Application of Simulation-Optimization modeling to suggest optimal hybrid in-situ flushing for nitrate attenuation

Uncertainties in efficiently managing contaminated groundwater still pertains. Several in-situ remediation technologies can be applied to treat nitrate contamination; however, those cannot be applied at aquifer which has high hydraulic conductivity. In this study, we apply Simulation-Optimization modeling (S-O modeling) to suggest optimal in-situ flushing integrated to pump-and-treat design that can reduce and manage nitrate contamination of groundwater. MODFLOW-2005 and MT3D-USGS are used to simulate groundwater flow and nitrate transport. Genetic Algorithm(GA) is used to suggest proper well location and pumping rate for reducing nitrate contamination. Our optimization modeling based on the field tests conducted on a multi-layered aquifer. There is an uncontaminated lower aquifer and an upper aquifer contaminated with nitrate. At the first stage, we generated hydraulic gradient for collecting pre-existed contamination with installing pumping well at the lower aquifer and injection well at the upper aquifer contaminated with nitrate. In the second stage, 1 moving well of variable location and pumping rate was used for pump-and treat well. Cost function satisfies minimizing the total expenses of drilling, pumping, injection, water treatment, and penalty for violating nitrate concentration. The early stage result of S-O modeling shows nitrate moves along the groundwater flow and is captured at the moving well that is located in the center of nitrate plume.

 

Keyword: Simulation-Optimization modeling (S-O modeling) ∙ Remediation ∙ On-site flushing ∙ Groundwater modeling

Acknowledgement: This work was supported by Korea Environment Industry & Technology Institute(KEITI) through "Activation of remediation technologies by application of multiple tracing techniques for remediation of groundwater in fractured rocks" funded by Korea Ministry of Environment (MOE) (Grant number:20210024800002/1485017890), Korea Environment Industry & Technology Institute(KEITI) through the Demand Responsive Water Supply Service Program (RE20191097) funded by the Korea Ministry of Environment (MOE) and Korea Ministry of Environment as "The SEM projects; RE2020002470001/1485017133".