Multicriteria Optimization of a Chemical Leaching Process for Sewage Sludge Decontamination

Sewage sludge decontamination requires the removal of toxic metals and it can be performed by chemical leaching. The commercialization of such a decontamination process needs to consider the preservation of the sludge fertilizing properties and the ease of dewatering of the acidic treated sludge. Moreover, operating costs must be acceptable under optimal operational parameters. Chemical leaching assays were performed at the laboratory bench scale with biological sludge. Afterwards, a multicriteria analysis has been conducted to determine the optimal operational parameters allowing the sludge decontamination while meeting all performance criteria. The analysis pointed out adequate working ranges in terms of sulfuric acid, ferric chloride, and hydrogen peroxide concentrations to be used for chemical decontamination of the sludge. Moreover, it allowed establishing a mathematical equation to help identify the optimal working range for further studies having different contamination scenarios.