Water Quality Research Journal of Canada Vol 47 No 1 pp 14–29 © IWA Publishing 2012 doi:10.2166/wqrjc.2012.038

Uncertainty analysis of WWTP control strategies made feasible

Lorenzo Benedetti, Damien J. Batstone, Bernard De Baets, Ingmar Nopens and Peter A. Vanrolleghem

The control of wastewater treatment plants can help to achieve good effluent quality, in a complex, highly non-linear environment. A key but time-demanding component of such modelling studies is uncertainty analysis (UA). The general aims of this paper are (a) to evaluate methods for reduction of the time necessary to conduct an UA, and (b) to evaluate the sensitivity of parameters and model subsystems. Two UA studies on the Benchmark Simulation Model no. 2 (BSM2) are used to illustrate how the above mentioned aims can be achieved: (1) robustness of performance evaluations against changing operation and design conditions; and (2) uncertainty of performance evaluations for a given plant layout and operation. The main conclusions are: (1) solver settings have a large impact on simulation speed and require proper attention; (2) to reach convergence in Monte Carlo simulations with Latin Hypercube Sampling, the number of simulations should be at least 50 times the number of sampled parameters, which is more than what is reported in similar studies; and (3) the number of uncertain parameters that needs to be considered to make a proper uncertainty assessment of a model can be reduced significantly by omitting parameters that have little influence.

Keywords: activated sludge; anaerobic digestion; BSM2; global sensitivity analysis; mathematical modelling; numerical methods

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