A mathematical model of a high sulphate wastewater, anaerobic treatment system

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dc.contributor.advisorLewis, Aen_ZA
dc.contributor.authorKnobel, Anthony Nen_ZA
dc.date.accessioned2016-05-04T12:49:00Z
dc.date.available2016-05-04T12:49:00Z
dc.date.issued1999en_ZA
dc.descriptionIncludes bibliographic references.en_ZA
dc.description.abstractHigh sulphate wastewaters, originating from industrial activity or from the biological oxidation of sulphide ores (acid mine drainage), cannot be discharged into the environment untreated. Apart from the high sulphate levels, these waters may be very acidic and have high dissolved heavy metal concentrations. One promising treatment technology is biological sulphate reduction in anaerobic reactors. During anaerobic treatment, sulphate is reduced to sulphide and alkalinity is generated, raising the pH and precipitating many of the heavy metals. The process requires a carbon source as an electron donor. This may be simple organics such as ethanol or volatile fatty acids, which are directly utilized by the sulphate reducing bacteria, or complex organics such as sewage sludge which must first undergo solubilization and fermentation by a different microbial group. As an aid to the design and operation of this treatment process, a mathematical model describing an anaerobic digester treating high sulphate waste waters has been developed. Apart from sulphate reduction, the model includes those reactions which occur either prior to sulphate reduction, or in competition with it. These include hydrolysis of solid substrates, acidogenesis, beta oxidation of long chain fatty acids, acetogenesis and methanogenesis. By incorporating terms for these reactions, the model is able to simulate sulphate reduction using a wide range of carbon sources. A comprehensive literature survey of the kinetic parameters for the above reactions was undertaken. Apart from the Monod equation describing substrate uptake the kinetic expressions used in the model also includes terms for: unionized fatty acid inhibition; unionized or total sulphide inhibition; hydrogen inhibition and hydrogen product regulation where appropriate; pH inhibition; and dual substrate uptake where appropriate. Acid/base equilibrium chemistry has been included in order to predict the pH and unionized component concentrations (needed for calculating inhibition). The weak acids, H₂CO₃, H₂S, a number of SCFAs, NH₃, and their ions, as well as the strongly dissociating sulphates Na₂SO₄ and H₂SO₄ are included. An activity based model was used, with the activity coefficients calculated using Debye-Hilckle theory. The mass transfer rates of hydrogen, methane, carbon dioxide and hydrogen sulphide from the liquid to the vapour phase are also included. A final aspect of the model is the equations describing the reactor geometry. A number of different reactors may be simulated, including a dynamic batch, steady state CSTR and dynamic CSTR. By separating the hydraulic and solids residence times, high rate reactors such as UASB and packed bed reactors may also be simulated. The model has been used to successfully predict the dynamic and steady state behaviour of a number of different reactor types, utilizing both simple and complex carbon sources.en_ZA
dc.identifier.apacitationKnobel, A. N. (1999). <i>A mathematical model of a high sulphate wastewater, anaerobic treatment system</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/19419en_ZA
dc.identifier.chicagocitationKnobel, Anthony N. <i>"A mathematical model of a high sulphate wastewater, anaerobic treatment system."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1999. http://hdl.handle.net/11427/19419en_ZA
dc.identifier.citationKnobel, A. 1999. A mathematical model of a high sulphate wastewater, anaerobic treatment system. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Knobel, Anthony N AB - High sulphate wastewaters, originating from industrial activity or from the biological oxidation of sulphide ores (acid mine drainage), cannot be discharged into the environment untreated. Apart from the high sulphate levels, these waters may be very acidic and have high dissolved heavy metal concentrations. One promising treatment technology is biological sulphate reduction in anaerobic reactors. During anaerobic treatment, sulphate is reduced to sulphide and alkalinity is generated, raising the pH and precipitating many of the heavy metals. The process requires a carbon source as an electron donor. This may be simple organics such as ethanol or volatile fatty acids, which are directly utilized by the sulphate reducing bacteria, or complex organics such as sewage sludge which must first undergo solubilization and fermentation by a different microbial group. As an aid to the design and operation of this treatment process, a mathematical model describing an anaerobic digester treating high sulphate waste waters has been developed. Apart from sulphate reduction, the model includes those reactions which occur either prior to sulphate reduction, or in competition with it. These include hydrolysis of solid substrates, acidogenesis, beta oxidation of long chain fatty acids, acetogenesis and methanogenesis. By incorporating terms for these reactions, the model is able to simulate sulphate reduction using a wide range of carbon sources. A comprehensive literature survey of the kinetic parameters for the above reactions was undertaken. Apart from the Monod equation describing substrate uptake the kinetic expressions used in the model also includes terms for: unionized fatty acid inhibition; unionized or total sulphide inhibition; hydrogen inhibition and hydrogen product regulation where appropriate; pH inhibition; and dual substrate uptake where appropriate. Acid/base equilibrium chemistry has been included in order to predict the pH and unionized component concentrations (needed for calculating inhibition). The weak acids, H₂CO₃, H₂S, a number of SCFAs, NH₃, and their ions, as well as the strongly dissociating sulphates Na₂SO₄ and H₂SO₄ are included. An activity based model was used, with the activity coefficients calculated using Debye-Hilckle theory. The mass transfer rates of hydrogen, methane, carbon dioxide and hydrogen sulphide from the liquid to the vapour phase are also included. A final aspect of the model is the equations describing the reactor geometry. A number of different reactors may be simulated, including a dynamic batch, steady state CSTR and dynamic CSTR. By separating the hydraulic and solids residence times, high rate reactors such as UASB and packed bed reactors may also be simulated. The model has been used to successfully predict the dynamic and steady state behaviour of a number of different reactor types, utilizing both simple and complex carbon sources. DA - 1999 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1999 T1 - A mathematical model of a high sulphate wastewater, anaerobic treatment system TI - A mathematical model of a high sulphate wastewater, anaerobic treatment system UR - http://hdl.handle.net/11427/19419 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/19419
dc.identifier.vancouvercitationKnobel AN. A mathematical model of a high sulphate wastewater, anaerobic treatment system. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1999 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/19419en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Chemical Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherChemical Engineeringen_ZA
dc.titleA mathematical model of a high sulphate wastewater, anaerobic treatment systemen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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