A systematic process optimization method for advanced environmental process

Abstract

A systematic approach is proposed to find optimal operational conditions for nitrogen and phosphorus (N, P) removal in a biological nutrient removal processes, which is the dual optimization strategy through modeling, variable selection, design of experiments, and optimization using multiple response surface methodology. It is focused on determining the interactive effects between independent variables for N and P removal, which are selected through a new sensitivity analysis for considering the effluent quality index. After selecting key operational variables, multi-response surface model based on a new desirability function is used for the dual optimization of N and P removal. Because the proposed method is a multi-response model which is the suitable methods to optimize the operational conditions in a process, it can simultaneously optimize the biological process in the aspect of N and P removal efficiency. The proposed method is applied to a standard A2O process. The model-based optimization results in 78.0% and 80.0% removal efficiencies of N and P removal with the optimal process conditions, where are internal recycle flowrate of 3,850 g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , dissolved oxygen (DO) concentration of 1.0 mg/l, and wasted sludge rate of 27.5 g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , respectively. The dual optimization suggests to maximize simultaneous nitrification and denitrification (SND) in A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O system. This study confirms that the proposed dual optimization method is useful to systematically optimize the N and P removal in any biological nutrient removal process.