Summary task of a Journal (Progressive Acidification : An Aspect of Chemical Leaching of Sewage Sludge)

The wastewaters treatment produces sewage sludge (SS) which varydifferent constituents with varying compositions in the sludge depend on wastewaters source. The method of treatment and disposal method of the sludge determined by the amount of sewage produced and the population size density. Because beside the nutrients, organic matter, and pathogens, the sewage sludge contains contaminants which must be treated to avoid prospective health risks when disposed off.

Heavy metal system (HMs) are bound in the sewage sludge, so that its removal by physical means difficult. The chemical form of the metals is a function of the method used to extract or reduce HMs from SS. Chemical extraction involves the use of both organic and inorganic acids to extract HMs from SS. Acid solubilization of HMs is a process of proton exchange from the acid to the sludge. After solubilization, the removal of the solubilized metals is achieved by chemical precipitation followed by a physical separation step. The HMs present in the sludge dissolves and exists in solution when acid is added to sludge. The optimum conditions for HMs removal from sludge can be achieved through variation of contact time between the acid and the sludge solution.

In this study, the researcher use some acids (organic and inorganic acids) to extract HMs (Cd, Mn, Pb, Ni, and Cu) in SS, such as HNO3, CH3COOH, H2SO4, C6H5COOH, and HCl. The sewage sample used in this study was obtained from the male hostel septic tank of the Federal University of Technology, Owerri, Nigeria. The septic tank has a capacity of about 800 m3/day of sludge. Data are given as arithmetic mean and standard deviation. The t-test was used to estimate significant difference in mean concentration using HCl as study digestion medium.

The researcher shows that the inorganic acid is more effective than organic acid on extracting of HMs in SS. It shown by the data results of analysis 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.

Source :

Ukiwe, L.N., Oze, R.N., & Nwoko, C.I.A. 2012. Progressive acidification : an aspect of chemical leaching of sewage sludge. International Journal of Chemistry.4(1): 62-68