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Sulphate-reducing bacteria are known to play an important role in anaerobic corrosion processes. They are often found associated with metal surfaces and their activities can be of particular economic significance in many industrial areas. The aim of this thesis was to investigate anaerobic corrosion of metals by the sulphate-reducing bacteria in the presence of mixed microbial consortia in various heterogeneous marine environments. A laboratory model system was designed, based on part of an offshore oil storage system. An extensive bacteriological analysis and comprehensive study of the consequent physicochemical parameters involved in the microbial corrosion process was carried out. Particular attention was paid to the activity of the sulphate-reducing bacteria on metal surfaces. A method was developed to measure both acid-volatile and non-acid-volatile sulphur formation, produced by the activity of the sulphate-reducing bacteria on mild steel coupons. The importance of this method is firmly stressed. Previous results involving rates of sulphate reduction estimated without considering non-acid-volatile sulphur product formation, must be interpreted with caution. A study of non-biological methods of analysing corrosion and their various limitations was carried out to assess their usefulness in determining the effect of microbial corrosion in various environments. It must be stated that no single technique can be used to study anaerobic microbial corrosion. Therefore, it is recommended that a series of tests should be utilised. These should include microbiological, chemical and metallurgical methods.

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Combined anaerobic/aerobic processes for municipal wastewater treatment is quite recent; the studies developed have shown these processes are feasible for the removal of organic, nutrient substances and reduction of sludge produced. Previous studies developed at the Marrero Wastewater pilot plant (fully aerobic system) revealed that the minimum solids contact chamber hydraulic residence (HRT) time in which bioflocculation occurs satisfactorily (effluent SS concentrations < 20 mg/L) is 15 min; however, in the combined anaerobic/aerobic system HRT< 100 minutes resulted in poor floc settling properties and turbid supernatants. Exocellular polymeric substances (EPS) have been found to be the key factor for bioflocculation to occur. Past studies in fully aerobic pilot plant demonstrated that the concentration of EPS increased with mixed liquor concentration and solids retention time. The main purpose of this research is to determine the effect of mixed volatile suspended solids(MLVSS), solids retention time(SRT), and dissolved oxygen(DO) in the production of EPS in the combined anaerobic/ solids contact chamber and its relationship with settling parameters. To carry out the objectives of this investigation three experimental phases were developed : 1) The MLVSS concentration was varied between 1000-4000 mg/l, keeping the SRT and DO as constant as possible 2) The SRT was changed between 2-8 days, keeping the MLVSS concentration between 1500-3500 mg/l and DO between 2-3 mg/l 3) the DO concentration was varied between 0-5mg/l. For a DO of zero, EPS were extracted from the sludge produced in the anaerobic reactor. Analysis of the data showed that the combined system proved to be unstable producing unexpected results such as no clear relationship between MLVSS and EPS. For a DO of zero, no EPS are produced and no flocculation takes place; therefore, effluents with poor quality can be expected from anaerobic treatment units. To meet secondary effluent standards in aeration chamber, capable of promoting the transformation from anaerobic to aerobic biota, and the generation of EPS, high SRT and HRT is required. Under these conditions the system anaerobic/solids contact chamber has an excellent potential for providing secondary treatment for municipal wastewater; nevertheless, the system is not as stable as the conventional aerobic one and bulking problems are common and difficult to content.

Introduction: Chronic peridontitis is an inflammatory disease that is caused by the accumulation of bacteria in the form of a biofilm in the periodontal pocket. It can be treated with oral hygiene in conjunction with β-lactam antibiotics. Many oral anaerobic bacteria associated with chronic periodontal diseases have developed resistance to β-lactam antibiotics by virtue of their production of β-lactamase enzymes. This study investigated the prevalence of β-lactamase-producing anaerobic bacteria in the oral cavities of South African patients with periodontitis and the genes responsible for these enzymes production. Methods: Periodontal pocket debri was collected from 48 patients with chronic periodontitis and cultured anaerobically on blood agar plates with and without β-lactam antibiotics. Presumptive β-lactamase-producing isolates were evaluated for definite β-lactamase production using the nitrocefin slide method and identified using the API Rapid 32A system. Antimicrobial sensitivity was performed using a disc diffusion test. Isolates were screened for the presence of the BlaTEM and BlacfxA genes using Polymerase Chain Reaction (PCR). Amplified PCR products were sequenced and the BlacfxA gene was further characterized using Genbank databases. Seventeen isolates containing BlacfxA gene were subjected to broth microdilution technique to determine minimum inhibitory concentrations of Amoxycillin, Augmentin, and Penicillin. Results: Seventy five percent (36 of 48) of patients carried, on average 2 strains of β-lactamase-producing oral anaerobic bacteria, which constituted 10% of the total cultivable oral flora. A total of 85 oral anaerobes were isolated from patients. The predominant isolates were gram negative species such as Prevotella spp (58%), Bacteroides spp (18%) and Porphyromonas spp (7%). The disc diffusion antimicrobial sensitivity test showed that 40% of the strains were resistant to β-lactam antibiotics. PCR results revealed that none of the anaerobes carried BlaTEM. The BlacfxA gene was identified in 51% of the β-lactamase-producing bacteria. Variants of the BlacfxA gene included cfxA2 (77%), cfxA3 (14%) and cfxA6 (9%). Minimum inhibitory concenration antimicrobial susceptibility test results showed that more than 53% of the strains were resistant to β-lactam antibiotics when the BlacfxA gene was present. Conclusions: A high prevalence of β-lactamase-producing oral anaerobic bacteria was found in South African patients with chronic periodontitis. Although, it comprised 10% of their oral flora these anaerobes can protect non-β-lactamase-producers by releasing these enzymes into the environment. The most prevalent β-lactamase gene in this population was BlacfxA subcategory cfxA2 which has epidemiological implications and genetic transfer can occur among these bacteria. On average fifty percent of the isolates that carried this gene were resistant to β-lactam antibiotics therefore alternative antimicrobial agents should be considered in patients that are non-responsive to β-lactam antibiotics. This study indicates that there is a need for education in the dental community regarding antibiotic resistance and regular surveillance with diagnostic testing is needed.

The use of off-farm materials as amendments in anaerobic digestion of manure is an interesting option due to the benefits of boosting biogas production, and making the process more economical for the farmer. The addition of varying amounts of glycerol, which is a by-product of biodiesel production, was used as an amendment to anaerobic digestion of hog manure in lab-scale tests. The use of 2% glycerol produced the greatest amount of methane and biogas, however stabilization time was high, and the digestion of nutrients in the manure decreased. The addition of 4% glycerol resulted in an overloading of COD and digester failure. The addition of 1% glycerol resulted in a doubling of the methane and biogas production and the acclimation period was quite short, while the effluent quality remained good. There were no detrimental effects of using crude glycerol observed compared to using pure glcyerol. Batch tests also showed that smaller additions of glycerol (0.5%, 1%) produced the highest methane yields and were recommended as good co-substrates for anaerobic digestion with hog manure. / February 2009

Tetracyanonickelate (K2(Ni(CN)4), TCN) is one of the most toxic organics to living organisms. In this study, Klebsiella oxytoca (K. oxytoca) SYSU-011 (a cyanide- degrading bacterium), which was isolated from the wastewater of a metal-plating plant, was shown to be able to biodegrade TCN under anaerobic conditions. Two different media (Burk and NFG) were used to grow K. oxytoca. Results indicate that higher TCN biodegradation rate was observed when Burk medium was used as the growth media for K. oxytoca. In the nitrogen source addition experiment, TCN degradation was inhibited by the addition of nitrite. In the carbon source addition experiment, TCN degradation was enhanced by the addition of glucose and fructose. These findings would be helpful in designing a practical in situ or on-site treatment system inoculated with K. oxytoca for the treatment of TCN-containing wastewater.

Nitric oxide (NO) is one of the most important air pollutants in atmosphere mainly emitted from combustion exhaust gas. In this research, a biotrickling filter was designed and operated to remove this pollutant from an air stream using bacteria extracted from the sewage sludge of a municipal sewage-treatment plant. The bacteria were cultured and enriched by either petri dish’s cultivation or liquid cultivation. The adsorption capacity of the ceramic material, which was used as the packing material, was determined to be 34 g-NO/L under 37℃. However, the saturated adsorption capacity of the packing material with the recycling solution is 236 mg-NO/L under the operation temperature 37℃.The result suggested that the microporous structure of the ceramic material not the humidity is the main contributor to the ceramic material adsorption capacity. Both the ceramic material adsorption capacity and the removal capacity of the liquid were limited and saturated in 540 min and 2 min operation, respectively. To obtain the best operation conditions for the biotrickling filter, orthogonal experiments (L9 (34)) were designed. The experimental data were analyzed by the signal to noise (S/N) ratio and ANOVA. The optimal conditions of the biotrickling filter occurred at a temperature of 40℃, a pH of 8.00.05 and a chemical oxygen demand (COD) of 165 mg/L in the recycled water with no oxygen in the system. Inlet oxygen concentration was found to be the most significant factor of the biotrickling filter that has a significant negative effect on the NO removal efficiency. The DNA sequencing of four clones of bacteria showed 93-98% similarity to Pseudomonas mendocina strain. This strain has been analysed by full gene sequencing and proved to be a brand-new strain named as Pseudomonas mendocina DLHK. This strain can transfer nitrate to organic nitrogen. This result indicated the assimilation nitrogen process in this system and suggested that the main nitrogen removal capacity in this system was through biological function. Through the isotope experimental analysis, two intermediate products (15NO and 15N2O) have been found during the biological process of the system by using quantitative gas analysis (QGA). These results indicated the denitrification function in this biotrickling filter. A model was developed to explain the biological process in the biotrickling filter. The averaged error of the measured and modeled data is -0.047. The standard deviation of the error is 0.039. The model prediction is in good agreement with the experimental data, particularly at small packing height. Most NO removal capacity was achieved at the first 5 cm packing material. The effects of the axial interstitial velocity and the biofilm coverage to the NO elimination were studied by the model that provided a basic for the design of a biotrickling filter. The biotrickling filter could be used for exhaust gases treatment. The assimilation function in the biological system could be another way to utilize the nitrogen component in the waste gas from harmful to benign nature. The isotope labeling technology is a new method to detect gas components for complex gas samples. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

The research represents a first approach to measure the utilization potential of ultrasonic pretreatment on six different substrates: fat, oil and grease (FOG), paper sludge, ground switch grass, ground hay, ground wheat straw, and cut wheat straw. Several laboratories techniques were applied to determine the influence of ultrasonication on biogas production and yield, biogas quality, and digestibility ratio. With the data, mathematical definitions of Net Energy Balance and Net Economy Balance were computed to draw a first justification or rejection of the use of this pretreatment technology for the specific substrates. Ultrasonic pretreatment has a significant effect on biogas production and yield as well as digestibility ratio (p-value < 0.0001) from the early stages of digestion until as far as 50 days of digestion. Ultrasonication and macro particle size management did not influence significantly the methane (CH4) content in the biogas (p-value = 0.1793). Also, the impact of ultrasonication on the substrate varies between all studied feedstock. Most of the ultrasonicated digestion cases studied provided a negative Net Energy and Economic Balance except for FOG where a certain window of utilization was found. In the context of an ultrasonication process retrofit upgrade, the technology looks to be more useful for substrates that are hard to digest when the retention time is, unfortunately, longer than common retention time. In the context of a new facility, a design that includes an understood ultrasonication technology has yet a small potential success depending on several variables. The ultrasonication technology for anaerobic digestion is hard to recommend due to its energy consumption that, in many cases, overshadows the energy surplus derived from its use. / MITACS