title: Risk mitigation by waste-based permeable reactive barriers for groundwater pollution control at e-waste recycling sites.
abstract: Permeable reactive barriers (PRBs) have proved to be a promising passive treatment to control groundwater contamination and associated human health risks. This study explored the potential use of low-cost adsorbents as PRBs media and assessed their longevity and risk mitigation against leaching of acidic rainfall through an e-waste recycling site, of which Cu, Zn, and Pb were the major contaminants. Batch adsorption experiments suggested a higher adsorption capacity of inorganic industrial by-products [acid mine drainage sludge (AMDS) and coal fly ash (CFA)] and carbonaceous recycled products [food waste compost (FWC) and wood-derived biochar] compared to natural inorganic minerals (limestone and apatite). Continuous leaching tests of sand columns with 10 wt% low-cost adsorbents were then conducted to mimic the field situation of acidic rainfall infiltration through e-waste-contaminated soils (collected from Qingyuan, China) by using synthetic precipitation leaching procedure (SPLP) solution. In general, Zn leached out first, followed by Cu, and finally delayed breakthrough of Pb. In the worst-case scenario (e.g., at initial concentrations equal to 50-fold of average SPLP result), the columns with limestone, apatite, AMDS, or biochar were effective for a relatively short period of about 20-40 pore volumes of leaching, after which Cu breakthrough caused non-cancer risk concern and later-stage Pb leaching considerably increased both non-cancer and lifetime cancer risk associated with portable use of contaminated water. In contrast, the columns with CFA or FWC successfully mitigated overall risks to an acceptable level for a prolonged period of 100-200 pore volumes. Therefore, with proper selection of low-cost adsorbents (or their mixture), waste-based PRBs is a technically feasible and economically viable solution to mitigate human health risk due to contaminated groundwater at e-waste recycling sites.
authors.affiliation: Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Jingzi
authors.initials: J
authors.lastname: Beiyuan
authors.affiliation: Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China. dan.tsang@polyu.edu.hk.
authors.forename: Daniel C W
authors.identifier: http://orcid.org/0000-0002-6850-733X
authors.initials: DC
authors.lastname: Tsang
authors.affiliation: Department of Chemical and Process Engineering, University of Canterbury, Christchurch, 8140, New Zealand.
authors.forename: Alex C K
authors.initials: AC
authors.lastname: Yip
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, 510275, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Korea Biochar Research Center, Kangwon National University, Chuncheon, Korea.
authors.forename: Yong Sik
authors.initials: YS
authors.lastname: Ok
authors.affiliation: Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Li
mesh_terms: D000327:Adsorption; D060587:Groundwater / Q000737:chemistry*; D059027:Recycling; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical
keywords: Charcoal; Compost; Groundwater remediation; Health risks; Metal contamination