Browsing by Author "Omur-Ozbek, Pinar, advisor"

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Open Access
An investigation of water quality considerations for premise plumbing systems in buildings
(Colorado State University. Libraries, 2021) Kalan, Duygu, author; Ozbek, Mehmet, advisor; Omur-Ozbek, Pinar, advisor; Grigg, Neil, committee member; Dooley, Gregory, committee member
Providing potable and palatable waterq to their consumers is a top priority for drinking water treatment utilities in the US. To ensure the safety of the drinking water, disinfection methods have been applied for over a century. Chlorine is the most extensively used disinfectant to control waterborne pathogen activities. Despite its effectiveness, chlorine is known to react with natural organic matter (NOM) and produce disinfection by-products (DBPs) (e.g., trihalomethanes and haloacetic acids) that are known to be harmful to humans. Currently, DBPs are regulated at the distribution system level. However, premise plumbing systems are unique and different from water distribution systems. Moreover, there are knowledge gaps for premise plumbing in residential and non-residential buildings under routine operations, and that has not been fully understood for different operation scenarios (e.g., use of water-efficient fixtures in conventional buildings) and building types (e.g., green-certified buildings). The primary purpose of this dissertation was to contribute to the body of knowledge on water quality in premise plumbing systems by addressing some of the knowledge gaps identified in the literature. This dissertation comprises three independent but complementary studies. Each study focused on essential aspects of water quality in premise plumbing systems as follows: i) identifying the effects of building type (e.g., conventional vs. green-certified) on water quality in premise plumbing systems, ii) providing a comprehensive literature review on existing contaminant prediction models for premise plumbing systems, and iii) developing a DBP prediction tool for premise plumbing systems. In the first study, effects of building type on premise plumbing water quality were addressed. For this purpose, trihalomethanes (THMs) and water quality parameters, including temperature, pH, free chlorine levels, and total organic carbon (TOC) were collected and compared between a combined conventional and green-certified (i.e., water-efficient) building drinking fountains. Even though the distributed water quality to the green and conventional building sides was the same, statistically significant differences in water quality parameters and TTHMs were observed due to the changes in water chemistry in the premise plumbing systems. The study findings point out the importance of the plumbing pipe age and its impacts on water chemistry. In the second study, a state-of-the-art review was conducted to provide background information on water quality and indoor air quality models that have been implemented in residential and non-residential building premise plumbing systems and indoor air environments. A systematic literature search was conducted in the Compendex, Web of Science, IEEE Explore, Science Direct, and PubMed databases. A total of 22 contaminant prediction modeling studies for premise plumbing and 12 for indoor air quality were reviewed in this study. Among the premise plumbing models, lead and copper prediction models have drawn more attention from researchers than any other contaminants. Due to increased inhalation exposure levels, shower models have been excessively included in risk exposure studies. This review aimed to draw attention to the research needs in modeling approaches, identify the gaps in the literature, and provide a baseline for future research attempts. In the third study, a chloroform prediction model was developed and incorporated into a simulation software to predict chloroform concentrations in a premise plumbing system for eight hours of water stagnation. The model coefficients were determined with the bench-scale experiments based on water quality parameter ranges that can be seen in premise plumbing systems. Chloroform concentrations were tested in a two-story townhouse; experimental and model prediction results were compared. The chloroform prediction model underpredicted chloroform concentrations by 27-37% compared with the house measurements. This study represents an important initial attempt in developing a simulation-based water quality prediction model, which can be implemented in premise plumbing systems. This study contributes to the body of knowledge on water quality in premise plumbing systems by providing a better insight into the effects of conventional and green-certified buildings, shedding light on the current state of numerical modeling research, and implementing a chloroform prediction tool in premise plumbing systems.
Open Access
Characterization and treatment of water for unconventional oil wells with temporal variability and fracturing fluid type
(Colorado State University. Libraries, 2017) Kim, Seongyun, author; Omur-Ozbek, Pinar, advisor; Carlson, Kenneth, committee member; Catton, Kimberly, committee member; Dooley, Gregory, committee member
Flowback/produced water from unconventional oil and gas wells cannot be optimized without an understanding of water quality which needs to be treated for reuse, the factors to be considered include the temporal variability and different frac fluid types used for hydraulic fracturing. Produced water treatment for reuse is becoming a critical factor for water management surrounding unconventional oil and gas industry. For this research flowback/produced water samples were collected over 200 days from two wells in the Wattenberg Field, located in northeast Colorado. One of the frac fluids had an initial pH greater than 10 and had a guar-based gel. The other frac fluid included a non-guar polysaccharide based polymer and an initial pH less than 6. Total dissolved solids (TDS) and total organic carbon (TOC) analyses were conducted as an indicator for presence of organic and inorganic solids, and the data was compared with key ions (barium, calcium, chloride, magnesium, sodium, strontium, boron and iron) with the different frac fluid types. High values of the coefficient of determinant (over 0.85) were observed between TDS and the key ions, showing that significant positive correlations between two. Despite the significant initial pH differences, the concentrations of calcium, chloride, sodium and strontium were statistically equivalent between the two frac fluids. A mass balance approach was applied to evaluate the quantity of mass of injected additives that was recovered over the 200-day period. Zirconium, potassium and aluminum were selected due either to the lack of contribution from the formation (Zr, Al) or the conservative (non-reactive) nature of the ion (K). Recoveries of these ions ranged from 3 % to 33 % after 200 days, and notable differences were observed between frac fluids. The fraction of cross-linking chemical (Zr) recovered was significantly less for the residue-free polysaccharide-based fluid than the derivatized guar-based fluid. It is hypothesized that the polysaccharide-based Zr cross-linked gel is broken down more completely than the guar-based gel, releasing the Zr metal with subsequent precipitation in the formation. Another study conducted for this dissertation involved the analysis and treatment of produced water samples from three wells that were fractured with different fracturing fluid types over 63 days. TOC analysis showed significantly higher organics composition in produced water from wells fractured by the gel and hybrid fluid (943-1,730 mg/L) compared to the well fractured by the slickwater (222-440 mg/L). TDS levels increased with time, varying from roughly 18,000 mg/L to 30,000 mg/L between 1 to 63 days at each well. Liquid chromatography–mass spectrometry (LC-MS) was applied to characterize the organic matters and similar mass spectra were observed from each well with no temporal trend. Chemical equilibrium modeling was used to predict the precipitation of metals from produced water mixed with groundwater. Chemical coagulation was successfully performed for reducing the turbidity from produced water samples at each well. LC-MS was performed to study the compositions of frac fluid prepared with fresh water (FWA) only and frac fluid prepared with recycled water (RWA) mixed with fresh water. Ethylene oxide and propylated glycol functional units were observed from both FWA and RWA samples. Qualitative analysis from FWA and RWA was performed through Agilent qualitative analysis software B.06.00 based on the exact mass of the chemical compound. Van Krevelen diagram proved FWA and RWA show highly saturated and low degree of oxidation of organic compounds. Kendrick mass defect (KMD) from ethylene oxide was below 0.1 while KMD analysis from propylated glycol were close to 1. FWA showed 32.3 average carbon number and 9.8 double bond equivalent and RWA showed 31.5 average carbon number and 9.5 double bond equivalent. For the last phase of this research, produced water samples were treated by electrocoagulation (EC), ultrafiltration (UF), granular activated carbon (GAC) and reverse osmosis (RO) in series. Total dissolved solids (TDS), total organic carbon (TOC), dissolved organic carbon (DOC), BTEX, total petroleum hydrocarbons (TPH), turbidity, propylene glycol, ethylene glycol and ethylene glycol monobutyl ether were measured after each treatment. Gas chromatography–mass spectrometry (GC-MS) with solid phase extraction (SPE) method was applied to detect propylene glycol (PG), ethylene glycol (EG) and ethylene glycol monobutyl ether (EGME) in the samples. EGME was not detected in any produced water samples. PG concentration was between 0.07ug/ml to 5.39ug/ml and EG ranged from 0.07 ug/ml to 5.52ug/ml. GAC removed both PG and EG for acceptable drinking water criteria. EC was effective at removing both turbidity (85%) and TPH (80%) and most of turbidity and 90% of TPH were removed after UF. This study confirmed that almost 95% of BTEX, TOC, and DOC in produced water samples were removed by GAC. GAC contributed approximately 15% of TDS removal while RO removed 90% of TDS (2550mg/L) which is still high for reuse for various purposes.
Open Access
Development of predictive geosmin models in northern Colorado lakes, reservoirs, and rivers
(Colorado State University. Libraries, 2014) Parr, Glenn, author; Omur-Ozbek, Pinar, advisor; Catton, Kimberly, advisor; Stednick, John, committee member
Geosmin is a taste and odor (T&O) compound that is naturally occurring, produced by bacteria, and released into drinking water source waters. Geosmin in many parts of the country is a seasonal issue, so drinking water providers often look for temporary solutions to the T&O caused by geosmin. Being able to predict when geosmin will be an issue is vital if drinking water providers are going to succeed in using temporary mitigation methods. Therefore research is being performed to develop predictive models. This study is a broad sampling of Northern Colorado water bodies investigating the role of watershed and elevation, as well as biotic and abiotic water quality parameters. Water quality and zooplankton samples were collected from 20 different lakes and reservoirs as well as 20 sites on 4 rivers in Northern Colorado. Statistical models were developed using Multiple Linear Regression and Principal Component Analysis. Models show significant correlations between geosmin and zooplankton, particularly the species Nauplii and Daphnia in the lakes and reservoirs data. Modeling of the river data revealed geosmin relationships with elevation and dissolved oxygen, but did not show a significant correlation with stream flow. As expected from previous studies month of the year was also shown to be a significant factor.
Embargo
Ethical and equity challenges in engineering: a reflexive thematic analysis of early-career engineers' workplace experiences
(Colorado State University. Libraries, 2024) Agha, Chika Winnifred, author; Atadero, Rebecca, advisor; Omur-Ozbek, Pinar, advisor; Scalia, Joseph, IV, committee member; Most, David, committee member
Society and engineering are inseparable, with engineers' work significantly impacting society. Engineering has a large role in building a sustainable society, and prioritizing ethics and equity is essential. The early stages of an engineer's career are important for shaping professionals who uphold ethical values and champion equity. Understanding how early-career engineers perceive ethical and equity issues in their workplaces is key to fostering ethically conscious and equity-minded engineers capable of navigating evolving roles and responsibilities. This research aims to understand early-career engineers' experiences navigating ethical dilemmas and equity challenges in their professional practices and the implications these experiences have for their professional development. The overall research design of this study is basic qualitative research. Through the analysis of interviews with 13 participants from North America using reflexive thematic analysis (RTA), four key themes were developed that describe early-career engineers' experiences with ethics and equity as they transition to professional practice. The first theme is that schools do not fully prepare early-career engineers when it comes to ethical and equity practices. This includes teaching about simplified concepts, lacking comprehensive preparation, and recognizing that some skills can't be learned in school. The second theme is that characteristics of individual workplaces shape the early-career experiences of engineers. This theme emphasizes how leadership, work culture, exclusionary practices, company policies, and the principle that companies' actions speak louder than words, shape engineers' professional experiences. The third theme, ethical decision-making influences, and processes, explores the pressures that can lead to unethical actions, the importance of policies, rules, and oversight to support ethical decisions, the challenges of managing competing priorities, and the dilemmas of acting on equity issues. The fourth theme about the self-confidence and self-worth of early career engineers underscores the importance of self-confidence, speaking up, asking questions, and knowing one's value. The formative experiences of early-career engineers can profoundly impact their ethical reasoning and commitment to equitable practices throughout their careers. Understanding how early-career engineers engage with these issues is important for developing educational programs, such as case studies and professional systems that support ethical and equitable engineering.
Open Access
Evaluation of oxidation and adsorption techniques for taste and odor and toxin removal
(Colorado State University. Libraries, 2017) Sampath, Muthukumaran, author; Omur-Ozbek, Pinar, advisor; Carlson, Kenneth, committee member; Dooley, Gregory, committee member
The cyanobacteria, also known as blue-green algae, owe their name to the presence of photosynthetic pigments. Cyanobacteria are a major group of bacteria that occur throughout the world. Freshwater cyanobacteria may accumulate in surface water supplies as "blooms" posing as an environmental hazard because of the release of water soluble toxic compounds, called cyanotoxins. Especially massive blooms of blue–green algae in the surface waters used as drinking water resources may lead to taste and odor problems during the summer and fall, they may also produce cyanotoxins. Since the taste and odor compounds, Geosmin (GSM) and 2-Methylisoborneol (2-MIB) can be easily detected by the human nose at low concentrations of 2-5 ng/L, the surveillance of harmful toxins such as microcystin-LR may be easily performed by sensory analyses due to the likely co-occurrences of the two types of metabolites. This research focused on removal of taste and odor compounds (GSM, 2-MIB) and microcystin-LR with five oxidants: chlorine, chlorine dioxide, potassium permanganate, ozone, mixed oxidants (MiOX) and powdered activated carbon (PAC) using Ralston Reservoir water as reagent water collected in early April, 2014. The objective of the study was to develop a bench scale treatment process efficacy information that Denver Water can utilize to decide on a treatment technique for taste and odor control. The Design Expert software was used to determine the optimum dose of the oxidants for an acceptable treatment level.
Open Access
Evaluation of oxidation treatment on algal toxins and cytotoxic effects of algal toxins post oxidation
(Colorado State University. Libraries, 2017) Giampà Fedchuk, Natalya, author; Omur-Ozbek, Pinar, advisor; Legare, Marie, committee member; Catton, Kimberly, committee member
Algal blooms are a growing threat to the water industry, and one of the major reasons is that they are often accompanied by proliferation of the harmful species cyanobacteria. Cyanobacteria produce a variety of toxins that can cause serious adverse health effects. Microcystin-LR (MC-LR) and cylindrospermopsin (CYN) are known hepatotoxins, both named priority toxins by the EPA. Cyanotoxins are usually treated with oxidation in conventional drinking water treatment plants this approach has shown to successfully break down the toxin molecules. The goal of this project was to evaluate the effects of standard oxidation treatments on the concentration and cytotoxicity of MC-LR and CYN. Toxin solutions were prepared in water and treated with three oxidants – chlorine, potassium permanganate, and ozone. Once the toxin solutions were treated with oxidants, two assays were conducted in parallel: (1) the PrestoBlue cytotoxicity assay was conducted on HepG2 carcinoma cells following treatment, and (2) an LC-MS/MS analysis of the toxin solutions was used to quantify the toxins concentration post-treatment. The results of the LC-MS analysis suggested that neither chlorine, potassium permanganate or ozone treatment were effective at reducing the concentrations of MC-LR or CYN. These findings are consistent with the results of the cytotoxicity assay, which did not show a significant reduction of cell death after exposure to toxins treated with oxidation compared to untreated toxins. The oxidation of MC-LR and CYN likely failed due to a high starting concentration of the toxin, much higher than what occurs naturally. Future research should focus on a biological endpoint other than apoptosis to evaluate the potential health risks of the toxin metabolites at concentrations relevant to natural exposure.
Open Access
Growth, recovery and bioaccumulation of alfalfa (Medicago sativa) and spinach (Spinacia oleracea) exposed to cyanotoxins in agricultural environments
(Colorado State University. Libraries, 2020) Nezat, Caryn Janel, author; Omur-Ozbek, Pinar, advisor; Peebles, Christie, committee member; Bailey, Ryan, committee member
Harmful algal blooms (HABs) are a growing concern for surface water resources around the globe. With increasing pressure on our limited fresh water resources due to climate change, the risk of contamination from HABs and the cyanobacterial toxins that accompany blooms, exacerbates the problem. Adverse health effects from cyanotoxin exposure has been documented in human and animal mortality and morbidity cases worldwide. Nationally, the presence and severity of HABs has prompted multiple cyanotoxins, including cylindrospermopsin (CYN) and microcystins (MCLR), to be listed on the USEPA Drinking Water Contaminant Candidate List-4 (CCL4) requiring many public systems to monitor for cyanotoxin presence. Recognizing this risk, the World Health Organization (WHO) has long established guidelines to acceptable levels in surface waters based on exposure pathways and use. Further concerns have arisen as our understanding about cyanotoxins has been expanded by research. The purpose of this experiment was to determine 1) effects of toxin exposure during germination, 2) the effects of CYN and MCLR on agricultural crops exposed to toxins during vegetative and mature growth stages, 3) crops ability to recover from toxin exposure and 4) to quantify amount of cyanotoxin accumulated within crop tissue after exposure to cyanotoxins. Germination results indicated exposure to CYN and MCLR did not decrease the rate of germination of alfalfa or spinach. Further, alfalfa and spinach had increased primary root growth for seeds exposed to cyanotoxins. During early vegetative exposure, spinach showed increased biomass and larger leaf area when exposed to MCLR and CYN. After a recovery period spinach plants exposed to CYN showed increased biomass compared to controls. Alfalfa plants exposed to MCLR in vegetative stages had significantly more biomass when compared to controls and this trend was observed after the recovery period. Results of alfalfa exposed during mature growth stages to CYN and MCLR indicated it was more sensitive to CYN, however both toxin treatments resulted in increased biomass production. After one- and two-weeks of recovery the MCLR treated alfalfa biomass remained higher than controls. Bioaccumulation of CYN and MCLR was observed in alfalfa exposed early to the toxins and detectable levels were observed after the one-week recovery period. Spinach accumulated MCLR during early exposures and had detectable levels in the stems after one-month recovery. During mature exposure, alfalfa initially only had detectable levels of MCLR, which decreased over the recovery periods. However, the presence of CYN was not detected until one-week prior to the final toxin exposure. These findings support the growing concern that use of cyanotoxin contaminated irrigation water can be an additional exposure route for ingestion of toxins and increased risk of adverse health effects. Further studies into the subsurface fate of cyanotoxins will further increase the understanding of their bioavailability and persistence in soil.
Open Access
Impacts of wildfires and retardants on surface water quality
(Colorado State University. Libraries, 2016) Morgensen, Brent D., author; Omur-Ozbek, Pinar, advisor; Carlson, Ken, committee member; Stednick, John, committee member
Wildfire retardant is one of the most beneficial tools used to prevent the spread of wildfire, yet its presence has been found to be of big concern when dropped into aquatic habitats. Many retardants are composed mainly of ammonium and phosphates, which can lead to troubles with eutrophication and fish kills at high doses. Iron is often included to help with the identification of retardant drops, but can result in aesthetic issues when gotten into waterways. Despite the risks associated with its use, retardant is still a needed tool to help reduce the spread of wildfire and the effects of wildfire on the increase of organics, nutrients, and metals into waters. This study aims to quantify the effects of wildfire and wildfire retardant on the quality of surface waters. A rainfall simulation was performed on soil plots to observe the influence of wildfire and wildfire retardant on the quality of runoff using Phos-Chek® LC-95A retardant. Soil plots were collected from a tallgrass prairie in Pingree, CO and plots were modified to simulate rainfall over unburned plots without retardant (Uwo), unburned plots with retardant (Uw), burned plots without retardant (Bwo), and burned plots with retardant (Bw). A Norton Ladder Type Rainfall Simulator was used to simulate rainfall over the plots at 165 mm/hr for 15 min and the runoff was collected and analyzed for ammonia, orthophosphate (Pi), Fe, and TOC immediately following the experiment. The experiment was performed on 3 consecutive days and the entire process of the experiment was performed on the same plots 2 months after the first set of runs. Retardant use showed a significant increase in nutrient and iron concentrations for unburned plots, while a significant increase was found for Pi concentrations in burned plots. Burned plots showed a noticeable increase in TOC compared to unburned plots, but retardant showed no influence on either. The second part of this study analyzed the leachate from soils collected from the burn area of the Royal Gorge on 3 separate occasions. Samples were collected from Uwo, Uw, Bwo, and Bw sites, as well as an unburned site with a high application of retardant (UwH). Nutrients and Fe were found to increase noticeably from Uwo to Uw + UwH soil, while ammonia was generally found to be higher in Bw than Bwo. Retardant was found to have no noticeable influence on TP and Fe in the first analysis, but Bw was found to show lesser concentrations than Bwo as the analyses carried on. Concentrations of Mn were generally less in Bw than Bwo for all of the analyses. These results show that concern is warranted when retardant is dropped near waterways.
Open Access
Measuring and modeling geosmin removal from Horsetooth Reservoir water by powdered activated carbon for selected contact times
(Colorado State University. Libraries, 2011) Koester, Kirk, author; Omur-Ozbek, Pinar, advisor; Carlson, Ken, committee member; Goemans, Chris, committee member
Presence of geosmin, an odorous algal metabolite produced by cyanobacteria and actinomycetes, has been an issue in drinking waters in Northern Colorado. Geosmin does not pose a health threat; however, it imparts an earthy taste and odor to the finished drinking water even at very low concentrations (4 -10 ng/L), resulting in consumer complaints and dissatisfaction. Geosmin cannot be removed by conventional water treatment processes, so further treatment is required to achieve concentrations below detection limits. This study investigated the geosmin removal from the raw water obtained from the Horsetooth Reservoir, in Fort Collins, CO by powdered activated carbon (PAC). Raw water samples were spiked with stock geosmin solution to obtain concentrations from 10 to 50 ng/L and stock PAC solution to obtain concentrations from 5 to 20 mg/L. Thirteen different geosmin/PAC concentrations were tested for 90 minutes contact time (and up to 6 hours for selected combinations) and the geosmin removal was determined by headspace solid phase microextraction and gas chromatography/mass spectrometry. Results indicated that 50 to 70% removal was achieved for lower doses of geosmin/PAC combinations, and 80 to 97% removal was achieved for higher PAC dose combinations. Most (65%) of the geosmin removal was achieved within the first thirty minutes. For 54% of the samples, geosmin concentrations in the treated water were lowered below 4 ng/L after 90 minutes, which is a low enough concentration to prevent consumer complaints. Furthermore, 38% of the samples lowered geosmin concentrations below 4 ng/L after 45 minutes. Additionally three PAC/geosmin combinations that contained 8 mg/L of total organic carbon were examined and a decrease in geosmin removal by 8-12% after 90 minutes was observed. Further analysis with Stat-Ease® Design Expert® (v.8) was used to model geosmin removal to predict required PAC dosages for geosmin levels not tested in this study. The model developed by the Design Expert® considered the initial geosmin concentration, PAC dosing and contact time, and a simple equation was obtained to predict the remaining geosmin concentrations in the treated water. Results from the model fit the data obtained from laboratory measurements and reliably predicted geosmin removal for concentrations not tested.
Open Access
Nutrient management control regulation and preparedness of a northern Colorado wastewater treatment plant
(Colorado State University. Libraries, 2013) Venkatapathi, Keerthivasan, author; Omur-Ozbek, Pinar, advisor; Carlson, Kenneth, committee member; Reardon, Kenneth, committee member
Excessive nutrients in wastewater treatment plant (WWTP) effluents instigate eutrophication of receiving water bodies. Colorado Department of Public Health and Environment (CDPHE) adopted nutrient management control regulation, also known as regulation 85, to moderate the nutrients released by point sources such as the WWTP effluents. City of Loveland WWTP was selected as the study plant to determine a new treatment process configuration to meet the new limits of total phosphorus < 1 mg/L and total inorganic nitrogen < 15 mg/L in the effluent. BioWin, a windows based modeling software, was used to model and simulate the City of Loveland WWTP. Existing activated sludge step feed process configuration was modeled along with proposed anaerobic, anoxic, oxic (A2O) process for design influent flow of 10 MGD and 5-stage Bardenpho process for future flow of 12 MGD along with A2O process. Existing configuration was modeled to establish the accuracy of BioWin. 5 stage Bardenpho process modeling indicates that higher design HRT of 2 days for anaerobic, 4 days for anoxic, 6 days for aerobic, 4 days for secondary anoxic and 1 day for reaeration has better treatment removal efficiency for nutrients with methanol dosage of 250 gal/d and 1Q internal recycle. Model simulations for A2O process reveals that aerobic reactor to anaerobic reactor volume ratios from 3 to 4 and aerobic reactor to anoxic reactor volume ratio of 2.2 along with internal recycle of 1Q has the better nutrient removal efficiency for design flow of 10 MGD. For 12 MGD influent flow, volume of reactors was increased by 20% to compensate for 20% increase in the flow. Previously mentioned reactor volume ratios are feasible for 12 MGD influent flow with volume ratios of 3 and 4 for aerobic to anaerobic reactors and volume ratios of 1.8 and 2 for aerobic to anoxic reactors. Modeling results indicates that increasing the reactor volume ratio for increased flow can result in better treatment for removal of nutrients with a conservative volume, reducing the operational and maintenance cost.
Open Access
Occurrence of cyclo-siloxanes in wastewater treatment plants - quantification and monitoring
(Colorado State University. Libraries, 2012) Kulkarni, Harshad Vijay, author; Omur-Ozbek, Pinar, advisor; Carlson, Kenneth, committee member; Dooley, Gregory, committee member
Siloxanes are persistent, bio-accumulative and toxic emerging contaminants introduced to wastewater from common healthcare and biomedical products, and various industrial processes. They remain unchanged through wastewater treatment and a considerable portion ends up in surface waters through effluent discharge. 30 to 60 ng/L Decamethylcyclopentasiloxane (D5) was detected in two UK Rivers, while ~400 ng/L of D5 may be found in wastewater effluents. Hence, siloxanes are under consideration by Canadian Environmental Assessment Agency and UK Environment Agency for drinking water regulations. Siloxanes are hydrophobic and also accumulate in activated sludge and biogas, causing mechanical problems due to scaling. This research aims: to quantify the siloxanes in sludge samples obtained from Loveland, CO wastewater treatment plant (WWTP); and to study their removal. A method was developed to effectively extract siloxanes from activated sludge samples using liquid extraction followed by quantification with gas chromatography/mass spectrometry. Results for Loveland Wastewater Treatment Plant samples indicated that Octamethylcyclotetrasiloxane (D4) and Decamethylcyclopentasiloxane D5 are present up to 17.11 µg/g dried-sludge. The effectiveness of H2O2 in siloxane removal was investigated. Sludge samples were spiked with D4 and D5 at 12 mg/g and were treated with 1ml, 3ml, and 5ml of 30% H2O2 for 1hr, 2hr, and 3hr reaction time each. Results indicated a 72% reduction in D4 and D5 levels after 3 hrs.
Open Access
The effects of the High Park fire on Cache la Poudre drinking water quality
(Colorado State University. Libraries, 2013) Steninger, Clare L., author; Omur-Ozbek, Pinar, advisor; Carlson, Ken, committee member; Dooley, Gregory, committee member; Stednick, John, committee member
The High Park fire burned 87,284 acres in the Cache la Poudre River watershed from June 9th to June 30th, 2012. The effects of the fire not only impacted the vegetation and soil within the watershed, but also induced changes in the water quality of the Poudre River, a local drinking water source. The utilities and food and beverage producers were concerned that the fire might impart a smoky flavor and other taste and odor issues to the water that may negatively impact their products. Sensory tests were performed on a variety of Poudre River water samples using Flavor Profile Analysis (FPA) according to Standard Method 2170. Results showed that there was not a smoky flavor in Poudre River water several months after the fire compared to smoky flavor just after the fire. In testing samples with a standard smoky compound, guaiacol, FPA results indicated that neither the conventional treatment nor the powdered activated carbon (PAC) treatments removed the smoky smell. However, the benchscale tests conducted with charred riverbed sediment indicated that the smoky flavor is removed by conventional and powdered activated treatments. In the second part of this study, nutrients, organics, and metals were shown to leach into the river water in a laboratory setting. The potential of these parameters to increase in the Cache la Poudre River may cause algal blooms and result in increases in taste and odor issues, as well as metallic tastes caused by the leaching of metals such as iron and manganese. So although the High Park fire did not impart a smoky flavor to the Poudre River water, there remains a potential for taste and odor issues in the future.