Evaluation of ASM1 parameters using large-scale WWTP monitoring data from a subtropical climate in Entebbe

Abstract
Evaluation and optimization of activated sludge model No.1 (ASM1) parameters that are crucial for the efficient operation of wastewater treatment plants (WWTPs). By maximizing large-scale WWTP monitoring data from a subtropical climate in Entebbe, enables us to gain valuable insights into the performance of the treatment system and ability toidentify opportunities for improvement. The ASM1 model is a widely used mathematical model that describes the biokinetics of organic matter and nitrogen removal in activated sludge systems. It consists of several parameters that need to be calibrated based on site-specific conditions to accurately simulate the behavior of the WWTP. These parameters include the maximum specific growth rate of microorganisms, the decay rate of biomass, the half-saturation constants for substrate utilization, and the stoichiometry of the biodegradation reactions.By using monitoring data from a large-scale WWTP in Entebbe, researchers can evaluate the performance of the ASM1 model and identify potential discrepancies between the model predictions and the actual plant operation.
This study aimed at providing a set of optimal kinetic and stoichiometric parameters of ASM1 representative of wastewater from a subtropical climate region of Entebbe. ASM1 was applied on the STOAT program, and the model parameters were evaluated and optimized with sensitivity analysis and Response Surface Methodology (RSM) to reach minimum prediction errors of effluent TSS, COD, and NH3. Six major parameters were used. YH, YA, μA, KNH, bA, and kOA. Predictions of RSM regression models were strongly correlated to the STOAT predictions. YH mainly affected TSS and COD, and the other parameters affected NH3. ASM1 calibration with estimated optimal values of sensitive parameters resulted in approximately null prediction errors for modeling state variables. NH3 presented almost the same results as ASM1 validationespecially around areas of katabi ; meanwhile, TSS and COD presented high errors related to the increase in YH due to the RSM optimization. The optimal parameters, mainly YA, μA, KNH, bA, and kOA, constitute references for other studies on ASM1 modeling using wastewater data from a subtropical climate . 
YH optimal value is analysed as well as the effect of sludge wastage methods and the simulation periods.

Keywords mathematical modeling, response surface methodology, sensitivity analysis, systematic model calibration kinetic parameters

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