Procedure for the use of sludge of anodizacao aluminum as a flocculant in industrial effluents and local purificacao

摘要

The sludge is dried with hot air under 75 degrees Celsius, for stabilisation, and is then ground down to a granulometry below 100 um. The resulting product is added to the effluent being treated in a dose between 25 and 75 g/l of a pulp with 10 percent dry sludge, gently agitating the mixture and allowing it to rest for a period longer than 30 minutes. Prior to the drying, the sludge can be modified by addition of sulphuric acid in a quantity less than stoichiometric with regard to its content of Al(OH)3, in which case, after the addition, the mixture is neutralised by adding the necessary quantity of caustic soda. Use of the modified sludge improves the turbidity of the solution and reduces the content of pollutants, especially the chemical oxygen deficit, by more than 90 percent. The technique is especially indicated in treatment of residual colloidal waters, especially from ink and paper factories.