Which method involves applying natural processes to detoxify contaminated groundwater?

Bioremediation is a method that utilizes natural processes involving microorganisms, such as bacteria, fungi, and plants, to detoxify and remove contaminants from groundwater. This technique harnesses the natural metabolic processes of these organisms, which can break down or transform hazardous substances into less harmful or non-toxic forms.

In contrast, other methods mentioned in the choices, such as pump and treat systems, involve mechanical processes that extract contaminated water, treat it, and then discharge or reinject it, without relying on the natural biodegradation capabilities of microorganisms. Reverse osmosis is a filtration process that separates contaminants from water but does not involve the use of living organisms to detoxify the groundwater. In-situ oxidation involves chemical reactions to convert contaminants into less harmful substances but again does not rely on the natural biological processes characteristic of bioremediation.

By facilitating the natural breakdown of pollutants, bioremediation offers a sustainable and often cost-effective solution to groundwater contamination, making it a preferred choice in many scenarios of groundwater remediation.