Impact of influent data frequency and model structure on the quality of WWTP model calibration and uncertainty

Abstract

Application of activated sludge models (ASMs) to full-scale wastewater treatment plants (WWTPs) is still hampered by the problem of model calibration of these over-parameterised models. This either requires expert knowledge or global methods that explore a large parameter space. However, a better balance in structure between the submodels (ASM, hydraulic, aeration, etc.) and improved quality of influent data result in much smaller calibration efforts. In this contribution, a methodology is proposed that links data frequency and model structure to calibration quality and output uncertainty. It is composed of defining the model structure, the input data, an automated calibration, confidence interval computation and uncertainty propagation to the model output. Apart from the last step, the methodology is applied to an existing WWTP using three models differing only in the aeration submodel. A sensitivity analysis was performed on all models, allowing the ranking of the most important parameters to select in the subsequent calibration step. The aeration submodel proved very important to get good NH(4) predictions. Finally, the impact of data frequency was explored. Lowering the frequency resulted in larger deviations of parameter estimates from their default values and larger confidence intervals. Autocorrelation due to high frequency calibration data has an opposite effect on the confidence intervals. The proposed methodology opens doors to facilitate and improve calibration efforts and to design measurement campaigns.

Activated sludge rheology: A critical review on data collection and modelling

“…It has proved itself a valuable tool for system analysis (knowledge build-up) or system optimization in various domains such as wastewater treatment (Gujer, 2008) and has also been used for modelling of rheograms as discussed earlier. Furthermore, modelling can form the basis for a sensitivity analysis (Saltelli et al, 2000), scenario analysis or uncertainty analysis (Belia et al, 2009;Benedetti et al, 2012;Cierkens et al, 2012) for the more experienced modeller. Despite the enormous variety of processes that can be modelled, and the diversity of models available, the modelling process is comprised of an almost universal algorithm (Fig.…”

Practical Application of Dynamic Process Models for Wastewater Treatment Plant Optimization: Work in Progress

“…This version included a storm tank model, a primary sedimentation tank model (a point settler model), a more detailed implementation of the controllers and a model of the cascade, which provides reaeration, in between the activated sludge tanks and the secondary clarifiers. In version EHV-7 a new model for the aeration, based on the work of Rosso et al (2005), was implemented (Cierkens et al, 2012). In the EHV-8 version of the model more attention was given to the wet weather behaviour.…”

Translating safety factors to sources of variability and uncertainty; Model-based design evaluation for the Eindhoven WWTP

“…The details of the WEST (www.mikebydhi.com) model can be found in Benedetti et al, (2010c), Nopens et al, (2010) and Cierkens et al (2012a).…”