Abstract: A plant for processing untreated water, particularly drilling water, to at least partially remove mircopollutants thereform. The plant includes at least one main feed pipe for feeding water into the bottom of a reactor via a submerged inlet at end of said main pipe for delivering ozone into the water, a means communicating with said main pipe for delivering hydrogen peroxide into the water, at least one liquid gas transfer system including at least one static mixer downstream from said ozone delivery means and said hydrogen peroxide delivery means, and upstream from said reactor; and a means for evenly distributing the flow of water out of said feed pipe and through the inlet and allowing a drop in the kinetic energy of the water as it enters said reactor.