Matching Items (16)
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- All Subjects: Environmental engineering
- All Subjects: Biodegradation
- All Subjects: Bioremediation
- Genre: Masters Thesis
- Creators: Krajmalnik-Brown, Rosa
- Member of: Theses and Dissertations
- Resource Type: Text
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
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
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
Description
Zero-Valent Metals (ZVM) are highly reactive materials and have been proved to be effective in contaminant reduction in soils and groundwater remediation. In fact, zero-Valent Iron (ZVI) has proven to be very effective in removing, particularly chlorinated organics, heavy metals, and odorous sulfides. Addition of ZVI has also been proved in enhancing the methane gas generation in anaerobic digestion of activated sludge. However, no studies have been conducted regarding the effect of ZVM stimulation to Municipal Solid Waste (MSW) degradation. Therefore, a collaborative study was developed to manipulate microbial activity in the landfill bioreactors to favor methane production by adding ZVMs. This study focuses on evaluating the effects of added ZVM on the leachate generated from replicated lab scale landfill bioreactors. The specific objective was to investigate the effects of ZVMs addition on the organic and inorganic pollutants in leachate. The hypothesis here evaluated was that adding ZVM including ZVI and Zero Valent Manganese (ZVMn) will enhance the removal rates of the organic pollutants present in the leachate, likely by a putative higher rate of microbial metabolism. Test with six (4.23 gallons) bioreactors assembled with MSW collected from the Salt River Landfill and Southwest Regional Landfill showed that under 5 grams /liter of ZVI and 0.625 grams/liter of ZVMn additions, no significant difference was observed in the pH and temperature data of the leachate generated from these reactors. The conductivity data suggested the steady rise across all reactors over the period of time. The removal efficiency of sCOD was highest (27.112 mg/lit/day) for the reactors added with ZVMn at the end of 150 days for bottom layer, however the removal rate was highest (16.955 mg/lit/day) for ZVI after the end of 150 days of the middle layer. Similar trends in the results was observed in TC analysis. HPLC study indicated the dominance of the concentration of heptanoate and isovalerate were leachate generated from the bottom layer across all reactors. Heptanoate continued to dominate in the ZVMn added leachate even after middle layer injection. IC analysis concluded the chloride was dominant in the leachate generated from all the reactors and there was a steady increase in the chloride content over the period of time. Along with chloride, fluoride, bromide, nitrate, nitrite, phosphate and sulfate were also detected in considerable concentrations. In the summary, the addition of the zero valent metals has proved to be efficient in removal of the organics present in the leachate.
ContributorsPandit, Gandhar Abhay (Author) / Cadillo – Quiroz, Hinsby (Thesis advisor) / Olson, Larry (Thesis advisor) / Boyer, Treavor (Committee member) / Arizona State University (Publisher)
Created2019
Description
The objective of this study was to evaluate possible bioremediation strategy for aerobic aquifers by combining ZVI chemical reduction and microbial reductive dechlorination for TCE and ClO4-. To achieve this objective, continuous flow-through soil columns were used to test the hypothesis that bioaugmentation with dechlorinating enrichment cultures downstream of the ZVI injection can lead to complete reduction of TCE and ClO4- in aerobic aquifers. We obtained soil and groundwater from a Superfund site in Arizona. The experiments consisted of 205 cm3 columns packed with soil and ZVI, which fed 1025 cm3 columns packed with soil, biostimulated with fermentable substrates and bioaugmented. Aerobic groundwater was pumped through the ZVI columns. The ZVI reduced the oxidation-reduction potential (ORP) of groundwater from +150 mV to -190 mV. The reduced groundwater and biostimulation with fermentable substrates created anaerobic conditions in the bioaugmentation columns favorable for anaerobic microbial activity. Perchlorate (ClO4-) reduction to non-detectable levels occurred after biostimulation. Reduction of TCE to cis-dichloroethene, vinyl chloride and ethene was observed only after bioaugmentation. Within ~120 days of continuous columns operation, ethene was produced in the bioaugmentation columns this dechlorination activity was sustained until the end of experiments. The groundwater from the Superfund site had high concentration of sulfate (~1000 mg/L). Substantial sulfate reduction occurred in the bioaugmentation columns. Complete microbial reduction of TCE and perchlorate is usually challenging in the presence of high sulfate concentration; however, the strategy tested in this study suggests that a bioremediation scheme for simultaneous reduction of TCE and perchlorate in aerobic aquifers containing high sulfate concentration is feasible.
ContributorsRao, Shefali (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Delgado, Anca G. (Thesis advisor) / LaPat-Polasko, Laurie (Committee member) / Arizona State University (Publisher)
Created2019
Description
Bioremediation of trichloroethene (TCE) using Dehalococcoides mccartyi-containing microbial cultures is a recognized and successful remediation technology. Our work with an upflow anaerobic sludge blanket (UASB) reactor has shown that high-performance, fast-rate dechlorination of TCE can be achieved by promoting bioflocculation of Dehalococcoides mccartyi-containing cultures. The bioreactor achieved high maximum conversion rates of 1.63 ± 0.012 mmol Cl- Lculture-1 h-1 at an HRT of 3.6 hours and >97% dechlorination of TCE to ethene while continuously fed 2 mM TCE. The UASB generated bioflocs from a microbially heterogeneous dechlorinating culture and produced Dehalococcoides mccartyi densities of 1.73x10-13 cells Lculture-1 indicating that bioflocculation of Dehalococcoides mccartyi-containing cultures can lead to high density inocula and high-performance, fast-rate bioaugmentation culture for in situ treatment. The successful operation of our pilot scale bioreactor led to the assessment of the technology as an onsite ex-situ treatment system. The bioreactor was then fed TCE-contaminated groundwater from the Motorola Inc. 52nd Street Plant Superfund site in Phoenix, AZ augmented with the lactate and methanol. The bioreactor maintained >99% dechlorination of TCE to ethene during continuous operation at an HRT of 3.2 hours. Microbial community analysis under both experimental conditions reveals shifts in the community structure although maintaining high rate dechlorination. High density dechlorinating cultures containing bioflocs can provide new ways to 1) produce dense bioaugmentation cultures, 2) perform ex-situ bioremediation of TCE, and 3) increase our understanding of Dehalococcoides mccartyi critical microbial interactions that can be exploited at contaminated sites in order to improve long-term bioremediation schemes.
ContributorsFajardo-Williams, Devyn (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Torres, César I (Committee member) / Popat, Sudeep C (Committee member) / Arizona State University (Publisher)
Created2015