Matching Items (109)
- All Subjects: Environmental engineering
- Genre: Masters Thesis
- Creators: Arizona State University
- Member of: ASU Electronic Theses and Dissertations
- Member of: Theses and Dissertations
Disinfection byproducts are the result of reactions between natural organic matter (NOM) and a disinfectant. The formation and speciation of DBP formation is largely dependent on the disinfectant used and the natural organic matter (NOM) concentration and composition. This study examined the use of photocatalysis with titanium dioxide for the oxidation and removal of DBP precursors (NOM) and the inhibition of DBP formation. Water sources were collected from various points in the treatment process, treated with photocatalysis, and chlorinated to analyze the implications on total trihalomethane (TTHM) and the five haloacetic acids (HAA5) formations. The three sub-objectives for this study included: the comparison of enhanced and standard coagulation to photocatalysis for the removal of DBP precursors; the analysis of photocatalysis and characterization of organic matter using size exclusion chromatography and fluorescence spectroscopy and excitation-emission matrices; and the analysis of photocatalysis before GAC filtration. There were consistencies in the trends for each objective including reduced DBP precursors, measured as dissolved organic carbon DOC concentration and UV absorbance at 254 nm. Both of these parameters decreased with increased photocatalytic treatment and could be due in part to the adsorption to as well as the oxidation of NOM on the TiO2 surface. This resulted in lower THM and HAA concentrations at Medium and High photocatalytic treatment levels. However, at No UV exposure and Low photocatalytic treatment levels where oxidation reactions were inherently incomplete, there was an increase in THM and HAA formation potential, in most cases being significantly greater than those found in the raw water or Control samples. The size exclusion chromatography (SEC) results suggest that photocatalysis preferentially degrades the higher molecular mass fraction of NOM releasing lower molecular mass (LMM) compounds that have not been completely oxidized. The molecular weight distributions could explain the THM and HAA formation potentials that decreased at the No UV exposure samples but increased at Low photocatalytic treatment levels. The use of photocatalysis before GAC adsorption appears to increase bed life of the contactors; however, higher photocatalytic treatment levels have been shown to completely mineralize NOM and would therefore not require additional GAC adsorption after photocatalysis.
Local municipalities in the Phoenix Metropolitan Area have voiced an interest in purchasing alternate source water with lower DBP precursors. Along the primary source is a hydroelectric dam in which water will be diverted from. This project is an assessment of optimizing the potential blends of source water to a water treatment plant in an effort to enable them to more readily meet DBP regulations. To perform this analysis existing water treatment models were used in conjunction with historic water quality sampling data to predict chemical usage necessary to meet DBP regulations. A retrospective analysis was performed for the summer months of 2007 regarding potential for the WTP to reduce cost through optimizing the source water by an average of 30% over the four-month period, accumulating to overall treatment savings of $154 per MG ($82 per AF).
Second-generation biofuel feedstocks are currently grown in land-based systems that use valuable resources like water, electricity and fertilizer. This study investigates the potential of near-shore marine (ocean) seawater filtration as a source of planktonic biomass for biofuel production. Mixed marine organisms in the size range of 20µm to 500µm were isolated from the University of California, Santa Barbara (UCSB) seawater filtration system during weekly backwash events between the months of April and August, 2011. The quantity of organic material produced was determined by sample combustion and calculation of ash-free dry weights. Qualitative investigation required density gradient separation with the heavy liquid sodium metatungstate followed by direct transesterification and gas chromatography with mass spectrometry (GC-MS) of the fatty acid methyl esters (FAME) produced. A maximum of 0.083g/L of dried organic material was produced in a single backwash event and a study average of 0.036g/L was calculated. This equates to an average weekly value of 7,674.75g of dried organic material produced from the filtration of approximately 24,417,792 liters of seawater. Temporal variations were limited. Organic quantities decreased over the course of the study. Bio-fouling effects from mussel overgrowth inexplicably increased production values when compared to un-fouled seawater supply lines. FAMEs (biodiesel) averaged 0.004% of the dried organic material with 0.36ml of biodiesel produced per week, on average. C16:0 and C22:6n3 fatty acids comprised the majority of the fatty acids in the samples. Saturated fatty acids made up 30.71% to 44.09% and unsaturated forms comprised 55.90% to 66.32% of the total chemical composition. Both quantities and qualities of organics and FAMEs were unrealistic for use as biodiesel but sample size limitations, system design, geographic and temporal factors may have impacted study results.
Ecolabels are the main driving force of consumer knowledge in the realm of sustainable product purchasing. While ecolabels strive to improve consumer's purchasing decisions, they have overwhelmed the market, leaving consumers confused and distrustful of what each label means. This study attempts to validate and understand environmental concerns commonly found in ecolabel criteria and the implications they have within the life cycle of a product. A life cycle assessment (LCA) case study of cosmetic products is used in comparison with current ecolabel program criteria to assess whether or not ecolabels are effectively driving environmental improvements in high impact areas throughout the life cycle of a product. Focus is placed on determining the general issues addressed by ecolabelling criteria and how these issues relate to hotspots derived through a practiced scientific methodology. Through this analysis, it was determined that a majority the top performing supply chain environmental impacts are covered, in some fashion, within ecolabelling criteria, but some, such as agricultural land occupation, are covered to a lesser extent or not at all. Additional criteria are suggested to fill the gaps found in ecolabelling programs and better address the environmental impacts most pertinent to the supply chain. Ecolabels have also been found to have a broader coverage then what can currently be addressed using LCA. The results of this analysis have led to a set of recommendations for furthering the integration between ecolabels and life cycle tools.
The presence of compounds such as pharmaceuticals and personal care products (PPCPs) in the environment is a cause for concern as they exhibit secondary effects on non-target organisms and are also indicative of incomplete removal by wastewater treatment plants (WWTPs) during water reclamation. Analytical methods and predictive models can help inform on the rates at which these contaminants enter the environment via biosolids use or wastewater effluent release to estimate the risk of adverse effects. The goals of this research project were to integrate the results obtained from the two different methods of risk assessment, (a) in silico modeling and (b) experimental analysis. Using a previously published empirical model, influent and effluent concentration ranges were predicted for 10 sterols and validated with peer-reviewed literature. The in silico risk assessment analysis performed for sterols and hormones in biosolids concluded that hormones possess high leaching potentials and that particularly 17-α-ethinyl estradiol (EE2) can pose significant threat to fathead minnows (P. promelas) via leaching from terrestrial depositions of biosolids. Six mega-composite biosolids samples representative of 94 WWTPs were analyzed for a suite of 120 PPCPs using the extended U.S. EPA Method 1694 protocol. Results indicated the presence of 26 previously unmonitored PPCPs in the samples with estimated annual release rates of 5-15 tons yr-1 via land application of biosolids. A mesocosm sampling analysis that was included in the study concluded that four compounds amitriptyline, paroxetine, propranolol and sertraline warrant further monitoring due to their high release rates from land applied biosolids and their calculated extended half-lives in soils. There is a growing interest in the scientific community towards the development of new analytical protocols for analyzing solid matrices such as biosolids for the presence of PPCPs and other established and emerging contaminants of concern. The two studies presented here are timely and an important addition to the increasing base of scientific articles regarding environmental release of PPCPs and exposure risks associated with biosolids land application. This research study emphasizes the need for coupling experimental results with predictive analytical modeling output in order to more fully assess the risks posed by compounds detected in biosolids.
Bacteroides have been suggested as alternative indicators of fecal pollution since they are highly abundant in feces and are thought to have limited potential to grow in environment. However, recent literature suggests that Bacteroides can potentially survive within water distribution systems. The first objective of this study was therefore to investigate the validity of Bacteroides as a fecal indicator for drinking water through laboratory experiments and field studies. Experiments were performed using a laboratory scale PVC model water distribution system that was spiked with 109 Bacteroides. Samples were collected over the following four and analyzed by culture and molecular-based techniques. Second, field studies were performed by collecting water meters from two large chlorinated water distribution systems in central Arizona. Upon removal for repair by city personnel, meters were collected and biofilms samples were gathered within two hours. The biofilms were then analyzed using culture and molecular-based assays. The results from these studies support the hypothesis that Bacteroides DNA may be found in water distribution systems despite the difficulty of cultivating these bacterial cells. These experiments present the importance of considering biofilm interactions with fecal indicator bacteria when performing molecular assays on environmental samples, as biofilms may provide protection from high oxygen concentrations and grazing protozoa in bulk water that limit the persistence Bacteroides in the environment. Although the significance of biofilm interactions with surface or recreational waters may be small, they are likely important when considering drinking water delivered through distribution systems. The second objective of this study was to investigate alternative detection methodologies for the fecal indicator Bacteroides. In particular, this study focused on using a simplified protocol of Nucleic Acid Sequence Based Amplification (NASBA) and Thermophilic Helicase-Dependent Amplification (tHDA) to amplify the highly conserved 16s rRNA gene in the genomic DNA of fecal indicator Bacteroides. The results of this study show that the simplified NASBA procedure was not able to amplify the target, while continuous problems with tHDA exposed the methods lack of reliability. These results suggest higher reliability in the isothermal amplification methods needs to be achieved before application to environmental samples.
Carbon capture and sequestration (CCS) is one of the important mitigation options for climate change. Numerous technologies to capture carbon dioxide (CO2) are in development but currently, capture using amines is the predominant technology. When the flue gas reacts with amines (Monoethanaloamine) the CO2 is absorbed into the solution and forms an intermediate product which then releases CO2 at higher temperature. The high temperature necessary to strip CO2 is provided by steam extracted from the powerplant thus reducing the net output of the powerplant by 25% to 35%. The reduction in electricity output for the same input of coal increases the emissions factor of Nitrogen Oxides, Mercury, Particulate matter, Ammonia, Volatile organic compounds for the same unit of electricity produced. The thesis questions if this tradeoff between CO2 and other emissions is beneficial or not. Three different methodologies, Life Cycle Assessment, Valuation models and cost benefit analysis are used to identify if there is a net benefit to the society on implementation of CCS to a Pulverized coal powerplant. These methodologies include the benefits due to reduction of CO2 and the disbenefits due to the increase of other emissions. The life cycle assessment using ecoindicator'99 methodology shows the CCS is not beneficial under Hierarchical and Egalitarian perspective. The valuation model shows that the inclusion of the other emissions reduces the benefit associated with CCS. For a lower CO2 price the valuation model shows that CCS is detrimental to the environment. The cost benefit analysis shows that a CO2 price of at least $80/tCO2 is required for the cost benefit ratio to be 1. The methodology integrates Montecarlo simulation to characterize the uncertainties associated with the valuation models.
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.
Six high-production-volume neonicotinoids were traced through a municipal wastewater treatment plant (WWTP) and engineered wetland located downstream, in a study motivated by reports on these insecticides posing threats to non-target invertebrate species and potentially playing a role in the global honeybee colony collapse disorder. An array of automated samplers was deployed in a five-day monitoring campaign and resultant flow-weighted samples were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) using the isotope dilution method. Concentrations in WWTP influent and effluent were 54.7 ± 2.9 and 48.6 ± 2.7 ng/L for imidacloprid, respectively, and 3.7 ± 0.3 and 1.8 ± 0.1 ng/L for acetamiprid, respectively. A mass balance over the WWTP showed no (p=0.09, CI = 95%) removal of imidacloprid, and 56 ± 6% aqueous removal of acetamiprid. In the constructed wetland downstream, a lack of removal was noted for both imidacloprid (from 54.4 ± 3.4 ng/L to 49.9 ± 14.6 ng/L) and acetamiprid (from 2.00 ± 0.03 ng/L to 2.30 ± 0.21 ng/L). Clothianidin was detected only inconsistently in the WWTP and wetland (>2 to 288 ng/L; 60% detection frequency), whereas thiamethoxam (<10 ng/L), thiacloprid (<2 ng/L), and dinotefuran (<180 ng/L) were not detected at all. Thus, imidacloprid and acetamiprid were identified as recalcitrant sewage constituents (estimated U.S. WWTP discharge of 1920- 4780 kg/y) that persist during conventional wastewater treatment to enter U.S. surface waters at potentially harmful concentrations.
Large-scale cultivation of photosynthetic microorganisms for the production of biodiesel and other valuable commodities must be made more efficient. Recycling the water and nutrients acquired from biomass harvesting promotes a more sustainable and economically viable enterprise. This study reports on growing the cyanobacterium Synechocystis sp. PCC 6803 using permeate obtained from concentrating the biomass by cross-flow membrane filtration. I used a kinetic model based on the available light intensity (LI) to predict biomass productivity and evaluate overall performance.
During the initial phase of the study, I integrated a membrane filter with a bench-top photobioreactor (PBR) and created a continuously operating system. Recycling permeate reduced the amount of fresh medium delivered to the PBR by 45%. Biomass production rates as high as 400 mg-DW/L/d (9.2 g-DW/m2/d) were sustained under constant lighting over a 12-day period.
In the next phase, I operated the system as a sequencing batch reactor (SBR), which improved control over nutrient delivery and increased the concentration factor of filtered biomass (from 1.8 to 6.8). I developed unique system parameters to compute the amount of recycled permeate in the reactor and the actual hydraulic retention time during SBR operation. The amount of medium delivered to the system was reduced by up to 80%, and growth rates were consistent at variable amounts of repeatedly recycled permeate. The light-based model accurately predicted growth when biofilm was not present. Coupled with mass ratios for PCC 6803, these predictions facilitated efficient delivery of nitrogen and phosphorus. Daily biomass production rates and specific growth rates equal to 360 mg-DW/L/d (8.3 g/m2/d) and 1.0 d-1, respectively, were consistently achieved at a relatively low incident LI (180 µE/m2/s). Higher productivities (up to 550 mg-DW/L/d) occurred under increased LI (725 µE/m2/s), although the onset of biofilm impeded modeled performance.
Permeate did not cause any gradual growth inhibition. Repeated results showed cultures rapidly entered a stressed state, which was followed by widespread cell lysis. This phenomenon occurred independently of permeate recycling and was not caused by nutrient starvation. It may best be explained by negative allelopathic effects or viral infection as a result of mixed culture conditions.