Effect of Recycling Ratio on the Combined Process of Nitritation-ANAMMOX for the Autotrophic Nitrogen Removal of Mature Landfill Leachate

A combined continuous-flow process of A/O_SHORTCUT-UASB_ANAMMOX was applied to treat mature leachate which contained high concentration of ammonia and low COD/nitrogen rate.The conversion rate of ammonia, nitrite accumulation ratio and the variation of FA and FNA concentrations in A/O reactor, the nitrogen removal activity of ANAMMOX and the variation of granules sizes at the same height (10 cm) were investigated at different recycling ratios (100%-600%). The results indicated that when the recycling ratio came to 300%, with the help of associated inhibition of FA and FNA to NOB, the conversion rate of ammonia and nitrite accumulation ratio in A/O reactor were kept above 93.5% and 95.6%, respectively. In addition, the ANAMMOX granules were well retained in the UASB reactor and kept a high level of total nitrogen removal rate. The nitrogen removal rate of UASB reactor kept above 1.04 kg/(m³·d). Also, the results of quantitative PCR(polymerase chain reaction) indicated that the proportions ofANAMMOXin UASB reactor were 3.78% which was the maximum value of the whole experiment.