Abstract
The present study aims at determining most likely values for the maximum growth rate (µA, max) and the endogenous decay rate (bA) of nitrifiers for activated sludge processes treating municipal wastewater operated at low temperature (10°).The work used nitrification rate data measured on 10 full-scale plants and 2 pilot plants fed with domestic sewage. This set of data was combined with a modelling and a theoretical approach. The unified values (µA, max = 0.45·d-1 and bA = 0.13·d-1) were obtained at 10°C for the kinetic parameters of the autotrophic biomass in the SRT range 10 to 50 d. In addition, the factors affecting the expected nitrification rate (rv, nit) were established by a theoretical approach and confirmed by experimental results. For a given SRT, a linear relationship with the nitrogen volumetric loading rate was shown. The COD/TKN ratio of the influent on the nitrification rate was demonstrated. Finally, an operational tool for the verification of the nitrification rate in the design procedure of activated sludge processes is proposed.
Highlights
IntroductionFor given influent characteristics and with chosen parameter values for the heterotrophic and the nitrifying biomass, the ASM1 model calculates the nitrification rates of the mixed liquor, and the nitrogen concentrations in the effluent
Activated sludge functioning with intermittent aeration is the main process used to remove nitrogen from municipal wastewaters in France
The present study aims at determining most likely values for the maximum growth rate and the endogenous decay rate of nitrifiers for activated sludge processes treating municipal wastewater operated at low temperature (10°C)
Summary
For given influent characteristics and with chosen parameter values for the heterotrophic and the nitrifying biomass, the ASM1 model calculates the nitrification rates of the mixed liquor, and the nitrogen concentrations in the effluent. This tool still requires bioprocess experience and time to be used correctly for design purposes. The use of validated parameter values for the conditions of the simulations is necessary (e.g. similar sludge retention time (SRT) and/or loading rate) These values are important when the processes are simulated at limiting conditions
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