Changes of Cu, Zn, and Ni chemical speciation in sewage sludge co-composted with sodium sulfide and lime.
A batch composting study was performed to evaluate the feasibility of co-composting sewage sludge with sodium sulfide and lime (SSL) mixture (Na2S/CaO = l: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 < or = 3% (w/w, dw) is recommended to co-compost with sewage sludge.
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. wangxj@mail.tongji.edu.cn
Xuejiang
X
Wang
Ling
L
Chen
Siqing
S
Xia
Jianfu
J
Zhao
D001937:Brassica / Q000187:drug effects / Q000254:growth & development; D017610:Calcium Compounds; D003300:Copper / Q000032:analysis* / Q000633:toxicity; D018525:Germination / Q000187:drug effects; D009532:Nickel / Q000032:analysis* / Q000633:toxicity; D010087:Oxides; D012722:Sewage; D013440:Sulfides; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000633:toxicity; D015032:Zinc / Q000032:analysis* / Q000633:toxicity
D017610:Calcium Compounds; D010087:Oxides; D012722:Sewage; D013440:Sulfides; D014874:Water Pollutants, Chemical; D003300:Copper; D009532:Nickel; C016538:lime; D015032:Zinc; C033479:sodium sulfide