The problem of leachate generated at municipal landfills, and the challenges of its logistics and disposal, are forcing the search for new, environmentally friendly methods of treatment, especially when it can be applied in situ. The method that combines constructed wetland system with conventional activated sludge process, hereinafter referred to as Vegetation-Activated Sludge Process (V-ASP), may be an interesting alternative, but still require research and comprehensive evaluation. Therefore, this study aimed to verify the effectiveness of V-ASP in the treatment of landfill leachate, the impact of two different fillings (biochar and zeolite) and hydraulic retention time (HRT) on the final removal of selected pollutants and the stability of the treatment process. The experiment was conducted for 138 days on a laboratory-scale V-ASP system layout as sequential batch reactors operating in a 24-hour cycle. The removal efficacy of N-NH