[Effect of HRT on Nitrogen Removal Using ANAMMOX and Heterotrophic Denitrification]

Real domestic sewage was first treated in SBR and partial nitrification was achieved. When average concentrations of NH₄⁺-N, NO₂^--N, and COD were 37.27, 39.97, and 120 mg·L^-1, respectively, the effluent was delivered as influent of an anaerobic ammonia oxidation reactor (ASBR). The effect of different HRTs (36 h, 33 h, 30 h, 27 h) on nitrogen removal of ANAMMOX and heterotrophic denitrification were investigated under conditions of temperature of 24℃ and pH of 7.2±0.2. Results showed that 1 nitrogen removal efficiency was optimum with HRT of 33 h. The average total nitrogen load rate(TNLR)and total nitrogen removal rate(TNRR)were 0.056 kg·(m³·d)^-1and 0.050 kg·(m³·d)^-1, respectively. The average effluent concentrations of NH₄⁺-N, NO₂^--N, and COD were 1.36, 0.47, and 49.79 mg·L^-1, and removal rates were 96.30%, 98.83%, and 56.17%, respectively. △NO₂^--N/△NH₄⁺-N and △NO₃^--N/△NH₄⁺-N were 1.17 and 0.15, 0.15 and 0.11 less than theoretical ANAMMOX values (1.32, 0.26) due to heterotrophic denitrification. 2 The contribution of ANAMMOX to nitrogen removal decreased; however, the contribution of heterotrophic denitrification to nitrogen removal gradually increased with decreasing HRT. This provides a point of reference for ANAMMOX in engineering applications.