A UNIQUE RESEARCH PROGRAM in Québec Stability of metal-rich solids from laboratory multi-step treatment system for ferriferous acid mine drainage M. Jouini 1 , T.V Rakotonimaro 1 , M. Benzaazoua 1 , T. Genty 1 , C.M. Neculita 1 1 Research Institute on Mines and Environment (RIME), University of Quebec in Abitibi-Temiscamingue (UQAT), CANADA NAXOS2018, June 15, Naxos, Greece
Outline o Introduction Context and issues Objectives o Methodology o Results and discussion o Conclusion and recommendations 2 The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusion Background o Multi-step passive treatment system combination of several passive treatment units (chemical/ biological/ aerobic/ anaerobic/ anoxic; USEPA, 2014) presently preferred to treat acid mine drainage (AMD) impacted-waters in closed and/or abandoned mine sites (Skousen et al., 2017) Examples: (PBR 1 ) (DAS 2 ) Passive biochemical reactor + Dispersed alkaline substrate (Rakotonimaro et al., 2018) (Canada, Quebec) DAS+ cascade aeration (Caraballo et al., 2011) (Spain) Aeration rock channel + PBR + re-aeration limestone (Clyde et al., 2016) (US, California) Aerobic reed beds + anaerobic cell + rock filters (Whitehead et al., 2005) (UK) 1 PBR : reactive mixtures of organic matter, neutralizing materials and structuring agents 3 2 DAS : mixtures of coarse-grained materials and neutralizing materials, The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusion Background o Typical physicochemical and mineralogical characteristics of residues (metal-rich solid precipitates) from passive AMD-treatment systems Physicochemical CaCO 3 -DAS rich in Fe and in Al, MgO-DAS rich in Zn (Macías et al., 2012), Wood Ash- DAS rich in Fe (Rakotonimaro et al., 2018) PBR rich in Fe (Neculita et al., 2008; Genty et al., 2018) and in As (Fernandez-Rojo et al., 2017) Mineralogical Crystallized and amorphous phase of (oxy)hyroxides rich in Fe, Al, Zn etc. Sulfates (gypsum) Carbonates Sulfides (biological treatment) 4 The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusion Background o Stability of metal-rich residues in AMD passive treatment systems Fe-rich residues from PBRs must be stored under water at a near neutral pH (Genty et al, 2012) As-rich residues from PBRs were not categorized as a hazardous wastes according to TCLP* test (Jong and Parry, 2005) Metal-rich residues (As, Cr and Se) from PBRs are relatively stable and could be classified as a non-hazardous material according to TCLP test (Simonton et al., 2000) Metal-rich residues (Fe, Al and Zn) from DAS systems should not be disposed in landfill and have to be stored in a dry environment according to TCLP test, EN 12457-2 test ** and SEP*** (Macías et al., 2012) *Toxicity Characteristic Leaching Procedure **European Leaching test used to discern the type of landfill disposal that better hosts wastes 5 ***Sequential Extraction Procedure The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions Background Issues Issues o Limited available knowledge on the storage / disposal of residues and of the fate of contaminants in this contaminated waste Inconsistent stability (chemical compositions and physical properties depending on the quality of the water to be treated) necessity of a case by case management approach 6 The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions 1 Solids sampling 2 Physicochemical and mineralogical characterization 3 Leaching tests Paste pH o Physicochemical characterization Chemical composition (digestion) o Scanning Electron Microscopy (SEM-EDS) o Mineralogical characterization X-ray Diffraction (XRD) o Single-batch leaching test: TCLP 1 o Leaching tests Parallel batch leaching test: pH-static leaching test 2 o 7 1 TCLP (USEPA, 1992; CEAEQ, 2012) 2 CEN/TS 14429, 2005; Method 1313 (USEPA, 2012) The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions Sampling of solids (laboratory) o Multi-step passive treatment system (Rakotonimaro et al., 2018) 2 units of Fe pre-treatment (50% wood ash and 50% wood chips- WA50-1 and WA50-2) 2- treatment (10% sand, 70% organic materials, 20% calcite) 1 unit of SO 4 1 polishing unit (50% calcite and 50% wood chips - C50) Treatment of Fe pre-treatment Polishing SO 4 2- Treatment of Fe pre-treatment Polishing 2- SO 4 8 The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions Physicochemical characterization Measured/ analyzed Interpretations parameters Neutral to weakly basic in all units (6.8-8.5); the highest in o Paste pH polishing unit- C50 (8.1-8.5) ; the lowest in the pretreatment unit-WA50 (6.8-7.8) Higher metal concentrations in WA50 (due to high contaminant o load in AMD) High Fe concentration found in WA50 (42000 ± 900 mg/kg) o Al found in all solids ; the highest value in WA50 ; 26000 ± 2500 o mg/kg for WA50, 5476 ± 408 mg/kg for PBR and 966 ± 300 mg/kg Chemical composition for C50 Total S varied from 7600 to17000 mg/kg; the highest in WA50 o (11000 ± 500 mg/kg) As, Cr, Cu, Mn, and Zn concentrations: below the detection o limit (<5 mg/kg) in PBR and C50 9 The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions Physicochemical Mineralogical characterization characterization o SEM-EDS and XRD Results Phases WA50 PBR C50 Oxyhydroxides • Phases consisting • Phases consisting • Hematite, mainly of Fe, O and Ca mainly of Fe and O, with ferrhydrite • Hematite, jarosite S, Mg and Ca • Schwertmannite, hematite Sulfides and sulfates • Anydrite, basanite, • Anhydrite, gypsum, • Native sulfur, Troilite native sulfur anhydrite Carbonates • Calcite, siderite • Calcite • Calcite Silicates • Quartz, sanidine, albite, • Quartz, oligoclase • Quartz orthoclase 10 The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions Physicochemical Mineralogical Leaching tests characterization characterization TCLP o Low Al and Fe concentrations in all solids Zn concentrations in WA50 exceed all TCLP regulatory limits UTS UTS Higher Ni concentrations TCLP UTS D019 in WA50 according to D019; CCC D019, MMER and CCC MMER UTS D019; D019 limits MMER CCC MMER Low Cr concentrations in CCC CCC CCC WA50 Low Cu concentrations in all solids As, Cd and Pb concentrations below detection limit D019: Québec’s provincial regulation MMER: Canadian discharge limits as specified in the metal mining effluent regulation 11 UTS: The worldwide or universal treatment standard CCC: The criterion of continuous concentration The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions Physicochemical Mineralogical Leaching tests characterization characterization o pH-static leaching test (pH=2 –13) Maximal Zn dissolution WA50 C50 highest ANC and presented the high natural pH highest values WA50: lowest ANC Between pH 6-12, Zn concentrations below D019 and MMER limits 2- , High release of SO 4 Al from WA50 and PBR especially in PBR strongly leached at pH<5 Low Al concentration was <1.1 mg/L concentrations over the entire pH range for C50 2- of SO 4 (<100 mg/L) at pH>7. D019: Québec’s provincial regulation 12 MMER: Canadian discharge limits as specified in the metal mining effluent regulation The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
Introduction Methodology Results Conclusions Physicochemical Mineralogical Leaching tests characterization characterization o pH-static leaching test (continuation) Weakly As leaching from Fe concentration <0.2 mg/L PBR and C50 relative to from all solids at pH 6.5–8 WA50 and respect the regulation limits As concentration above Higher Fe concentration at the limits of D019 (0.2 pH<4 and pH>9; the mg/L) at pH <3 and highest in WA50 and PBR pH>11 in WA50 High Cu concentration at High Ni concentration at pH<6 and pH>12 in WA50 acidic and strongly basic pH and PBR for WA50 and PBR Low Ni concentration Low concentration of Cu from C50 (below D019 in C50 and respect D019 and MMER) and MMER limits D019: Québec’s provincial regulation 13 MMER: Canadian discharge limits as specified in the metal mining effluent regulation The 6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018
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