Optimal groundwater remediation design considering effects of natural attenuation processes: pumping strategy with enhanced-natural-attenuation

A simulation-optimization model is proposed to investigate the effect of natural attenuation processes on pump-and-treat and to enhance the application efficiency of the remediation method. Numerical experiments under varying retardation and attenuation conditions demonstrate that the efficacy and the feasibility of pump-and treat are considerably sensitive to the retardation factor and the attenuation rates. The severe retarded condition and attenuation are, the more remediation costs are required and even success of the remediation can not be guaranteed. For these conditions, long pumping strategy or enhancement of biodegradability can be cost-effective and safe. These results indicate that optimal remediations with or without considering natural attenuation processes result in quite different pumping schedules and well locations, and this should be noticed in real practices of groundwater remediation design. The enhanced-natural-attenuation (ENA) optimization process developed to overcome some limitations of the pump-and-treat method determines the locations injecting oxygen to attenuate residual contaminants remained in the aquifer after applying the pump-and-treat. The performances of the ENA model with the cost and the contaminant removal are evaluated for three scenarios. Among these scenarios, second scenario designed for each 0.5 years was most suitable to efficiently remove a low concentration of contaminants remained in the aquifer. This optimization model will be helpful to improve the efficiency in contaminated sites applying the pump-and-treat system.