Cold ambient temperatures can negatively affect the performance of passive and semi-passive landfill leachate treatment systems and decrease treatment efficiency. Cold temperature leachate treatment efficiencies were compared between a commercially available semi-passive treatment system and a passive peat and wood shaving biological trickling filter. The addition of an active fixed-film pretreatment stage in the treatment train was also assessed. Results indicated that the internal temperature of the peat filters was independent of influent water temperature; exothermic reactions maintained internal system temperatures. It was determined that pretreatment of the leachate did not affect the overall removal of chemical oxygen demand (COD), but did increase nitrification in the subsequent passive treatment systems and allowed for the removal of dissolved inorganic constituents prior to the passive treatment system, which will extend the useful life of the entire treatment train. The hybrid-passive treatment systems reduced COD concentrations by 10 ± 3% and 15 ± 3%, in the semi-passive treatment system and the peat and wood shaving biological trickling filter-based systems, respectively, and indicated that nitrifying biomass was starting to populate the treatment systems. It was therefore concluded that operation of these systems would be feasible under cold climate and should be assessed at the pilot-scale.
Keywords: cold climate, landfill leachate, passive treatment, pretreatment, sub-surface flow