Microbial cultivation using mathematical representations accounting for the reaction kinetics in two-stage nitritation/ANAMMOX process

Abstract

Mathematical representations accounting for the reaction kinetics were used to improve the cultivation rate of ANAMMOX microorganisms in the pilot-scale partial nitritation (PN)/anaerobic ammonium oxidation (ANAMMOX) reactor. In line with the fluctuations in the properties of raw reject water, control strategies of the hydraulic retention time (HRT) and the mixed liquid suspended solid (MLSS) concentration calculated by the mass balance-based model were proposed to improve PN performance. As a result, control of the MLSS concentration to cope with the fluctuation of C/N ratio resulted in a higher nitrite production rate (NPR) that was suitable for enhancing the cultivation rate of the ANAMMOX microorganisms. Based on the performance in the optimized PN, the observed yield of ANAMMOX microorganisms was calculated to be 0.091 gVSS/gNH4+−N. The biomass as volatile suspended solids (VSS) wasted was 309.8–554.3 gVSS/d. Based on the reaction kinetics of ANAMMOX, the quantity of stored microorganisms over time was simulated using a modified first-order exponential decay model; the calculated value was 6.3–11.2 kg/m3/year. These results can be used for the scale-up or design of the ANAMMOX process.