Elsevier

Desalination

Volume 247, Issues 1–3, October 2009, Pages 466-475
Desalination

Nitrogen removal in a combined vertical and horizontal subsurface-flow constructed wetland system

https://doi.org/10.1016/j.desal.2009.03.003Get rights and content

Abstract

This study was conducted to (1) determine appropriate conditions for nitrogen removal by a combined constructed wetland (CW) system and (2) evaluate the effects of hydraulic loading rate (HLR), nitrogen loading rate (NLR), effluent recirculation, plant uptake, and seasonal change on the removal efficiency of nitrogen. A three-stage experimental CW system consisting of a vertical flow-gravel filtration (v-GF) bed without plants, a horizontal-subsurface flow (h-SSF) bed planted with Iris australis, and a vertical-subsurface flow (v-SSF) bed planted with Phragmites australis in series were fed with primary-treated domestic wastewaters. The beds with plants produced effluents of better quality than the v-GF bed without plants. It was observed that the average removal efficiencies increased as the HLR (from 100 to 30 L/m2 d) decreased and the recycle ratios (to 100%) increased. The average removal efficiencies in the summer period were found higher of approximately 6% for the v-GF and h-SSF beds and 11% for v-SSF bed. Nitrogen removal by plant uptake was very low and only 3% (Iris) to 7%(Phragmites) of the N-input compared to other mechanisms such as nitrification and denitrification. The volume-base first-order nitrification and denitrification removal constants (1/d) were 0.388 and 0.785 for the h-SSF bed, and 0.412 and 0.293 for the v-SSF bed, respectively.

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    Hybrid flow CWs have been widely implemented by combining various types of CWs to overcome the drawbacks of horizontal flow and vertical flow CWs (Details have been provided in Section S2 of the supplementary material) (Martinez-Guerra et al., 2018; Wang et al., 2017; X. Zhang et al., 2017). Lin et al. (2002) and Tunçsiper (2009) achieved >90% TN removal efficiency using hybrid-CWs. Masi et al. (2002) employed single-stage (HF-CW) and hybrid systems (HF: FWS-CW) for winery wastewater treatment in Italy.

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