Optimizing nitrogen removal in vertical-flow constructed wetland: Effect of glucose addition and aeration duration

【Objective】Constructed wetlands are an effective technique for removing various organic and inorganic pollutants from wastewater. This study investigates the impact of glucose addition and intermittent aeration duration on nitrogen removal efficiency in vertical-flow constructed wetlands (VSFCWs) filled with substrates of varying particle sizes.【Method】The experiment was conducted in two phases. In the first phase, VSFCWs were tested with three glucose addition levels (10, 20, and 30 g) and five substrate types: fine particles (2 to 4 mm), medium particles, coarse particles, positive gradation, and negative gradation. Nitrogen removal efficiency was assessed for each treatment. In the second phase, the optimal combination of glucose addition and substrate type from the first phase was used to evaluate the effect of aeration durations ranging from 0 to 8 hours on nitrogen removal.【Result】When the glucose addition was the same, the VSFCWs filled with fine-grained matrix by particles with diameter of 2 to 4 mm was most effective in removing nitrogen. When the particle sizes were the same, adding 10 g of glucose was most effective in removing nitrogen. VSFCWs filled with matrix of positive and negative gradation reduced matrix porosity; VSFCW filled with the fine particle size gradation combined with a 10 g of glucose addition was most effective in nitrogen removal, with the total nitrogen removal rate reaching approximately 50%. The optimal aeration duration was 4 h, with its associated total nitrogen removal rate reaching 86.9%.【Conclusion】The most efficient nitrogen removal in the VSFCWs was achieved by using fine-sized zeolite substrate, 10 g of glucose addition, and a 4-hour aeration duration. These findings provide a reference for designing and operating constructed wetlands for enhancing nitrogen removal efficiency.