In a process for treating effluent water, a stream of effluent water is fed to a porous ceramic media filled reactor. Organic and inorganic impurities are absorbed and/or oxidized from the effluent water into the media and/or off-gases. The remainder of the effluent water stream is dispensed from the reactor in an outlet stream suitable for direct discharge to the sea or for recycling without incurring the disadvantages of generating a solid sludge. The reactor includes a chamber containing activated media, such as pellets of porous ceramic material. The pellets are stored in a vertical stacks of sub chambers defined by horizontal perforated trays and/or in a horizontal chains of sub chambers defined by vertical perforated baffles.