Abstract: The invention relates to a method for chemically treating a liquid medium loaded with nitrates, primarily comprising a step in which zinc is brought into contact with said liquid medium whose pH is preferably less than 4. When this contacting step leads to the presence of residual zinc in the liquid medium, the liquid medium is circulated through at least one electrolytic cell. The invention also relates to a device for treating a liquid medium loaded with nitrates, to applications of this method, and to a device for reducing the proportion of nitrates in ground water.