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- All Subjects: Environmental engineering
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- Creators: Krajmalnik-Brown, Rosa
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- Genre: Masters Thesis
- Member of: Theses and Dissertations
Description
Intimate coupling of Ti2 photocatalysis and biodegradation (ICPB) offers potential for degrading biorecalcitrant and toxic organic compounds much better than possible with conventional wastewater treatments. This study reports on using a novel sponge-type, Ti2-coated biofilm carrier that shows significant adherence of Ti2 to its exterior and the ability to accumulate biomass in its interior (protected from UV light and free radicals). First, this carrier was tested for ICPB in a continuous-flow photocatalytic circulating-bed biofilm reactor (PCBBR) to mineralize biorecalcitrant organic: 2,4,5-trichlorophenol (TCP). Four mechanisms possibly acting of ICPB were tested separately: TCP adsorption, UV photolysis/photocatalysis, and biodegradation. The carrier exhibited strong TCP adsorption, while photolysis was negligible. Photocatalysis produced TCP-degradation products that could be mineralized and the strong adsorption of TCP to the carrier enhanced biodegradation by relieving toxicity. Validating the ICPB concept, biofilm was protected inside the carriers from UV light and free radicals. ICPB significantly lowered the diversity of the bacterial community, but five genera known to biodegrade chlorinated phenols were markedly enriched. Secondly, decolorization and mineralization of reactive dyes by ICPB were investigated on a refined Ti2-coated biofilm carrier in a PCBBR. Two typical reactive dyes: Reactive Black 5 (RB5) and Reactive Yellow 86 (RY86), showed similar first-order kinetics when being photocatalytically decolorized at low pH (~4-5), which was inhibited at neutral pH in the presence of phosphate or carbonate buffer, presumably due to electrostatic repulsion from negatively charged surface sites on Ti2, radical scavenging by phosphate or carbonate, or both. In the PCBBR, photocatalysis alone with Ti2-coated carriers could remove RB5 and COD by 97% and 47%, respectively. Addition of biofilm inside macroporous carriers maintained a similar RB5 removal efficiency, but COD removal increased to 65%, which is evidence of ICPB despite the low pH. A proposed ICPB pathway for RB5 suggests that a major intermediate, a naphthol derivative, was responsible for most of the residual COD. Finally, three low-temperature sintering methods, called O, D and DN, were compared based on photocatalytic efficiency and Ti2 adherence. The DN method had the best Ti2-coating properties and was a successful carrier for ICPB of RB5 in a PCBBR.
ContributorsLi, Guozheng (Author) / Rittmann, Bruce E. (Thesis advisor) / Halden, Rolf (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2011
Description
To address sustainability issues in wastewater treatment (WWT), Siemens Water Technologies (SWT) has designed a "hybrid" process that couples common activated sludge (AS) and anaerobic digestion (AD) technologies with the novel concepts of AD sludge recycle and biosorption. At least 85% of the hybrid's AD sludge is recycled to the AS process, providing additional sorbent for influent particulate chemical oxygen demand (PCOD) biosorption in contact tanks. Biosorbed PCOD is transported to the AD, where it is converted to methane. The aim of this study is to provide mass balance and microbial community analysis (MCA) of SWT's two hybrid and one conventional pilot plant trains and mathematical modeling of the hybrid process including a novel model of biosorption. A detailed mass balance was performed on each tank and the overall system. The mass balance data supports the hybrid process is more sustainable: It produces 1.5 to 5.5x more methane and 50 to 83% less sludge than the conventional train. The hybrid's superior performance is driven by 4 to 8 times longer solid retention times (SRTs) as compared to conventional trains. However, the conversion of influent COD to methane was low at 15 to 22%, and neither train exhibited significant nitrification or denitrification. Data were inconclusive as to the role of biosorption in the processes. MCA indicated the presence of Archaea and nitrifiers throughout both systems. However, it is inconclusive as to how active Archaea and nitrifiers are under anoxic, aerobic, and anaerobic conditions. Mathematical modeling confirms the hybrid process produces 4 to 20 times more methane and 20 to 83% less sludge than the conventional train under various operating conditions. Neither process removes more than 25% of the influent nitrogen or converts more that 13% to nitrogen gas due to biomass washout in the contact tank and short SRTs in the stabilization tank. In addition, a mathematical relationship was developed to describe PCOD biosorption through adsorption to biomass and floc entrapment. Ultimately, process performance is more heavily influenced by the higher AD SRTs attained when sludge is recycled through the system and less influenced by the inclusion of biosorption kinetics.
ContributorsYoung, Michelle Nichole (Author) / Rittmann, Bruce E. (Thesis advisor) / Fox, Peter (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2011
Description
DehaloR^2 is a previously characterized, trichloroethene (TCE)-dechlorinating culture and contains bacteria from the known dechlorinating genus, Dehalococcoides. DehaloR^2 was exposed to three anthropogenic contaminants, Triclocarban (TCC), tris(2-chloroethyl) phosphate (TCEP), and 1,1,1-trichloroethane (TCA) and two biogenic-like halogenated compounds, 2,6-dibromophenol (2,6-DBP) and 2,6-dichlorophenol (2,6-DCP). The effects on TCE dechlorination ability due to 2,6-DBP and 2,6-DCP exposures were also investigated. DehaloR^2 did not dechlorinate TCC or TCEP. After initial exposure to TCA, half of the initial TCA was dechlorinated to 1,1-dichloroethane (DCA), however half of the TCA remained by day 100. Subsequent TCA and TCE re-exposure showed no reductive dechlorination activity for both TCA and TCE by 120 days after the re-exposure. It has been hypothesized that the microbial TCE-dechlorinating ability was developed before TCE became abundant in groundwater. This dechlorinating ability would have existed in the microbial metabolism due to previous exposure to biogenic halogenated compounds. After observing the inability of DehaloR^2 to dechlorinate other anthropogenic compounds, DehaloR^2 was then exposed to two naturally occurring halogenated phenols, 2,6-DBP and 2,6-DCP, in the presence and absence of TCE. DehaloR^2 debrominated 2,6-DBP through the intermediate 2-bromophenol (2-BP) to the end product phenol faster in the presence of TCE. DehaloR^2 dechlorinated 2,6-DCP to 2-CP in the absence of TCE; however, 2,6-DCP dechlorination was incomplete in the presence of TCE. Additionally, when 2,6-DBP was present, complete TCE dechlorination to ethene occurred more quickly than when TCE was present without 2,6-DBP. However, when 2,6-DCP was present, TCE dechlorination to ethene had not completed by day 55. The increased dehalogenation rate of 2,6-DBP and TCE when present together compared to conditions containing only 2,6-DBP or only TCE suggests a possible synergistic relationship between 2,6-DBP and TCE, while the decreased dechlorination rate of 2,6-DCP and TCE when present together compared to conditions containing only 2,6-DCP or only TCE suggests an inhibitory effect.
ContributorsKegerreis, Kylie (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Halden, Rolf U. (Committee member) / Torres, César I (Committee member) / Arizona State University (Publisher)
Created2012
Description
To further the efforts producing energy from more renewable sources, microbial electrochemical cells (MXCs) can utilize anode respiring bacteria (ARB) to couple the oxidation of an organic substrate to the delivery of electrons to the anode. Although ARB such as Geobacter and Shewanella have been well-studied in terms of their microbiology and electrochemistry, much is still unknown about the mechanism of electron transfer to the anode. To this end, this thesis seeks to elucidate the complexities of electron transfer existing in Geobacter sulfurreducens biofilms by employing Electrochemical Impedance Spectroscopy (EIS) as the tool of choice. Experiments measuring EIS resistances as a function of growth were used to uncover the potential gradients that emerge in biofilms as they grow and become thicker. While a better understanding of this model ARB is sought, electrochemical characterization of a halophile, Geoalkalibacter subterraneus (Glk. subterraneus), revealed that this organism can function as an ARB and produce seemingly high current densities while consuming different organic substrates, including acetate, butyrate, and glycerol. The importance of identifying and studying novel ARB for broader MXC applications was stressed in this thesis as a potential avenue for tackling some of human energy problems.
ContributorsAjulo, Oluyomi (Author) / Torres, Cesar (Thesis advisor) / Nielsen, David (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Popat, Sudeep (Committee member) / Arizona State University (Publisher)
Created2013
Description
As engineered nanomaterials (NMs) become used in industry and commerce their loading to sewage will increase. However, the fate of widely used NMs in wastewater treatment plants (WWTPs) remains poorly understood. In this research, sequencing batch reactors (SBRs) were operated with hydraulic (HRT) and sludge (SRT) retention times representative of full-scale biological WWTPs for several weeks. NM loadings at the higher range of expected environmental concentrations were selected. To achieve the pseudo-equilibrium state concentration of NMs in biomass, SBR experiments needed to operate for more than three times the SRT value, approximately 18 days. Under the conditions tested, NMs had negligible effects on ability of the wastewater bacteria to biodegrade organic material, as measured by chemical oxygen demand (COD). NM mass balance closure was achieved by measuring NMs in liquid effluent and waste biosolids. All NMs were well removed at the typical biomass concentration (1~2 gSS/L). However, carboxy-terminated polymer coated silver nanoparticles (fn-Ag) were removed less effectively (88% removal) than hydroxylated fullerenes (fullerols; >90% removal), nano TiO2 (>95% removal) or aqueous fullerenes (nC60; >95% removal). Although most NMs did not settle out of the feed solution without bacteria present, approximately 65% of the titanium dioxide was removed even in the absence of biomass simply due to self-aggregation and settling. Experiments conducted over 4 months with daily loadings of nC60 showed that nC60 removal from solution depends on the biomass concentration. Under conditions representative of most suspended growth biological WWTPs (e.g., activated sludge), most of the NMs will accumulate in biosolids rather than in liquid effluent discharged to surface waters. Significant fractions of fn-Ag were associated with colloidal material which suggests that efficient particle separation processes (sedimentation or filtration) could further improve removal of NM from effluent. As most NMs appear to accumulate in biosolids, future research should examine the fate of NMs during disposal of WWTP biosolids, which may occur through composting or anaerobic digestion and/or land application, incineration, or landfill disposal.
ContributorsWang, Yifei (Author) / Westerhoff, Paul (Thesis advisor) / Krajmalnik-Brown, Rosa (Committee member) / Rittmann, Bruce (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2012
Description
Selenium oxyanions (i.e., selenate and selenite) can be released into the environment from surface mining. Selenium is an essential micronutrient, but high selenium in water has adverse health effects for aquatic animals and humans. Mine-influenced water is often co-contaminated with high concentrations of nitrate, selenium oxyanions, and sulfate. The Saturated Rock Fill (SRF) is a treatment technology that utilizes waste rocks from surface mining to create a biological treatment system that can be effective at removing nitrate and selenium-oxyanions from the mine-influenced water. The Selenium, Sulfur, and Nitrogen species (SeSANS) model can be used to estimate the respiration, synthesis, and endogenous decay of biomass in an SRF. The goal of this thesis is to simulate SRF biofilms using a biofilm version of SeSANS. Three nitrate loads (100, 250, and 450 kg NO3-N/day) with a low flow rate (1000 m3/d) or a high flow rate (5000 m3/d) -- a total of six scenarios -- were simulated for 5000 days of operation. The influent water contained 0.18 g Se/m3 of selenate, 0.02 Se/m3 selenite, and 800 S/m3 of sulfate; the input nitrate concentration was 100, 250, and 450 g N/m3 for the low flow rate and 20, 50, and 90 g N/m3 for the high flow rate. Methanol was injected as the electron donor. These criteria were used to define a successful simulation: effluent nitrate < 3 mg N/L and total dissolved Se < 0.029 mg Se/L, minimal sulfate reduction, and an average biofilm-biomass density of 96 kg TS/m3. To achieve those criteria, the following model parameters were adjusted: rate for methanol addition, biofilm thickness, SRF volumes, and biofilm-detachment rates. The most important parameter for achieving all the goals was the methanol addition ratio: 3.56 g COD/g NO3-N. Another important outcome was that the high-flow-rate scenarios required a larger total SRF volume to achieve target nitrate and Se-oxyanion reductions. The results of the simulations can be used to estimate biofilm characteristics and optimize the SRF configuration and treatment operation.
ContributorsKuo, Jacqueline (Author) / Rittmann, Bruce E (Thesis advisor) / Boltz, Joshua P (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2023
Description
This study investigated the difference in biofilm growth on pristine and aged polypropylene microplastics exposed to Tempe Town Lake water for 8 weeks. The research question here is, does the aging of microplastic (MPs) change the biofilm formation rate and composition of the biofilm in comparison with the pristine MPs. To answer this question, the biofilm formation was quantified using different methods over time for both pristine polypropylene and aged polypropylene using agar plate counts and crystal violet staining. Colony counts based on agar plating showed an increase in microbial growth over the 8 weeks of treatment, with the aged MPs accumulating higher microbial counts than the pristine MPs. The diversity of the biofilm decreased over time for both MPs and the aged MPs had overall less diversity in biofilm, based on phenotype enumeration, in comparison with the pristine MPs. Higher biofilm growth on aged MPs was confirmed using crystal violet staining, which stains the negatively charged biological compounds such as proteins and the extracellular polymeric substance matrix of the biofilm. Using this complementary approach to colony counting, the same trend of higher biofilm growth on aged MPs was found. Further studies will focus on confirming the phenotype findings using microbiome analysis following DNA extraction. This project created a methodology to quantify biofilm formation on MPs, which was used to show that MPs may accumulate more biofilms in the environment as they age under sunlight.
ContributorsMushro, Noelle (Author) / Perreault, Francois (Thesis advisor) / Hamilton, Kerry (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2022
Description
Energy can be harvested from wastewater using microbial fuel cells (MFC). In order to increase power generation, MFCs can be scaled-up. The MFCs are designed with two air cathodes and two anode electrodes. The limiting electrode for power generation is the cathode and in order to maximize power, the cathodes were made out of a C-N-Fe catalyst and a polytetrafluoroethylene binder which had a higher current production at -3.2 mA/cm2 than previous carbon felt cathodes at -0.15 mA/cm2 at a potential of -0.29 V. Commercial microbial fuel cells from Aquacycl were tested for their power production while operating with simulated blackwater achieved an average of 5.67 mW per cell. The small MFC with the C-N-Fe catalyst and one cathode was able to generate 8.7 mW. Imitating the Aquacycl cells, the new MFC was a scaled-up version of the small MFC where the cathode surface area increased from 81 cm2 to 200 cm2. While the MFC was operating with simulated blackwater, the peak power produced was 14.8 mW, more than the smaller MFC, but only increasing in the scaled-up MFC by 1.7 when the surface area of the cathode increased by 2.46. Further long-term application can be done, as well as operating multiple MFCs in series to generate more power and improve the design.
ContributorsRussell, Andrea (Author) / Torres, Cesar (Thesis advisor) / Garcia Segura, Sergio (Committee member) / Fraser, Matthew (Committee member) / Arizona State University (Publisher)
Created2022
Description
In order to optimize the ability of Geobacter sulfurreducens to produce electrical current and remediate wastewater, several physiological challenges must be overcome. The accumulation of protons at the electrode surface of a microbial fuel cell (MFC) decreases the pH, and, thus, the ability of the bacteria to maintain baseline metabolic conditions. To evaluate the extent to which this pH change hinders performance, the buffer concentration supplied to G. sulfurreducens reactors was varied. The resulting biofilms were subjected to chronoamperometry, cyclic voltammetry, and confocal microscopy to determine metabolic function and biofilm thickness. Biofilms grown with a 30-mM bicarbonate buffer experienced limitations on cell function and current output due to proton accumulation, while 90- and 150-mM conditions alleviated these limitations most of the measurements. Based on the current output, estimated biofilm thickness, and the medium-rate and slow-rate scan rate cyclic voltammetry, benefits exist for buffer concentrations greater than 30 mM. If the kinetics of G. sulfurreducens electron transfer are optimized, the potential of the technique to be implemented for energy recovery is improved.
ContributorsCoulam, Jordan (Author) / Torres, Cesar (Thesis advisor) / Delgado, Anca (Committee member) / Rittmann, Bruce (Committee member) / Arizona State University (Publisher)
Created2024
Description
Widespread use of chlorinated solvents for commercial and industrial purposes makes co-occurring contamination by 1,1,1-trichloroethane (TCA), trichloroethene (TCE), and 1,4-dioxane (1,4-D) a serious problem for groundwater. TCE and TCA often are treated by reductive dechlorination, while 1,4-D resists reductive treatment. Aerobic bacteria are able to oxidize 1,4-D, but the biological oxidation of 1,4-D could be inhibited TCA, TCE, and their reductive transformation products. To overcome the challenges from co-occurring contamination, I propose a two-stage synergistic system. First, anaerobic reduction of the chlorinated hydrocarbons takes place in a H2-based hollow-fiber “X-film” (biofilm or catalyst-coated film) reactor (MXfR), where “X-film” can be a “bio-film” (MBfR) or an abiotic “palladium-film” (MPfR). Then, aerobic removal of 1,4-D and other organic compounds takes place in an O2-based MBfR. For the reductive part, I tested reductive bio-dechlorination of TCA and TCE simultaneously in an MBfR. I found that the community of anaerobic bacteria can rapidly reduce TCE to cis-dichloroethene (cis-DCE), but further reductions of cis-DCE to vinyl chloride (VC) and VC to ethene were inhibited by TCA. Also, it took months to grow a strong biofilm that could reduce TCA and TCE. Another problem with reductive dechlorination in the MBfR is that mono-chloroethane (MCA) was not reduced to ethane. In contrast, a film of palladium nano-particles (PdNPs), i.e., an MPfR, could the simultaneous reductions of TCA and TCE to mainly ethane, with only small amounts of intermediates: 1,1-dichloroethane (DCA) (~3% of total influent TCA and TCE) and MCA (~1%) in continuous operation. For aerobic oxidation, I enriched an ethanotrophic culture that could oxidize 1,4-D with ethane as the primary electron donor. An O2-based MBfR, inoculated with the enriched ethanotrophic culture, achieved over 99% 1,4-D removal with ethane as the primary electron donor in continuous operation. Finally, I evaluated two-stage treatment with a H2-based MPfR followed by an O2-MBfR. The two-stage system gave complete removal of TCA, TCE, and 1,4-D in continuous operation.
ContributorsLuo, Yihao (Author) / Rittmann, Bruce E. (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Zhou, Chen (Committee member) / Arizona State University (Publisher)
Created2018