Uncertainty analysis in the measurement of nitrification kinetics in urban wastewater treatment plants

The kinetics of nitrification play a decisive role in the calculation of aerobic sludge age as a limiting factor in wastewater treatment plant design. In this study, the sensitivity of the growth rate calculation states to the initial active biomass concentration and underlying modelling assumptions was examined for four different wastewater treatment plants. An uncertainty analysis of these parameters was conducted and parameter estimations were made specifically for each plant. Maximum specific growth rates were determined via modelling using MS Excel and parameter estimations were conducted using the least squares method. The approximate confidence intervals were visualized as contour plots based on critical values calculated at a 95% confidence level for each plant. The errors in the maximum growth rate estimation of nitrifiers were calculated to be on the order of 5-9%. The importance of the factors that may arise from the initial conditions of the experiment was emphasized and suitable experimental conditions were examined.