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To investigate the role of granular activated carbon (GAC) on nitrogen removal performance of elemental sulfur-based constructed wetlands (S⁰-based CWs), three systems were constructed according to the different configurations in the functional layer, namely S-CW (S⁰ added in the functional layer), CSC-CW (GAC, S⁰ and GAC placed in layers in the functional layer) and SC-CW (S⁰ and GAC mixed evenly in the functional layer). In CSC-CW and SC-CW, the volumetric ratio of S⁰:GAC was 9:1. Three CWs were operated under four different hydraulic retention times (HRTs) ranged from 48 h to 6 h. Over the experiment, total inorganic nitrogen (TIN) removal rates of the three CWs were 3.1 – 23.6 g m⁻² d⁻¹, 3.5 – 24.1 g m⁻² d⁻¹ and 3.4 – 11.5 g m⁻² d⁻¹, respectively; CSC-CW remained high TIN removal efficiency (from 74.7 ± 20.2 % to 93.4 ± 1.9 %) while SC-CW had significant lower values when HRT = 6 h (29 …