Low energy treatment of landfill leachate using simultaneous partial nitrification and partial denitrification with anaerobic ammonia oxidation

An up-flow anaerobic sludge blanket reactor (UASB), anoxic/oxic (A/O)-anaerobic ammonia oxidation reactor (ANAOR or anammox reactor), and anaerobic sequencing batch reactor (ASBR) were employed in the treatment of landfill leachate with partial nitrification-anammox and half-denitrification-anammox. The Chemical Oxygen Demand (COD) concentration, ammonium nitrogen (NH4+-N) concentration, and total nitrogen (TN) concentration of the basal leachate was 2200-2500 mg/L, 1200-1300 mg/L, and 1300-1400 mg/L, respectively. After a 1:2 dilution using domestic sewage, the COD, NH4+-N, and TN concentrations in the influent were 800-1000 mg/L, 400-430 mg/L, and 420-440 mg/L, respectively. After treatment, the final COD, NH4+-N, and TN were decreased to 90-100 mg/L, 13-14 mg/L, and 35-38 mg/L, respectively. In the ASBR, organic carbon sources in sewage-diluted landfill leachate were introduced for the conversion of nitrate nitrogen (NO3--N) into nitrite nitrogen (NO2--N). This enabled the continued reaction of NO2--N with NH4+-N from the newly introduced sewage-diluted landfill leachate via anammox. As a result, complete TN removal was achieved in the system. Microbial diversity analysis indicated that the relative abundance of ammonia-oxidizing bacteria (AOB) was four to five times greater than nitrite-oxidizing bacteria (NOB) in the A/O reactor, showing that partial nitrification was prevalent. The relative abundance of the anammox bacterium Candidatus Kuenenia gradually increased in each reactor, reaching a maximum of 1.17%-1.39%. Using this set-up, we achieved advanced, efficient, and economical, COD reduction and nitrogen removal. Taken together, the findings provide important insights into the optimal operation of landfill leachate treatments.