A passive sink-zeolite permeable reactive barrier to control NH₄⁺-N pollution plume within groundwater: Conceptual...

Ammonium nitrogen (NH₄⁺-N) is a typical inorganic pollutant in the groundwater at landfill sites, and high-concentration NH₄⁺-N is toxic to humans and organisms. Zeolite can effectively remove NH₄⁺-N in water by adsorption, and it is suitable to be used as a type of reactive materials for permeable reactive barriers (PRBs). A passive sink-zeolite PRB (PS-zPRB) with higher capture efficiency than a continuous permeable reactive barrier (C-PRB) was proposed. And a passive sink configuration was integrated with PRB in the PS-zPRB, this configuration enabled the high hydraulic gradient of groundwater at the treated sites to be fully utilized. In order to explore treatment efficiency for groundwater NH₄⁺-N using the PS-zPRB, numerical modeling on decontamination of NH₄⁺-N plumes at a landfill site was performed. The results indicated that the NH₄⁺-N concentrations of PRB effluent gradually decreased from 21.0 mg/L to 0.5 mg/L within 5 y, and met the drinking water standards after treatment for 900 d. The decontamination efficiency index of PS-zPRB was consistently higher than 95% within 5 y, and the service life of PS-zPRB appeared over 5 y. The capture width of PS-zPRB effectively exceeded the PRB length by around 47%. Compared with C-PRB, the capture efficiency of PS-zPRB was increased by around 28%, and the reactive material of PS-zPRB was saved by approximately 23% in volume.