Dheepak Maharajh - Academia.edu (original) (raw)
Papers by Dheepak Maharajh
Edizioni Ca’Foscari Digital Publishing, Mar 1, 2015
International Journal of Environment and Waste Management, 2022
Chemical Engineering Transactions, 2019
Acid mine drainage (AMD) is a worldwide problem caused mainly by mining activities and is known f... more Acid mine drainage (AMD) is a worldwide problem caused mainly by mining activities and is known for its adverse impacts on the environment due to low pH, high metal content and high sulphate concentrations. Lime neutralisation is a conventional way of treating AMD, however, this method is costly and produces sludge that is difficult to dispose of. Biological treatment of AMD using sulphate reducing bacteria has been identified as a cost-effective alternative treatment method due to its advantages that include simultaneously precipitating metals, reducing sulphate concentration and increasing pH. In this study, the effect of temperature and pH using complex organic compounds as substrates in a downflow packed bed reactor was investigated. Temperature was found to have a major impact on sulphate reduction. Sulphate reduction dropped from about 88 % to about 67 % when the temperature was slowly decreased from 30 °C to 10 °C. The decrease in pH from pH 6 to pH 5 was observed to have min...
Datasets consists of audio recordings of the interviews and the reports from the qualitative anal... more Datasets consists of audio recordings of the interviews and the reports from the qualitative analysis from Atlas Ti as well as audio files of interviews from mining sector.
Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in r... more Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in reducing concentrations of nitrogenous wastes and inhibiting growth of fish pathogens. In vivo efficacy and tolerance to a range of physiological conditions in systems used to rear Cyprinus carpio make this isolate an excellent candidate for aquaculture applications. Production cost is an impor-tant consideration in development of commercially relevant biological products, and this study examines the optimiza-tion of nutrient supplementation, which has an impact on high-density production of spores by fermentation. Corn steep liquor (CSL) was identified as a lower cost and more effective nutrient source in comparison to conventional nutrient substrates, in particular yeast extract and nutrient broth. The improved sporulation performance of B. cereus could be related to the increased availability of free amino acids, carbohydrates, and minerals in CSL, which had a positive effect on sporul...
11 Abstract Biological products offer advantages over chemo-12 therapeutics in aquaculture. Adopt... more 11 Abstract Biological products offer advantages over chemo-12 therapeutics in aquaculture. Adoption in commercial applica-13 tion is lacking due to limitations in process and product 14 development that address key end user product requirements 15 such as cost, efficacy, shelf life and convenience. In previous 16 studies, we have reported on the efficacy, physiological 17 robustness and low-cost spore production of a Bacillus cereus 18 isolate (NRRL 100132). This study examines the develop-19 ment of suitable spore recovery, drying, formulation and tablet 20 production from the fermentation product. Key criteria used 21 for such downstream process unit evaluation included spore 22 viability, recovery, spore balance, spore re-germination, 23 product intermediate stability, end product stability and 24 efficacy. A process flow sheet comprising vertical tube 25 centrifugation, fluidised bed agglomeration and tablet press-26 ing yielded a suitable product. The formulation included corn...
Copyright: Edizioni Ca’Foscari digital Publishing. Due to copyright restrictions, the attached PD... more Copyright: Edizioni Ca’Foscari digital Publishing. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published Algae as a Potential Source of Food and Energy in Developing Countries: Sustainability, Technology and Selected Case Studies.
Performance of Biological Sulphate Reduction at Low pH, Low Temperature and Low Hydraulic Retenti... more Performance of Biological Sulphate Reduction at Low pH, Low Temperature and Low Hydraulic Retention Time Mukhethwa J. Mukwevho*, Evans M.N. Chirwa, Dheepak Maharajh a University of Pretoria, Department of Chemical Engineering, Water Utilisation and Environmental Engineering Division, Private Bag X20, Hatfield, Pretoria 0002, South Africa b Biotechnology Division, Mintek, Private Bag X3015, Randburg 2125, South Africa [Style: CET Address] mukhethwa.judy@gmail.com
CSIR 3rd biennial conference: 2010 science real and, relevant, CSIR International Convention Cent... more CSIR 3rd biennial conference: 2010 science real and, relevant, CSIR International Convention Center, Pretoria, South Africa, 30 August-1 September 2010.
Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) Abstract Mine impac... more Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) Abstract Mine impacted water includes all water impacted by mining activities, from process efuents to polluted water courses due to mining activities. In South Africa, mine impacted water has caused severe and long term degradation of the environment. As a result, much research is focused on treating mine impacted water, speci cally increasing or neutralising the pH of the water and decreasing the sulphate and metals concentrations. South African mine impacted water generally contains high levels of sulphate, o en in excess of 3g/L, and stringent regulations enforce low sulphate discharge limits of 200 600 mg/L. Biological sulphate reduction has been demonstrated as a feasible treatment technology for removal of sulphate and precipitation of metals from mine impacted water. Sulphate is biologically converted to sulphide in this process, which is either released as hydrogen sulphide gas, or remains in solu...
The environmental effects of burning fossil fuels and the increased crude oil prices have trigger... more The environmental effects of burning fossil fuels and the increased crude oil prices have triggered increased interest in biofuels. Biodiesel is traditionally produced from oil seed crops, which have lower yields per land area and threaten food security when compared to algae which have high oil yields (~ 90 times more oil per area of land in comparison to the best oil seed crop) and do not require arable land for cultivation. CSIR Biosciences has commenced research in this area with the aim of implementing an algal biodiesel production technology. Lipid producing algal isolates from the United States Department of Energy Aquatic Species Program (ASP) were obtained to benchmark technology performance. The best strains obtainable were assessed in laboratory studies, the results of which formed the basis of a techno-economic evaluation to identify key variables and parameters influencing the implementation of algal biodiesel production. The model demonstrated a feasible business case ...
Letters in Applied Microbiology, 2008
Applied Microbiology and Biotechnology, 2009
Applied Microbiology and Biotechnology, 2008
Applied Microbiology and Biotechnology, 2009
Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in r... more Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in reducing concentrations of nitrogenous wastes and inhibiting growth of fish pathogens. In vivo efficacy and tolerance to a range of physiological conditions in systems used to rear Cyprinus carpio make this isolate an excellent candidate for aquaculture applications. Production cost is an important consideration in development of commercially relevant biological products, and this study examines the optimization of nutrient supplementation, which has an impact on high-density production of spores by fermentation. Corn steep liquor (CSL) was identified as a lower cost and more effective nutrient source in comparison to conventional nutrient substrates, in particular yeast extract and nutrient broth. The improved sporulation performance of B. cereus could be related to the increased availability of free amino acids, carbohydrates, and minerals in CSL, which had a positive effect on sporulation efficiency. The impact of nutrient concentration on spore yield and productivity was modeled to develop a tool for optimization of nutrient concentration in fermentation. An excellent fit of the model was confirmed in laboratory fermentation studies. A cost comparison revealed that production using liquid phytase and ultrafiltered-treated CSL was less expensive than spray-dried CSL and supported cultivation of B. cereus spores at densities higher than 1×10 10 CFU ml −1 .
Water
Biological sulphate reduction (BSR) has been identified as a promising alternative for treating a... more Biological sulphate reduction (BSR) has been identified as a promising alternative for treating acid mine drainage. In this study, the effect of pH, temperature, and hydraulic retention time (HRT) on BSR was investigated. The Box–Behnken design was used to matrix independent variables, namely pH (4–6), temperature (10–30 °C), and HRT (2–7 days) with the sulphate reduction efficiency and sulphate reduction rate as response variables. Experiments were conducted in packed bed reactors operating in a downflow mode. Response surface methodology was used to statistically analyse the data and to develop statistical models that can be used to fully understand the individual effects and the interactions between the independent variables. The analysis of variance results showed that the data fitted the quadratic models well as confirmed by a non-significant lack of fit. The temperature and HRT effect were significant (p < 0.0001), and these two variables had a strong interaction. However, ...
Edizioni Ca’Foscari Digital Publishing, Mar 1, 2015
International Journal of Environment and Waste Management, 2022
Chemical Engineering Transactions, 2019
Acid mine drainage (AMD) is a worldwide problem caused mainly by mining activities and is known f... more Acid mine drainage (AMD) is a worldwide problem caused mainly by mining activities and is known for its adverse impacts on the environment due to low pH, high metal content and high sulphate concentrations. Lime neutralisation is a conventional way of treating AMD, however, this method is costly and produces sludge that is difficult to dispose of. Biological treatment of AMD using sulphate reducing bacteria has been identified as a cost-effective alternative treatment method due to its advantages that include simultaneously precipitating metals, reducing sulphate concentration and increasing pH. In this study, the effect of temperature and pH using complex organic compounds as substrates in a downflow packed bed reactor was investigated. Temperature was found to have a major impact on sulphate reduction. Sulphate reduction dropped from about 88 % to about 67 % when the temperature was slowly decreased from 30 °C to 10 °C. The decrease in pH from pH 6 to pH 5 was observed to have min...
Datasets consists of audio recordings of the interviews and the reports from the qualitative anal... more Datasets consists of audio recordings of the interviews and the reports from the qualitative analysis from Atlas Ti as well as audio files of interviews from mining sector.
Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in r... more Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in reducing concentrations of nitrogenous wastes and inhibiting growth of fish pathogens. In vivo efficacy and tolerance to a range of physiological conditions in systems used to rear Cyprinus carpio make this isolate an excellent candidate for aquaculture applications. Production cost is an impor-tant consideration in development of commercially relevant biological products, and this study examines the optimiza-tion of nutrient supplementation, which has an impact on high-density production of spores by fermentation. Corn steep liquor (CSL) was identified as a lower cost and more effective nutrient source in comparison to conventional nutrient substrates, in particular yeast extract and nutrient broth. The improved sporulation performance of B. cereus could be related to the increased availability of free amino acids, carbohydrates, and minerals in CSL, which had a positive effect on sporul...
11 Abstract Biological products offer advantages over chemo-12 therapeutics in aquaculture. Adopt... more 11 Abstract Biological products offer advantages over chemo-12 therapeutics in aquaculture. Adoption in commercial applica-13 tion is lacking due to limitations in process and product 14 development that address key end user product requirements 15 such as cost, efficacy, shelf life and convenience. In previous 16 studies, we have reported on the efficacy, physiological 17 robustness and low-cost spore production of a Bacillus cereus 18 isolate (NRRL 100132). This study examines the develop-19 ment of suitable spore recovery, drying, formulation and tablet 20 production from the fermentation product. Key criteria used 21 for such downstream process unit evaluation included spore 22 viability, recovery, spore balance, spore re-germination, 23 product intermediate stability, end product stability and 24 efficacy. A process flow sheet comprising vertical tube 25 centrifugation, fluidised bed agglomeration and tablet press-26 ing yielded a suitable product. The formulation included corn...
Copyright: Edizioni Ca’Foscari digital Publishing. Due to copyright restrictions, the attached PD... more Copyright: Edizioni Ca’Foscari digital Publishing. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website. The definitive version of the work is published Algae as a Potential Source of Food and Energy in Developing Countries: Sustainability, Technology and Selected Case Studies.
Performance of Biological Sulphate Reduction at Low pH, Low Temperature and Low Hydraulic Retenti... more Performance of Biological Sulphate Reduction at Low pH, Low Temperature and Low Hydraulic Retention Time Mukhethwa J. Mukwevho*, Evans M.N. Chirwa, Dheepak Maharajh a University of Pretoria, Department of Chemical Engineering, Water Utilisation and Environmental Engineering Division, Private Bag X20, Hatfield, Pretoria 0002, South Africa b Biotechnology Division, Mintek, Private Bag X3015, Randburg 2125, South Africa [Style: CET Address] mukhethwa.judy@gmail.com
CSIR 3rd biennial conference: 2010 science real and, relevant, CSIR International Convention Cent... more CSIR 3rd biennial conference: 2010 science real and, relevant, CSIR International Convention Center, Pretoria, South Africa, 30 August-1 September 2010.
Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) Abstract Mine impac... more Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) Abstract Mine impacted water includes all water impacted by mining activities, from process efuents to polluted water courses due to mining activities. In South Africa, mine impacted water has caused severe and long term degradation of the environment. As a result, much research is focused on treating mine impacted water, speci cally increasing or neutralising the pH of the water and decreasing the sulphate and metals concentrations. South African mine impacted water generally contains high levels of sulphate, o en in excess of 3g/L, and stringent regulations enforce low sulphate discharge limits of 200 600 mg/L. Biological sulphate reduction has been demonstrated as a feasible treatment technology for removal of sulphate and precipitation of metals from mine impacted water. Sulphate is biologically converted to sulphide in this process, which is either released as hydrogen sulphide gas, or remains in solu...
The environmental effects of burning fossil fuels and the increased crude oil prices have trigger... more The environmental effects of burning fossil fuels and the increased crude oil prices have triggered increased interest in biofuels. Biodiesel is traditionally produced from oil seed crops, which have lower yields per land area and threaten food security when compared to algae which have high oil yields (~ 90 times more oil per area of land in comparison to the best oil seed crop) and do not require arable land for cultivation. CSIR Biosciences has commenced research in this area with the aim of implementing an algal biodiesel production technology. Lipid producing algal isolates from the United States Department of Energy Aquatic Species Program (ASP) were obtained to benchmark technology performance. The best strains obtainable were assessed in laboratory studies, the results of which formed the basis of a techno-economic evaluation to identify key variables and parameters influencing the implementation of algal biodiesel production. The model demonstrated a feasible business case ...
Letters in Applied Microbiology, 2008
Applied Microbiology and Biotechnology, 2009
Applied Microbiology and Biotechnology, 2008
Applied Microbiology and Biotechnology, 2009
Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in r... more Previous studies have demonstrated the efficacy of our Bacillus cereus isolate (NRRL 100132) in reducing concentrations of nitrogenous wastes and inhibiting growth of fish pathogens. In vivo efficacy and tolerance to a range of physiological conditions in systems used to rear Cyprinus carpio make this isolate an excellent candidate for aquaculture applications. Production cost is an important consideration in development of commercially relevant biological products, and this study examines the optimization of nutrient supplementation, which has an impact on high-density production of spores by fermentation. Corn steep liquor (CSL) was identified as a lower cost and more effective nutrient source in comparison to conventional nutrient substrates, in particular yeast extract and nutrient broth. The improved sporulation performance of B. cereus could be related to the increased availability of free amino acids, carbohydrates, and minerals in CSL, which had a positive effect on sporulation efficiency. The impact of nutrient concentration on spore yield and productivity was modeled to develop a tool for optimization of nutrient concentration in fermentation. An excellent fit of the model was confirmed in laboratory fermentation studies. A cost comparison revealed that production using liquid phytase and ultrafiltered-treated CSL was less expensive than spray-dried CSL and supported cultivation of B. cereus spores at densities higher than 1×10 10 CFU ml −1 .
Water
Biological sulphate reduction (BSR) has been identified as a promising alternative for treating a... more Biological sulphate reduction (BSR) has been identified as a promising alternative for treating acid mine drainage. In this study, the effect of pH, temperature, and hydraulic retention time (HRT) on BSR was investigated. The Box–Behnken design was used to matrix independent variables, namely pH (4–6), temperature (10–30 °C), and HRT (2–7 days) with the sulphate reduction efficiency and sulphate reduction rate as response variables. Experiments were conducted in packed bed reactors operating in a downflow mode. Response surface methodology was used to statistically analyse the data and to develop statistical models that can be used to fully understand the individual effects and the interactions between the independent variables. The analysis of variance results showed that the data fitted the quadratic models well as confirmed by a non-significant lack of fit. The temperature and HRT effect were significant (p < 0.0001), and these two variables had a strong interaction. However, ...