Investigation into the technical feasibility of biological treatment of precious metal refining wastewater
- Authors: Moore, Bronwyn Ann
- Date: 2013
- Subjects: Sewage -- Purification -- Biological treatment -- South Africa Sewage -- Purification -- Activated sludge process -- South Africa Water reuse -- South Africa Flotation -- South Africa Platinum mines and mining -- Waste disposal -- South Africa Platinum mines and mining -- Economic aspects -- South Africa Mine water -- Environmental aspects -- South Africa Platinum mines and mining -- Waste minimization -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3888 , http://hdl.handle.net/10962/d1002013
- Description: The hydrometallurgical refining of platinum group metals results in large volumes of liquid waste that requires suitable treatment before any disposal can be contemplated. The wastewater streams are characterized by extremes of pH, high inorganic ion content (such as chloride), significant residual metal loads and small amounts of entrained organic compounds. Historically these effluents were housed in evaporation reservoirs, however lack of space and growing water demands have led Anglo Platinum to consider treatment of these effluents. The aim of this study was to investigate whether biological wastewater treatment could produce water suitable for onsite reuse. Bench-scale activated sludge and anaerobic digestion for co-treatment of an acidic refinery waste stream with domestic wastewater were used to give preliminary data. Activated sludge showed better water treatment at lab scale in terms of removal efficiencies of ammonia (approximately 25%, cf. 20% in anaerobic digestion) and COD (70% cf. 43% in digestion) and greater robustness when biomass health was compared. Activated sludge was consequently selected for a pilot plant trial. The pilot plant was operated on-site and performed comparably with the bench-scale system, however challenges in the clarifier design led to losses of biomass and poor effluent quality (suspended solids washout). The pilot plant was unable to alter the pH of the feed, but a two week maturation period resulted in the pH increasing from 5.3 to 7.0. Tests on algal treatment as an alternative or follow-on unit operation to activated sludge showed it not to be a viable process. The activated sludge effluent was assessed for onsite reuse in flotation and it was found that there was no significant difference between its flotation performance and that of the process water currently used, indicating the effluent generated by the biological treatment system can be used successfully for flotation. Flotation is the method whereby minerals refining operations recover minerals of interest from ore through the addition of chemicals and aeration of the ore slurry. Target minerals adhere to the bubbles and can be removed from the process.
- Full Text:
- Date Issued: 2013
- Authors: Moore, Bronwyn Ann
- Date: 2013
- Subjects: Sewage -- Purification -- Biological treatment -- South Africa Sewage -- Purification -- Activated sludge process -- South Africa Water reuse -- South Africa Flotation -- South Africa Platinum mines and mining -- Waste disposal -- South Africa Platinum mines and mining -- Economic aspects -- South Africa Mine water -- Environmental aspects -- South Africa Platinum mines and mining -- Waste minimization -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3888 , http://hdl.handle.net/10962/d1002013
- Description: The hydrometallurgical refining of platinum group metals results in large volumes of liquid waste that requires suitable treatment before any disposal can be contemplated. The wastewater streams are characterized by extremes of pH, high inorganic ion content (such as chloride), significant residual metal loads and small amounts of entrained organic compounds. Historically these effluents were housed in evaporation reservoirs, however lack of space and growing water demands have led Anglo Platinum to consider treatment of these effluents. The aim of this study was to investigate whether biological wastewater treatment could produce water suitable for onsite reuse. Bench-scale activated sludge and anaerobic digestion for co-treatment of an acidic refinery waste stream with domestic wastewater were used to give preliminary data. Activated sludge showed better water treatment at lab scale in terms of removal efficiencies of ammonia (approximately 25%, cf. 20% in anaerobic digestion) and COD (70% cf. 43% in digestion) and greater robustness when biomass health was compared. Activated sludge was consequently selected for a pilot plant trial. The pilot plant was operated on-site and performed comparably with the bench-scale system, however challenges in the clarifier design led to losses of biomass and poor effluent quality (suspended solids washout). The pilot plant was unable to alter the pH of the feed, but a two week maturation period resulted in the pH increasing from 5.3 to 7.0. Tests on algal treatment as an alternative or follow-on unit operation to activated sludge showed it not to be a viable process. The activated sludge effluent was assessed for onsite reuse in flotation and it was found that there was no significant difference between its flotation performance and that of the process water currently used, indicating the effluent generated by the biological treatment system can be used successfully for flotation. Flotation is the method whereby minerals refining operations recover minerals of interest from ore through the addition of chemicals and aeration of the ore slurry. Target minerals adhere to the bubbles and can be removed from the process.
- Full Text:
- Date Issued: 2013
Biosorption of precious metals from synthetic and refinery wastewaters by immobilized saccharomyces cerevisiae
- Authors: Mack, Cherie-Lynn
- Date: 2008
- Subjects: Metals -- Refining Metals -- Absorption and adsorption Saccharomyces cerevisiae Factory and trade waste Water reuse Platinum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4071 , http://hdl.handle.net/10962/d1006977
- Description: The process of precious metal refining can be up to 99.99% efficient at best, and although it may seem small, the amount of valuable metal lost to waste streams is appreciable enough to warrant recovery. The method currently used to remove entrained metal ions from refinery wastewaters, chemical precipitation, is not an effective means for selective recovery of precious metals from a wastewater. Biosorption, the ability of certain types of biomass to bind and concentrate metals from even very dilute aqueous solutions, may be an effective point-source metal recovery strategy. The yeast, Saccharomyces cerevisiae, has been found capable of sorbing numerous precious and base metals, and is a cheap and abundant source of biomass. As such, it represents a possible precious metal sorbent for application to refining wastewaters. In this investigation, S. cerevisiae biomass was immobilized, using polyethyleneimine and glutaraldehyde, to produce a suitable sorbent, which was found to be capable of high platinum uptake (150 to 170 mg/g) at low pH (< 2). The sorption mechanism was elucidated and found to be a chemical reaction, which made effective desorption impossible. The sorption process was investigated in a packed bed column conformation, the results of which showed that the diameter and height of the column require further optimization in order to attain the metal uptake values achieved in the batch studies. When applied to a refinery wastewater, two key wastewater characteristics limited the success of the sorption process; the high inorganic ion content and the complex speciation of the platinum ions. The results proved the concept principle of platinum recovery by immobilized yeast biosorption and indicated that a more detailed understanding of the platinum speciation within the wastewater is required before the biosorption process can be applied. Overall, the sorption of platinum by the S. cerevisiae sorbent was demonstrated to be highly effective in principle, but the complexity of the wastewater requires that pretreatment steps be taken before the successful application of this process to an industrial wastewater.
- Full Text:
- Date Issued: 2008
- Authors: Mack, Cherie-Lynn
- Date: 2008
- Subjects: Metals -- Refining Metals -- Absorption and adsorption Saccharomyces cerevisiae Factory and trade waste Water reuse Platinum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4071 , http://hdl.handle.net/10962/d1006977
- Description: The process of precious metal refining can be up to 99.99% efficient at best, and although it may seem small, the amount of valuable metal lost to waste streams is appreciable enough to warrant recovery. The method currently used to remove entrained metal ions from refinery wastewaters, chemical precipitation, is not an effective means for selective recovery of precious metals from a wastewater. Biosorption, the ability of certain types of biomass to bind and concentrate metals from even very dilute aqueous solutions, may be an effective point-source metal recovery strategy. The yeast, Saccharomyces cerevisiae, has been found capable of sorbing numerous precious and base metals, and is a cheap and abundant source of biomass. As such, it represents a possible precious metal sorbent for application to refining wastewaters. In this investigation, S. cerevisiae biomass was immobilized, using polyethyleneimine and glutaraldehyde, to produce a suitable sorbent, which was found to be capable of high platinum uptake (150 to 170 mg/g) at low pH (< 2). The sorption mechanism was elucidated and found to be a chemical reaction, which made effective desorption impossible. The sorption process was investigated in a packed bed column conformation, the results of which showed that the diameter and height of the column require further optimization in order to attain the metal uptake values achieved in the batch studies. When applied to a refinery wastewater, two key wastewater characteristics limited the success of the sorption process; the high inorganic ion content and the complex speciation of the platinum ions. The results proved the concept principle of platinum recovery by immobilized yeast biosorption and indicated that a more detailed understanding of the platinum speciation within the wastewater is required before the biosorption process can be applied. Overall, the sorption of platinum by the S. cerevisiae sorbent was demonstrated to be highly effective in principle, but the complexity of the wastewater requires that pretreatment steps be taken before the successful application of this process to an industrial wastewater.
- Full Text:
- Date Issued: 2008
Spatial and temporal variations in metals in the sediment and water of selected Eastern Cape Estuaries, South Africa
- Authors: Orr, Kyla Kathleen
- Date: 2008
- Subjects: Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5769 , http://hdl.handle.net/10962/d1005457 , Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Description: The spatio-temporal patterns in concentrations of selected metals within the sediment (Cd, Co, Cu, Fe, Pb, Ni and Zn) and water (Cd and Pb) of three permanently open estuaries (Kariega, Kowie, Great Fish) and six temporary open-closed estuaries (Mpekweni, East Kleinemonde, West Kleinemonde, Riet, Kasouga, Boknes) were investigated. The concentrations of metals were influenced by size composition and total organic content of the sediments. Enrichment factors (EFs), using Fe as a reference element, and baseline linear regression models for metals vs. Fe were calculated to assess the extent of metal enrichment in the sediments. The mean concentrations of metals in the sediments(mg·kg⁻¹) showed ranges of 0.28 – 2.31 for Cd, 1.26 – 6.24 Co, 0.69 – 6.93 for Cu, 2119 – 14912 for Fe, 2.29 –14.01 for Ni, 4.81 – 22.20 for Pb and 5.77 – 21.75 for Zn. Mean normalized enrichment factors ranged between 0.75 – 6.19 for Cd, 0.53 – 2.71 for Co, 0.22 – 0.84 for Cu, 0.30 – 1.87 for Ni, 0.99 – 3.17 for Pb and 0.14 – 0.98 for Zn. All nine estuaries had average enrichment factors of greater than 1 for Cd. In general there was no enrichment of Cu and Zn in the sediments of any of the estuaries included in this study (EFs < 1). The Kariega, East Kleinemonde, West Kleinemonde, Riet and Great Fish Estuaries showed some degree of enrichment for Co (1 < EF < 4), Ni (1 < EF < 2) and Pb (1 < EF < 4), while the Mpekweni, Kasouga, Boknes and Kowie Estuaries were unenriched with these metals (EF < 1). Enrichment factors for Cd, Co and Pb typically followed the development gradient along the estuaries, suggesting anthropogenic enrichment. The concentrations of Cd and Pb in the water of the nine estuaries were also determined. The average concentrations of Cd and Pb in the water (μg·ℓ⁻¹) ranged between 0.05 – 3.32 and 0.75 – 34.13 respectively. On average the concentrations of Cd and Pb in the water of all the estuaries were below the South African recommended water quality guidelines for coastal marine waters. Variations in metal concentrations associated with changes in hydrology (wet vs. dry season) were determined in the water and sediment of the Kariega, East Kleinemonde and Riet Estuaries. Cobalt, Pb and Ni enrichment in the Kariega Estuary sediment was significantly higher during the dry season, and the mean concentrations of Pb and Cd in the water column were 19-fold and 66-fold higher in the dry season. The elevated concentration of metals during the dry season could be related to accumulation of diffuse pollution from human activities within the catchment area. Conversely, inflow of fresh water into the estuary had the net effect of reducing the concentration and enrichment of these metals within the Kariega Estuary due to scouring and outflow of estuarine water and sediment into the marine environment. The temporal variations in metal concentrations and enrichment factors were less pronounced in the temporary open-closed estuaries than the permanently open Kariega Estuary. The observed trend can probably be related to the low anthropogenic impact within the catchment areas of these systems, and the relatively smaller size of the catchments. Significant spatial variations existed in metal enrichment in the sediment of both the East Kleinemonde and Riet estuaries, with the highest degrees of enrichment occurring in the sediments from the marine environment and lower reaches.
- Full Text:
- Date Issued: 2008
- Authors: Orr, Kyla Kathleen
- Date: 2008
- Subjects: Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5769 , http://hdl.handle.net/10962/d1005457 , Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Description: The spatio-temporal patterns in concentrations of selected metals within the sediment (Cd, Co, Cu, Fe, Pb, Ni and Zn) and water (Cd and Pb) of three permanently open estuaries (Kariega, Kowie, Great Fish) and six temporary open-closed estuaries (Mpekweni, East Kleinemonde, West Kleinemonde, Riet, Kasouga, Boknes) were investigated. The concentrations of metals were influenced by size composition and total organic content of the sediments. Enrichment factors (EFs), using Fe as a reference element, and baseline linear regression models for metals vs. Fe were calculated to assess the extent of metal enrichment in the sediments. The mean concentrations of metals in the sediments(mg·kg⁻¹) showed ranges of 0.28 – 2.31 for Cd, 1.26 – 6.24 Co, 0.69 – 6.93 for Cu, 2119 – 14912 for Fe, 2.29 –14.01 for Ni, 4.81 – 22.20 for Pb and 5.77 – 21.75 for Zn. Mean normalized enrichment factors ranged between 0.75 – 6.19 for Cd, 0.53 – 2.71 for Co, 0.22 – 0.84 for Cu, 0.30 – 1.87 for Ni, 0.99 – 3.17 for Pb and 0.14 – 0.98 for Zn. All nine estuaries had average enrichment factors of greater than 1 for Cd. In general there was no enrichment of Cu and Zn in the sediments of any of the estuaries included in this study (EFs < 1). The Kariega, East Kleinemonde, West Kleinemonde, Riet and Great Fish Estuaries showed some degree of enrichment for Co (1 < EF < 4), Ni (1 < EF < 2) and Pb (1 < EF < 4), while the Mpekweni, Kasouga, Boknes and Kowie Estuaries were unenriched with these metals (EF < 1). Enrichment factors for Cd, Co and Pb typically followed the development gradient along the estuaries, suggesting anthropogenic enrichment. The concentrations of Cd and Pb in the water of the nine estuaries were also determined. The average concentrations of Cd and Pb in the water (μg·ℓ⁻¹) ranged between 0.05 – 3.32 and 0.75 – 34.13 respectively. On average the concentrations of Cd and Pb in the water of all the estuaries were below the South African recommended water quality guidelines for coastal marine waters. Variations in metal concentrations associated with changes in hydrology (wet vs. dry season) were determined in the water and sediment of the Kariega, East Kleinemonde and Riet Estuaries. Cobalt, Pb and Ni enrichment in the Kariega Estuary sediment was significantly higher during the dry season, and the mean concentrations of Pb and Cd in the water column were 19-fold and 66-fold higher in the dry season. The elevated concentration of metals during the dry season could be related to accumulation of diffuse pollution from human activities within the catchment area. Conversely, inflow of fresh water into the estuary had the net effect of reducing the concentration and enrichment of these metals within the Kariega Estuary due to scouring and outflow of estuarine water and sediment into the marine environment. The temporal variations in metal concentrations and enrichment factors were less pronounced in the temporary open-closed estuaries than the permanently open Kariega Estuary. The observed trend can probably be related to the low anthropogenic impact within the catchment areas of these systems, and the relatively smaller size of the catchments. Significant spatial variations existed in metal enrichment in the sediment of both the East Kleinemonde and Riet estuaries, with the highest degrees of enrichment occurring in the sediments from the marine environment and lower reaches.
- Full Text:
- Date Issued: 2008
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