Thesis (Ph. D.)--New York University, School of Education. / Also on film. eContent provider-neutral record in process. Description based on print version record.

In food processing, inadequate surface sanitation procedures lead to the formation of biofilms in which bacteria attach and aggregate in a hydrated polymeric matrix of their own synthesis. Formation of these sessile communities and their inherent resistance to existing sanitation procedures and agents are at the root of the risk of bacterial infections for consumers. Due to this existing problem, an effective method for reducing biofilm formation in dairy processing equipment is necessary for dairy products processing. Ultraviolet Pulsed light Technology has shown a positive effect in eliminating microorganism populations on food products. The objective of this work is to evaluate the effect of Pulsed light Technology on a biofilm of different dairy component matrices (e.g. Water (control); whey protein isolates (WPI), lactose, and sweet whey). This evaluation will be performed using the three strains of spore forming Bacillus species most common in commercial milk powder (B. subtilis, B. coagulans, and B. licheniformis). The matrix in which the evaluation was made consisted on allowing the attachment of endospores to on to a square 2.5cm x 2.5cm ASI 304 stainless steel coupon. Four Xenon light treatment levels (no treatment, 5 bursts, 10 seconds, 20 seconds and 30 seconds) were applied to the coupon surfaces using the Xenon model RC847 machine. The attachment of Bacillus to stainless steel in water as matrix was 1000 to 3000/ sq cm as measured in our laboratory. Results showed that there was a significant difference in spore reduction depending on the matrix of the biofilm and with the intensity of the Xenon treatment. Reduction in spores ranged from 1 to 4.7 logarithmic reduction cycles depending on the material of the biofilm, the strain of spores and the intensity of treatment. We conclude that there is significant potential to use this technology in maintaining low spore counts in commercial dairy powders.

Occurrence of organic micropollutants (OMPs) in aquatic environment is a worldwide concern. A long list of anthropogenic substances, including pharmaceuticals, hormones, etc., are frequently detected in natural water sources. Wastewater treatment plants are one main source of OMPs pollution, but also a key step to control OMPs dissemination into the environment. This dissertation focuses on the evaluation of Membrane Aerated Biofilm Reactor (MABR) as a sustainable process to treat wastewater polluted by OMPs. Furthermore, application of high intensity pulsed light is proposed as an innovative tertiary treatment to produce reclaimed water of high quality. In Chapter 1, a literature review was performed to investigate the occurrence and toxicity of 12 selected organic micropollutants (OMPs) in surface and ground water and the limitations of current available biological processes. Among these technologies, systems with enriched nitrifying activity were able to enhance the removal of specific OMPs through cometabolic activities. Thus, I proposed the use of a MABR with enriched nitrifying biomass to treat OMP polluted water. In Chapter 2, I studied the influence of biofilm thickness on the removal of 13 OMPs via MABR. Results demonstrated OMP removal was dependent on biofilm thickness and bacterial cell density. MABR demonstrated important efficiencies in the removal of ammonium, COD, acetaminophen and triclosan at early stages of biofilm thickness. However, the removal of nonpolar, hydrophobic 4 OMPs and anionic, acidic OMPs required thicker biofilms, achieving maximum removal at biofilm with 1.02 mm thickness and 2.2 × 106 cell mL-1. In Chapter 3, the contribution of sorption and biodegradation in the removal of OMPs via MABR was evaluated. At three stages of biofilm thickness studied, biodegradation dominated the removal for most OMPs. Heterotrophs played an important role in OMP biodegradation at all biofilm thickness, while autotrophic nitrifiers enhanced their contribution at thickness beyond 0.58 mm. Increased removal of pollutants like estrone and ethinyl estradiol were linked to the MABR enrichment with nitrifying bacteria. Sorption was essential for the removal of lipophilic and recalcitrant pollutants like triclosan. Finally, to provide high quality treated water for reuse, Chapter 4 explores the use of high-intensity pulsed light (HIPL) as post-treatment. The number of pulses and optical energy dose have a significant impact on the OMPs removal. HIPL demonstrated fast kinetics and efficient photodegradation – with significant OMPs removal within milliseconds. The findings from my Ph.D. dissertation indicate that MABR combined with high-intensity pulse light may be an effective treatment train for the efficient removal OMPs present in municipal wastewaters. This combined treatment process could potentially pave the way to produce high quality reclaimed water for various reuse purposes.

Active layer morphology of polymer-based solar cells plays an important role in improving power conversion efficiency (PCE). In this thesis, the focus is to improve the device efficiency of polymer-based solar cells. In the first objective, active layer morphology of polymer-solar cells was optimized though a novel solvent annealing technique. The second objective was to explore the possibility of replacing the highly sensitive aluminum cathode layer with a low-cost and stable alternative, copper metal. Large scale manufacturing of these solar cells is also explored using roll-to-roll printing techniques. Poly (3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl (PCBM) were used as the active layer blend for fabricating the solar cell devices using bulk heterojunction (BHJ), which is a blend of a donor polymer and an acceptor material. Blends of the donor polymer, P3HT and acceptor, PCBM were cast using spin coating and the resulting active layers were solvent annealed with dichlorobenzene in an inert atmosphere. Solvent annealed devices showed improved morphology with nano-phase segregation revealed by atomic force microscopy (AFM) analysis. The roughness of the active layer was found to be 6.5 nm. The nano-phase segregation was attributed to PCBM clusters and P3HT domains being arranged under the solvent annealing conditions. These test devices showed PCE up to 9.2 % with current density of 32.32 mA/cm2, which is the highest PCE reported to date for a P3HT-PCBM based system. Copper was deposited instead of the traditional aluminum for device fabrication. We were able to achieve similar PCEs with copper-based devices. Conductivity measurements were done on thermally deposited copper films using the two-probe method. Further, for these two configurations, PCE and other photovoltaic parameters were compared. Finally, we studied new techniques of large scale fabrication such as ultrasonic spray coating, screen-printing, and intense pulse light sintering, using the facilities at the Conn Center for Renewable Energy Research at the University of Louisville. In this study, prototype devices were fabricated on flexible ITO coated plastics. Sintering greatly improved the conductivity of the copper nano-ink cathode layer. We will explore this technique’s application to large-scale fabrication of solar cell devices in the future work.