Removal of selected pollutants from landfill leachate in the vegetation-activated sludge process

Abstract

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-NH₄⁺, regardless of the substrate and the HRT that varied from 3 to 14 days, remained at around 99 %. Longer HRT favoured higher total nitrogen (TN) reduction in all examined variants, with the highest achieved at 14 days, and average TN removal ranging from 38 to 54 %. Also, the chemical oxygen demand removal efficacy increased along with HRT, while phosphorus removal efficacy remained low in all examined systems throughout the experiment. The proposed technological system fits into new trends in environmental engineering, combining technical, pro-environmental solutions and enabling potential reductions in material and energy costs.