Progressive Acidification: An Aspect of Chemical Leaching of Sewage Sludge

Abstract

<p>The effect of progressive acidification using inorganic and organic acids in chemical leaching of sewage sludge was studied. Results of analyses using Atomic Absorption Spectrophotometer (AAS) showed that Mn was the most metal solubilized totaling 4.760 and 4.220 mg/l using 30 % (v/v) HNO3 and 50 % (v/v) acetic acids respectively for digestion, while Cd (0.038 and 0.027 mg/l) was the least metal extracted using 10 % (v/v) H2SO4 and 50 % (v/v) benzoic acid respectively for digestion. HCl was generally observed to be the best extraction medium for the metals; Cd, Mn, Pb, Ni, and Cu at all acid range 10-90 % (v/v) concentrations. However, comparing the leaching capability of both acids type, the inorganic acids were observed to be more effective than organic acids in leaching heavy metals from sewage sludge.</p

Investigation of Combined Fenton/Bioleaching and Bio-Acidification/Fenton-Like Processes in the Removal of Sludge-Borne Metals

“…However, physical and chemical processes involved in wastewater treatment cause heavy metals that are present in raw sewage to accumulate in sludge, which limits utilization of sludge as a fertilizer (1). Up to now, several techniques have been investigated for removal and recovery of heavy metals from wastewater sludge, including chemical precipitation, electrochemical methods using organic and inorganic acids, and bioleaching (2,3). Each of these methods have advantages as well as disadvan-tages, such as using large amounts of reagents and chemicals, toxic sludge production, high costs, long process, and problems related to disposal of their remainders.…”