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Title:Nonlinear programming model of a wastewater treatment system: Sensitivity analysis and a robustness constraint
Author(s):Uber, James Gregory; Brill Jr., E. Downey; Pfeffer, John T.
Contributor(s):University of Illinois at Urbana-Champaign
Subject(s):Water resource development--Illinois
Water resources development
Sensitivity analysis
Wastewater treatment
Mathematical models
Waste water
Geographic Coverage:Illinois (state)
Abstract:A method for sensitivity analysis in nonlinear programming is described and then illustrated using a least-cost model of a secondary wastewater treatment system. A sensitivity equation approach is used to calculate normalized sensitivity coefficients, which approximate the percent changes in model variables and objective function due to a small parameter variation. Design changes predicted by the sensitivity coefficients are confirmed by a perturbation analysis of the optimal solution. Sensitivity concepts are used to develop a robustness measure which is incorporated into the constraint set of the nonlinear model. Robustness is narrowly defined as the ability of a model solution to maintain a level of performance that meets the system design criteria even if the actual values of model parameters are not exactly the same as the values assumed for design. A gradient optimization procedure is used to examine the tradeoff between total cost and the robustness measure. A preliminary analysis shows that the trends in robust wastewater treatment plant design are in direct conflict with the optimal decisions obtained when minimizing cost without a constraint on robustness but are in agreement with those designs observed to work in practice. The robustness constraint method presented should be applicable to other optimization models of water resources systems.
Issue Date:1985-06
Publisher:University of Illinois at Urbana-Champaign. Water Resources Center
Genre:Report (Grant or Annual)
Sponsor:U.S. Department of the Interior
U.S. Geological Survey
Rights Information:Copyright 1985 held by James G. Uber, E. Downey Brill, Jr., John T. Pfeffer
Date Available in IDEALS:2016-06-13

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