Matching Items (51)
Description
To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of oxygen limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi-species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) oxygen limitation, giving modest long-term nitrite build up; (iii) FA inhibition, giving no long-term nitrite accumulation; and (iv) FA inhibition plus oxygen limitation, giving major long-term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2–4 in the short term, but long-term nitrite accumulation was maintained only in sets 2 and 4, which involved oxygen limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long-term nitrite accumulation. Nitrite-oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended-growth process. Additional findings were that the biofilm exposed to low dissolved oxygen (DO) limitation and FA inhibition was substantially denser and probably had a lower detachment rate.
ContributorsPark, Seongjun (Author) / Chung, Jinwook (Author) / Rittmann, Bruce (Author) / Bae, Wookeun (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor)
Created2015-01-01
Description
Chloroform and methanol are superior solvents for lipid extraction from photosynthetic microorganisms, because they can overcome the resistance offered by the cell walls and membranes, but they are too toxic and expensive to use for large-scale fuel production. Biomass from the photosynthetic microalga Scenedesmus, subjected to a commercially available pre-treatment technology called Focused-Pulsed® (FP), yielded 3.1-fold more crude lipid and fatty acid methyl ester (FAME) after extraction with a range of solvents. FP treatment increased the FAME-to-crude-lipid ratio for all solvents, which means that the extraction of non-lipid materials was minimized, while the FAME profile itself was unchanged compared to the control. FP treatment also made it possible to use only a small proportion of chloroform and methanol, along with isopropanol, to obtain equivalent yields of lipid and FAME as with 100% chloroform plus methanol.
ContributorsLai, Yenjung Sean (Author) / Parameswaran, Prathap (Author) / Li, Ang (Author) / Baez, Maria (Author) / Rittmann, Bruce (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor)
Created2014-12-01
Description
Sulfadiazine (SD), one of broad-spectrum antibiotics, exhibits limited biodegradation in wastewater treatment due to its chemical structure, which requires initial mono-oxygenation reactions to initiate its biodegradation. Intimately coupling UV photolysis with biodegradation, realized with the internal loop photobiodegradation reactor, accelerated SD biodegradation and mineralization by 35 and 71 %, respectively. The main organic products from photolysis were 2-aminopyrimidine (2-AP), p-aminobenzenesulfonic acid (ABS), and aniline (An), and an SD-photolysis pathway could be identified using C, N, and S balances. Adding An or ABS (but not 2-AP) into the SD solution during biodegradation experiments (no UV photolysis) gave SD removal and mineralization rates similar to intimately coupled photolysis and biodegradation. An SD biodegradation pathway, based on a diverse set of the experimental results, explains how the mineralization of ABS and An (but not 2-AP) provided internal electron carriers that accelerated the initial mono-oxygenation reactions of SD biodegradation. Thus, multiple lines of evidence support that the mechanism by which intimately coupled photolysis and biodegradation accelerated SD removal and mineralization was through producing co-substrates whose oxidation produced electron equivalents that stimulated the initial mono-oxygenation reactions for SD biodegradation.
ContributorsPan, Shihui (Author) / Yan, Ning (Author) / Liu, Xinyue (Author) / Wang, Wenbing (Author) / Zhang, Yongming (Author) / Liu, Rui (Author) / Rittmann, Bruce (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor)
Created2014-11-01
Description
We studied the microbial community structure of pilot two-stage membrane biofilm reactors (MBfRs) designed to reduce nitrate (NO[subscript 3]–) and perchlorate (ClO[subscript 4]–) in contaminated groundwater. The groundwater also contained oxygen (O[subscript 2]) and sulfate (SO[2 over 4]–), which became important electron sinks that affected the NO[subscript 3]– and ClO[subscript 4]– removal rates. Using pyrosequencing, we elucidated how important phylotypes of each “primary” microbial group, i.e., denitrifying bacteria (DB), perchlorate-reducing bacteria (PRB), and sulfate-reducing bacteria (SRB), responded to changes in electron-acceptor loading. UniFrac, principal coordinate analysis (PCoA), and diversity analyses documented that the microbial community of biofilms sampled when the MBfRs had a high acceptor loading were phylogenetically distant from and less diverse than the microbial community of biofilm samples with lower acceptor loadings. Diminished acceptor loading led to SO[2 over 4]– reduction in the lag MBfR, which allowed Desulfovibrionales (an SRB) and Thiothrichales (sulfur-oxidizers) to thrive through S cycling. As a result of this cooperative relationship, they competed effectively with DB/PRB phylotypes such as Xanthomonadales and Rhodobacterales. Thus, pyrosequencing illustrated that while DB, PRB, and SRB responded predictably to changes in acceptor loading, a decrease in total acceptor loading led to important shifts within the “primary” groups, the onset of other members (e.g., Thiothrichales), and overall greater diversity.
ContributorsOntiveros-Valencia, Aura (Author) / Tang, Youneng (Author) / Zhao, Heping (Author) / Friese, David (Author) / Overstreet, Ryan (Author) / Smith, Jennifer (Author) / Evans, Patrick (Author) / Rittmann, Bruce (Author) / Krajmalnik-Brown, Rosa (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor) / Julie Ann Wrigley Global Institute of Sustainability (Contributor) / School of Sustainability (Contributor)
Created2014-07-01
Description
The Combined Activated Sludge-Anaerobic Digestion Model (CASADM) quantifies the effects of recycling anaerobic-digester (AD) sludge on the performance of a hybrid activated sludge (AS)-AD system. The model includes nitrification, denitrification, hydrolysis, fermentation, methanogenesis, and production/utilization of soluble microbial products and extracellular polymeric substances (EPS). A CASADM example shows that, while effluent COD and N are not changed much by hybrid operation, the hybrid system gives increased methane production in the AD and decreased sludge wasting, both caused mainly by a negative actual solids retention time in the hybrid AD. Increased retention of biomass and EPS allows for more hydrolysis and conversion to methane in the hybrid AD. However, fermenters and methanogens survive in the AS, allowing significant methane production in the settler and thickener of both systems, and AD sludge recycle makes methane formation greater in the hybrid system.
ContributorsYoung, Michelle (Author) / Marcus, Andrew (Author) / Rittmann, Bruce (Author) / Biodesign Institute (Contributor) / Swette Center for Environmental Biotechnology (Contributor)
Created2013-08-13
Description
This report investigates the mass-transfer kinetics of gas diffusion through an asymmetrical hollow-fiber membrane developed for the membrane biofilm reactor (MBfR) when it is used to microbiologically convert syngas (a mixture of H2, CO2, and CO) to organic products. The asymmetric Matrimid® membrane had superior diffusion fluxes compared to commercially available symmetric, three-layer composite and polypropylene single-layer membranes. The Matrimid® asymmetric membrane had a H2 gas-gas diffusion flux between 960- and 1600-fold greater than that of the composite membrane and between 32,000- and 46,800-fold greater than that of the single-layer membrane. Gas-gas diffusion experiments across the Matrimid® membrane also demonstrated plasticization behavior for pure CO2 and H2 gas feeds. In particular, a 10 psia increase in inlet pressure resulted in a 12-fold increase in permeance for H2 and a 16-fold increase for CO2. Plasticization was minimal for symmetric composite and single-layer membranes. Thus, diffusion fluxes were much higher for the asymmetric membrane than for the symmetric composite and single-layer membranes, and this supports the promise of the asymmetric membrane as a high-efficiency means to deliver syngas to biofilms able to convert the syngas to organic products. Gas-liquid diffusion was much slower than gas-gas diffusion, and this supports the benefit of using the MBfR approach over fermentation reactors that rely on sparging syngas.
ContributorsArafa, Omar M. (Author) / Rittmann, Bruce (Thesis director) / Torres, Cesar (Committee member) / Chemical Engineering Program (Contributor) / W.P. Carey School of Business (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The microalgae Scenedesmus have been regarded as a potential source for biofuel production, having up to ~30% of dry weight as lipids used for biodiesel fuel production. Electro-selective fermentation (ESF) is a novel approach that can selectively degrade proteins and carbohydrates while conserving lipids within algal cells, while simultaneously enhancing lipid wet-extraction and biohydrogenation. ESF is a combination of SF and Microbial Electrolysis Cell (MEC) technologies. Experiments reported here prove that ESF is an effective means of enhancing lipid wet-extraction by ~50% and achieving 36% higher lipid saturation conversion, compared to SF, over 30 days of semi-continuous operation. Anode-respiring bacteria (ARB) residing on the anode surface produced a current that led to increased rate of organic substrate utilization, protein degradation, and ultimately enhanced lipid extraction and biohydrogenation that converted unsaturated to saturated fatty-acids. Thus, ESF provides a promising method for enhancing lipid extraction for biofuel production.
ContributorsRastogi, Neil K (Author) / Rittmann, Bruce (Thesis director) / Liu, Liu (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
While biodiesel production from photosynthesizing algae is a promising form of alternative energy, the process is water and nutrient intensive. I designed a mathematical model for a photobioreactor system that filters the reactor effluent and returns the permeate to the system so that unutilized nutrients are not wasted, addressing these problems. The model tracks soluble and biomass components that govern the rates of the processes within the photobioreactor (PBR). It considers light attenuation and inhibition, nutrient limitation, preference for ammonia consumption over nitrate, production of soluble microbial products (SMP) and extracellular polymeric substance (EPS), and competition with heterotrophic bacteria that predominately consume SMP. I model a continuous photobioreactor + microfiltration system under nine unique operation conditions - three dilution rates and three recycling rates. I also evaluate the health of a PBR under different dilution rates for two values of qpred. I evaluate the success of each run by calculating values such as biomass productivity and specific biomass yield. The model shows that for low dilution rates (D = <0.2 d-1) and high recycling rates (>66%), nutrient limitation can lead to a PBR crash. In balancing biomass productivity with water conservation, the most favorable runs were those in which the dilution rate and the recycling rate were highest. In a second part of my thesis, I developed a model that describes the interactions of phototrophs and their predators. The model also shows that dilution rates corresponding to realistic PBR operation can washout predators from the system, but the simulation outputs depend heavily on the accuracy of parameters that are not well defined.
ContributorsWik, Benjamin Philip (Author) / Marcus, Andrew (Thesis director) / Rittmann, Bruce (Committee member) / School of Sustainability (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Terrestrial crude oil spills compromise a soil’s ability to provide ecosystem services by inhibiting plant life and threatening groundwater integrity. Ozone gas, a powerful oxidant, shows promise to aid in soil recovery by degrading petroleum hydrocarbons into more bioavailable and biodegradable chemicals. However, previous research has shown that ozone can change the soil pH and create harmful organic compounds.
The research objective was to determine the short-term ecological toxicity of ozonation byproducts on seed germination of three distinct plant types (radish, lettuce, and grass) compared to untreated and uncontaminated soils. We hypothesize that the reduction of heavy hydrocarbon contamination in soil by ozone application will provide more suitable habitat for the germinating seeds. The effect of ozone treatment on seed germination and seedling quality was measured using ASTM standards for early seedling growth in conjunction with a gradient of potting soil amendments. Ozonation parameters were measured using established methods and include total petroleum hydrocarbons (TPH), dissolved organic carbon (DOC), and pH.
This study demonstrated the TPH levels fall up to 22% with ozonation, suggesting TPH removal is related to the amount of ozone delivered as opposed to the type of crude oil present. The DOC values increase comparably across crude oil types as the ozonation dose increases (from a background level of 0.25 g to 6.2 g/kg dry soil at the highest ozone level), suggesting that DOC production is directly related to the amount of ozone, not crude oil type. While ozonation reduced the mass of heavy hydrocarbons in the soil, it increased the amount of ozonation byproducts in the soil. For the three types of seeds used in the study, these changes in concentrations of TPH and DOC affected the species differently; however, no seed type showed improved germination after ozone treatment. Thus, ozone treatment by itself had a negative impact on germination potential.
Future research should focus on the effects of post-ozonation, long-term bioremediation on eco-toxicity. By helping define the eco-toxicity of ozonation techniques, this research can improve upon previously established ozone techniques for petroleum remediation and provide economic and environmental benefits when used for soil treatment.
The research objective was to determine the short-term ecological toxicity of ozonation byproducts on seed germination of three distinct plant types (radish, lettuce, and grass) compared to untreated and uncontaminated soils. We hypothesize that the reduction of heavy hydrocarbon contamination in soil by ozone application will provide more suitable habitat for the germinating seeds. The effect of ozone treatment on seed germination and seedling quality was measured using ASTM standards for early seedling growth in conjunction with a gradient of potting soil amendments. Ozonation parameters were measured using established methods and include total petroleum hydrocarbons (TPH), dissolved organic carbon (DOC), and pH.
This study demonstrated the TPH levels fall up to 22% with ozonation, suggesting TPH removal is related to the amount of ozone delivered as opposed to the type of crude oil present. The DOC values increase comparably across crude oil types as the ozonation dose increases (from a background level of 0.25 g to 6.2 g/kg dry soil at the highest ozone level), suggesting that DOC production is directly related to the amount of ozone, not crude oil type. While ozonation reduced the mass of heavy hydrocarbons in the soil, it increased the amount of ozonation byproducts in the soil. For the three types of seeds used in the study, these changes in concentrations of TPH and DOC affected the species differently; however, no seed type showed improved germination after ozone treatment. Thus, ozone treatment by itself had a negative impact on germination potential.
Future research should focus on the effects of post-ozonation, long-term bioremediation on eco-toxicity. By helping define the eco-toxicity of ozonation techniques, this research can improve upon previously established ozone techniques for petroleum remediation and provide economic and environmental benefits when used for soil treatment.
ContributorsJanuszewski, Brielle (Author) / Rittmann, Bruce (Thesis director) / Yavuz, Burcu (Committee member) / Civil, Environmental and Sustainable Eng Program (Contributor) / School of International Letters and Cultures (Contributor) / School of Politics and Global Studies (Contributor, Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Magnetic nanomaterials exist in the brain tissues of neurodegenerative patients, particularly those suffering from Alzheimer’s disease (AD). These nanoparticles likely originated as airborne particles small enough to penetrate human blood-brain barriers (BBBs), ultimately reaching AD brains and potentially inducing cellular oxidative stress, contributing to AD development. The mechanism leading to AD is still unclear, significantly limiting effective treatment and prevention strategies. Clarifying these mechanisms requires identifying potential sources and oxidative reactivity of submicron magnetic particles.The goal of my dissertation is to investigate magnetite nanoparticles from biogenic, anthropogenic, and commercial sources. I aim to reveal their heterogeneous nature and oxidative reactivity to induce cellular oxidative stress. I developed strategies to quantify magnetic particles and statistically compare their chemical composition, mineral structural, and oxidative reactivity. My research seeks to provide investigation strategies to study magnetic particles in cellular environments and pollution sources, which ultimately aims to reveal the particle relative abundance, particle size, elemental composition, and metal speciation of magnetic particles to inform and guide current AD researchers.
I achieved five research objectives guided by the overarching research goal. Firstly, I characterized urban pollution magnetic particles, discovering their mixed structure (~40% metallic iron, ~60% magnetite) containing trace metals like copper. This finding suggested a novel oxidative mechanism involving metallic iron and copper. Secondly, I developed an analytical workflow to identify airborne particles smaller than 200 nm capable of penetrating BBBs, quantifying their abundance and distinguishing chemical groups in environmental samples. Thirdly, I created a similar workflow for analyzing particles in biological samples, providing essential methodological recommendations. Fourthly, I compared single-particle analytical techniques, evaluating their strengths and limitations to guide future studies of heterogeneous particles. Finally, I compared biogenic magnetite with high-purity commercial magnetite, revealing enhanced oxidative reactivity due to impurity metals in biogenic forms rather than magnetite itself.
The five objectives allowed me to understand critical factors influencing cellular oxidative stress linked to neurodegeneration, highlighting impurities in magnetite particles as key contributors. These new findings provided a new insight to understand the role of the mysterious magnetic nanoparticles in the development of neurodegenerative diseases.
ContributorsLong, Xiangxing (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Thesis advisor) / Herckes, Pierre (Committee member) / Arizona State University (Publisher)
Created2025