Changes of Cu, Zn, and Ni chemical speciation in sewage sludge co-compostedwith sodium sulfide and lime
WANG Xuejiang , CHEN Ling , XIA Siqing , ZHAO Jianfu
DOI:
Received April 13, 2007,Revised July 16, 2007, Accepted , Available online
Volume 20,2008,Pages 156-160
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A batch composting study was performed to evaluate the feasibility of co-composting sewage sludge with sodium sulfide and lime
(SSL) mixture (Na2S/CaO=1:1), aiming at reducing the availability of heavy metals in the sludge compost. Sewage sludge with sawdust
as a bulking agent was amended with SSL at 3% (w/w, dw), and composted for 15 d in laboratory batch reactors. The four stages of
the Tessier sequential extraction method was employed to investigate changes in heavy metal fractions of Cu, Zn, and Ni in sewage
sludge composted with SSL. For all the three metals, the mobile fractions, such as, exchangeable and carbonate bound were mainly
transformed into low availability fractions (organic matter and sulfide, Fe-Mn oxides bound and residual forms), and the addition of
SSL enhanced this transformation. Therefore, SSL is a suitable material to co-compost with sewage sludge to reduce the availability of
heavy metals. According to the cabbage seed germination test, a SSL amendment of 63% (w/w, dw) is recommended to co-compost
with sewage sludge.
