Perchlorate contamination of drinking water sources in the United States is widespread and represents a public health concern. Biological treatment is an attractive option because perchlorate-reducing bacteria (PRB) are ubiquitous in the environment and can reduce perchlorate completely to chloride. Treatment of perchlorate-contaminated water in fixed-bed bioreactors has been demonstrated at the laboratory- and pilot-scale. However, full-scale development of reliable biological drinking water treatment processes requires a better understanding of the microbial ecology and activity of perchlorate-reducing communities in bioreactors. The objective of this research was to develop molecular biology tools (MBTs) to quantify PRB and expression of genes required for complete perchlorate reduction (pcrA and cld). The development of MBTs targeting specific genes requires that the sequence of the genes be known. In this work, an MBT called prokaryotic Suppression Subtractive Hybridization (SSH) PCR complementary DNA (cDNA) Subtraction was developed to rapidly isolate target genes for sequencing. This new tool was developed and validated using the model bacterium Pseudomonas putida mt-2 and the model pollutant toluene. For this system, over 90% of the isolated gene fragments encoded toluene-related enzymes, and 20 distinct toluene-related genes from three key operons were identified. Based on these results, prokaryotic SSH PCR cDNA Subtraction shows promise as a targeted method for gene identification; however, application to a PRB did not yield new pcrA and cld sequences. Therefore, to support the development of biological perchlorate treatment processes, quantitative PCR (qPCR) and reverse transcription qPCR (RT-qPCR) assays targeting pcrA and cld were developed using existing sequences. The qPCR and RT-qPCR assays were applied to a laboratory-scale bioreactor and two pilot-scale bioreactors treating perchlorate-contaminated water. Higher quantities of perchlorate reduction genes and transcripts generally were observed when bioreactor performance was superior. Although no quantitative correlations were established, these assays detected differences in the quantity of PRB and changes in gene expression levels during the course of bioreactor operation and between bioreactors with different performance levels. Furthermore, these assays provided an additional line of evidence that microbial perchlorate reduction was occurring. This marks the first application of qPCR assays to quantify perchlorate reduction genes and transcripts in bioreactors. / text

Foodborne illness continues to be a substantial public health issue in the United States, with fresh produce being one of the leading causes of outbreaks. Understanding routes of contamination of fresh produce and how pathogens survive on plant surfaces is paramount in improving food safety and reducing risk to public health. The objectives of this study were to select environmental E.coli isolates as pathogen surrogates of Salmonella typhimurium and E.coli O157:H7, assess lettuce plant contamination by spray irrigation water, and evaluate a common industry quality control (QC) E.coli strain (ATCC 25922). Selections of E.coli surrogates were made utilizing biofilm and leaf attachment data from lab scale assays. Five surrogates were found to be similar in biofilm formation and leaf attachment capabilities of the pathogens, while the common QC strain was significantly different than Salmonella in both biofilm formation and leaf attachment (p < 0.05). Persistence of surrogates, pathogens and the QC strain on lettuce plants was assessed in greenhouse scale experiments, where it was found that all isolates were above detection levels for 22 days. Die-off rates were calculated for all isolates, with the QC strain having the greatest rate of die-off in the first experiment (k = -4.52) and the second greatest in the second experiment (-2.82) while the pathogens and selected surrogates had statistically similar and lower rates of die-off. Based on this information, current policies concerning the sampling and management of irrigation waters and crops for microbial safety may be insufficient. It is recommended that sampling methods and frequencies be adjusted for irrigation waters and fresh produce, and the use of projected die-off rates not be used for the determination of time intervals needed before a crop is safe to harvest.

M. Tech. Food Technology. / Problems to be solved in this project was to validate isolation and detection methods for C. koseri; to assess the environmental prevalence of C. koseri by testing a range of raw South African food products and to determine the specific risk of neonatal infections by monitoring powdered infant formula on the South African market for the presence of this organism.

M. Tech. Chemical Engineering / The lack of clean and fresh water has become a worldwide problem because of water pollution caused by industrialization. Contamination of natural water sources by heavy metal is a worldwide public health problem, leading to waterborne outbreaks of infectious hepatitis, viral gastroenteritis, and cancer. Therefore it very important to remove these toxic metal ions from municipal and industrial effluents in order to protect plants, animals and human beings from their adverse effect before discharging into natural water bodies. Although, several separation methods such as filtration, reverse osmosis and membrane technology have been developed to remove these toxic heavy metal ions from wastewater, however these conventional treatments technologies were found to be expensive on a sustainable basis. Adsorption process was identified as the most effective, and extensively used essential process in wastewater treatment, and in order for adsorption process to feasibly remove pollutants from wastewater, there should be a need for a suitable adsorbent which will have a large porous surface area, and a controllable porous structure. Through the application of nanotechnology, nano adsorbents can be developed as effective adsorbents to treat wastewater. The main objective of this project was to apply magnetic metal doped iron oxides as an efficient adsorption media for the removing of Cr(VI), Cd(II) and V(V) ions from wastewater.

M. Tech. Pharmaceutical Sciences Tshwane University of Technology 2013. / Aims of the present study was to evaluate the inhibitory activities of essential oils against Fusarium isolates and their corresponding biofilms. In this study, the chemical compositions of the oils were established using gas chromatography with both mass spectrometric and flame ionization detection, for identification and quantification, respectively.

M. Tech. Chemistry. / Aims to evaluate, compare and modify existing methods and investigate new methods for the qualitative and quantitative determination of melamine. Specific aims were to: evaluate and modify an existing GC-MS15 and HPLC-DAD method16, published by US FDA, for the determination of melamine in pet food and baby milk powder formulae ; develop a novel HPLC fluorescence detection (FLD) method for the determination of melamine in pet food and baby milk powder formulae ; compare these methods to a commercial ELISA detection method for the determination of melamine in pet food samples previously implicated in the poisoning of dogs ; apply NIR spectroscopy with subsequent multivariate analysis to rapidly determine melamine in pet food; and compare the different methods statistically with respect to their analytical performances.

Contaminated sites are found all around the world. In order to contain these contaminants, engineers propose capping the contaminated sediments with a sand cap. When capping these contaminants, the sand causes consolidation to occur and could cause a slope failure if the contaminants were on a slope. Investigating the properties of these contaminated sediments allows for proper analysis of a slope failure. The primary objective of this research was to determine the shear strength of contaminated sediments. Since soil samples from actual contaminated sites are highly variable and difficult to explain, the soil used in this research project was mixed and controlled in the lab. A mixture of Kaolinite, water and mineral oil (NAPL, non-aqueous phase liquid) was used for the specimens. Different oil amounts were placed into the specimens to create different scenarios. The different oil combinations included: 100% water, 100% oil, 90% oil, 70% oil, and 50% oil. All of the specimens were fully saturated, and the specimens that had less than 100% oil contained water in the remaining percentage. Consolidated Undrained and Consolidated Drained triaxial tests were performed on the specimens. The constructed specimens were subjected to consolidation stages ranging from 0.6psi to 29psi in confining pressure. The main focus of the study was on low confining pressures. After consolidation the specimens were sheared either undrained or drained. Both tests were utilized in order to see the difference in the pore pressures generated. Failure envelopes were developed for the different oil contents that contained three dimensions included the shear strength, the effective stress, and the pore pressure difference between the pore oil pressures and the pore water pressures. Also, the behavior of oil-dominated versus water-dominated was determined. Results from the 100% water specimens were comparable to previous data. The shear strength for the 100% oil specimens was higher than the 100% water specimens, but lower than the 90% oil and 70% oil specimens. The 50% oil specimens resulted in a great deal of variability on whether the specimen was water-dominated or oil-dominated. The main conclusion was that the Kaolinite had an increase in strength with the introduction of mineral oil. / text

Το πρόβλημα της ρύπανσης του εδάφους και του υδροφόρου ορίζοντα έχει πάρει ανησυχητικές διαστάσεις τις τελευταίες δεκαετίες. Η βιομηχανική ανάπτυξη πέρα απο τις θετικές συνέπειες που έχει για την ζωή των ανθρώπων, έχει δυστυχώς επιφέρει προβλήματα ρύπανσης του υπεδάφους και του υδροφόρου ορίζοντα με επικίνδυνες οργανικές ενώσεις. Η αλόγιστη και ανεύθυνη διαχείριση και διάθεση των αποβλήτων έχει αρνητικές και συχνά μη αντιστρεπτές συνέπειες για το οικοσύστημα και την δημόσια υγεία. Ανάμεσα στις μεθόδους για την αντιμετώπιση του προβλήματος της ρύπανσης του εδάφους και των υπογείων υδάτων, οι βιολογικές μέθοδοι κερδίζουν ολοένα έδαφος λόγω του χαμηλού κόστους, της αποτελεσματικότητας και του ελάχιστου αριθμού παραπροϊόντων. Οι βιολογικές μέθοδοι αποσκοπούν στην αποκατάσταση των εδαφών με την χρήση γηγενών μικροοργανισμών του εδάφους. Η κινητική ανάπτυξης των μικροοργανισμών στο έδαφος διαφέρει σημαντικά από την κινητική ανάπτυξης όταν οι μικροοργανισμοί αιωρούνται σε καλά αναδευόμενα περιβάλλοντα. Η συγκεκριμένη εργασία έχει σαν στόχο να μελετηθεί η κινητική ανάπτυξης ενός γηγενούς βακτηριακού πληθυσμού, του Pseudomonas fluorescens κατά την βιοαποδόμηση της φαινόλης σε κατάλληλη πειραματική διάταξη, χρησιμοποιώντας ως πρότυπο πορώδες μέσο πυριτική άμμο (SiO2) η οποία αποτελεί ένα από τα βασικότερα συστατικά του εδάφους. Η φαινόλη είναι μία αρωματική ένωση η οποία χρησιμοποιείται συχνά στην βιομηχανία για την παρασκευή χρωμάτων, πλαστικών και φαρμάκων. Εξαιτίας της ευρείας χρήσης της, συναντάται συχνά στο έδαφος και τον υδροφόρο ορίζοντα. Για τον σκοπό αυτό έγιναν αρχικά πειράματα σε διαφορικές κλίνες άμμου με πηγή άνθρακα την γλυκόζη έτσι ώστε να αναπτυχθεί η κατάλληλη πειραματική διάταξη και διαδικασία για την περαιτέρω μελέτη της κινητικής ανάπτυξης του μικροοργανισμού Pseudomonas fluorescens. Στην συνέχεια μελετήθηκε η κινητική ανάπτυξης του μικροοργανισμού χρησιμοποιώντας ως πηγή άνθρακα την φαινόλη σε κλίνες άμμου. Παράλληλα έγιναν και πειράματα διαλείποντος έργου για την μελέτη της κινητικής ανάπτυξης του συγκεκριμένου μικροοργανισμού σε υγρές καλλιέργειες με θρεπτικό υπόστρωμα τόσο την γλυκόζη όσο και την φαινόλη. Σκοπός των πειραμάτων αυτών ήταν ο προσδιορισμός των κινητικών παραμέτρων. Τέλος αναπτύχθηκε κατάλληλο θεωρητικό μοντέλο για την προσομοίωση της κινητικής ανάπτυξης ενός βακτηριακού πληθυσμού στην μικροσκοπική κλίμακα. Απώτερος στόχος του θεωρητικού μοντέλου σε συνδυασμό με τα πειραματικά αποτελέσματα είναι να γίνει αποσαφήνιση των μηχανισμών αποδόμησης τοξικών ρύπων στην μικροσκοπική κλίμακα απο γηγενή βακτήρια και να αναπτυχθούν απλά κριτήρια για την πρόβλεψη και τον σχεδιασμό αποτελεσματικών μεθόδων αντιμετώπισης περιπτώσεων ρύπανσης του υπεδάφους και του υδροφόρου ορίζοντα. / The problem of soil and groundwater contamination has been increasing in the last few decades. Industrial growth is usually accompanied by pollution of groundwater with hazardous organic compounds. Irresponsible disposal of organic compounds into the soil has serious adverse consequences for the ecosystem and public health. Among methods that have been proposed for remediation of contaminated soils, biological methods using microorganisms which are indigenous in soil, are preferable because of their low cost, effectiveness and the low production of byproducts. Growth kinetics of microorganisms in soil differs significantly from growth kinetics of microorganisms suspended in a well-mixed stirred tank reactor. The aim of the present work was the experimental study of growth kinetics of a soilindigenous strain of the bacterium Pseudomonas fluorescens in sand packs (model soil) during the biodegradation of phenol. Phenol is an aromatic organic compound, which is widely used in industry, e.g. in paints, plastics, pharmaceuticals and many other products. Due to its extensive use, phenol is a common pollutant, especially in soil and groundwater. Experiments were initially conducted in sand packs, using glucose as a carbon source. The purpose of these experiments was the setup and test of the experimental procedure. Further experiments of growth kinetics in sand packs were conducted using phenol as a carbon source. In order to determine the growth kinetic parameters of Pseudomonas fluorescens for glucose and phenol biodegradation, batch experiments in liquid cultures were conducted. Finally, a hybrid simulator was developed for the theoretical investigation of growth kinetics of a bacterial population consisted a biofilm in microscale. The further aim of the theoretical simulator combined with the experimental results, was the elucidation of biodegradation mechanisms of toxic compounds by soil-indigenous bacteria in microscale, in order simple criteria for the prediction and remediation of polluted soils and groundwater to be developed.

Trends show that the fraction of the world's population with electronic devices using modern integrated circuits is increasing at a rapid rate. To meet consumer demands: less expensive, faster, and smaller electronics; while still making a profit, manufacturers must shrink transistor dimensions while increasing the number of transistors per integrated circuit; a trend predicted by Gorden E. Moore more than 44 years prior. As CMOS transistors scale down in size, new techniques such as atomic-layer deposition (ALD) are used to grow features one atomic layer at a time. ALD and other manufacturing processes are requiring increasingly stringent purities of process gases and liquids in order to minimize circuit killing defects which reduces yield and drives up manufacturing cost. Circuit killing defects caused by impurity incursions into UHP gas distribution system can come from a variety of sources and one of the impurity transport mechanisms investigated was back diffusion; the transport of impurities against convective flow. Once impurity incursions transpire, entire production lines are shut down and purging with UHP gas is initiated; a process that can take months thus resulting in tens of millions of dollars in lost revenue and substantial environment, safety, and health (ESH) impacts associated with high purge gas consumption. A combination of experimental investigation and process simulation was used to analyze the effect of various operational parameters on impurity back diffusion into UHP gas distribution systems. Advanced and highly sensitive analytical equipment, such as the Tiger Optics MTO 1000 H2O cavity ring-down spectrometer (CRDS), was used in experiments to measure real time back diffusing moisture concentrations exiting an electro-polished stainless-steel (EPSS) UHP distribution pipe. Design and operating parameters; main and lateral flow rates, system pressure, restrictive flow orifice (RFO) aperture size, and lateral length were changed to impact the extent of back diffusing impurities from a venting lateral. The process model developed in this work was validated by comparing its predictions with data from the experiment test bed. The process model includes convection, molecular diffusion in the bulk, surface diffusion, boundary layer transport, and all modes of dispersion; applicable in both laminar and turbulent flow regimes. Fluid dynamic properties were directly measured or were obtained by solving Navier-Stokes and continuity equations. Surface diffusion as well as convection and dispersion in the bulk fluid played a strong role in the transport of moisture from vents and lateral branches into the main line. In this analysis, a dimensionless number (Peclet Number) was derived and applied as the key indicator of the relative significance of various transport mechanisms in moisture back-diffusion. Guidelines and critical values of Peclet number were identified for assuring the operating conditions meet the purity requirements at the point of use while minimizing UHP gas usage. These guidelines allowed the determination of lateral lengths, lateral diameters, flow rates, and restrictive flow device configurations to minimize contamination and UHP gas consumption. Once a distribution system is contaminated, a significant amount of purge time is required to recover the system background due to the strong interactions between moisture molecules and the inner surfaces of the components in a gas distribution system. Because of the very high cost of UHP gases and factory downtime, it is critical for high-volume semiconductor manufacturers to reduce purge gas usage as well as purge time during the dry-down process. The removal of moisture contamination in UHP gas distribution systems was approached by using a novel technique dubbed pressure cyclic purge (PCP). EPSS piping was contaminated with moisture, from a controlled source, and then purged using a conventional purge technique or a PCP technique. Moisture removal rates and overall moisture removal was determined by measuring gas phase moisture concentration in real time via a CRDS moisture analyzer. When compared to conventional purge, PCP reduced the time required and purge gas needed to clean the UHP gas distribution systems. However, results indicate that indiscriminately initiating PCP can have less than ideal or even detrimental results. An investigation of purge techniques on the removal of gas phase, chemisorbed, and physisorbed moisture, coupled with the model predictions, led to the testing of hybrid PCP. The hybrid PCP approach proved to be the most adaptable purge technique and was used in next phase of testing and modeling. Experiments and modeling progressed to include testing the effectiveness of hybrid PCP in systems with laterals; more specifically, laterals that are "dead volumes" and results show that hybrid PCP becomes more purge time and purge gas efficient in systems with increasing number and size of dead volumes. The process model was used as a dry-down optimization tool requiring inputs of; geometry and size, temperature, starting contamination level, pressure swing limits of inline equipment, target cleanliness, and optimization goals; such as, minimizing pure time, minimizing purge gas usage, or minimizing total dry-down cost.

Copper based interconnects with low dielectric constant layers are currently used to increase interconnect densities and reduce interconnect time delays in integrated circuits. The technology used to develop copper interconnects involves Chemical Mechanical Planarization (CMP) of copper films deposited on low-k layers (silica or silica based films), which is carried out using slurries containing abrasive particles. One issue using such a structure is copper contamination over dielectric layers (SiO2 film), if not reduced, this contamination will cause current leakage. In this study, the conditions conducive to copper contamination onto SiO2 films during Cu-CMP process were studied, and a post-CMP cleaning technique was discussed based on experimental results. It was found that the adsorption of copper onto a silica surface is kinetically fast (< 0.5 minute). The amount of copper absorbed is pH and concentration dependent and affected by presence of H2O2, complexing agents, and copper corrosion inhibitor Benzotrazole. Based on de-sorption results, DI water alone was unable to reduce adsorbed copper to an acceptable level, especially for adsorption that takes place at a higher pH condition. The addition of complex agent, citric acid, proved effective in suppressing copper adsorption onto oxide silica during polishing or post-CMP cleaning by forming stable copper-CA complexes. Surface Complexation Modeling was used to simulate copper adsorption isotherms and predict the copper contamination levels on SiO2 surfaces.Another issue with the application of copper CMP is its environmental impact. CMP is a costly process due to its huge consumption of pure water and slurry. Additionally, Cu-CMP processing generates a waste stream containing certain amounts of copper and abrasive slurry particles. In this study, the separation technique electrocoagulation was investigated to remove both copper and abrasive slurry particles simultaneously. For effluent containing ~40 ppm dissolved copper, it was found that ~90% dissolved copper was removed from the waste streams through electroplating and in-situ chemical precipitation. The amount of copper removed through plating is impacted by membrane surface charge, type/amount of complexing agents, and solid content in the slurry suspension. The slurry particles can be removed ~90% within 2 hours of EC through multiple mechanisms.