THE CHEMICAL FORMS' CHANGE OF HEAVY METALS IN THE SEWAGE SLUDGE DURING ACID-ASSOCIATED S/S PROCESS

摘要

Dewatered sewage sludge (DSS) was stabilized and solidified (S/S) by different portions of Portland cement, fly-ash and calcium chloride. Concentrated acid solutions were used to pre-treat the sludge before S/S process. From the sequential extraction results, we could find that the pre-treatment of acid in S/S could help convert more Cr, Cu, Zn, Pb and Ni into residual phase. This was also supported by TCLP tests, in which we could observe samples treated by acid had lower concentrations of metals in the leachate than the blank sample. Compressive strength results of DSS+H_2SO_4+B samples using 80% cement + 19% fly-ash + 1% CaCl_2 as the binder could reach 1,746 kPa, 2,456 kPa and 2,733 kPa for 7 days, 14 days and 28 days of curing, respectively, compared to 1,212 kPa, 1,455 kPa and 1,821 kPa of the blank samples. SEM photos helped us to learn the differences in the microstructure between samples.