The effect of ammonia loading and operating temperature on nitrification and denitrification of a high ammonia landfill leachate

The effect of ammonia loading and operating temperature on the treatment of high ammonia, methanogenic, landfill leachate was investigated. Two single-sludge, nitrification–predenitrification systems were operated in parallel: one with a 10-day aerobic solids retention time, and the other with a 20-day aerobic solids retention time. The study consisted of two phases: an ammonia loading phase and a cold temperature phase. From the first phase, it was found that, at an influent leachate ammonia level of up to 1500 mg N/L, both systems produced an effluent of < 1 mg NH4-N/L and approximately 170 mg NOx−-N/L. Aerobic nitrite and anoxic "free" ammonia were both observed to increase as the ammonia loading was increased. When the influent ammonia was raised from 1500 to 2000 mg N/L, nitrification in both systems failed. During the second phase, the temperature was decreased from 20 to 10 °C while maintaining the leachate ammonia level at 1500 mg N/L. Aerobic nitrite accumulation and rising aerobic BOD5 were observed to begin at 14 °C. When the temperature was dropped from 12 to 10 °C, nitrification failed in both systems. In both cases, nitrification was re-established at 10 °C, by ceasing to waste solids and by stopping methanol addition. Key words: ammonia, biological, denitrification, landfill, leachate, nitrification, temperature, treatment.