ALUMINUM RECOVERY FROM WATER TREATMENT SLUDGES

This study investigates the recovery of aluminum from water treatment sludges, specifically focusing on aluminum sulfate and polyaluminum chloride used as coagulants in treatment plants. With approximately 66,000 tons of sludge disposed of annually in Portugal, government restrictions and rising disposal costs underscore the urgency for alternative treatments that can facilitate aluminum recovery and reuse. The research method involved characterizing centrifuged chemical sludge from a treatment facility, assessing its composition in terms of aluminum, iron, manganese, and other impurities. The study compared both acidic and alkaline leaching processes for aluminum recovery, identifying concentrated sulfuric acid as an effective leaching medium. Experiments varied operating conditions such as the ratio of dry sludge to sulfuric acid, pH levels, and stirring and settling times. Results indicated optimal aluminum recovery at a pH of 13, with the maximum aluminum solubilization under specific conditions (sludge dosage, stirring, and settling times). The efficiency of metal dissolution was also noted, with iron and manganese exhibiting varying solubilization rates across different pH levels. This research contributes to the understanding of sludge management in water treatment, highlighting recovery methods applicable for environmental sustainability.