Ph.D. Theses
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Item Analysis of CO2 emissions resulting from electricity sector in Turkey by using Boğaziçi University Energy Modeling System (BUEMS) modeling framework(Thesis (Ph.D.) - Bogazici University. Institute of Environmental Sciences, 2022., 2022) Kalkan, Emre.; Erdinçler, Ayşen.Due to factors such as industrialization, increase in population and economic growth electricity demand has shown a significant increase at global scale. This increase has put forward discussions concerning electricity supply security, source diversification and clean electricity generation. Fossil based electricity generation featured the transition to clean generation in this sector. Particularly, towards the goal of the Paris Agreement, policy developments have gained momentum to reach carbon neutral electricity sector by 2050. These developments have been closely monitored by Turkey. The purpose of this thesis is to evaluate long-term results of the CO2 emissions resulting from electricity sector in Turkey by using BUEMS model in line with latest available data and updated policy papers. Total electricity installed capacity, generation portfolio and increase in electricity demand were investigated. In the context of the thesis, a Base scenario was established. The response of the electricity sector under carbon tax and emission restrictions and their effect to CO2 emissions were analyzed. The results of the study showed that tax and emission targets played an important role for CO2 emission reduction. In Base Scenario, Total CO2 emissions exceeded 1,000 Million tons and electricity sector’s contribution was almost 680 Million tons in the year 2057. Among all scenarios the highest decrease was obtained under Peak Emission Scenario. Total emissions reduced to 705 Million tons and emissions from electricity sector decreased by 61% compared to Base Scenario and fell to 244 Million tons in 2057 by means of renewables and nuclear penetration.Item Electrocoagulation and advanced oxidation as intermediate effluent treatment steps for water reuse in a textile dyeing plant(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2005., 2005.) Alaton, Gilbert İzzet.; İnce, Nilsun.Dyehouse effluents are highly colored and contain significant amounts of dissolved and suspended solids so that in most cases the use of membrane separation technologies as a final treatment stage becomes inevitable to achieve high quality process water for reuse purposes. The inherent disadvantage associated with most chemical treatment processes is that they increase the salinity of the final, treated effluent and hence chemical intense methods are generally considered as impractical or impossible to prepare water for reuse. A successful reuse plant for textile dyehouse effluent should ideally involve a system, which will compensate for all sudden changes in the biotreated effluent in order to ensure safe and stable operation of the membrane units. Consequently, the treatment unit that is going to be implemented has to be flexible enough to comply with the existing treatment units. The present experimental work aimed at proposing advanced chemical treatment schemes (electrolysis and ozonation) for the effective and economical remediation of biologically pre-treated textile industry wastewater (average CODo = 370 mg/L; BOD5 < 20 mg/L; Suspended Solids (SS) = 130 mg/L; Dissolved Solids (DS) = 10,000 mg/L; Color as absorbance at 436 nm = 0.280 1/cm; pH = 7.5; SO42- = 1250 mg/L) instead of the more commonly applied "phase - transfer" - limited multi-stage filtration processes. In addition, a more recently developed advanced oxidation process (sonochemical treatment) was employed for the degradation of the most problematic effluent stream of the textile dyeing and finishing sector, namely the dyebath effluent. Spent dyebaths were simulated to explore the effect of ultrasound on decoloration and degradation of dyes in auxiliaries present in spent dyebaths under varying reaction conditions.Electrolysis of biotreated dyehouse effluent appeared to be effective in terms of COD, color and SS once optimized for operating conditions (pH, current, contact time) and electrode materials (iron, aluminum, iron/aluminum). It was also shown that different color removal mechanisms existed for different electrode materials. Indirect redox reactions were found to be responsible for color abatement during electrolysis using iron electrodes, whereas color removal with aluminum electrodes occurred via physical adsorption. A continuous electrochemical system was also developed to simulate real electrochemical treatment conditions and estimate operating costs. The system enabled satisfactory floc formation, coagulation, flotation and sludge separation in one single reactor with iron electrode. However, it did not qualify when Al was used as the electrode. Results indicated that the efficiency of the electrochemical systems did not change when the biotreated effluent was of much lower quality, emphasizing the robustness of electrochemical process as a "buffer" stage between secondary and tertiary treatment.A detailed cost evaluation in terms of operating expenses was also undertaken for all investigated systems.Item Ultrasonic destruction of trihalomethanes: optimization of system parameters(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2006., 2006.) Ercümen, Yonca.; İnce, Nilsun.Disinfection of drinking waters is a major public health triumph of our age. However, while the pathogenic microorganisms provide the primary health risk from drinking water, chemical disinfection by-products also introduce an unintended health hazard. Trihalomethanes are the most common by-products of disinfection with chlorination. Due to their carcinogenic properties, removal of trihalomethanes from drinking water has become an important public health concern. Research into the use of ultrasound in environmental protection has received a considerable amount of attention with the majority of investigations focusing on the harnessing of cavitational effects for the destruction of biological and chemical pollutants in water. Sonochemical removal of hydrophilic compounds has been investigated more than hydrophobic compounds. In this study sonolytical removal of trihalomethanes from aqueous solutions has been investigated. Chloroform was selected as a model compound for the investigation of factors affecting sonolytical trihalomethanes removal. The sonolytical removal of chloroform was studied at three distinct frequencies and at different power densities. The effect of different sparging gases on chloroform removal was investigated using argon, air, nitrogen and oxygen. The effect of hydroxyl radical reactions on chloroform removal was investigated through the use of radical scavangers. The effect of trihalomethanes combinations on the removal rates of chloroform and bromoform were investigated. The results obtained from the model compound studies were compared with results obtained from tap water treatment studies. Finally, the effect of sonolysis on the acute toxicity of tap water was investigated using the Microtox test method.Item Optimization of ultrasonic reactors for bacterial and organic matter decay(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2005., 2005.) Kıdak, Rana.; İnce, Nilsun.Public concern for the environment has taken on a new prominence with wastemanagement becoming a priority. As a consequence, new and environmental friendly methods for pollutant degradation are vastly investigated. Advanced Oxidation Processes,involving ozonolysis, photolysis, electron beams and ultrasonic irradiation have beenidentified as viable alternatives to such research. In recent years, chemistry with ultrasoundwaves has become a method of interest among other Advanced Oxidation Processes, owing to the extreme conditions generated during acoustic cavitation. These extremes aresuch that water molecules are fragmented into radical species, such as the hydroxyl radical,which is the most powerful chemical oxidant ever known.The dissertation presented herein is about the investigation of advanced oxidation techniques particularly, ultrasound for the remediation of water contaminated withbacterial and organic constituents. The method of study involved the application of threeultrasonic frequencies under various ambient conditions on infected water samples andsynthetic effluents containing phenol and phenolic derivatives. Reactor effluents were monitored for assessing the reduction in bacterial density and phenolic concentration.The results were evaluated with the aim of optimizing process parameters anddetermining the reaction kinetics. Moreover, the study with phenol covered comparison ofultrasonic decay with that of ozonolysis and assessing impacts of combined ultrasound, ozone and UV applications.It was found that the efficiency of bacterial decay under 20 kHz ultrasonicirradiation could be enhanced by the addition of solid catalysts such as activated carbon,metallic zinc, ceramic beads. The reaction kinetics was found to represent that of chemical disinfection with chlorine.The degradation of phenol was found to proceed with maximum efficiency under300 kHz irradiation at acidic pH and ultrasound rendered detoxification of water samples along with phenol degradation, although mineralization was not effective. Combination ofultrasound with ozone and UV irradiation was found to induce synergistic effects as aconsequence of the enhancement in the mass transfer rate of ozone and photolysis ofultrasound-induced hydrogen peroxide to generate excess hydroxyl radicals.Item Degradability of synthetic dyestuff by acoustic cavitation: impacts of system conditions and physical /chemical agents(Thesis (Ph.D.)-Bogazici University. Institute of for Environmental Science, 2003., 2003.) Güyer, Gökçe Tezcanlı.; İnce, Nilsun.The use of ultrasound in environmental applications is a novel advanced oxidation process that is currently being investigated as a method to degrade refractory organic wastes, which can not be degraded by conventional wastewater treatment methods such as biological, chemical and combinations thereof. The application of ultrasound to environmental problems relies on the process of acoustic cavitation: the formation, growth, and implosive collapse of micro bubbles in a liquid. The collapse of such bubbles creates hot spots with temperatures as high as 5000 K, and pressures up to 800 atm, and cooling rates in excess of 1010 K s-1. These conditions are responsible for a variety of physical and chemical effects. Hydroxyl radicals that are formed during the homolytic cleavage of water molecules upon bubble collapse can be utilized to degrade many compounds including persistent environmental pollutants. In addition, radical formation can be enhanced by coupling of ultrasound with oxidants and/or UV light. In this dissertation, the degradation of pure and synthetic dyebath solutions of 9 textile dyes were investigated in three ultrasonic systems (System I: 300 kHz, SystemII: 520 kHz, and System III: 3 x 520 kHz frequency), in the presence and absence of chemical oxidants (ozone, hydrogen peroxide, ferrous ion) and/or UV light. The impacts of system conditions, physical/chemical agents, dye properties and dye-bath matrix on sonolytic destruction of textile dyes were studied. The performance of the systems was assessed and compared with each other by monitoring color, organic matter, toxicity, total dissolved solids, total organic carbon, and chemical oxygen demand degradation, and the increase in biochemical oxygen demand.In case of system comparison, the efficiency of the studied systems with respect to decolorization of the test solutions was such that: System I > System II > System III. System efficiency with respect to the calculated product yield was in the order: System II > System I > System III. Injection of different gasses during ultrasonic irradiation showed that rate of decolorization increased in the sequence: Ar > O2 > Air, and maximum decolorization was obtained with an Ar:O2 gas mixture, at a ratio of 66 per cent Ar to 34 per cent O2.It was found that, the decolorization rate of all dyes was more closely related to their structural properties than to the composition of the dye-baths. Anthraquinone dyes bleached faster than azo dyes. The presence of a-substituents around the -N=N- bond accelerated the decolorization rate. Decolorization of dyes with a single OH substituent in ortho position to their reactive component was faster than those with a second a-substituent such as SO3. Decolorization was decelerated by the formation of ionic sites. Decolorization in dyebath effluents was inhibited only in the presence of sufficiently large carbonate and chloride ions.The abatement in the visible absorption of sonicated dye solutions and dyebaths was always larger than the abatement in their UV absorption. Toxic dyes were detoxified by ultrasound within short contact, but ultrasound was not effective in the overall degradation of the dyes as measured by chemical oxygen demand and total organic carbon of the effluents, unless combined with physical/chemical agents. Sonication of dye solutions in the presence of O3, Fe2+, H2O2, and/or UV irradiation increased degradation yields considerably with respect to those applied individually. The most effective combined scheme was ultrasound/ozone/UV irradiation.Estimated bimolecular rate coefficient of azo dyes with hydroxyl radicals was calculated as 1.22 x 109 M-1s-1. Estimated operational costs of System I, II and III for 45 per cent bleaching of azo dyes were 3.52 USD m-3, 3.37 USD m-3, 9.98 USD m-3, respectively. The cost of O3/US combination in System III was 2.57 USD m-3, and the operation cost of ozonation was 3.60 USD m-3.Item Application of mechanical vapor recompression (MVR) evaporator system on industrial wastewater treatment(Thesis (Ph.D.)-Bogazici University. Institute of , 2005., 2005.) Ashraf, Muhammad.; Saygın, Ömer.As a principle "recycling should be preferred over treatment wherever possible". In line with this, a multipurpose Mechanical Vapor Recompression (MVR) evaporator pilot plant was designed, fabricated and tested at a pilot plant level with the aim of recovering water and valuable components from industrial wastewaters. A cost of 2.5-3.0 US$ was found to be necessary for evaporation of one ton of wastewater. It was found with different wastewaters that generally the distillate was of a quality which is comparable to many raw water sources used today by the industry (200-500 uS/cm), which have a value of about 1.0 US$. The experiments showed distillates are not of required quality in the presence of solvents or foaming detergents. Even if the distillate is marketed the total cost does not allow this technology to compete with classical wastewater treatment except in cases where classical methods fail (high organic, inorganic or toxic load). Experiments with zinc-bath wastewaters showed that MVR technology can easily separate pure ZnSO4 by fractionated crystallization from other constituents, the value of which is in order of magnitude greater than the evaporation costs. It is believed that this feasibility situation should be the rule for chemicals recovered from wastewater.Item Cometabolic degration of trichloroethylene (TCE) and 1,2-dichloroethane (1,2-DCA) in nitrification systems(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2005., 2005.) Kocamemi, Bilge Alpaslan.; Çeçen, Ferhan.Public concern for the environment has taken on a new prominence with wastemanagement becoming a priority. As a consequence, new and environmental friendlymethods for pollutant degradation are vastly investigated. Advanced Oxidation Processes, involving ozonolysis, photolysis, electron beams and ultrasonic irradiation have beenidentified as viable alternatives to such research. In recent years, chemistry with ultrasoundwaves has become a method of interest among other Advanced Oxidation Processes,owing to the extreme conditions generated during acoustic cavitation. These extremes are such that water molecules are fragmented into radical species, such as the hydroxyl radical,which is the most powerful chemical oxidant ever known.The dissertation presented herein is about the investigation of advanced oxidationtechniques particularly, ultrasound for the remediation of water contaminated with bacterial and organic constituents. The method of study involved the application of threeultrasonic frequencies under various ambient conditions on infected water samples andsynthetic effluents containing phenol and phenolic derivatives. Reactor effluents weremonitored for assessing the reduction in bacterial density and phenolic concentration. The results were evaluated with the aim of optimizing process parameters anddetermining the reaction kinetics. Moreover, the study with phenol covered comparison ofultrasonic decay with that of ozonolysis and assessing impacts of combined ultrasound,ozone and UV applications. It was found that the efficiency of bacterial decay under 20 kHz ultrasonicirradiation could be enhanced by the addition of solid catalysts such as activated carbon,metallic zinc, ceramic beads. The reaction kinetics was found to represent that of chemicaldisinfection with chlorine. The degradation of phenol was found to proceed with maximum efficiency under300 kHz irradiation at acidic pH and ultrasound rendered detoxification of water samplesvalong with phenol degradation, although mineralization was not effective. Combination ofultrasound with ozone and UV irradiation was found to induce synergistic effects as a consequence of the enhancement in the mass transfer rate of ozone and photolysis ofultrasound-induced hydrogen peroxide to generate excess hydroxyl radicals.Item Removal of organics in reverse osmosis concentrate by advanced treatment(Thesis (Ph.D.) - Bogazici University. Institute of Environmental Sciences, 2020., 2020.) Birben, Nazmiye Cemre.; Bekbölet, Miray.Due to its effective and reliable purification performance, reverse osmosis technology is one of the practical and affordable ways to produce high quality recycled water. However, a major drawback of reverse osmosis is the production of concentrate usually accounting for 15-20% of the input stream containing high levels of organic pollutants some of which could be toxic and bio-accumulative. Possessing a threat to the environment, reverse osmosis concentrate (ROC) must be treated to reduce or even eliminate the negative impact associated with the presence of organic pollutants. The main objective of this research was to investigate the applicability of homogeneous and heterogeneous advanced oxidation processes on municipal wastewater derived reverse osmosis concentrate treatment. For this purpose, reverse osmosis concentrate samples in the absence and presence of emerging contaminants were synthetically prepared with respect to physicochemical characteristics reported in the literature. Sulfamethoxazole and Carbamazepine were selected as target emerging contaminants owing to their common presence in wastewater sources. UVC/H2O2 and Fenton processes were selected as homogeneous advanced oxidation processes whereas solar photocatalysis by using commercially available photocatalysts as well as synthesized ones was considered as heterogeneous advanced oxidation process. Assessment of selected processes for their effectiveness on the removal of complex organic matter was presented in comparison to the sole photolytic oxidation conditions. Since molecular size distribution profiles of organic compounds in ROC plays an important role in order to assess the removal of different pollutants with respect to different molecular size fractions ROC samples were exposed to molecular size fractionation prior to and following photolytic and photocatalytic degradation processes. Expected potential risk was investigated through toxicity assessment prior to and following photodegradation and photocatalytic degradation processes. Organic fraction of reverse osmosis concentrate samples were monitored mainly by UV-vis and advanced fluorescence spectroscopic techniques in combination with PARAFAC modeling as well as organic carbon content.Item Elucidation of Ammonia inhibition in anaerobic treatment process by using 16S rRNA /DNA based microbial identification techniques(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences,2003., 2003.) Çallı, Barış.; Yenigün, Orhan.A high ammonia landfill leachate was anaerobically treated for more than 1000 days in laboratory scale two different anaerobic reactors configured as sludge blanket and hybrid bed. Effects of high ammonia concentrations on reactor performances were correlated to the variations in methanogenic diversity by using 16S rRNA/DNA based microbial identification techniques such as FISH (fluorescent in-situ hybridization), DGGE (denaturing gradient gel electrophoresis), cloning and DNA sequencing. However, sudden and unexpected fluctuations in the characteristics of leachate resulted in complications during evaluation of results. Therefore, five laboratory scale anaerobic reactors seeded with different sludges were operated for 450 days under stable COD loads and gradually increasing total ammonia levels from 1000 to 6000 mg/l. Methanosaeta-related species mainly prevailing in seed sludges were substituted for Methanosarcina when FAN (free ammonia nitrogen) exceeded 100 mg/l. Subsequently, as FAN level elevated, rather than any shifts in the methanogenic community, single coccus shaped Methanosarcina cells formed stringent multicellular packets. However, when the FAN level exceeded 600 mg/l, disintegration of Methanosarcina clusters was observed. In contrast, inorganic particles originated from seed sludge provided a good support for Methanosarcina clusters in one reactor and with this special feature it successfully resisted to FAN level as high as 750 mg/l.Item Identification of micropollutants in Ergene river and their biotransformation potential under anaerobic conditions(Thesis (Ph.D.) - Bogazici University. Institute of Environmental Sciences, 2019., 2019.) Emadian, SeyedMehdi.; Tezel, Ulaş.Ergene River spans Thrace from northeast to southwest and joins to Maritsa River, then falls to Aegean Sea at Turkey-Greece border. The river suffers pollution from different sources such as industrial and urban discharges, runoff from agricultural and animal farms. In this study, 222 micropollutants which are listed as contaminants of emerging concern or priority substances, 18 heavy metals and 13 conventional water pollution parameters were measured in 300 samples taken from 75 points on Ergene River at four seasons in the years of 2017-2018. Moreover, major source of micropollutants as well as pollutant fingerprint of major pollution source zones in the watershed were identified. Among the most important conventional parameters, COD, varied between 17 to 1660 mg/L during the year. The highest COD values were observed next to the Evrensekiz OIZ as well as Büyükkarıştıran OIZ consist of different industries such as textiles, dyes, food and chemical industries. Arsenic, aluminum, zinc, copper, lead and chromium concentrations reached to 1.0, 83.9, 33.6, 14.6 and 7.1 mg/L next to the OIZs, respectively. 131, 135, 96 and 103 organic micropollutants were detected in at least one point during summer, fall, winter and spring sampling, respectively. Concentration of micropollutants ranged from 10 ng/L to 330 mg/L. The micropollutants embraced a wide spectrum of chemicals originated from various industrial, agricultural and domestic activities. Benzotriazoles, hexa(methoxymethyl) melamine (HMMM), tris (2-butoxyethyl) phosphate (TBEP) and benzalkonium chlorides (BACs) were the most frequently detected chemicals as well as the ones with the highest concentration. OIZs located next to the Çorlu and Ergene Creeks as well as Büyükkarıştıran OIZ were the main sources of those pollutants. For instance, HMMM was mainly originated from the textile industries located in Büyükkarıştıran OIZ. In addition, biotransformation potential of the aforementioned micropollutants which are mainly discharged from textile and metal industries into the river, at the simulated water-sediment system was tested under anaerobic and sulfate reducing conditions. Benzotriazoles and TBEP were degraded partially whereas no biodegradation was determined for HMMM and BACs. The outcomes of this study can be used to understand the fate of dominant contaminants in the river sediment and develop future pollution mitigation strategies for Ergene River.Item Toxicity-oriented control of advanced oxidation processes a case study on phenol derivatives(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2013., 2013.) Karcı, Akın.; Bekbölet, Miray.; Arslan, İdil.Advanced oxidation processes are expected to be carefully operated and monitored based on their ecotoxicological impact because the partial oxidation of organic contaminants may result in the formation of intermediates more toxic than parent compounds. Toxicity tests in combination with the transformation product analyses could be an important tool for the control of advanced oxidation processes. Considering the commercial importance as well as toxicological properties of chlorophenol and nonylphenol polyethoxylate group phenolic compounds, degradation and detoxification of 2,4-dichlorophenol (2,4-DCP) and nonylphenol decaethoxylate (NP-10) in distilled water and synthetically prepared freshwater were investigated by applying the H2O2/UV-C, Fenton and photo-Fenton advanced oxidation processes that are well-known for their effectiveness in removing many organic pollutants from waste streams. Although not an advanced oxidation process, UV-C photolysis was also included in the study due to the fact that it is becoming an attractive technology in water treatment facilities due to several advantages. The marine photobacteria Vibrio fischeri were employed as the test organism to assess changes in acute inhibitory effect during the studied treatment processes, whereas the umu-test using Salmonella typhimurium TA1535/pSK1002 strain was selected as the genotoxicity assay. Toxicity results were complemented by transformation product analyses performed by means of high performance liquid chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, colorimetry and ion chromatography in order to gain a deeper insight into acute toxicity and genotoxicity patterns during application of the studied treatment processes. The H2O2/UV-C and photo-Fenton processes ensured complete 2,4-DCP removal and near-complete mineralization as well as effective abatement of UV280/254 absorbances. Hydroquinone, chlorohydroquinone, maleic and formic acids and aldehydes were identified as the common transformation products of the studied treatment processes. The most rapid decrease in the acute inhibitory effect was achieved by the H2O2/UV-C and photo-Fenton processes, however a re-increase in toxic effect was evidenced in the former advanced oxidation process when extending the treatment time beyond 30 min. The acute inhibitory effect ultimately measured in synthetic freshwater was higher than that recorded in distilled water for UV-C photolysis and lower for the H2O2/UV-C and Fenton processes, whereas the photo-Fenton process was not significantly affected by the inorganic constituents of synthetic freshwater based on acute toxicity test results. During application of the studied treatment processes in distilled water no significant genotoxic effect was observed with and without metabolic activation. Complete NP-10 degradation that is very fast accompanied with high total organic carbon removal efficiencies were achieved by the H2O2/UV-C and photo-Fenton processes, whereas the Fenton’s reagent provided only poor NP-10 abatement and insignificant mineralization. Aliphatic carboxylic acids including formic, acetic and oxalic acids, aldehydes and polyethylene glycols containing 2-8 ethoxy units were all identified as the degradation products of NP-10 by the studied treatment processes. The photo-Fenton process appeared to be toxicologically safer both in distilled water and synthetic freshwater based on the acute toxicity tests since the inhibitory effect did not increase relative to the original NP-10 solution after treatment. The genotoxic effects obtained in distilled water both with and without metabolic activation followed the order; Fenton > H2O2/UV-C > photo-Fenton > UV-C. Formation of weakly to moderately genotoxic transformation products was evidenced in the presence and absence of metabolic activation when the H2O2/UV-C process was applied to synthetically prepared freshwater. The genotoxic effect levels were typically lower during photo-Fenton treatment of synthetic freshwater contaminated with NP-10 as compared to those achieved with the H2O2/UV-C process both in the presence and absence of metabolic activation.Item Photocatalytic oxidation of humic acid in heterogeneous aqueous systems: a comparative investigation between montmorillonite and kaolinite(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2013., 2013.) Şen, Sibel.; Bekbölet, Miray.Humic acids representing the major fraction of the naturally occurring humic substances are composed of highly functionalized carbon rich polydisperse organic fractions. Clay minerals which are responsible for the transport of inorganic and organic contaminants constitute the main component of the suspended inorganic material in natural waters. The understanding of interactions between humic substances and clay minerals is an important task for the achievement of an effective water treatment performance. The aim of this research was to investigate the influence of montmorillonite and kaolinite as representative clay minerals on the TiO2 photocatalytic degradation of humic acid as the model compound of natural organic matter. The interactions prevailing between humic acid, montmorillonite, kaolinite and TiO2 surface were assessed prior to the application of photocatalysis in order to evaluate the adsorptive and photolytic behavior of humic acids. Adsorption of humic acid onto sole TiO2 and TiO2 in the presence of clay minerals either montmorillonite or kaolinite were assessed by batch adsorption experiments. The changes attained in humic acid were described by UV-vis spectroscopic parameters i.e. color forming moieties (Color436) and UV absorbing centers (UV365, UV280 and UV254), and dissolved organic carbon (DOC) contents. Photocatalytic oxidation of humic acid in the presence of clay particles i.e. montmorillonite or kaolinite was also followed by using specific UV-vis parameters (SUVA365, SUVA280, SUVA254 and SCoA) calculated by respective absorbance measurements (E) through conversion to mass of carbon. Fractional UV-vis parameters (E254/E365; E254/E436; E280/E365; E280/E436, and E365/E436) that signify the removal of color forming groups in relation to the removal of UV absorbing centers revealing further information on the different oxidation pathways through photocatalysis. No noteworthy variation could be detected for fractional UV-vis parameters under photocatalytic conditions for sole humic acid as well as for humic acid in the presence of either montmorillonite or kaolinite. However, a significant correlative interaction was attained between the specific UV-vis and fractional UV-vis parameter (E254/E436) (r2 > 0.80). Therefore, it could be concluded that E365/E436 parameter could be effectively used as a discriminative indicator parameter for the type of clay minerals. Application of the pseudo first order kinetic model revealed both enhancement and retardation effect with respect to the applied montmorillonite and kaolinite doses. Upon non-selective oxidation, a slight rate enhancement could be indicated for Color436, UV365, UV280 and UV254 of HA in the presence of either montmorillonite or kaolinite. However, the presence of clay particles did not significantly change the DOC degradation rate of HA. The effect of ionic strength (Ca2+ loading from 5x10-4 M to 5x10-3 M) was also assessed for the photocatalytic degradation of sole HA and HA in the presence of either montmorillonite or kaolinite. The overall effect of montmorillonite and kaolinite on the photocatalytic degradation of humic acid was also evaluated in terms of molecular size distribution profiles (0.45 μm filtered fraction, 100 kDa fraction, 30 kDa fraction and 3 kDa fraction) described by the specified and DOC normalized specific UV-vis parameters. Besides the effective removal of higher molecular size fractions (100 kDa and 30 kDa fractions), transformation to lower molecular size fractions (< 3kDa) was more pronounced for sole humic acid rather than humic acid in the presence of clay minerals. Scanning electron microscopic (SEM) images accompanying with energy dispersive X-ray analysis were also examined for the elucidation of the surface morphologies of the binary and ternary systems composed of humic acid, TiO2 and montmorillonite or kaolinite both prior to and following photocatalysis. Excitation emission matrix (EEM) fluorescence spectral features were also evaluated for the elucidation of the photocatalytic degradation of sole humic acid and humic acid in the presence of clay minerals either as montmorillonite or kaolinite. The role of Ca2+ ions was also visualized through EEM under the specified conditions. EEM features reflected the irradiation time dependent transformation of the humic like fluorophores to fulvic like fluorophores in accordance with the photocatalytic removal of humic acid. Adsorption of humic acid onto sole TiO2 and TiO2 in the presence of either montmorillonite or kaolinite with Ca2+ were evaluated by the application of batch adsorption experiments. Adsorption properties of humic acid onto sole TiO2 and TiO2 in the presence of clay minerals either as montmorillonite or kaolinite were evaluated in terms of the specified UV-vis parameters as well as DOC. Adsorption isotherms were evaluated in terms of the adsortion isotherm types (Types S, L, and C). Adsorption data of the indicated humic parameters were further modeled by Freundlich and Langmuir adsorption isotherm model. It could be concluded that, the presence of clay particles i.e. montmorillonite and kaolinite would not significantly alter the photocatalytic degradation efficiency of humic acid. This result signifies that photocatalysis could be an alternative treatment option for the successful removal of natural organic matter in water treatement systems. As shown by the results attained through the application of the UV-vis and fluorescence spectroscopic techniques, the chemical composition of the resultant organic matter would be the indicative parameter for the assessment of the drinking water quality. Since chlorination and/or ozonation is widely applied as the final disinfection step, from public health point of view, it is highly recommended that further research should be directed to the evaluation of the possible side effects related to the formation of the disinfection by-products.Item Rapid detection and identification of bacterial pathogens in drinking water sources using DNA-BASED methods and immunoimmobilization technology(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2013., 2013.) Çelikkol Aydın, Şükriye.; İnce, Bahar Kasapgil.; Avcı, Recep.Clean water is a basic requirement for the survival of the planet and is essential for human health. Water-borne pathogens and the diseases they cause have been a serious threat to public health. Drinking water is a major route for spreading of such pathogens. Monitoring of microbial community is one of the most significant practices for prevention of water-related diseases and potential outbreaks. Comprehensive analysis of chemical composition and microbiological structure of drinking water reservoirs is essential for understanding the levels of contamination and pathogenic threats. Rapid pathogen detection methods are critical for on-site experiments. This study involves two parts. The first part covers investigation of physicochemical and bacteriological composition o drinking water reservoirs in İstanbul. Physicoche ical quality was monitored in terms of pH, conductivity, total dissolved solids, salinity, dissolved organic carbon, heavy metals, anions and cations. Bacteriological characterization was performed using culture-independent, DNA-based methods such as DGGE, sequencing and qPCR. The second part includes development of a rapid and sensitive detection method based on immunoimmobilization for selected E. coli strains. A recently developed BiyoTra ® technology was used in co ination with immunoimmobilization method for analyzing field samples taken from water reservoirs. Water samples were taken from water intake chambers of drinking water treatment plants. Chemical quality parameters were mostly in agreement with regulation limits. Bacterial diversity was investigated with a combination of DGGE, band excising and sequencing of excised bands. DGGE revealed the presence of 66 OTUs in samples. Similarity research of DGGE band sequences, bacteria available in reservoir samples belong to the members of Bacteria, Cyanobacteria, Proteobacteria, Actinobacteria, and Bacteroidetes with abundances of 53%, 24%, 16%, 5%, 3% respectively. According to principal component and correlation analysis, Cr, Zn, Co, F-, and NO3- were found to have a significant impact on bacterial community. qPCR was used for quantification of ETEC, EHEC, Legionella and Salmonella targeting specific genes namely LT, stx, mip and hilA respectively. Maximum gene copy numbers for ETEC, EHEC, Legionella and Salmonella were quantified as 6.74x1011, 1.63x104, 1.48x106 and 1.33x106 per 25 ng DNA/l respectively. Pathogenic E. coli strains were efficiently immobilized on gold surfaces activated with antibodies specific to their fimbrial and LPS antigens. The strains were selectively sorted on antibody microarrays. Minimum antibody requirement for effective immobilization of bacteria was determined as 4 g/ml. Minimum detection limit of immunoimmobilization method was 104 cfu/ml. Pre-concentration o environ ental samples using BiyoTrap® considera ly enhanced the immobilization efficiency of target bacteria on antibody modified chips. Minimum detection limit was improved to 102 c u/ l using BiyoTrap®.Item Cake filtration at high biomass nitrogen removing systems(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2013., 2013.) Özdemir, Burcu.; Yenigün, Orhan.Pilot scale cake filtration biological reactor (CFBR) and membrane bioreactor (MBR) were operated (capacity: 100 m3/d) for 26 months. The system was evaluated according to conventional cake filtration theory using its plots of V vs. t and t/V vs. V. Standard blocking model plots of CFBR were compatible (R2> 0.95) for the initial period; the latter was best fitted to the cake filtration model (R2> 0.99). The linearity between t/V and V was observed individually, showing a change of filtration characteristics at the transition point. Results of a particular period (six months) with complete sludge retention were presented to state the sludge production pattern and, the activity and diversity of nitrogen converters. The average sludge yield reached equilibrium after day 105 (0.25 kgMLSS/kgCOD, MLSS~15,000 mg/L). Volatile portion of mixed liquor suspended solids (MLVSS/MLSS) increased– decreased–increased and stabilized around 0.57. Inert material stabilization showed that inerts could be degraded at sufficiently long SRTs. The nitrifier population was adversely affected by gradually increased biomass with insignificant effluent quality change. However, coexistence of aerobic and anaerobic ammonia oxidizers in a partially aerated system was confirmed. The total operation cost of such high biomass filtration system could be 9–15 percent less than that of a biological nutrient removal (BNR) plant because of the decreased expenses for sludge disposal.Item Life cycle management of agricultural and animal wastes through integrated energy systems for a particular region(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2011., 2011.) Şişman, Figen.; Cılız, Nilgün.Life cycle management is very essential to sustainable development which aims a balance between environmental, social and economic dimensions over products’ life cycle. Life cycle management consists of methods to quantify and compare the environmental, social and economical analysis of providing goods and services. While Life Cycle Assessment (LCA) is used for estimating the potential environmental impacts of a product; Life Cycle Costing, LCC, is used to assess the total cost of that product during its life cycle. In this study, GaBi4 software is used as the LCA & LCC tool and EDIP 2003 is used as the LCA methodology. The proposed thesis has been prepared as an application of life cycle management to succeed integrated waste minimization and energy conservation for a specific region in Turkey. The thesis covers the environmental and economical evaluation of a pilot scale anaerobic digestion (AD) and biogas recovery system which has been built in Kocaeli, Turkey. The waste recipe which is utilized for biogas production consists of cattle manures, poultry manures, slaughterhouse wastes, vegetable wastes and grass as raw material. The environmental evaluation is made according to the category indicators which are global warming, acidification, aquatic eutrophication, terrestrial eutrophication, photochemical ozone formation (impact on vegetation), stratospheric ozone depletion and the results are compared with six other scenarios including AD of only cattle manure, fossil fuel resources (coal power plant (PP), natural gas PP) and other renewable energy sources (hydro PP, wind PP, Integrated gasification combined cycle (IGCC)). With a different point of view, these energy production scenarios were evaluated in broad system boundaries and it is determined with this study that if the animal and agricultural wastes are not utilised in anaerobic digestion and biogas recovery system, even the renewable energy systems will be less environmentally friendly. It is determined that only an integrated interpretation of the scenarios can conclude the potential environmental impacts.Item Effect of high concentration granients on hydrodynamic dispersion(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2011., 2011.) Sarıoğlu, Murat Savaş.; Copty, Nadim.The hydrodynamic dispersion of contaminants in the subsurface is commonly described by Fick's Law which expresses the dispersive mass flux as a linear function of the concentration gradient with a constant dispersion coefficient. However, recent research has shown that the relationship deviates from linearity under high concentration gradient conditions. Although, several modifications of Fick’s Law have been proposed in order to account for this deviation under specific conditions, there is still not a broadly accepted tool for modeling the dispersion flux in real environmental applications. This study investigates the effect of high concentration gradients on hydrodynamic dispersion for experimental conditions beyond those considered in the literature, namely, existence of multiple species and low velocity conditions similar to those commonly encountered in natural subsurface systems. In order to test alternative dispersion models and determine transport parameters for subsequent model applications, three sets of stable miscible displacement experiments were conducted in two different types of porous media: (i) tracer experiments, (ii) brine experiments with varying flow rates and concentration gradients, (iii) mixture experiments where brine was mixed with a low concentration contaminant. The laboratory experiments showed that dispersive behavior deviates from Fickian Theory when high density gradients exist, for all high and low concentration solute components in groundwater. A numerical model was developed and validated using the experimental results. The model was then used to perform Monte-Carlo simulations of a transport problem where high concentration gradients exist along with heterogeneity in hydrogeological parameters. Simulation results suggested that non-Fickian behavior may significantly affect observations of transport, subsequent parameter estimations and potential effectiveness of groundwater remediation activities.Item Evaluation of different waste streams as fermentation substrates for microbial biopolymer production(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2010., 2010.) Küçükaşık, M. Faruk.; Yenigün, Orhan.; Öner, Ebru Toksoy.The growing reliance on synthetic polymers has raised a number of environmental and human health concerns. Most plastic materials are derived from nonrenewable resources and not biodegradable. Their distinguishing properties like durability and strength also ensure their persistence in the environment and complicate their disposal. Replacing synthetic polymers with biopolymers offers advantages in terms of biodegradability and biocompatibility however still suffers from high production costs. Therefore most research has shifted towards development of cost-effective ways of producing these biopolymers. Levan is a homopolymer of fructose with many outstanding properties like high solubility in oil and water, strong adhesivity, good biocompatibility and film-forming ability. However its industrial use has long been hampered by costly production processes which rely on mesophilic bacteria and plants. Halomonas sp. AAD6 halophilic bacteria were found to be the only extremophilic species producing levan at high titers and hence considerable research effort has been directed to combine the advantages of osmoadaptation and halophilicity to favor high yield levan production. As part of this on-going research, in this thesis work, the potential uses of different waste streams like sugar beet and starch molasses, cheese whey powder, sugar beet pulp, olive mill wastewater, and orange bagasses were investigated and based on EPS yields, pretreated sugar beet molasses was found to be superior to others. FT-IR analysis showed that EPSs produced under different conditions were all levan-type polymers and rheological studies revealed that these EPSs have shown the characteristic of low viscosity and appeared to exhibit pseudoplastic behaviours. Flocculating activity of these EPSs were dynamically monitored with a photometric dispersion analyser and one sample was found to exhibit flocculation performance and particles removal efficiency comparable with commercial synthetic polyelectrolytes. Finally, a rough economic analysis revealed that replacing pure sucrose with molasses not only increased the production yields but also resulted in five-fold lower costs of fermentation medium per gram of levan produced.Item Oxidation of aqueous humic substances by ozonation(Thesis (Ph.D) - Bogazici University. Institute of Environmental Sciences, 2002., 2002.) Kerç, Aslıhan.; Bekbölet, Miray.Chemical oxidation techniques have been used in water treatment for the removal of natural organic matter, which produce halogenated organic compounds upon chlorination. Although being a powerful oxidant, ozone is known to be ineffective for oxidizing recalcitrant organics. Accumulation of carboxylic acids upon ozonation makes the complete mineralization impossible or unfeasible. Therefore, in this study ozonation was combined with photocatalytic oxidation using TiO2 for humic acid degradation. First part of this study covers the ozonation kinetics in humic acid solutions. An empirical model was proposed for defining humic acid degradation with ozonation. The proceeding sections cover the combination of ozonation with photocatalytic oxidation in a sequential system in which ozonation was applied as a pretreatment stage. Langmuir-Hinshelwood model as well as first order degradation kinetics model was studied for defining the photocatalytic oxidation of humic acids. Pretreatment by ozonation resulted in increased first order degradation rates during photocatalysis. Adsorption characteristics of humic acids on the catalyst surface were also evaluated. UV absorbance and color were the parameters used to monitor humic acid degradation. The changes in the molecular size distributions were determined in oxidized humic acid samples using ultrafiltration. Trihalomethane formation potential (THMFP) was measured to demonstrate the oxidation efficiencies.Item Analysis of microbial communities associated with anaerobic solvent degradation in sequencing batch reactors by traditional and molecular tools(Thesis (Ph.D.)-Bogazici University. Institute of Environmental Sciences, 2008., 2008.) Öz, Nilgün Ayman.; İnce, Bahar Kasapgil.In recent years, discharges of the organic solvents have been subjected to stringent environmental regulations because of their undesirable effect on living organisms in aquatic environments and human health. Organic solvents such as methanol, isopropanol and toluene are found in wastewaters of several industries such as refineries, paint and pharmaceutical manufacturers. Treatment of solvent-containing wastewaters using anaerobic reactors has gained much attention in recent years as a cost-effective option compared to other treatment methods. However, there are still some concerns in the application of anaerobic treatment processes for this kind of wastewaters due to possible detrimental effect of the compounds present in the waste streams on both activity and microbial community playing crucial role in anaerobic digestion. Defining the effects of solvents on both microbial community structure and activity changes in anaerobic reactors may lead to improvements in the understanding of interactions in the bioreactors, thereby obtaining better reactor performance. Within the scope of the thesis, effects of methanol, propanol and toluene on microbial diversity and activity have been examined for acclimated and unacclimated sludge in anaerobic sequencing batch reactors (ASBR) using particularly Fluorescent in situ Hybridization (FISH), Denaturant Gradient Gel Electrophoresis (DGGE) techniques and Specific Methanogenic Activity (SMA) tests, respectively. In the ASBRs fed with solvents, microbial diversity changed significantly throughout the course of the operation where different wastewater compositions were fed to the anaerobic reactors. In ASBRs fed with solvent-containing synthetic wastewater, percentage of active population in the reactor decreased over the period of operation of the reactors.|Keywords: Bioreactors, Anaerobic treatment, Sequencing batch reactors, Microbial Ecology, Organic SolventsItem A simple method for small scale wastewater treatment plants for the thickening of sludges: mesh filter and foam filter(Thesis (Ph.D.)-Bogazici University. Environmental Sciences, 2008., 2008.) Gökyay, Orhan.; Erdinçler, Ayşen.The ultimate disposal of wastewater sludge (biosolids) continues to be one of the most difficult and expensive problems in the field of wastewater engineering. Wastewater treatment plants generate different sludges, like primary settled sludge, waste activated sludge, chemical sludge and anaerobic sludge, according to their operating systems. These excess sludges have to be managed by reducing their volume and stabilizing them before their ultimate disposal. Generally used volume reduction methods are thickening and dewatering that are usually coupled with conditioning. Sludge thickening and dewatering require either a big capital investment or a big surface area. Moreover, most of the mechanical dewatering technologies use polymers to condition the sludge before dewatering. These polymers have high cost rendering the mechanical dewatering uneconomical. Small-scale wastewater treatment facilities play an important role in the aquatic environment in many countries. Although sludge treatment is essential for overall wastewater treatment, it is difficult and non-economical for small-scale treatment plants to use mechanical equipments. Considering these points, there is therefore a need for alternative technologies for high performance and easy to operate small-scale wastewater treatment facilities. In this study, mesh filter and foam filter are used as a liquid-solid separator instead of the conventional equipments like gravity sludge thickener, dissolved air flotation or centrifuge. By this way, it is possible to reduce the water content of the sludge as mechanical devices and make thickening process economical.