Iterative Approach to Many-Objective Engineering Design: Balancing Conflicting Objectives for Engineered Injection and Extraction
Amy N. Piscopo, Joseph R. Kasprzyk, R. M. Neupauer, D. C. Mays · World Environmental and Water Resources Congress 2014 · 2014
Engineering design problems are often characterized by multiple, conflicting objectives. Multiobjective evolutionary algorithms (MOEAs) can optimize these complex problems using embedded simulation models to calculate objective function values without simplifying assumptions, which are often required by traditional search algorithms. This study contributes a demonstration of how the performance of the MOEA can be improved through iterative reformulations of the problem objectives and constraints. We illustrate this iterative design approach using a case study of engineered injection and extraction (EIE), a strategy developed to enhance contaminant degradation during in situ groundwater remediation. During EIE, clean water is injected or extracted at wells surrounding a contaminated groundwater plume following the one-time injection of a treatment chemical. This sequence of injections and extractions reconfigures the plume and increases its contact with the treatment chemical, which ultimately increases the rate of contaminant degradation. The MOEA is used to optimize the EIE design, which consists of the sequence of pumping rates and well locations that dictate the plume reconfiguration. The optimization problem is a challenging one, characterized by uncertainty from randomness associated with hydrodynamic dispersion of the plume. The objectives and constraints of the remediation are refined iteratively during the optimization process, after considering tradeoffs between objectives for design solutions generated by the MOEA. Tradeoff data not only informs the design of solutions, it provides valuable information about the structure and conflicts of the design problem, which represents crucial support for stakeholders in their decision-making analyses for in situ groundwater remediation project planning with EIE.