Municipal wastewater treatment with anodizing solid waste

In this study we have investigated the feasibility of the use of aluminium anodizing waste as coagulant for the treatment of municipal wastewaters instead of conventional inorganic materials. We have selected three different anodizing aluminium facilities for this study. The fresh mud was collected in the industrial facilities and prepared for tests. The anodizing muds were tested in two different forms: as powder and as mud suspension. For the powder form the fresh muds were submitted to a stabilisation process, homogenised and grinded. For the mud suspension form, water was added to the fresh mud in a way that the content of solids was known. A series of coagulation/flocculation tests were made, being controlled important parameters as pH, coagulant dose, and impeller type, stirring conditions (time and speed) and settling time for the different sludges. The effective coagulant capacity of the anodizing sludges was verified based on the final turbidity and on the pollutant removal (COD) of the supernatant samples as a function of the coagulant dose and pH.