Leaching tests conducted on raw sludge waster from a glasscomponents manufacturing factory using the US EPA TCLP procedureshowed that Pb, Hg, As and Ba leached at pH<3.5 whilst Cd and Cr didnot. To control the leaching, asphalt, a mixture of asphalt andpowdered activated carbon (PAC) and Portland cement were used asfixing agents to stabilize the sludge. Leaching tests on thestabilized sludge using leachants of pH 2.5-7.0 showed that thelowest leachate metal concentration were obtained from the sludgewhich had been stabilized using a mixture of asphalt and PAC.Portland cement at a cement-to-sludge ratio of 0.5 also reduced theleaching of metals from the solidified sludge with metalsconcentrations in the leachate lower than the US EPA regulatorylimits.
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