Landfill leachate treatment with a novel process: Anaerobic ammonium oxidation (Anammox) combined with soil infiltration system

A novel combined process was proposed to treat municipal landfill leachate with high concentrations of ammonium and organics. This process consisted of a partial nitritation reactor (PNR), an anaerobic ammonium oxidation (Anammox) reactor (AR) and two underground soil infiltration systems (USIS-1 and USIS-2). Based on the optimum operating conditions obtained from batch tests of individual unit, the combined process was continuously operated on a bench scale for 166 days. Partial nitritation was performed in a fixed bio-film reactor (PNR, working volume= 12 L). Ammonium nitrogen-loading rate (Nv) and DO were combined to monitor partial nitritation, and at T = 30 +/- 1 degrees C, Nv = 0.27-1.2 kg/(m(3).d), DO = 0.8-2.3 mg/L, the ratios of nitrite nitrogen (NO2--N) to ammonium nitrogen (NH4+-N) were successfully kept close to 1.0-1.3 in the effluent. Nitrate nitrogen (NO3--N) less than 43 mg/L was observed. The effluent of PNR was ideally suited as influent of AR. Sixty-nine percent CODcr from the raw leachate was degraded in the PNR. Anammox was carried out in a fixed bio-film reactor (AR, working volume= 36 L). At T = 30 +/- 1 degrees C. Nv = 0.06-0.11 kg/(m(3).d), about 60% NH4+-N and 64% NO2--N in the influent of AR were simultaneously removed. Inhibition of high-strength NO2--N (up to 1011 mg/L) should be responsible for the low removal rate of nitrogen. About 35% aquatic humic substance (AHS) was degraded in the AR. With the same working volume (200 L), USIS-1 and USIS-2 were alternately performed to treat the effluent from AR at one cycle of about 30 days. At hydraulic loading rate (HLR) = 0.02-0.04 m(3)/m(3).d, pollutant loading rates (PLR) = NH4+-N <= 14 g/m(3).d, TN <= 25 g/m(3).d, and CODcr <= 13 g/m(3).d, average removal efficiencies of 88% NH4+-N, 67% TN and 55% CODcr were obtained. Overall, raw leachate with 1430-2720 mg NH4+-N/L, 1524-2912 mg TN/L and 1165-2599 mg CODcr/L, was treated by the process and the effluent with 22-58 mg NH4+-N/L, 108-300 mg TN/L and 32-250 mg CODcr/L was obtained with average removal efficiencies of 97% NH4+-N, 87% TN and 89% CODcr. The test results indicated that the combined system could work stably over a long period under the operating conditions, and that the process was feasible for the leachate treatment. AR should be the key to the performance of the combined process. (c) 2007 Elsevier B.V. All rights reserved.