Enhanced vacuum UV-based process (VUV/H2O2/PMS) for the effective removal of ammonia from water: Engineering configuration and mechanistic considerations

Abstract

In this work, the VUV, VUV/H₂O₂, VUV/PMS, and VUV/H₂O₂/PMS processes were compared with the corresponding UVC-based AOPs under identical experimental conditions for the ammonia removal. Among the examined AOPs, the VUV/H₂O₂/PMS demonstrated the highest performance in converting NH₄⁺ to N₂. A 82.7 % removal of 100 mg/L NH₄⁺, with N₂ selectivity over 99 % was obtained in the VUV/H₂O₂/PMS process within 60 min, operated under near neutral pH. Under these operation conditions, [NO₃^-] was around 0.5 mg-N/L with [NO₂^-] remaining below detection. The VUV-mediated generation of SO₄^•-and HO^• with NH₄⁺ had a relative contribution of 37.9 and 62.1 %, respectively. The VUV/H₂O₂/PMS process operated under a flow-through mode achieved efficient removal of 100 mg/L NH₄⁺ (80.5 %) in a hydraulic retention time (HRT) of 40 min. The continuous-flow VUV/H₂O₂/PMS process efficiently treated a real ammonia-laden groundwater and the concentration of NH₄⁺ decreased from 30 mg/L to around 1 mg/L within 60 min HRT. In summary, the VUV/H₂O₂/PMS process was effective from the technical and energetical point of view, hence is a viable and promising technique for treating effluent containing high concentrations of ammonia.

Keywords: Advanced Oxidation Processes (AOPs); Ammonia nitrogen; Hydroxyl radical; Sulfate radical; VUV.