Matching Items (17)
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- All Subjects: Environmental engineering
- Creators: Rittmann, Bruce
- Member of: ASU Electronic Theses and Dissertations
Description
This work focuses on a generalized assessment of source zone natural attenuation (SZNA) at chlorinated aliphatic hydrocarbon (CAH) impacted sites. Given the numbers of sites and technical challenges for cleanup there is a need for a SZNA method at CAH impacted sites. The method anticipates that decision makers will be interested in the following questions: 1-Is SZNA occurring and what processes contribute? 2-What are the current SZNA rates? 3-What are the longer-term implications? The approach is macroscopic and uses multiple lines-of-evidence. An in-depth application of the generalized non-site specific method over multiple site events, with sampling refinement approaches applied for improving SZNA estimates, at three CAH impacted sites is presented with a focus on discharge rates for four events over approximately three years (Site 1:2.9, 8.4, 4.9, 2.8kg/yr as PCE, Site 2:1.6, 2.2, 1.7, 1.1kg/y as PCE, Site 3:570, 590, 250, 240kg/y as TCE). When applying the generalized CAH-SZNA method, it is likely that different practitioners will not sample a site similarly, especially regarding sampling density on a groundwater transect. Calculation of SZNA rates is affected by contaminant spatial variability with reference to transect sampling intervals and density with variations in either resulting in different mass discharge estimates. The effects on discharge estimates from varied sampling densities and spacings were examined to develop heuristic sampling guidelines with practical site sampling densities; the guidelines aim to reduce the variability in discharge estimates due to different sampling approaches and to improve confidence in SZNA rates allowing decision-makers to place the rates in perspective and determine a course of action based on remedial goals. Finally bench scale testing was used to address longer term questions; specifically the nature and extent of source architecture. A rapid in-situ disturbance method was developed using a bench-scale apparatus. The approach allows for rapid identification of the presence of DNAPL using several common pilot scale technologies (ISCO, air-sparging, water-injection) and can identify relevant source architectural features (ganglia, pools, dissolved source). Understanding of source architecture and identification of DNAPL containing regions greatly enhances site conceptualization models, improving estimated time frames for SZNA, and possibly improving design of remedial systems.
ContributorsEkre, Ryan (Author) / Johnson, Paul Carr (Thesis advisor) / Rittmann, Bruce (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2013
Description
Biofuel from microbial biomass is a viable alternative to current energy production practices that could mitigate greenhouse gas levels and reduce dependency on fossil fuels. Sustainable production of microbial biomass requires efficient utilization of nutrients like phosphorus (P). P is a limited resource which is vital for global food security. This paper seeks to understand the fate of P through biofuel production and proposes a proof-of-concept process to recover P from microbial biomass. The photosynthetic cyanobacterium Synechocystis sp. PCC 6803 is found to contain 1.4% P by dry weight. After the crude lipids are extracted for biofuel processing, 92% of the intercellular P is found within the residual biomass. Most intercellular P is associated with nucleic acids which remain within the cell after lipids are extracted. Phospholipids comprise a small percentage of cellular P. A wet chemical advanced oxidation process of adding 30% hydrogen peroxide followed by 10 min of microwave heating converts 92% of the total cellular P from organic-P and polyphosphate into orthophosphate. P was then isolated and concentrated from the complex digested matrix by use of resins. An anion exchange resin impregnated with iron nanoparticles demonstrates high affinity for P by sorbing 98% of the influent P through 20 bed volumes, but only was able to release 23% of it when regenerated. A strong base anion exchange resin sorbed 87% of the influent P through 20 bed volumes then released 50% of it upon regeneration. The overall P recovery process was able to recover 48% of the starting intercellular P into a pure and concentrated nutrient solution available for reuse. Further optimization of elution could improve P recovery, but this provides a proof-of-concept for converting residual biomass after lipid extraction to a beneficial P source.
ContributorsGifford, James McKay (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Committee member) / Vannela, Ravindhar (Committee member) / Arizona State University (Publisher)
Created2012
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
Population growth and fresh water depletion challenge drinking water utilities. Surface water quality is impacted significantly by climate variability, human activities, and extreme events like natural disasters. Dissolved organic carbon (DOC) is an important water quality index and the precursor of disinfection by-products (DBPs) that varies with both hydrologic and anthropogenic factors. Granular activated carbon (GAC) is a best available technology for utilities to meet Stage 2 D/DBP rule compliance and to remove contaminants of emerging concern (CECs) (e.g., pharmaceutical, personal care products (PCPs), etc.). Utilities can operate GAC with more efficient and flexible strategies with the understanding of organic occurrence in source water and a model capable predicting DOC occurrence. In this dissertation, it was found that DOC loading significantly correlated with spring runoff and was intensified by dry-duration antecedent to first flush. Dynamic modeling based on reservoir management (e.g., pump-back operation) was established to simulate the DOC transport in the reservoir system. Additionally, summer water recreational activities were found to raise the level of PCPs, especially skin-applied products, in raw waters. GAC was examined in this dissertation for both carbonaceous and emerging nitrogenous DBP (N-DBP) precursors (i.e., dissolved organic nitrogen (DON)) removal. Based on the experimental findings, GAC preferentially removes UV254-absorbing material, and DOC is preferentially removed over DON which may be composed primarily of hydrophilic organic and results in the low affinity for adsorption by GAC. The presence of organic nitrogen can elevate the toxicity of DBPs by forming N-DBPs, and this could be a major drawback for facilities considering installation of a GAC adsorber owing to the poor removal efficiency of DON by GAC. A modeling approach was established for predicting DOC and DON breakthrough during GAC operation. However, installation of GAC adsorber is a burden for utilities with respect to operational and maintenance cost. It is common for utilities to regenerate saturated GAC in order to save the cost of purchasing fresh GAC. The traditional thermal regeneration technology for saturated GAC is an energy intensive process requiring high temperature of incineration. Additionally, small water treatment sites usually ship saturated GAC to specialized facilities for regeneration increasing the already significant carbon footprint of thermal regeneration. An innovative GAC regeneration technique was investigated in this dissertation for the feasibility as on-site water treatment process. Virgin GAC was first saturated by organic contaminant then regenerated in-situ by iron oxide nanocatalysts mixed with hydrogen peroxide. At least 70 % of adsorption capacity of GAC can be regenerated repeatedly for experiments using modeling compound (phenol) or natural organic matter (Suwannee River humic acid). The regeneration efficiency increases with increasing adsorbate concentration. Used-iron nanocatalysts can be recovered repeatedly without significant loss of catalytic ability. This in-situ regeneration technique provides cost and energy efficient solution for water utilities considering GAC installation. Overall, patterns were found for DOC and CEC variations in drinking water sources. Increasing concentrations of bulk (DOC and DON) and/or trace organics challenge GAC operation in utilities that have limited numbers of bed-volume treated before regeneration is required. In-situ regeneration using iron nanocatalysts and hydrogen peroxide provides utilities an alternative energy-efficient operation mode when considering installation of GAC adsorber.
ContributorsChiu, Chao-An (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2012
Description
The waterways in the United States are polluted by agricultural, mining, and industrial activities. Recovery of valuable materials, such as energy and nutrients, from these waste streams can improve the economic and environmental sustainability of wastewater treatment. A number of state-of-the-art anaerobic bioreactors have promise for intensified anaerobic biological treatment and energy recovery, but they have drawbacks. The drawbacks should be overcome with a novel anaerobic biological wastewater treatment process: the anaerobic biofilm membrane bioreactor (AnBfMBR). This research works aims to advance key components of the AnBfMBR. The AnBfMBR is a hybrid suspended growth and biofilm reactor. The two main components of an AnBfMBR are plastic biofilm carriers and membranes. The plastic biofilm carriers provide the surface onto which the biofilms grow. Membranes provide liquid-solid separation, retention of suspended biomass, and a solids-free effluent. Introducing sufficient surface area promotes the biofilm accumulation of slow-growing methanogens that convert volatile fatty acids into methane gas. Biofilms growing on these surfaces will have a mixed culture that primarily consists of methanogens and inert particulate solids, but also includes some acetogens. Biomass that detaches from biofilms become a component of the suspended growth. A bench-scale AnBfMBR was designed by the AnBfMBR project team and constructed by SafBon Water Technology (SWT). The primary objective of this thesis project was to evaluate the ability of plastic biofilm carriers to minimize ceramic-membrane fouling in the AnBfMBR setting. A systematic analysis of mixing for the bench-scale AnBfMBR was also conducted with the plastic biofilm carriers. Experiments were conducted following a ‘run to failure’ method, in which the ceramic membranes provide filtration, and the time it takes to reach a ‘failure transmembrane pressure (TMP)’ was recorded. The experiments revealed two distinct trends. First, the time to failure TMP decreased as mixed liquor suspended solids concentration (MLSS) concentration increased. Second, increasing the carrier fill extend the time to failure, particularly for higher MLSS concentrations. Taken together, the experiments identified an optimized “sweet spot” for the AnBfMBR: an operating flux of 0.25-m/d, a failure TMP of 0.3-atm pressure, MLSS of 5,000 – 7,500 mg/L, and 40% carrier fill.
ContributorsRoman, Brian Aaron (Author) / Rittmann, Bruce (Thesis advisor) / Boltz, Joshua (Committee member) / Perreault, Francois (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2021
Description
Widespread use of halogenated organic compounds for commercial and industrial purposes makes halogenated organic pollutants (HOPs) a global challenge for environmental quality. Current wastewater treatment plants (WWTPs) are successful at reducing chemical oxygen demand (COD), but the removal of HOPs often is poor. Since HOPs are xenobiotics, the biodegradation of HOPs is usually limited in the WWTPs. The current methods for HOPs treatments (e.g., chemical, photochemical, electrochemical, and biological methods) do have their limitations for practical applications. Therefore, a combination of catalytic and biological treatment methods may overcome the challenges of HOPs removal.This dissertation investigated a novel catalytic and biological synergistic platform to treat HOPs. 4-chlorophenol (4-CP) and halogenated herbicides were used as model pollutants for the HOPs removal tests. The biological part of experiments documented successful co-oxidation of HOPs and analog non-halogenated organic pollutants (OPs) (as the primary substrates) in the continuous operation of O2-based membrane biofilm reactor (O2-MBfR). In the first stage of the synergistic platform, HOPs were reductively dehalogenated to less toxic and more biodegradable OPs during continuous operation of a H2-based membrane catalytic-film reactor (H2-MCfR). The synergistic platform experiments demonstrated that OPs generated in the H2-MCfR were used as the primary substrates to support the co-oxidation of HOPs in the subsequent O2-MBfR. Once at least 90% conversation of HOPs to OPs was achieved in the H2-MCfR, the products (OPs to HOPs mole ratio >9) in the effluent could be completely mineralized through co-oxidation in O2-MBfR. By using H2 gas as the primary substrate, instead adding the analog OP, the synergistic platform greatly reduced chemical costs and carbon-dioxide emissions during HOPs co-oxidation.
ContributorsLuo, Yihao (Author) / Rittmann, Bruce (Thesis advisor) / Krajmalnik-Brown, Rosa (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2022
Description
Bacterial biofilms exist on surfaces within pressurized water systems, posing threats to water quality and causing fouling or microbial induced corrosion. Germicidal UV irradiation has shown promise in deactivating planktonic pathogens in water but challenges in delivering light to surfaces where biofilms exist have limited advancement in understanding biofilm response to UV-C light. This dissertation aims to overcome the limitation of delivering UV-C light through use of side-emitting optical fibers (SEOFs), advance capabilities to produce SEOFs and understand if a minimum UV-C irradiance can prevent biofilm formation. Two scalable manufacturing approaches were developed for producing kilometer lengths of thin (≤500-µm) and physically flexible SEOFs. One strategy involved dip-coating amine-functionalized SiO2 nanoparticles (NPs) on bare optical fiber, followed by a coating of UV-C transparent polymer (CyTop). I showed that NPs closer to the surface achieved with higher ionic strength solutions increased side-scattering of UV-C light. This phenomenon was primarily attributed to the interaction between NPs and evanescent wave energy. The second strategy omitted NPs but utilized a post-treatment to the UV-C transparent polymer that increased surface roughness on the outer fiber surface. This modification maintained the physical flexibility of the fiber while promoting side-emission of UV-C light. The side emission was due to the enhancement of refracted light energy. Both methods were successfully scaled up for potential commercial production.
Experimental platforms were created to study biofilm responses to UV light on metal or flexible plastic pipe (1/4” ID) surfaces. Delivering UV-C light via SEOFs with irradiances >8 µW/cm2 inhibited biofilm accumulation. Neither UV-A nor UV-B light inhibited biofilm growth. At very low UV-C irradiance (<3 µW/cm2), biofilms were not inhibited. Functional genomic analysis revealed that biofilms irradiated by insufficient UV-C irradiance upregulated various essential genes related to DNA repair, energy metabolism, quorum sensing, mobility, and EPS synthesis. When net UV-C biofilm inactivation rates exceeded the biofilm growth rate, biofilms were inhibited. Insights gained from this dissertation work shed light on the prospective applications of UV-C technology in addressing biofilm challenges within water infrastructure across multiple sectors, from potable water to healthcare applications.
ContributorsZhao, Zhe (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Committee member) / Abbaszadegan, Morteza (Committee member) / Álvarez, Pedro (Committee member) / Arizona State University (Publisher)
Created2023
Description
Mining-influenced water (MIW) is an acidic stream containing a typically acidic pH (e.g., 2.5), sulfate, and dissolved metal(loid)s. MIW has the potential to affect freshwater ecosystems and thus MIW requires strategies put in place for containment and treatment. Lignocellulosic sulfate-reducing biochemical reactors (SRBRs) are considered a cost-effective passive treatment for MIW and have been documented to continuously treat MIW at the field-scale. However, long-term operation (> 1 year) and reliable MIW treatment by SRBRs at mining sites is challenged by the decline in sulfate-reduction, the key treatment mechanism for metal(loid) immobilization. This dissertation addresses operational designs and materials suited to promote sulfate reduction in lignocellulosic SRBRs treating MIW. In this dissertation I demonstrated that lignocellulosic SRBRs containing spent brewing grains and/or sugarcane bagasse can be acclimated in continuous mode at hydraulic retention times (HRTs) of 7-12 d while simultaneously removing 80 ± 20% – 91 ± 3% sulfate and > 98% metal(loid)s. Additionally, I showed that decreasing the HRT to 3 d further yields high metal(loid) removal (97.5 ± 1.3% – 98.8 ± 0.9%). Next, I verified the utility of basic oxygen furnace slag to increase MIW pH in a two-stage treatment involving a slag stage and an SRBR stage containing spent brewing grains or sugarcane bagasse. The slag reactor from the two-stage treatment increased MIW pH from 2.6 ± 0.2 to 12 ± 0.3 requiring its re-combination with fresh MIW to reduce pH to 5.0 ± 1.0 prior to entering the lignocellulosic SRBRs. The lignocellulosic SRBRs from the two-stage treatment successfully continued to remove metal(loid)s, most notably cadmium, copper, and zinc at ≥ 96%. In additions to these outcomes, I performed a metadata analysis of 27 SRBRs employing brewers spent grains, sugarcane bagasse, rice husks and rice bran, or a mixture of walnut shells, woodchips, and alfalfa. I found that sugarcane bagasse SRBRs can remove between 94 and 168 mg metal(loid) kg–1 lignocellulose d–1. In addition, Bacteroidia relative abundances showed a positive correlation with increasing sulfate removal across all 27 SRBRs and are likely essential for the degradation of lignocellulose providing electron donors for sulfate reduction. Clostridia and Gammaproteobacteria were negatively correlated with sulfate reduction in the 27 SRBRs, however SRBRs that received alkalinized MIW had lower relative abundances of Clostridia, Gammaproteobacteria, and methanogenic archaea (known competitors for sulfate-reducing bacteria). Overall, my dissertation provides insight into lignocellulosic materials and operational designs to promote long-term sulfate-reduction in lignocellulosic SRBRs treating MIW.
ContributorsMiranda, Evelyn Monica (Author) / Delgado, Anca G (Thesis advisor) / Santisteban, Leonard (Committee member) / Hamdan, Nasser (Committee member) / Rittmann, Bruce (Committee member) / Arizona State University (Publisher)
Created2023
Description
While most household surfactants are biodegradable in aerobic conditions, their presence in a microbiological treatment process can lead to the proliferation of antimicrobial-resistance genes (ARG) in bacteria, such as Pseudomonas aeruginosa. Surfactants can be cationic, anionic, or zwitterionic, and these different classes may have different effects on the proliferation of ARG. This study evaluated how the three classes of surfactants affected the microbial community’s structure and ARG in O2-based membrane biofilm reactors (O2-MBfRs) that provided at least 98% surfactant removal. Cationic cetrimonium bromide (CTAB) had by far the strongest impact with highest ARG abundance in the biofilm. In particular, Pseudomonas and Stenotrophomonas, the two main genera in the biofilm treating CTAB, were highly correlated to the abundance of ARG for efflux pumps and antibiotic inactivation. CTAB also promoted potential of horizontal gene transfer (HGT) of ARG. Combining results from the metabolome and metagenome identified four possible pathways for CTAB biodegradation. Of special important is a new pathway: β-carbon oxidation of CTAB to produce betaine. An insufficient nitrogen source could lead to irreversible ARB and ARG enrichment in the MBfR biofilm. Finally, a two-stage O2-MBfR successfully removed a high concentration (730 mg/L) of CTAB: Partial CTAB removal in the Lead reactor relieved inhibition in the Lag reactor. Metagenomic analysis also revealed that the Lag reactor was enriched in genes for CTAB and metabolite oxygenation.
ContributorsZheng, Chenwei (Author) / Rittmann, Bruce (Thesis advisor) / Delgado, Anca (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Lai, Yen-Jung (Committee member) / Arizona State University (Publisher)
Created2023
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