Date of Defense
13-11-2023 8:00 AM
Location
F1-1117
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Chemical Engineering
College
COE
Department
Chemical Engineering
Keywords
Biogas, Biohydrogen, Oxygen scavenging, Algal-bacterial co-culture, Photobioreactor, Activated sludge.
Abstract
Hydrogen is a clean source and carbon-free source of energy that can be generated photobiologically using green microalgae with 122 kJ/g of energy output which is 2.75 times that of hydrocarbon-based fuels. However, challenges, such as presence of molecular oxygen (O2) within the cells, hinder their practical application. Molecular O2, emanating from the activity of photosynthesis, acts as a powerful and effective switch that turns off bioH2 production activity. The objective of this research is to develop an innovative approach to increase the yield and sustain bioH2 photoproduction. For this purpose, a consortium of microalgae and wastewater activated sludge (WWAS) will be used to scavenge intracellular molecular O2 within representative species of microalgae. The relatively recent studies investigated the co-culture of microalgae and pure bacterial strains; however, the current study proposes the co-culture system integrated with WWAS. The bacteria present in the WWAS will consume the molecular O2 produced during algal metabolism. The co-culture showed exact inverse relation between H2 and O2 during incubation period. Almost 45% of the gas composition comprises H2 in the final concentration. 1246 mL H2 L−1 was produced with least 57 mL O2 L−1 during 6 days of incubation. The co-culture with optimized conditions will be employed on semi continuous and continuous flow reactors to check the feasibility for sustained bioH2 yield. The maximum bioH2 concentrations of 421.1 μmol L−1 and 56.6 μmol L−1 were observed in the exponential and steadystate phases while operating in sequential flow batch reactor (SFBR) mode. The proposed system will also remove organics while improving water quality for reuse, accumulating biomass for biofuel production, and generating valuable gasses such as bioH2. The co-culture inoculum ratio of 1:1.5 v/v (Chlorella vulagris:WWAS) achieved ∼33% COD and ∼47% TS removal efficiencies in O2-deficient trisacetate- phosphate (TAP) medium during five days of incubation period. This project will contribute to the shift from a traditional mode of energy production from fossil fuels, use, and disposal to a circular economy wherein the vast potential of wastewater as a source of valuable nutrients and energy is exploited.
Included in
A CONSORTIUM OF MICROALGAE AND WASTEWATER ACTIVATED SLUDGE TO GENERATE BIOHYDROGEN
F1-1117
Hydrogen is a clean source and carbon-free source of energy that can be generated photobiologically using green microalgae with 122 kJ/g of energy output which is 2.75 times that of hydrocarbon-based fuels. However, challenges, such as presence of molecular oxygen (O2) within the cells, hinder their practical application. Molecular O2, emanating from the activity of photosynthesis, acts as a powerful and effective switch that turns off bioH2 production activity. The objective of this research is to develop an innovative approach to increase the yield and sustain bioH2 photoproduction. For this purpose, a consortium of microalgae and wastewater activated sludge (WWAS) will be used to scavenge intracellular molecular O2 within representative species of microalgae. The relatively recent studies investigated the co-culture of microalgae and pure bacterial strains; however, the current study proposes the co-culture system integrated with WWAS. The bacteria present in the WWAS will consume the molecular O2 produced during algal metabolism. The co-culture showed exact inverse relation between H2 and O2 during incubation period. Almost 45% of the gas composition comprises H2 in the final concentration. 1246 mL H2 L−1 was produced with least 57 mL O2 L−1 during 6 days of incubation. The co-culture with optimized conditions will be employed on semi continuous and continuous flow reactors to check the feasibility for sustained bioH2 yield. The maximum bioH2 concentrations of 421.1 μmol L−1 and 56.6 μmol L−1 were observed in the exponential and steadystate phases while operating in sequential flow batch reactor (SFBR) mode. The proposed system will also remove organics while improving water quality for reuse, accumulating biomass for biofuel production, and generating valuable gasses such as bioH2. The co-culture inoculum ratio of 1:1.5 v/v (Chlorella vulagris:WWAS) achieved ∼33% COD and ∼47% TS removal efficiencies in O2-deficient trisacetate- phosphate (TAP) medium during five days of incubation period. This project will contribute to the shift from a traditional mode of energy production from fossil fuels, use, and disposal to a circular economy wherein the vast potential of wastewater as a source of valuable nutrients and energy is exploited.