The invention relates to a process for treating effluents of high organic charge. According to the invention, the process consists in that the effluent is preliminarily treated by mechanical means in order to remove the suspended matter, after which it is passed in a basin for secondary treatment, in the presence of an oxidation-coagulation agent prepared from red mud as ferrate-type suspension containing Fe(VI) in a suspension:effluent volume ratio of 1:50…1:150 and 0.3…0.7% coagulation adjuvant of red mud-type fixed on ceramic foam, with aeration, at a flow rate of 80…120 l/h, for 10 min, and 20…40 l/h, for 15 min, after which it is left to settle, resulting in treated water having the values of chemical and biochemical oxygen consumption 8…10 times lower than the untreated water and a sediment amount representing 0.35…0.75% of the initial mass.