Leachate treatment in newly built peat filters: A pilot-scale study

The purpose of this short-term pilot-scale (1 m³) experiment was to focus on the efficiency of leachate treatment during the initial period of a newly built peat filter. The initial start-up period of a filter is dynamic and differs for different types of peat and leachate. Reduction of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and nutrient concentrations from leachate of different age and composition was targeted in experimental filters of three types of peat. Well-mineralised fen peat with undisturbed structure showed a significantly better reduction when treating methanogenic leachate with respect to the concentrations of COD, total nitrogen (N _tot), and ammonium-nitrogen (NH4-N), which were reduced by up to 36, 62, and 99%, respectively, compared to the poorly mineralised milled Sphagnum peat (with no reduction of COD, 52% reduction of N_tot, and 67% of NH4-N). Good results in the reduction of BOD and total phosphorus (P _tot) (50%) in well-mineralised Sphagnum peat were achieved when treating acidogenic leachate. Generally, even if a considerable amount of pollutants was removed in newly built peat filters (milligrams per metre per day) during the first days in operation, the target values were still above the Estonian limit for wastewater discharge into the environment. The best results were achieved for removal of P_tot, which was reduced below the target values.