title: Transformation of heavy metal speciation during sludge drying: mechanistic insights.
abstract: Speciation can fundamentally affect on the stability and toxicity of heavy metals in sludge from wastewater treatment plants. This research investigated the speciation of heavy metals in sludge from both municipal and industrial sources, and metal speciation change as a result of drying process to reduce sludge volume. The changes in sludge properties including sludge moisture content, temperature, density, and electrical conductivity were also monitored to provide insights into the mechanisms causing the change in heavy metal speciation. The results show that the drying process generally stabilized Cr, Cu, Cd, and Pb in sludge by transforming acid-soluble, reducible, and oxidizable species into structurally stable forms. Such transformation and stabilization occurred regardless of the sludge source and type, and were primarily caused by the changes in sludge properties associated with decomposition of organic matter and sulfide. The results enhanced our understanding of the geochemical behavior of heavy metals in municipal sludge, and are useful for designing a treatment system for environment-friendly disposal of sludge.
authors.affiliation: Institute of Environment & Biogeochemistry, Zhejiang University, Hangzhou 310027, PR China. Electronic address: gswenghx@zju.edu.cn.
authors.forename: Huan-Xin
authors.initials: HX
authors.lastname: Weng
authors.affiliation: Research Institute for Environmental Science, Shanxi University, Taiyuan, 030006, PR China.
authors.forename: Xue-Wen
authors.initials: XW
authors.lastname: Ma
authors.affiliation: Institute of Environment & Biogeochemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Feng-Xia
authors.initials: FX
authors.lastname: Fu
authors.affiliation: Institute of Environment & Biogeochemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Jin-Jun
authors.initials: JJ
authors.lastname: Zhang
authors.affiliation: Institute of Environment & Biogeochemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Zan
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Institute of Environment & Biogeochemistry, Zhejiang University, Hangzhou 310027, PR China.
authors.forename: Li-Xun
authors.initials: LX
authors.lastname: Tian
authors.affiliation: Geochemistry, Fundamental, and Computational Science Directorate, Pacific Northwest National Laboratory, USA. Electronic address: chongxuan.liu@pnnl.gov.
authors.forename: Chongxuan
authors.initials: C
authors.lastname: Liu
mesh_terms: D003890:Desiccation; D004553:Electric Conductivity; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000032:analysis / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D019216:Metals, Heavy; D012722:Sewage; D014874:Water Pollutants, Chemical; D014867:Water
keywords: Heavy metal; Sewage sludge drying; Stabilization; Transformation