Groundwater remediation methods can be executed either in-situ or ex-situ. For in-situ treatment, water purification occurs on-site, employing biological or chemical techniques, and is generally the more cost-effective option for groundwater remediation. 

Ex-situ treatment is often more expensive and time-intensive, involving the extraction and transportation of contaminated groundwater to a treatment facility. However, it offers the immediate benefit of reducing further groundwater pollution. In cases where on-site remediation methods are inadequate due to the complexity of the contamination, ex-situ treatment becomes a necessary and effective solution.