Nitrification of Landfill Leachate Ammonia Nitrogen in a Two-stage Moving Bed Biofilm Reactor

The aim of this work was to ascertain how the loading of the two-stage moving bed biofilm reactor (MBBR) with ammonia nitrogen influences the rate, efficiency and products of the nitrification process. It was found that at a 1.1 gNH(4)(+)/m(2)d load the efficiency of ammonia nitrogen oxidation at the 1st stage totaled 93%. To achieve complete nitrification (with ammonia nitrogen concentration in the effluent lower than 1 gNH(4)(+)/m(3)), it was necessary to make use of a two-stage MBBR. The increase of the MBBR load to 2.0 gNH(4)(+)/m(2)d caused the effluent concentration of ammonia nitrogen to rise to the level of 33.4 gNH(4)(+)/m(3), which is equivalent to approx. 86% efficiency of nitrification. With the MBBR load of 2.8 gNH(4)(+)/m(2)d and 3.8 gNH(4)(+)/m(2)d, the efficiency of ammonia nitrogen oxidation was similar (about 70%), but the final products of the process were different. At 2.8 gNH(4)(+)/m(2)d, the value of the [NO(2)(-)]//[NO(2)(-)]+[NO(3)(-)]) ratio was 0.16, and increased to 0.99 at the load of 3.8 gNH(4)+/m(2)d. This finding indicates that with the MBBR load of 3.8 gNH(4)(+)/m(2)d, phase II of nitrification was inhibited, and that the predominant product of ammonia nitrogen oxidation was nitrites. It was furthermore found that the rate of nitrification in the single-stage MBBR (1st treatment system) increased with the increase in the MBBR load (from 1.0 gNH(4)(+)/m(2)d to 2.4 gNH(4)(+)/m(2)d); in the two-stage MBBR (2nd treatment system) nitrification rate was substantially lower.