Optimization of Denitrification Process

by Richard P. Michael, Research Asst.; Dept. of Civ. Engrg., Univ. of Vermont, Burlington, Vt.; also with Dufresne and Henry Consulting Engrs., North Springfield, Vt.,
William J. Jewell, (M.ASCE), Assoc. Prof.; Cornell Univ., Ithaca, N.Y.,

Serial Information: Journal of the Environmental Engineering Division, 1975, Vol. 101, Issue 4, Pg. 643-657

Document Type: Journal Paper


A denitrification system composed of a completely stirred tank reactor (CSTR) followed in series with a plug flow reactor (PFR) was tested in order to minimize the disadvantages of each process when used separately. High efficiency of NO3-N removal and good process control can be achieved with the series treatment system using 25% of the volume required with a single CSTR reactor. Most influent NO3-N concentrations were greater than 1000 mg/l, and these usually result in effluent concentrations less than 50 mg/l. The effluent NO3-N concentration was reduced to less than 0.5 mg/l with a total hydraulic detention time of 1.7 hr when the influent NO3-N concentration was 80 mg/l. Design conditions which would minimize treatment volume requirements would include microbial mass loadings (g NO3-N g VSS/ day in the CSTR and PFR of 2.0 day-¹, and 0.2 day-¹, respectively, resulting in a 40% removal efficiency in the CSTR reactor and greater than 95% NO3-N removal efficiency in the total system. The microbial yield averaged 0.11 g VSS synthesized per g of COD removed.

Subject Headings: Denitrification | Influents | Effluents | Microbes | Flow separation | Hydraulics | Load factors | Oxygen demand

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