Aerobic sludge granulation is a new technology that has been developed for biological wastewater treatment. Compared with conventional activated sludge, aerobic granules allow better sludge-water separation and a higher biomass concentration. However, the mechanism of the transformation from sludge flocs to granular sludge under the aerobic condition is still unclear. Deterioration of aerobic granules in long-term operation is also a concern for its scale-up application. The present study was conducted to investigate the crucial factors for aerobic granulation and its underlying mechanism. In addition, the stability of aerobic granules under unfavorable conditions and the recovery of deteriorated granules in bioreactors were also studied. For formation of aerobic granules, gelation-facilitated biofilm growth was proposed as a new mechanism for the granulation process. Simulation of granule formation was performed in a well-controlled chemical system to provide an experimental proof for the proposed aerobic granulation theory. Granule formation was achieved in a particle suspension with latex microspheres for bacterial cells and alginate and peptone for extracellular polymeric substances (EPS), together with the cation addition and floc discharge. In the mixture with the dosing of alginate and a small amount of peptone, artificial gels and granules could be well formed, and the artificial granules share the similar micro-structure as the aerobic bacterial granules. However, as the dose of peptone increased, gels were not formed and only large particle flocs were produced. The formation of artificial granules proves that effective EPS interactions with cations and the subsequent gelation are crucial to aerobic granulation in bioreactors. In relation to granulation, the effect of the substrate feeding pattern on the microbial yield was tested. The results show that the bioreactor with a more frequent substrate feeding interval had a lower sludge yield than the reactor (0.45 vs. 0.55) with a less frequent feeding. The sludge fed less frequently was able to store more substrates as intracellular substances, resulting in more biomass growth. Moreover, a long feeding interval would force the biomass into the feast-famine regime, which was found to enhance microbial growth and granulation, producing granules with a compact and stable structure. For the stability of aerobic granules, various factors that would been countered in biological wastewater treatment were experimented. The results show that granules deteriorated in structure under unfavorable conditions, such as a low solution pH (pH~6.0), a high loading rate, and feed of starch instead of glucose into the bioreactors. In some deterioration cases, filamentous bacterial growth became more dominant and the granules became loose and fluffy flocs. Compared to mature granules, fresh granules were less stable and more vulnerable to the unfavorable conditions. As the granules deteriorated in structure, their surface roughness values increased considerably from 35 or less to more than 230. Under a favorable condition with a feed of sodium acetate, the deteriorated granules could be recovered in some reactors. However, deterioration of the granules caused by filamentous growth at a low pH or high loading rate could hardly be recovered. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

Anaerobic digestion (AD), as one of the oldest human biotechnology, has attracted revived research focus on the underpinning biological principle in recent years due to its potential in renewable green energy. With the assistance of the latest 454 deep sequencing technology, two independent studies were conducted with a shared goal to understand the operational influences on the AD microbiology from the unprecedented depth and breadth of genetic information. The first study aimed to decipher the contribution of a newly-devised waste sludge pretreatment method, which promised significant improvement in downstream biogas production. The first application of whole genome metagenomic approach on this topic revealed extensive shifts in both microbial and functional consortia towards higher biodegradation after pretreatment; meanwhile dominant acetoclastic and hydrogenotrophic methanogenesis pathways were identified concurrently with an alternative enzymology in Methanosaeta. The second study focused on the temporal dynamics of bacteria residing in production-scale biogas bioreactor coupled with multiple-sampling strategy for a realistic description of the actual microbial structure. Both bacterial fingerprint marked by feedstock and evolutionary drive towards biodegradation were revealed by 16S rDNA amplicon multiplex pyrosequencing, where clustering analyses further delineated the taxonomic plasticity and functional resilience of the bacterial communities over time. Phylogeny coverage of the highly diverse population was also improved by the adopted strategy, providing insights for sampling and sequencing standards. Altogether, the combined results garnered knowledge enrichment to the relationship between AD microbiology and operational parameters, which will assist the design of more efficient bioenergy platform in future. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

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Many studies have demonstrated that sewage treatment plants do not efficiently degrade pharmaceuticals such as antibiotics, hormones, and analgesics. Ozonation has been identified as a promising technique to degrade those compounds. A series of experiments was used to evaluate the impact of three parameters on the efficiency and kinetics of degradation of sulfamethoxazole, an antibiotic, by ozonation. An ozone reactor was designed to perform experiments. Analytical techniques, based on liquid and gas chromatography and mass spectrometry, were developed to measure concentrations of sulfamethoxazole and identify degradation products. / It was shown that the rate constant and the degradation efficiency are greater when the initial concentration of sulfamethoxazole is lower; the presence of other contaminants in solution decreases the percentage of degradation observed, and the concentration of hydrogen peroxide, used as catalyst, must be well adjusted since an inappropriate concentration hinders the reaction. Finally, the analysis of ozonated samples allowed the identification of degradation products and resulted in a proposed degradation mechanism.

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Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on May 22, 2009. Major professor: Nirupam Pal, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Civil and Environmental Engineering." "March 2009." Includes bibliographical references (p. 88-90). Also available on microfiche.