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Modeling and Optimization of Wastewater Treatment and Lipid Production using a Mixed-Culture of Algae and Bacteria in a High Rate Algal Pond

  • Author / Creator
    Radfar, Marjan
  • Biofuels are being considered as an alternative source of energy produced from fossil fuels. Among various biological resources, microalgae have captured lots of attention in recent years due to their potential use as renewable energy source for biofuel production since they offer high growth rate, high lipid content and potential for carbon dioxide (CO2) capture. Cultivation of microalgae with other microorganisms in terms of promoting biomass production and other associated compounds is increasing compared to pure culture of algae. Studies on mixed culture of algae and bacteria have demonstrated the significant role of bacteria in enhancing algal growth and valuable products based on mutualistic relationship. One of the systems that is inherent in providing such medium for the interaction between algae and bacteria is high rate algal ponds (HRAPs) for wastewater treatment, with the potential for cost-effective production of biofuel. However, little attention has been devoted to study the nature of interactions from a modeling perspective. In this work, a dynamic mathematical model is presented to investigate the behavior of algal-bacterial consortium in an open pond. Wastewater serves as feed, providing substrate for bacteria and essential nutrients for the growth of algae. CO2 is supplied into the pond as additional source of carbon for algae to grow faster and CO2 footprint mitigation. To study the dynamic behavior of this system, the model was constituted of mass balance equations for each biological and chemical component. Gas-liquid mass transfer of CO2 and oxygen between the atmosphere and the pond, mass transfer of the additional supplied CO2 gas, and the effect of light intensity on algal growth were considered in the equations. The model was validated against multiple sets of experimental data in the literature and a good agreement for continuous and batch cultures was obtained. The lipid production model was incorporated into the model structure, providing reasonable predictions of the accumulated lipid in the algae for the potential generation of biofuels. The developed process model was optimized under different operating conditions to predict the optimal paths for the combined purposes of wastewater treatment and algal growth to produce biofuel. The supplementation of CO2 with increasing the inlet concentration of nitrogen and feeding in a stepwise pattern promoted the algal growth and lipid formation. The proposed model can be used as a tool to estimate the performance of practical algal ponds according to the desired functionality.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-5tjw-bb51
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.