Enhanced Removal of Nitrogen and Organic Matter from Wastewater in Constructed Wetland Technology by Artificial Aeration

The main aim of this study was to investigate the enhanced performance of a horizontal subsurface flow constructed wetland (HSSFCW) in terms of nitrogen and organics removal through a proper spatial distribution of aeration to ensure simultaneous aerobic and anaerobic conditions. Two HSSFCWs, one aerated in its front section only and the other one non-aerated (as control), were operated in parallel at a hydraulic retention time (HRT) of 24 h, a hydraulic rate (HLR) of 0.16 m day and a water depth of 0.4 m. Three distinct types of synthetic effluents were prepared and fed in the systems to simulate a wide range of wastewaters. The rate of aeration provided in the aerated (or intensified) bed was also varied to assess its impact on the intensified removal of ammonium-N (NH₄-N) and chemical oxygen demand (COD).The enhanced performance of the aerated bed, when compared to the non-aerated one, in terms of COD, NH₄-N and total nitrogen (TN) removal efficiency were found to be 26.0 ± 14.7% (N = 68), 61.6 ± 11.7% (N = 60) and 18.2 ± 5.5% (N = 60), respectively. Aeration did impact significantly (p < 0.05) and positively on the aerated bed performance in terms of COD and NH₄-N removal efficiency. The rate constant of COD and NH₄-N degradation in the aerated bed were 3 times and 10 times higher than in control bed, indicating that aeration indeed enhanced the performance of HSSFCW. This study shows that without aeration, such a natural treatment system may not be capable of effectively treating medium to high strength wastewater. This aeration strategy had overcome its oxygen transfer limitation and will constitute a sustainable solution to treat different kind of wastewater with high organic and nitrogen concentration.