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Nitroaromatic compounds are a class of toxic, synthetic chemicals used in a variety of industries, including explosives, pharmaceuticals, and pesticides. They may enter the environment through wastewater discharge or deposition onto soil surfaces, i.e. on firing ranges. Rainwater can dissolve nitroaromatics and transport them into the subsurface, where they may encounter anaerobic conditions. There, soil microbes and/or reduced minerals may catalyze the reduction of nitroaromatics to aromatic amines via three, two-electron transfers per nitro group. This study builds on previous work on the fate of 2,4-dinitroanisole (DNAN), an insensitive munitions compound that is replacing trinitrotoluene (TNT) in explosives formulations to reduce the risk of accidental detonations. It was found that DNAN formed azo dimers and trimers, which can be more toxic than nitroaromatic compounds, when incubated in anaerobic sludge and soil. Furthermore, 14C-radiolabeled DNAN became immobilized to the insoluble fraction of soil organic matter (humus) in soil incubations, which was enhanced under reducing conditions. This could be used as a strategy to “remove” nitroaromatics from the subsurface environment. The objective of this work is to understand the mechanisms that caused DNAN to form azo compounds and become incorporated into humus in anaerobic incubations. The hypothesis was that once DNAN became reduced biologically (catalyzed by microbes), abiotic nucleophilic substitution reactions occurred, either between reduced intermediates of DNAN to form azo compounds or between humic moieties, such as quinones, and DNAN-derived aromatic amines to form “bound residues.” These reactions were originally thought to take place only under aerobic conditions, with aromatic amines forming free radical species. We conducted biological incubations of 4-nitroanisole in anaerobic granular sludge and chemical pairing experiments between reduced 4-nitroanisole intermediates, 4-nitrosoanisole and 4-amin

Engineered nanoparticles (NPs) have many unique electronic, chemical, and optical properties. Gallium arsenide (GaAs) NPs and indium arsenide (InAs) NPs are being considered in different semiconductors and electronic devices due to their favorable properties such as high electron mobility with wide and adjustable band gaps and their reduced power consumption. Polishing of thin films in a process known as chemical and mechanical planarization (CMP) could lead potentially to the release of byproducts from GaAs and InAs, such as soluble III-V materials (Ga, In, and arsenic (As) species) and particulate III-V materials (GaAs NPs, InAs NPs, gallium oxide (Ga2O3), indium oxide (In2O3)) into the wastewater stream. Furthermore, the CMP process utilizes cerium oxide (CeO2), silica (SiO2), and alumina (Al2O3) as abrasive particles in slurries to polish and create flat surfaces. As a result, CeO2, SiO2, and Al2O3 NPs will also be present in the waste streams of the semiconductor industry. Additionally, some NPs can promote the transport of toxic chemicals into cells through the “Trojan Horse” effect, which can potentially alter the toxicity of the NPs via adsorbed chemicals. Among the soluble III-V ions, arsenic is a concern for the Trojan Horse effect because it is a highly toxic and carcinogenic element with soluble species that can become adsorbed onto NP surfaces. Although the toxicity of soluble arsenic species is well established, little is known about the potential toxicity of other soluble III-V materials and III-V NPs. Therefore, it is important to study and understand the environmental fate and toxicity of these materials. The objectives of this work are to investigate the potential toxicity and environmental fate of III-V nanomaterials and byproducts that could be formed in CMP slurries of semiconductor manufacturing effluents as well as to study the impact of CeO2 NPs on the sorption and toxicity of As species. The acute toxicity of GaAs, InAs, Ga2O3, and In2O3 par

Nutrient supply is one of the critical obstacles limiting algal biofuel industrialization. It has been demonstrated that anaerobic digestion is an effective method to release nitrogen and phosphorus from algal biomass, but the nutrient recycle system of cultivation-extraction-digestion-recultivation has not been completely evaluated. In this dissertation, algae were cultivated on nutrients released from anaerobic digestion of lipid extracted algae. Algae recovery was calculated to demonstrate the feasibility of the nutrient recycle process. The quality of recultivated algae for algal biofuel was validated and the limiting nutrient was analyzed. Initial nitrogen concentration was shown to have significant impact on the entire process including algae and lipid productivity, as well as lipid and nitrogen content of the biomass. The nitrogen balance for each step of the entire process was closed within experimental error. Total nitrogen recoveries throughout the whole process were all approximately 65% regardless of the different initial nitrogen concentration. The biggest nitrogen losses occurred in lipid extraction and algae cultivation steps. The work described in this dissertation demonstrates the effectiveness of this nutrient recycle system, and therefore provides a promising method to significantly lower nutrient cost for algal biofuel production. Nitrogen analysis validates the experimental and analytical methods in this dissertation and provides points of future work to further optimize this recycle process.

We initially studied the treatment of acid rock drainage using a sulfate-reducing bioreactor with zero-valent iron as the electron donor. The results demonstrate that this electron donor can serve as the sole exogenous slow-release electron donor to drive sulfate reduction over 400 operational days at short HRTs (1-3 days). The synthetic acid rock drainage contained high heavy metal concentrations (up to 50 mg/L of copper) and pH values ranging from 3.0 to 7.0. Treatment of this acid rock drainage efficiently removed Cu, Cd and Pb (>99.7%) and increased pH to circumneutral values (7.3-7.7). Elemental analysis indicated that formation of insoluble metal sulfides was responsible for the effective metal removal in the zero valent iron columns. In the second study, three inoculated columns containing anaerobic granular sludge were fed a synthetic medium containing H₂SO₄ and Cu²⁺ during the experimental period of 4 months. Algae biomass promoted 80% of sulfate removal (12.7 mg SO₄²⁻ d-1), enabling near complete Cu removal (>99.5 %), and alkalinity generation, raising the effluent pH to 6.5. In the algae amended columns Cu²⁺ was precipitated with biogenic H2S produced by sulfate reduction. Whole cell algae and lipid extracted algae biomasses were both shown to be effective e-donors in driving sulfate reduction of ARD, thus enabling the precipitation and removal of Cu²⁺. The precipitate retained in the columns was composed mostly of insoluble copper sulfide formed from the biogenic sulfide, as shown by sequential extraction and X-ray diffraction. In the third study, several pretreatments, i.e., thermal, chemical, sonication and combinations thereof, that enhance anaerobic biodegradability of Chlorella protothecoides biomass were evaluated. The results demonstrate that anaerobic digestion of pretreated Chlorella protothecoides biomass generates energy-rich methane and recovers nitrogen nutrients. Sonication of algal biomass under optimized conditions provided a significant

Anaerobic ammonium oxidizing (Anammox) bacteria are known to utilize ammonium and nitrite as electron donor and acceptor, respectively, to produce nitrogen gas as their main final product with by-product formation of nitrate. Anammox bacteria provide the advantages of significant saving in aeration, no requirement for external electron donor, reduction of greenhouse gas emission, lowered sludge production, and higher specific nitrogen-removing activity compared to the conventional nitrification-denitrification process used in nutritent-N removal. Therefore, the anammox process has recently been widely studied and applied as a state-of-the-art biotechnology to remove nutrient nitrogen from ammonium-rich wastewater. However, the inhibitory impact of nitrite (one of the two main substrates) on the anammox process has been reported in both lab- and full-scale anammox systems, which limits the application of anammox process. Based on the current knowledge, a wide range of nitrite concentrations causing anammmox inhibition was reported to be correlated to the pH and energy status of anammox bacteria, and the understanding of the mechanisms of nitrite inhibition to anammox bacteria is still not clear. Therefore, the purpose of this work is to investigate the mechanism of nitrite inhibition and develop a strategy for recovering nitrite inhibited anammox processes. The effects of pre-exposing anammox bacteria to nitrite alone on their subsequent activity and metabolism after ammonium has been added was evaluated in batch bioassays. The results showed that pre-exposure of anammox bacteria to nitrite without ammonium caused dramatic inhibition with observed 50% inhibition concentration (IC₅₀) of 52 mg NO₂⁻-N L⁻¹, compared to an IC₅₀ of 384 mg NO₂⁻-N L⁻¹ obtained in the control group with ammonium and nitrite added simultaneously. The accumulated nitric oxide (NO) found in the group with anammox bacteria pre-inhibited by nitrite indicated that pre-exposure to nitrite most likel

Engineered nanomaterials are increasingly used in a variety of industrial processes and consumer products. Numerous studies have reported toxicity of different NPs during the last years. Thus, there are growing concerns about the potential impacts to the health and environment of engineered nanoparticles (NPs). However, some methodological problems complicate the interpretation of nanotoxicity studies. On the one hand, some NPs have shown to interfere with classical toxicity assays based on colorimetric or fluorescent measurements. On the other hand, most NPs tend to aggregate in media used in toxicity tests, which complicates the interpretation of the toxicity results. The first objective of this dissertation was to evaluate a novel impedance-based and label-free real time cell analyzer (RTCA) as a high throughput method for screening the cytotoxicity of nanoparticles and to validate the RTCA results using a conventional cytotoxicity test (MTT). Several inorganic NPs were tested for potential cytotoxicity to human bronchial epithelial cells (16HBE14o-). In general, there was a good correlation in cytotoxicity measurements between the two methods. Moreover, none of the NPs tested showed interference with the impedance measurements performed by the RTCA system. The results demonstrate the potential and validity of the impedance-based RTCA technique to rapidly screen for NP toxicity. The second objective of this dissertation was to assess the toxicity of different inorganic NPs to the eukaryotic cell model Saccharomyces cerevisiae, and to test the influence of NP aggregation state in their toxicity. Nanotoxicity was assessed by monitoring oxygen consumption in batch cultures and by analysis of cell membrane integrity. Mn₂O₃ NPs showed the highest inhibition of O₂ consumption and cell membrane damage, while the other NPs caused low or no toxicity to the yeast. Most NPs showed high tendency to aggregate in the assay medium, so a non-toxic dispersant was used to improve

Engineered nanomaterials are increasingly used in a variety of industrial processes and consumer products. Numerous studies have reported toxicity of different NPs during the last years. Thus, there are growing concerns about the potential impacts to the health and environment of engineered nanoparticles (NPs). However, some methodological problems complicate the interpretation of nanotoxicity studies. On the one hand, some NPs have shown to interfere with classical toxicity assays based on colorimetric or fluorescent measurements. On the other hand, most NPs tend to aggregate in media used in toxicity tests, which complicates the interpretation of the toxicity results. The first objective of this dissertation was to evaluate a novel impedance-based and label-free real time cell analyzer (RTCA) as a high throughput method for screening the cytotoxicity of nanoparticles and to validate the RTCA results using a conventional cytotoxicity test (MTT). Several inorganic NPs were tested for potential cytotoxicity to human bronchial epithelial cells (16HBE14o-). In general, there was a good correlation in cytotoxicity measurements between the two methods. Moreover, none of the NPs tested showed interference with the impedance measurements performed by the RTCA system. The results demonstrate the potential and validity of the impedance-based RTCA technique to rapidly screen for NP toxicity. The second objective of this dissertation was to assess the toxicity of different inorganic NPs to the eukaryotic cell model Saccharomyces cerevisiae, and to test the influence of NP aggregation state in their toxicity. Nanotoxicity was assessed by monitoring oxygen consumption in batch cultures and by analysis of cell membrane integrity. Mn₂O₃ NPs showed the highest inhibition of O₂ consumption and cell membrane damage, while the other NPs caused low or no toxicity to the yeast. Most NPs showed high tendency to aggregate in the assay medium, so a non-toxic dispersant was used to improve

Arsenic (As) is a highly toxic chemical that is widely distributed in groundwater around the world. As-bearing sulfide minerals (ASM) are known to contribute to high background concentrations of As in groundwater in regions where the geochemistry of the parent material is dominated by sulfide minerals. The fate of As in groundwater depends on the activity of microorganisms which can oxidize arsenite (Asᴵᴵᴵ), or reduce arsenate (Asᵛ). In oxidizing environments, Asᵛ is the predominant species, and the accumulation of As is limited by the sorption of As onto iron (Fe) oxides and hydroxides. Under reducing environments, Asᴵᴵᴵ is the predominant specie, and while the sorption strength of Asᴵᴵᴵ on the Fe-surface of Fe (oxy)hydroxides is weaker, the accumulation of As in water can be limited by the precipitation of As as part of an ASM. The main aim of this research is to study the impact of microbial activity on the mobilization and immobilization of As in the environment. The first objective of this research was to characterize the metabolic activity of three Asᴵᴵᴵ-oxidizing bacteria, Azoarcus sp. pb-1 strain EC1, Azoarcus sp. pb-1 strain EC3 and Diaphorobacter sp. pb-1 strain MC, isolated from a non-contaminated, pristine environment. These Asᴵᴵᴵ-oxidizing bacteria demonstrated a great metabolic flexibility to use oxygen and nitrate to oxidize Asᴵᴵᴵ as well as organic and inorganic substrates as alternative electron donors (e-donors) explains their presence in non-As-contaminated environments. The findings suggest that at least some Asᴵᴵᴵ-oxidizing bacteria are flexible with respect to electron-acceptors and e-donors and that they are potentially widespread in low As concentration environments. The second objective of this research was to investigate the stability of orpiment (As₂S₃) and arsenopyrite (FeAsS), at circumneutral pH and 30°C, under aerobic- and or anoxic conditions (nitrate amended as electron acceptor (e-acceptor)), in order to assess the feasibility of im

For perhaps eleven months of the year, surface water flow in the Santa Cruz River consists entirely of wastewater effluent from the Roger Road Wastewater Treatment Plant (RRWTP) and the Ina Road Water Pollution Control Facility (IRWPCF). Like other conventional plants that treat primarily domestic wastewater, effluents from the RRWTP and IRWPCF contain numerous trace organic contaminants--an unintended consequence of our reliance on water to carry waste from points of generation to central treatment facilities. The fates of these compounds in the environment are not entirely clear since the instruments necessary to measure process-dependent changes in concentrations at levels relevant to environmental health are just now coming into widespread use. Chemical fate during planned or incidental infiltration and transport to points of recovery is therefore relevant to the quality of delivered water, as water and contaminants are transported in surface waters and unintentionally reused. Interventions that reduce human and environmental exposures to contaminants present in this water, including natural processes, are thus important to protect human health. Here, it is hypothesized that there is a reasonably continuous discharge of trace organics from wastewater treatment effluents to the Santa River. Because the river is effluent dependent, and travel times can be determined from gauging station flows, some measure of fate and transport of trace organics in the surface water can be obtained. The relative levels of trace contaminants in wastewater treatment plant effluent and downstream waters will provide compound specific attenuations due to dilution with native ground water, sorption on sediments, biodegradation, etc. If destructive mechanisms can be distinguished from dilution, the resultant analysis will be of general interest--an indication of the combination of travel distance and time of travel that is necessary to protect the public when recovered water is eligible

Uranium contamination of groundwater from mining and milling operations is an environmental concern. Reductive precipitation of soluble and mobile hexavalent uranium (U(VI)) contamination to insoluble and immobile tetravalent uranium (U(IV)) constitutes the most promising remediation approach for uranium in groundwater. Previous research has shown that many microorganisms are able to catalyze this reaction in the presence of suitable electron-donors. The purpose of this work is to explore lowcost, effective alternatives for biologically catalyzed reductive precipitation of U(VI). Methanogenic granular sludge from anaerobic reactors treating industrial wastewaters was tested for its ability to support U(VI)-reduction. Due to their high microbial diversity, methanogenic granules displayed intrinsic activity towards U(VI)-reduction. Endogenous substrates from the slow decomposition of sludge biomass provided electron-equivalents to support efficient U(VI)-reduction without external electrondonors. Continuous columns with methanogenic granules also demonstrated sustained reduction for one year at high uranium loading rates. One column fed with ethanol, only enabled a short-term enhancement in the uranium removal efficiency, and no enhancement over the long term compared to the endogenous column. Nitrate, a common co-contaminant of uranium, remobilized previously deposited biogenic U(IV). U(VI) also caused inhibition to denitrification. An enrichment culture (EC) was developed from a zero-valent iron (Fe⁰)/sand packed-bed bioreactor. During 28 months, the EC enhanced U(VI)-reduction rates by Fe⁰ compared with abiotic Fe⁰ controls. Additional experiments indicated that the EC prevented the passivation of Fe⁰ surfaces through the use of cathodic H₂ for the reduction of Fe(III) in passivating corrosion mineral phases (e.g. magnetite) to Fe²⁺. This contributed to the formation of secondary minerals more enriched with Fe(II), which are known to be chemically reactive with U(V

The new Maximum Contaminant Level (MCL) of arsenic in drinking water has caused a significant increase in the volume of arsenic-bearing solid residuals (ABSR) generated by drinking water utilities. Iron sorbents are being widely utilized for water treatment and comprise the bulk of the waste generated. Based on Toxicity Characteristic Leaching Procedure (TCLP) results, these ABSR may be disposed in municipal solid waste (MSW) landfills. However unlike the conditions in the TCLP, a mature landfill is a biotic, reducing environment where iron and arsenic may be reduced and, as a consequence, arsenic may be released to the leachate. The primary route of iron reduction in landfills is microbially mediated and biomineralization is a common by-product. In this case, biomineralization is the transformation of ferric (hydr)oxides into ferrous iron crystalline forms, such as siderite, vivianite and iron sulfide, and into mixed valent mineral forms, such as magnetite and green rust. In this work, biomineralization is evaluated as a possible process to control arsenic leaching from ABSR in landfills. Understanding biomineralization impacts, however, requires a precise knowledge of the various mechanisms of arsenic release under landfill conditions. To this end, we describe flow-through laboratory column experiments in which controlled conditions similar to those found in a mature landfill prevail. In these simulated landfill column experiments, the results show that biomineralization would naturally occur in typical non-hazardous MSW landfills. Without any intervention, As leaching was higher than 80% of the initial quantity loaded, in contrast to Fe leaching values, which were less than 10% of the initial quantity loaded. Phosphate and bicarbonate played an important role in the experiments, as probably arsenic competitors for sorption sites and as components of the secondary iron mineral phases, vivianite and siderite respectively. Although these minerals have less surface a

Semiconductor manufacturing is one of the most advancing, growing and evolving industries. The production of semiconductors presents several challenges, both technologically and environmentally. The amount and complexity of the chemical substances utilized in the manufacturing process has been growing exponentially, and new chemicals are often introduced to the process and the environment. Two steps of this process play a special important role in the introduction of new chemical and demand of natural resources: Chemical Mechanical Planarization (CMP) and Photolithography.Wastewaters from the semiconductor manufacturing are complex and have several chemicals in different concentrations. Heavy metals, acids, chelators, surfactants and other chemicals are found in semiconductor effluents. Part of the scope of this study is to evaluate and remediate wastewaters produced in semiconductor manufacturing.During the development of this project it was found that copper can be successfully removed and recovered from CMP wastewaters by the use of a sulfate reducing bioreactor and a crystallization reactor, promoting precipitation of copper sulfides on the surface of silica sand. High removal and recovery efficiencies were found as result of the study. Another finding include that citrate is a readily biodegradable compound which can be successfully utilized as electron donor for anaerobic processes such as methanogenesis and sulfate reductions. However other important chelator, like EDTA, can cause toxicity to these microorganisms and affect important biological processes. PFOS is an important chemical for the semiconductor industry; however, the physical and chemical properties make this compound persistent in the environment and bioaccumulative. New substitutes for PFOS were tested and evaluated for their environmental impact. It was found that perfluorination plays an important role in the chemical properties of PFOS and removal of this characteristic improves the environme

Domestic wastewater is the most abundant type of wastewater. Direct discharge of untreated domestic wastewater has environmental and public health risks due to the presence of organics, nutrients and pathogens. Application of anaerobic processes for the treatment of domestic sewage, which at present is largely treated by aerobic processes, has drawn considerable attention recently. Anaerobic processes can be applied for the removal of organic matter (methanogenesis) and nitrogen (anaerobic ammonium oxidation (Anammox)).The toxicity of fluoride to methanogenesis was investigated. The results indicate that acetoclastic were more susceptible to fluoride than hydrogenotrophic methanogens. The concentration of fluoride causing 50% inhibition (IC50) to acetoclastic ranged from 18.1 to 155.7 mg L-1 while for hydrogenotrophic methanogens was > 400.0 mg L-1.The feasibility of a combined system consisting of anaerobic up-flow anaerobic sludge blanket (UASB) followed by aerobic activated sludge (AS) reactor for removal of carbonaceous and nitrogenous contaminants from strong synthetic sewage (2.5 g chemical oxygen demand (COD) L-1) was also studied. The average combined removal of total COD, volatile fatty acids (VFA) and protein was higher than 89.0%, 99.0% and 97.0%; respectively. Extensive nitrification (96.0%) was observed when dissolved oxygen (DO) concentration was > 2.0 mg L-1. In contrast, only partial nitrification occurred when the AS received high organic loads and/or the DO level was below 2.0 mg L-1.The inhibitory effect of nitrite and nitrate on methanogenesis was evaluated. Methanogenic activity was inhibited by the presence of NOx- compounds (i.e., nitrite and nitrate). The inhibition imparted by nitrate was not due to the nitrate itself, but rather to its reduced intermediate, nitrite. The toxicity of NOx- to methanogens was found to be reversible after all the NOx- were reduced during denitrification.Moreover, the development of Anammox enrichment cultures wa

Arsenic is a naturally occurring contaminant in ground water. The link between human exposure to elevated levels of arsenic and the increase in cancerous and non-cancerous diseases is well documented. Consequently, arsenic removal from drinking water has been thoroughly investigated.Lowering the maximum contaminant limit of arsenic (from 50 to 10 ppb) will burden small water utilities, who either lack the financial or technical ability to comply. Adsorption onto solid media has been one of the most attractive options for small water utilities (EPA, 2001), but this process generates huge amounts of arsenic bearing solid residuals (ABSRs) complicating further this matter.Numerous studies have suggested that the Toxicity Characteristics Leaching Procedure (TCLP) does not properly reflect the actual leaching behavior of ASBRs under landfills (Ghosh et al., 2004). This work focuses on testing different arsenic iron- oxide and non- iron- based sorbents, likely to be used for arsenic removal, and assessing the long term behavior of these sorbents under landfill conditions. Our results indicate that microbial processes play a major role in the mobilization of As from granular ferric hydroxide (GFH). Long term operation of GFH sorbent showed that Fe (III) was reduced to Fe(II) and As(V) was reduced to As(III) under anaerobic/reducing conditions. Under semi batch landfill simulation experiments, our results show that non iron based media leached arsenic above the Toxicity Characteristics limit (TC) and it was observed that sorbate (As) might leach at a faster rate than the sorbent itself. It is thought that arsenic mobilization from iron-based sorbent occurs mostly due to iron reduction and its subsequent dissolution. However, measured arsenic leaching rates from the sorbents used in this study are comparable with that of the ferric hydroxide media, which indicates that the mechanism of arsenic mobilization might be independent of the possible dissolution of the sorbent. Desp

Arsenic (As) contamination of groundwater and surface water is a worldwide problem. Exposure to arsenic in drinking water is an important current public health issue. Arsenic is well known for its carcinogenic and teratogenic effects. The U.S. Environmental Protection Agency (USEPA) has recently enacted a stricter drinking water standard for arsenic that lowers the maximum contaminant level (MCL) from 50 to 10 ug l-1.Localized elevated As concentrations in groundwater or surface water have been attributed to the natural release of As from the weathering of As bearing minerals. Microbial reduction of arsenate (As(V)) to arsenite (As(III)) and ferric (hydr)oxides to Fe(II) is hypothesized to be the dominant mechanisms of As mobilization in subsurface environments. If oxidizing conditions can be restored, As can be immobilized by the formation of As(V) and ferric (hydr)oxides. As(V) is more strongly adsorbed than As(III) at circumneutral conditions by common non-iron metal oxides in sediments such as those of aluminum. Ferric (hydr)oxides have strong affinity for both As(III) and As(V) in circumneutral environments. Oxygen can be introduced into the anaerobic zone by injection of gaseous O2 to promote oxidation reactions of As(III) and Fe(II), but O2 is poorly soluble and chemically reactive and thus difficult to distribute in the subsurface. Nitrate or chlorate can be considered as alternative oxidants with advantages over elemental oxygen due to their high aqueous solubility and lower chemical reactivity which together enable them to be better dispersed in the saturated subsurface.The objective of this study is to evaluate the importance of anoxic oxidation of As(III) to As(V) by anaerobic microorganisms such as chemolithotrophic denitrifying bacteria and chlorate respiring bacteria in the biogeochemical cycle of arsenic. This study also investigated a arsenic potential bioremediation strategy based on injecting nitrate or chlorate into contaminated groundwat

Perfluorooctane sulfonate (PFOS) and related perfluoroalkyl surfactants (PFAS) are ubiquitous contaminants of increasing public concern due to their environmental persistence, toxicity, and bioaccumulation. These perfluorinated compounds have been used for more than half a century in a wide variety of industrial and consumer products ranging from stain repellents such as Teflon® to aqueous fire-fighting foams and to grease-proof food packing. The public health and environmental risks posed by PFAS have driven environmental agencies and the industry to restrict their use to specific applications where they cannot be replaced by other chemicals. The sources and pathways of PFOS and its derivatives in the environment are not well understood. Analysis of environmental samples is critical to understand the fate, transport and persistence of these emerging contaminants. Techniques based on fluorine nuclear magnetic resonance (¹⁹F NMR) spectroscopy and high performance liquid chromatography (HPLC) with suppressed conductivity detection were successfully developed to monitor the presence of PFAS in water samples. Chromatographic separation of C₄ to C₈ PFAS surfactants was achieved using a C₁₈ reversed-phase column and a mobile phase consisting of a mixture of boric acid and acetonitrile at mixing ratios ranging from 75:25 to 45:55 (v/v). The combination of these two techniques was very effective for characterization and routine quantification of PFOS and related chemicals. Analytical methods based on ¹⁹F NMR, HPLC-suppressed conductivity detection, and liquid chromatography with tandem mass spectrometry (LC-MS/MS) were employed to characterize commercial PFOS samples. Linear and branched PFOS isomers in a percentage ratio of 75:25 were identified. Municipal wastewater treatment systems are one of the major sources of PFAS emissions into the environment. The presence of PFAS in sewage sludge from two wastewater treatment plants in Tucson, Arizona, was investigated. Sludge sa

Arsenic (As) is a common occurring environmental pollutant. The USEPA has a stricter regulation for arsenic in drinking water (10 ug/L). Small drinking water suppliers from regions with high arsenic backgrounds levels, will need to remove arsenic from drinking water in order to meet the new standard. The proposed treatment by the USEPA is the oxidation of arsenite (AsIII) to arsenate (AsV) followed by the adsorption onto metal oxides (e.g. granular ferrihydrite (GFH)). Large amounts of arsenic-bearing solid waste will be generated and disposed in municipal landfills based on EPA's recommendation. The alkaline and anaerobic conditions prevailing in mature landfills combined with the high content of organic matter and the microbial activity prevailing in landfill could play an important role in the biotransformation and mobilization of sorbed arsenic in landfills. The extensive use of organo arsenical compounds such as pesticides in agriculture has become an emerging source of arsenic contamination in the environment. Roxarsone (4-hydroxy-3-nitrophenylarsonic acid) is a compound supplemented in the poultry feed to enhance growth by controlling coccidian parasites. Chickens excrete the roxarsone without changes in its chemical structure. Land application of chicken manure in agricultural fields is a common practice. Approximately 900 metric tons of roxarsone is estimated to be released into environment in the U.S. annually. The environmental impact is significant when considering that these quantities of arsenic are spread onto relative small land areas in the direct vicinity of poultry houses. The aim of this study is to evaluate the role of anaerobic bioconversion on the fate and mobility of inorganic and organic arsenic compounds. The results taken as a whole suggest that arsenic in drinking water residuals is susceptible to enhanced mobilization due to anaerobic microbial activity, and therefore As mobilization should be expected in mature landfills. Roxarsone was

Site characterization methods for measuring the occurrence, magnitude, and rate of microbial mediated transformation processes were evaluated to assess the implementation of monitored natural attenuation (MNA) at chlorinated ethenes contaminated sites. A model site in Arizona, the Park-Euclid WQARF site in Tucson, was selected for the study. Field, geochemical, and compound specific carbon isotope fractionation (CSI) data confirm intrinsic biodegradation is occurring in the perched aquifer. Use of the BIOCHLOR model and a screening protocol support the potential for reductive dehalogenation found in the perched aquifer. Biotransformation of tetrachloroethene to cis-1,2-dichloroethene (cis-DCE) was achieved in microcosm studies. Transformation of cis-DCE to vinyl chloride and to ethene is, at the moment, the laboratory rate limiting step. PCR analysis established that the aquifer contains Dehalococcoides sp. and other dechlorinating microorganisms, though genes that encode for enzymes capable of achieving complete dehalogenation of the chlorinated contaminants were confirmed only in one monitoring well. The regional aquifer shows little evidence of intrinsic biodegradation. This study corroborates that CSI analysis can be used as an additional line of evidence to evaluate and verify MNA. Microbial analysis provides relevant information about the capabilities of native microbial communities to carry out reductive dehalogenation and thus, to naturally attenuate chlorinated compounds at a contaminated site. The combination of microcosm studies, CSI analysis, and bacterial DNA identification is becoming a convincing line of evidence for the assessment of MNA application to chloroethenes contaminated sites.

This research investigated the mechanism, kinetics and feasibility of nitrate, arsenate, and trichloroethylene inactivation on zerovalent iron (ZVI), mixed-valent iron oxides, and boron doped diamond film electrode surfaces, respectively. Nitrate ( ) is a common co-contaminant at sites remediated using permeable reactive barriers (PRBs). Therefore, understanding nitrate reactions with ZVI is important for understanding the performance of PRBs. This study investigated the reaction mechanisms of with ZVI under conditions relevant to groundwater treatment. Tafel analysis and electrochemical impedance spectroscopy were used to probe the surface reactions. Batch experiments were used to study the reaction rate of with freely corroding and cathodically protected iron wires. The removal kinetics for the air formed oxide (AFO) were 2.5 times slower than that of water formed oxide (WFO).This research also investigated the use of slowly corroding magnetite (Fe3O4) and wustite (FeO) as reactive adsorbent media for removing As(V) from potable water. Observed corrosion rates for mixed valent iron oxides were found to be 15 times slower than that of zerovalent iron under similar conditions. Electrochemical and batch and column experiments were performed to study the corrosion behavior and gain a deeper understanding on the effects of water chemistry and operating parameters, such as, empty bed contact times, influent arsenic concentrations, dissolved oxygen levels and solution pH values and other competing ions. Reaction products were analyzed by X-Ray diffraction and XPS to determine the fate of the arsenic.This research also investigated use of boron doped diamond film electrodes for reductive dechlorination of trichloroethylene (TCE). TCE reduction resulted in nearly stoichiometric production of acetate. Rates of TCE reduction were found to be independent of the electrode potential at potentials below -1 V with respect to the standard hydrogen electrode (SHE). However, at smal

The recent lowering of the arsenic MCL from 50 ppb to 10 ppb in 2006 will cause many utilities to implement new technologies for arsenic removal. Most of the affected utilities are expected to use adsorption onto solid sorbents for arsenic removal, especially in the arid Southwest, where conserving and re-using water is of utmost importance. This would cause the generation of more than 6 million pounds of arsenic residuals every year, which then would be disposed of in landfills. This thesis effort focuses on the testing of different aluminum and iron (hydr)-oxide based sorbents that are likely to be used for arsenic removal and assessing the behavior of these Arsenic Bearing Solid Residuals (ABSRs) under landfill conditions. It was demonstrated that the Toxicity Characteristic Leaching Procedure (TCLP) test underestimates the arsenic mobilization in landfills. Desorption of arsenic from ABSRs was quantified as a function of the range of pH and concentrations of competitive anions like phosphate, bicarbonate, sulfate and silicate and NOM found in landfills. The effect of pH is much more significant than the anions and NOM. Arsenic release due to competition of different anions is neither additive nor purely competitive. Landfill conditions were simulated inside long-term, continuous flow-through column reactors, and arsenic mobilization from sorbents was measured under those conditions. The results indicate that under reducing conditions, and in the presence of other competitive anions and high organics, microbes reduce arsenate to arsenite, which is a much more mobile species. Fe(III) is also reduced to Fe(II) under these conditions. Arsenic is transported in the particulate phase, associated with the iron, much more than in the dissolved phase. It was also observed that the sorbent itself might leach away at a faster rate than the arsenic sorbate causing a depletion of surface sites and a sudden spike in the release rate of arsenic, after a long residence time. Fi