The invention relates to a process for the treatment of industrial effluents using marine algae to produce potable water which process comprises the steps of: (i) contacting diluted effluents with marine red algae selected from Porphyra and Liagora, containing polysaccharides and having sulfate/acetyl functional group on the cell wall and galactopyranose on their cell membrane, for a period of at least 30 minutes preferably under stirring; (ii) treating the effluents from step (i) with calcareous material for a period of at least 30 minutes, preferably under stirring; (iii) separating the coagulated material so formed from the supernatant by conventional methods; and (iv) treating the supernatant with conventional ion-exchange resins such as cationic ion-exchange resins, anionic-ion exchange resins and activated charcoal to produce potable water.