A　novel　fully　passive　permeable　reactive　barrier　(PRB)　with　oxygen-releasing　compound　(ORC)　and　clinoptilolite　was　proposed　for　the　removal　of　ammonium-nitrogen　from　groundwater.　The　PRB　involves　a　combination　of　oxygen　release,　biological　nitrification,　ion　exchange,　and　bioregeneration.　A　pilot-scale　performance　comparison　experiment　was　carried　out　employing　three　parallel　columns　to　assess　the　proposed　PRB.　The　results　showed　that　the　PRB　achieved　nearly　complete　NH4+　-　N　depletion　(＞99%).　NH4+　-　N　of　5.23-10.88　mg/L　was　removed,　and　NO2-　-　N　of　＜1.93　mg/L　and　NO3-　-　N　of　2.03　-19.67　mg/L　were　generated.　Ion　exchange　and　biological　nitrification　both　contributed　to　NH4+　-　N　removal,　and　the　latter　played　a　dominant　role　under　the　condition　of　sufficient　oxygen.　Biological　nitrification　favored　a　delay　in　sorption　saturation　and　a　release　of　exchange　sites.　The　ORC　could　sufficiently,　efficiently　supply　oxygen　for　approximately　120　pore　volumes.　The　clinoptilolite　ensured　a　robust　NH4+　-　N　removal　in　case　of　temporary　insufficient　biological　activities.　No　external　alkalinity　sources　had　to　be　supplied　and　no　inhibition　of　aerobic　metabolism　occurred.　The　ceramicite　had　a　negligible　effect　on　the　biomass　growth.　Based　on　the　research　findings,　a　full-scale　continuous　wall　PRB　was　installed　in　Shenyang,　China　in　2012.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.