%), bicarbonate (93.12%), calcium (66.83%), sodium (73.08%), and potassium (79.18%), also plants in this unit exhibited greater pigment, protein, starch, and sugar contents, while antioxidative enzymes were lower, indicating reduced oxidative stress. These results suggest that initiating treatment with a vertical flow stage promotes better oxygenation, enhanced microbial activity, and healthier plant performance. Overall, the vertical-horizontal flow to horizontal-vertical flow configuration represents a more effective and biologically favorable hybrid constructed wetland design for sustainable textile wastewater treatment. Extended pilot- and field-scale assessments coupled with integrated eco-technologies and cost analysis are needed to refine key design variables and validate system performance under real-world conditions, to support the development of scalable, cost-effective, and sustainable treatment strategies for large-scale applications.