Sustainable technologies in the chemical industry need to incorporate cleaning processes of effluents and recycling media. Substituted aromatics present in high concentration in industrial waste waters, originating mainly from pharmaceutical and dye industries are usually refractory and/or toxic for a biologically active sludge. A catalytic wet oxidation of water seems to be an economic alternative to an incineration process. The key factors of the possible wet oxidation are discussed and a case study of two different industrial problems (water with sulphonaphthol or acrylic acid) is presented. The efficiency of a wet oxidation system depends on reaction conditions and it is possible to improve it by initiation with hydrogen peroxide. The treatment capacity, strong corrosive conditions and a utilization of reaction heat are necessary to account for design purposes.