Аннотация:Since landfill leachates frequently have a high COD (> 10 g/l) and nitrogen (> 1 g total N/l) content, an application of conventional aerobic treatment is accompanied by high energy expenses. This paper presents a substantially more energy efficient alternative based on sequenced anaerobic-aerobic treatment of landfill leachates. As a first step, the UASB reactor for the elimination of the major part of biodegradable COD and heavy metals (HM) was applied. In a subsequent step, the biofilter operating in alternative aerobic-anoxic regime was used for the removal of remaining BOD and nitrogen. Both steps were investigated at submesophilic (202 oC) and psychrophilic (102) regimes. The laboratory testing of this concept with the real leachates from Khmet’yevo landfill (Moscow region, total COD – 10.7-20.8 g/l, N-NH4 - 562-822 mg/l) showed that both (submesophilic and psychrophilic) anaerobic regimes were quite efficient for COD (50-70%) and HM (>90%) removals. However, the subsequent submesophilic aerobic-anoxic treatment of submesophilic anaerobic effluents led to only 75% of total N removal due to COD deficiency for denitrification created by too efficient anaerobic step. On the contrary, psychrophilic anaerobic effluents (richer in COD compared to the submesophilic ones) were more suitable for subsequent aerobic-anoxic treatment giving the total N removal of 95 and 92% at 20 and 10 oC, respectively. The resting BOD was negligible in both cases. Finally, iron coagulation was applied for inert COD and phosphate precipitation. The calculations based on the results obtained showed that an application of sequenced anaerobic-aerobic treatment of landfill leachate led to energy economy of 1.25 kWh per each kg of COD removed on anaerobic stage due to elimination of energy expenses for aeration. Moreover, each kg of COD removed in this way generates 0.5 m3 of biogas (70% CH4, or 11.5 kJ, or 0.5 kWh under standard efficiency of biogas conversion into electricity). Additional energy savings are expected from performing treatment at low temperature (without heating of leachates) and from substantially reduced volume of activated sludge generated.