Enhanced Enrichment Characteristics and Inhibition Kinetics Characteristics of the Anammox Granular Sludge

Abstract

The anammox granular sludge was enriched by shortening the hydraulic retention time (HRT) (from 27 h to 6.67 h) in the UASB reactor, which was fed with ammonium chloride and nitrite as the substrates, and the effect of different HRTs on the nitrogen removal performance of anammox granule sludge was studied. After 159 d of operation, the total nitrogen loading rate (NLRTN) reached 1.72 Kg/(m3·d), the total nitrogen removal rate (NRRTN) reached 1.33 Kg/(m3·d), and the removal efficiencies of NH+4-N (NRENH+ 4-N) and NO-2-N (NRENO-2-N) were over 95%. The ratio of DNO-2-N/DNH+4-N was 1.31 and DNO-3-N/DNH+ 4-N was 0.24, which complied with the chemical reaction stoichiometry of anammox. The colour of anammox granular sludge changed from light red to deep red; the percentage of granular sludge larger than 1.5 mm was the highest, which proportionately accounted for 62.32%; and the surface of the granular sludge was found, via Fourier transform infrared spectroscopy (FTIR), to contain abundant functional groups. The inhibitory effect of substrates (NH+4-N and NO-2-N) on anammox was studied via an inhibition kinetics batch test using anammox granular sludge (Day 159) in the UASB reactor, and the test results were fitted in the Haldane inhibition model with correlation coefficients (R2) of 0.9912 and 0.9949.

Keywords

• anammox granular sludge, hydraulic retention time, nitrogen removal performance, inhibition kinetics