STABILIZATION OF HEAVY METALS IN SEWAGE SLUDGE USING SOREL CEMENT

Excessive heavy metals contents in sewage sludge maybe hinder the recycling of the sludge and should be mitigated effectively using engineered processes such stabilization as reported. In this work, Sorel cement is used as additive to stablize heavy metals present in sewage sludge. It was found that the contents of Zn, Cu, As, Cr, and Pb in sewage sludge were stabilized as high as 96%, 87%, 84%, 99% and 92%, respectively in the leachability test. The sequential extraction procedure tests showed that the increase of immobile fractions of heavy metals in mixtures, e.g. organic or residual forms, inhibited the transferability of heavy metals to the solution. In addition, the SEM photos of the stabilized microstructures proved that hydration of Sorel cement was changed with various ratios. Therefore, the increase of pH towards highly alkaline value and the formation of ternary hydration in the mixtures appear to have developed to stable heavy metals in sewage sludge.