title: Synergistic effect of rice husk addition on hydrothermal treatment of sewage sludge: fate and environmental risk of heavy metals.
abstract: Hydrothermal treatment (HTT) at 200°C was applied to immobilize heavy metals (HMs) and the effect of rice husk (RH) addition was investigated based on total HMs concentration, fractionation and leaching tests. The results indicated that a synergistic effect of RH addition and HTT could be achieved on reducing the risk of HMs from medium and low risk to no risk. Metals were redistributed and transformed from weakly bounded state to stable state during the HTT process under RH addition. Notably at a RH/sludge ratio of 1/1.75 (d.w.), all the HMs showed no eco-toxicity and no leaching toxicity, with the concentrations of leachable Cr, Ni, Cu and Cd decreased by 17%, 89%, 95% and 93%, respectively. This synergistic effect of RH addition and HTT on the risk reduction of HMs implies that HTT process with RH addition could be a promising and safe disposal technology for sewage sludge treatment in practice.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan; School of Water Resources and Environment, China University of Geosciences, Beijing 100083, China.
authors.forename: Wansheng
authors.initials: W
authors.lastname: Shi
authors.forename: Chunguang
authors.initials: C
authors.lastname: Liu
authors.forename: Youju
authors.initials: Y
authors.lastname: Shu
authors.forename: Chuanping
authors.initials: C
authors.lastname: Feng
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Lei
authors.forename: Zhenya
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D006851:Hydrochloric Acid / Q000737:chemistry; D019216:Metals, Heavy / Q000302:isolation & purification*; D012275:Oryza / Q000737:chemistry*; D012306:Risk; D018570:Risk Assessment; D012722:Sewage / Q000737:chemistry*; D012995:Solubility; D013696:Temperature; D014866:Waste Products / Q000032:analysis; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D014876:Water Pollution / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
chemical_list: D019216:Metals, Heavy; D012722:Sewage; D014866:Waste Products; D014874:Water Pollutants, Chemical; D014867:Water; D006851:Hydrochloric Acid
keywords: Environmental risk; Heavy metals; Hydrothermal treatment; Rice husk; Sewage sludge