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Browsing Çevre Bilimleri by Subject "Anaerobic bacteria."
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Item Anaerobic biodegradation of petroleum based waste(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2018., 2018.) Çalışıyor, Aslınur.; İnce, Bahar Kasapgil.; Aydın, Sevcan.Petroleum is the most common raw energy source which causes soil and groundwater pollution during the exploration, refining, transport and storage. Since the physical and chemical treatment methods have some disadvantages as high cost and secondary waste production, biological treatment methods have become important in environmental studies. Besides aerobic degradation, anaerobic biodegradation is an alternative method that has specific properties such as less biomass production and production of biogas under different electron accepting conditions. In this study, the biodegradability of petroleum-contaminated soil was observed under methanogenic and sulphatereducing conditions at different temperatures in microcosms were inoculated with an aquifer from Leuna, Germany. Biodegradation efficiency, microbial community profile and biogas production rates of microcosms were monitored under different conditions and run for approximately 200 days. Microbial community profiles were observed by using quantitative real time polymerase chain reaction (qRT-PCR), high resolution melting (HRM) and Next Generation Sequencing (NGS) based metagenomics analyses. The performance of biodegradation was determined via Total Organic Carbon (TOC) analysis which can be pre-study for total petroleum hydrocarbon (TPH) analysis. According to the results, degradation of organic matter was more efficient under sulphate-reducing conditions than methanogenic conditions. The TOC removal efficiency was as high as 70% under sulphate-reducing conditions while the TOC removal was ignorable under methanogenic conditions. Especially, microbial community profile under 16S rRNA gene expression is highly related with chemical analysis components as TOC removal, gas production and electron acceptor utilization. Molecular microbial analyses showed that aliphatic and aromatic hydrocarbon degradation occurred in the microcosms and the higher TOC removal efficiencies were related to the change in the microbial community profiles under sulphate-reducing conditions.Item Anaerobic mono-digestion and co-digestion of agricultural wastes and comparison of valorization potentials(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2020., 2020.) Öter, Merve.; İnce, Bahar Kasapgil.Anaerobic digestion is an immense technology for not only waste disposal but also biogas production for agricultural-based residues, however the economic value of the biogas is limited. The transition of anaerobic digestion to produce carboxylates can provide a sustainable future and better valorization. In this study, Turkish delight (D), sunflower head (S), and tea waste (T) were mono-digested and co-digested at neutral pH under mesophilic conditions to determine the best set of substrates that can produce maximum methane gas. Methane yield for each digester was recorded as D (388 ml CH4/g TVSused), S (206 ml CH4/g TVSused), T (69 ml CH4/g TVSused), DS (312 ml CH4/g TVSused), DT (213 ml CH4/g TVSused), ST (173 ml CH4/g TVSused), and DST (234 ml CH4/g TVSused) after 30-day in anaerobic digestion. According to the results, the three sets D, DS, and DST were the ones that produced the highest amount of methane gas within their groups. Bacterial community composition for these three sets was determined using MinIONTM. The family Pseudomonadaceae was observed more numerous in D digester that producing the highest methane than the digesters of DS and DST. Moreover, acidification was also conducted to the three sets D, DS, and DST to determine VFA productions under mesophilic condition at pH 5.5 ± 0.2. According to the valorization results, market values of VFAs (sum of acetic and butyric acid) were 6-13 times higher than methane.Item Behaviour of oxytetracycline in two-phase anaerobic cattle manure digesters and its effects on microbial communities(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2013., 2013.) Akyol, Çağrı.; İnce, Bahar Kasapgil.Antibiotics used in veterinary practice may have inhibitory effects on microorganisms in anaerobic digestion of manure for biogas production as a renewable energy. Since microbial community plays a key role in the digestion process, defining the effects of antibiotics on microbial diversity and activity can lead to improvements in better understanding of interactions between microbial communities and biochemical processes, thus achieving a more efficient system performance in terms of higher digestion capacity and biogas production. In this study, inhibitory effects and behaviour of commonly used veterinary antibiotic, oxytetracycline (OTC) on the system performance and biogas production in a two-phase anaerobic digestion of cattle manure was investigated, as well as degree of acidification of cattle manure was improved. In the first part, different combinations of batch anaerobic digesters were set-up to investigate the optimum operational conditions for acidogenic phase. The digesters were operated at different pH ranges between 5.0 and 6.0; and at different % total volatile solids (TVS). pH of 5.5±0.1 and 6% TVS were found to be optimal due to higher production of VFA and acidification rate. In the second part, a commercially available hydrolytic enzyme mixture was added in order to improve the acidification rate of the cattle manure in the acidogenic phase of a two-phase anaerobic digestion system. Better solubilization resulted in higher VFA productions which caused higher biogas productions than previously achieved. In the third part, 2 seperate two-phase anaerobic cattle manure digesters, one operated with non-medicated manure and the other operated with medicated manure, and furthermore, 2 single-phase digesters were operated for comparison in semi-continuous mode for 60 days. SRT/HRT for two-phase and single-phase operations were 5 days for acidogenic digesters, 15 days for methanogenic digesters and 20 days for single-phase digesters. Organic loading rates were 6.25±0.15 kg TVS/m3 day in two-phase digesters and 1.50±0.02 kg TVS/m3 day in single-phase digesters. Biogas yields of non-medicated two-phase and single-phase manure digesters were almost the same, 299±26 and 289±25 L biogas/kg-TVS added, respectively; however, non-medicated two-phase digester had higher methane yield as 173±15 L CH4/kg-TVS added, which was 150±13 L CH4/kg-TVS added in single-phase digester. In medicated manure digesters, OTC concentration of 3.11±0.12 mg/L caused 35% inhibition on biogas yield and 43% inhibition on methane yield in the two-phase digester. In single-phase digester, OTC concentration of 3.07±0.14 mg/L caused 47% and 52% inhibitions on biogas and methane production, respectively. Reduction in OTC concentrations could have been attributed to abiotic and biotic reduction mechanisms such as photodegradation, temperature, humidity, pH, dilution during feeding of digesters and other environmental conditions, binding to organics and microbial degradation. The results indicated that the two-phase anaerobic digestion performed more efficient in the presence of OTC with respect to the biogas and methane production. According to DGGE and FISH results, almost all bacterial and Archaeal species were negatively affected by OTC. During the digestion period, DGGE results showed that the bacterial diversity in acidogenic digesters and Archaeal diversity in methanogenic digesters were higher than single-phase digesters. Bacteria groups of Firmicutes and Gammaproteobacteria; and Archaeal groups of Methanobacteriales and Methanosarcinales were found as the most abundant microorganisms. FISH results indicated that the relation between digestion period and the activity of microorganisms were mostly effective on Firmicutes and Gammaproteobacteria, showing a decreasing trend towards the end of digestion. In methanogenic activity, OTC presence was comparatively more effective on Methanosarcinales. The activity of Methanobacteriales and Methanosarcinales showed a more stable trend compared to bacteria; however, the ratios of active methanogenic cells were higher in methanogenic digesters compared to single-phase digesters, both in the absence and presence of OTC.Item Effect of different rations of treatment plant sludge on the stabilization of solid wastes at anaerobic and aerobic landfill areas(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2005., 2005.) Güneş, Gıyasettin.; Kocasoy, Günay.Sanitary landfilling is one of the solid waste disposal methods. Sanitary landfills have created problems related to biogas emissions, generation of leachate, and long times required for the area recovery. Aerobic landfilling is a new solid waste disposal method. The supply of proper air flow and leachate recycle to an aerobic landfill accelerates the decomposition of organic materials. In this study, the reactors were loaded with solid wastes mixed with different types and ratios of sludge in order to find out the stabilization of solid wastes under anaerobic and anaerobic conditions. Moreover, after 55th day of the research, both aerobic and anaerobic decomposition rates were tried to enhance by using yeast as additive. The results of the study suggested that disposal of sludges mixed to the solid wastes was an effective technique for the stabilization of the solid wastes. At the end of the analyses, the highest ratio 1/4 was found as the optimum sludge ratio for the stabilization of the solid wastes in both the aerobic and the anaerobic reactors. Moreover, the yeast solution addition was an effective technique for the enhancement of biodegradation. Among the different reactor types, the aerobic reactors were more effective than the anaerobic ones.Item Improvement of biomethane production using rumen bacteria in anaerobic cattle manure digesters(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2017., 2017.) Günel, Gülşah.; İnce, Bahar Kasapgil.One of the most important difficulty of energy production from animal manure in anaerobic conditions is the high cellulose and lignin concentration that limits the speed in hydrolysis stage. Rumen bacteria which reside in the digestive system of herbivores are indicated as an alternative solution to this case. In this study, effect of rumen fluid addition on biogas production and microbial dynamics in batch-wise operated serum bottles with cow manure was investigated. Three experiment sets were conducted, namely Set 1, Set 2 and Set 3 and operated at 36 oC, 41 oC and 43 oC, respectively for 40 days. The highest specific methane yield was found in the Set 2, digester containing 40% as a supportive inocula. Addition of rumen fluid to inoculum effectively improved the bio-methane yield especially in 20 days, resulting in a methane yield of 262 mL CH4/g VS, in which methane content of the biogas was around 52%. Bacterial and methanogenic profiles were detected through NGS-based metagenomics analysis. The phylum Firmicutes, Bacteroidetes and Proteobacteria were determined as the most dominant bacterial phyla. The results from Q-PCR showed that set3, with a high heat of 43 oC, could not set favorable conditions for the rumen bacteria.Item Scale effect of modelling on biogas generation(Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 1984., 1984.) Çukurova, Recep.; Curi, Kriton,Anaerobic decomposition of manure i s an outstanding alternative energy source, appropriate for most developing countries. Several studies related to this subject were conducted so far, however, the effect of the size of the inodel on the efficiency obtained was not investigated. The main purpose of the present study was t o investigate, the scale effect on the perfomance of an anaerobic digestion. To achieve this three digesters , each of different size and voluue, were installed and operated under ambient conditions. The results obtained have shown that: 1. The size of the model has as light effect on the efficiency of anaerobic digestion, better performance being obtained in larger model. 2. Any digester can be operated under ambient conditions if proper insulating precautions are taken. 3. Mixing has a positive effect on biogas generation. 4. The positive effect of yeast on anaerobic decomposition is verified .