Dynamic Optimal Control of In-Situ Bioremediation of Ground Water

Abstract

A coupled optimal control and simulation model is presented that selects injection and extraction well sites and pumping rates for cost-effective in-situ bioremediation design. Application of the model to a hypothetical site identified a number of findings that may be useful for improving in-situ bioremediation design: (1) As with pump-and-treat design, time-varying pumping strategies for in-situ bioremediation are significantly less expensive than time-invariant pumping strategies, despite the typically shorter duration of in-situ bioremediation; (2) when expensive oxygen sources are used for oxygen injection, downgradient extraction pumping is used in lieu of extensive injection pumping to pull the oxygen across the contaminant plume; (3) when biodegradation rates are limited by mass transfer, expensive oxygen sources may not be worth the added expense; (4) longer cleanups significantly reduce pumping costs by exploiting natural transport and degradation processes; (5) prespecified potential well locations have a significant effect on model results; and (6) optimal pumping strategies with high levels of contaminant adsorption alternated between higher and lower levels of pumping.