Aeration strategies and total nitrogen removal in a hybrid aerated treatment wetland

Abstract

This study investigates the impact of aeration strategy on the performance of total nitrogen (TN) removal in a compact hybrid aerated treatment wetland (TW), called Rhizosph'air®. The system combines a single-stage French vertical flow wetland with an aerated horizontal-flow wetland, offering a unique and flexible approach for optimizing TN removal. In total, seven experimental conditions were tested, with different aeration modes, hydraulic loading rates and ammonium addition. The wetland system demonstrated high performance in terms of chemical oxygen demand removal (>85%) and solids removal (>90%), regardless of the experimental condition. However, TN removal was found to be directly impacted by operational changes. Increasing the hydraulic loading rate from 0.15 to 0.25 m/day led to an improvement in TN removal, achieving over 60%. Furthermore, when ammonium was added to the inlet and when the aeration timing was synced with the timing of the influent batch load, the environmental conditions facilitated the denitrification process, resulting in TN removal of approximately 70% and the lowest effluent NO3-N concentrations (8.70 ± 4.40 mg/L). In summary, the timing of the aeration strategy according to influent batch loading improved TN removal, suggesting its potential for optimization in future studies.