Çevre Teknolojisi

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Reuse of textile dyebaths by treatment with advanced oxidation
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 1998., 1998.) Tezcanlı, Gökçe.; İnce, Nilsun.
The urgent need to conserve, recycle, and reuse the limited water resources of the earth has forced mankind to research and develop new methods and technologies for treating and managing used waters from process, cooling and/or rinse facilities of industrial applications. This is especially important in textile dyeing and finishing industries, where huge amounts of water are consumed in dyeing and washing/rinsing ofthe fabrics. The purpose of this study was to investigate the reusability of dyebath effluents in a textile batch dyeing process, by a homogeneous advanced oxidation system, involving H20 2 and ferrous sulfate in the presence and absence of UV-light. Synthetic dye bath effluents were prepared using a reactive azo-dye, Procion Red HE-7B, which was selected as a model compound for its wide use in the industry. Effectiveness of the system was tested by monitoring the degree of color and total organic carbon degradation. Parameters such as chemical oxygen demand and total dissolved solids were also monitored. Reusability of the treated water was tested in a dyehouse with various azo dyes. Under the experimental conditions employed, it was found that complete color removal and 71 % total organic carbon degradation is possible in 20 min of UV irradiation. The treated effluent was found to be reusable in cotton batch dyeing, yielding satisfactory dye quality on the fabric. Estimated cost of reusing dyebath effluents after treatment with the proposed technique was found to be 1.54 per m3 • The corresponding cost of using commercial water supply was estimated to be 2.42 per m3.
Powdered activated carbon addition to activated sludge in the treatment of landfill leachate
(Thesis (M.S.) - Bogazici University. Institute of Environmental Engineering, 1999., 1999.) Aktaş, Özgür.; Çeçen, Ferhan.
Powdered activated carbon (PAC) addition to activated sludge is a convenient method in the treatment of wastewaters that contain high amounts of nonbiodegradable and inhibitory organics. In the biological treatment of leachate in combination with domestic wastewater, leachate constituents may exert adverse effects on the efficiency of the activated sludge process. The purpose of this study was to investigate the effectiveness and applicability of PAC added activated sludge systems in the treatment of leachate in combination with synthetic domestic wastewater. The first step in the experimental path of the study was the determination of adsorption characteristics of the activated carbon used in the study. The succeeding steps involved the biological treatment studies in PAC added activated sludge reactors. The second step was treatment of leachate in batch reactors. The third step was treatment in Semi-Continuously Fed Batch reactors which were used to simulate the Continuous-Flow Stirred Tank: Reactor (CFSTR). The fourth step was PAC addition to a continuous-flow activated sludge reactor. The results of the study demonstrated that PAC addition to activated sludge is a promising method for the treatment of leachate in combination with domestic wastewater. PAC addition resulted in considerable reductions in the effluent concentrations of organic matter due to the adsorption of nonbiodegradable organics. It was found that the removal of organic matter was a simple combination of adsorption and biodegradation in the PAC added activated sludge systems for the conditions encountered in this study. Also, bioregeneration of activated carbon hypothesis was not valid. But, PAC addition increased nitrification rates through the enhancement of nitrifier activities by adsorbing the inhibitory and/or toxic compounds in the leachate.
Deretmination of the remaining stabilization potential of landfilled solid waste by sludge addition
(Thesis (M.S.)- Bogazici University. Institute of Environmental Technology, 1999., 1999.) Güleç, Şükran Başak.; Onay, Turgut T.
Research activities on the innovative landfill management techniques are becoming attractive research areas in the last decades due to increasing amounts of solid waste by increasing industrialization and urbanization. In these landfill management techniques, determination of the stabilization potential of solid waste and the degree of stabilization at the site play important role because the degree and rate of stabilization in a landfill can be valuable parameter for future predictions of leachate and gas generation, determination of the feasibility of a landfill methane recovery program, evaluation of the closure time and the final use of the site. In this study, the remammg stabilization potential of solid waste retrieved from an operating landfill was investigated by the anaerobic digestion of the waste with anaerobically digested sludge with differing sludge:waste ratios. Four reactors were placed in a temperature controlled aquarium and loaded with different sludge:waste ratios in order to determine the remaining stabilization potential, to find the optimum ratio for the highest methane yield and to investigate the use of sludge as an enhancement technique for the waste degradation. The results of the study suggested that the addition of anaerobically digested sludge was an effective technique for the enhancement of solid waste degradation. Among the different sludge:waste ratios, the highest ratio 1:4 was found the optimum one for the enhancement and for the methane production in the study. The remaining stabilization potential of the retrieved solid waste was determined as 7% at the end of the study.
Evaluation of in situ leachate management alternatives on municipal solid waste stabilization in sanitary landfills
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 1999., 1999.) San, İrem.; Onay, Turgut T.
An alternative approach for treating municipal solid waste involves the treatment of the waste after landfilling by addition of moisture to the waste. Increasing attention is being given to municipal solid waste landfill leachate recycle (recirculation) as a means of in situ leachate treatment and landfill stabilization. Using a leachate recycle, a landfill may be operated as a municipal solid waste bioreactor treatment system rather than as a conventional waste dumping site. In order to study the feasibility of an in situ leachate management alternative to provide leachate treatment and waste stabilization two landfill simulating reactors, one with leachate recycle and one without, were constructed and sited in the laboratory's hot room (34°C). Leachate recirculation volume and frequency of recirculation were changed periodically to investigate the effects of different operational moisture regimes on waste stabilization and leachate treatment. Both reactors were filled with municipal solid waste having typical solid waste composition determined in Istanbul. This research showed that the leachate recirculation is a feasible way to treat the leachate in situ, and, therefore, decrease the cost of further external treatment. Leachate recirculation management strategy accelerates the stabilization rate of waste matrix, decreasing time required for stabilization to a matter of months rather than years. Four times per week recirculation strategy was found to provide highest degree of waste stabilization.|Keywords: leachate recirculation, landfill stabilization
An state-of-the-art design technique in landfill engineering :|a case study
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2001., 2001.) Aykan, S. Birkan.; Onay, Turgut T.
Disposal of solid wastes, the final functional element of the solid waste management system. is a major problem throughout the industrialized world. Sanitary landfilling is today widely recognized as the most common and economic method and viable solution for the disposal of municipal and industrial solid wastes. Despite the implementation of waste reduction recycling and transformation technologies disposal in landfills still remains an important component of integrated solid waste management strategy. The purpose of this study was to present the design steps of sanitary landfills through Sinop (Meşedağı) sanitary landfill project. The study indicates that planning and design of modern landfills involves the application of a variety of scientific. economic and engineering principles. The main criteria in design studies were the Turkish Environmental Regulations. The other main feature of the study was the evaluation of the differeat models and approaches employed in the design of modern landfills. In this manner. it is intended to gather appropriate data by comparing the results. The major topics covered in this study include description of the landfill site, estimation of population and solid waste generation. definition of waste properties, slope and berm stability analysis. design of sub-base liners and Dnal (ap, estimation of leachate generation and design of leachate collection system. design of surface water drainage system, estimation of gas generation and design of gas venting system, design of leachate treatment plant and closure of landfill and longterm monitoring.
Soil metal interactions and investigation of extractive metal removal pathways
(Thesis (Ph.D.) - Bogazici University. Institute of Environmental Sciences, 2001., 2001.) Özkaraova, Emre Burcu.; Bekbölet, Miray.
The aim of this work was to interprete the interaction of zinc with soils varying in composition and investigate methods for the removal of zinc from soil. The adsorption behaviour of zinc was evaluated with isotherms, kinetic studies and sequential fractionation. The findings derived from isotherms were in consistence with the results of sequential extraction experiments, suggesting the presence of more than two sites participating in the adsorption of zinc. Thus, it was presented that high affinity sites with high binding energies like iron and manganese oxides and carbonates were occupied at lower zinc concentrations, and low affinity sites with low binding energies like exchangeable sites at higher zinc concentrations. The removal of zinc with naturally occurring humic and fulvic acids was found to be low. The reason of this could not be explained by the number of functional groups involved in the extractions. The adsorption of humic and fulvic acid was proposed as the mechanism hindering the removal of zinc. The removal of zinc with synthetic chelating agents such as EDT A and DTPA increased with increasing EDT A and DTP A concentrations, revealing efficiencies over 100 %. These observations were well explained with the stoichiometric molar ratios and the pH dependent speciation of EDT A and DTP A. Sequentia.l extraction experiments helped to understand from which soil fraction zinc was taken by humic acid, EDT A and DTP A. Thus, humic acid preferred to remove zinc adsorbed by the exchangeable sites of soils, whereas EDT A and DTP A took the zinc associated with carbonates and iron and manganese oxides.
In situ immobilization of the selected heavy metals by sulfide compounds in landfills under methanogenetic conditons
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2001., 2001.) Erses, Aliye Suna.; Onay, Turgut T.
Co-disposal is a technique for the controlled disposal of hazardous wastes together with municipal solid waste. Co-disposal of industrial wastes including heavy metals and disposal of household hazardous substances such as batteries, paints, dyes and inks -in paper result in release of heavy metals into a landfill environment. Zinc, iron, nickel, copper and cadmium are the most common heavy metals disposed to landfills. These metals are controlled by several attenuation mechanisms including adsorption, acid-base, oxidation-reduction and precipitation-complexation reactions. This research aimed to better understand the extent of heavy metal attenuation in landfills by means of precipitation by sulfide compounds. The effect of selected heavy metals (Zn, Cu, Cd, Fe, Ni) on solid waste stabilization together with the effect of leachate recirculation on the attenuation mechanisms was also investigated. For this purpose, two landfill simulating reactors were used in the laboratory. These reactors were constructed and filled with shredded and compacted municipal solid waste having typical solid waste composition determined for istanbul region. Two reactors, one with leachate recirculation, the other without were operated in the constant temperature room of 32°C to enhance the growth of anaerobic microorganisms. Moreover, moisture addition was done into the reactors in order to simulate the annual rainfall. After the onset of the methanogenetic conditions in both reactors, the selected heavy metals including iron, copper, nickel, cadmium and zinc were added into the simulated landfill reactors. The metals (Fe, Cu, Ni, Cd, Zn ) were prepared by dissolving the metal salts in one liter deionized water and introduced into the bioreactors according to the amounts suggested for co-disposal under the directives of the Turkish Hazardous Waste Control Regulations to prevent inhibition of the microbially mediated processes during waste stabilization This research indicated that when sulfide concentration was very low or insufficient, the removal of the metals was controlled by other anions such as C03 = and P04- 3 until the reduction of sulfate coming from loaded metal salts into the reactors Moreover, leachate recirculation offers opportunities for more rapid waste stabilization including attenuation of co-disposed heavy metals.
Surfactant sorption & desorption on soil surfaces of varying clay content
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2001., 2001.) Küçükaşık, M. Faruk.; Yenigün, Orhan.; Atay, Zeynep.
In this research, sorption and desorption behavior of selected surfactants were investigated on a soil sample that was mixed with different clays at different ratios. The surfactants investigated were a cationic surfactant Benzethonium chloride (Hyamine 1622) and an anionic surfactant Sodium Dodecyl Sulphate (SDS). The clays were Kaolin, Attapulgite, and Calcium-Montmorillonite. The sorption and desorption isotherms of soils were fitted to the Langmuir and Freundlich isotherm equations, and related sorption and desorption constants were calculated from these isotherms. It was found that the sorption capacities for all of the three different types of clay at different mixing ratio for Hyamine were higher compared to those of SDS. On the other hand, desorption capacities for SDS is better than those of Hyamine.
Microbial population dynamics in an anaerobic completely stirred tank reactor treating a pharmaceutical wastewater
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2001., 2001.) Öz, Nilgün Ayman.; İnce, Bahar Kasapgil.
In this study, effects of a chemical synthesis based pharmaceutical wastewater on performance of an anaerobic completely stirred tank reactor (CSTR) and activity of acetoclastic methanogens, number and composition of methanogens and non-methanogens were evaluated. The CSTR was initially fed with glucose. After that, it was fed with preaerated pharmaceutical wastewater diluted by glucose at different dilution ratios and then with raw pharmaceutical wastewater diluted with pre-aerated wastewater to enable acclimization of acetoclastic methanogens to the wastewater which contains nonbiodegradable/ toxic compounds for the anaerobic treatment. At initial study with glucose, 92% soluble COD removal efficiency was achieved with the CSTR at an organic loading rate (OLR) of 6 kgCOD/m3.d corresponding to an FIM ratio of 0.43 with a HRT of 2.5 days. Methane yield was 0.32 m3CfLJkgCOD and specific methanogenic activity (SMA) was found to be 336 mICHJgTVS.d. After initial study with glucose, the CSTR was fed with several dilutions of pre-aerated pharmaceutical wastewater with glucose (10%, 30% and 70%) and then 100% pre-aerated pharmaceutical wastewater. Due to the deteriation in the performance and decrease in the activity of acetoclastic methanogens after feeding with 100% pre-aerated pharmaceutical wastewater, HRT was increased from 2.5 days to 3.5 days. 71% soluble COD removal efficiency was obtained with a HRT of 3.5 days where methane yield was 0.28 m3CH4/kgCOD. However, SMA value was found to be 166 mICHJgTVS.d indicating approximately 47% activity loss ofthe acetoclastic methanogens compared with the results of feeding with glucose. Finally, raw pharmaceutical wastewater diluted with pre-aerated wastewater was fed into the CSTR in increasing ratios of 10%, 30% and 60%. Although a slight decrease in the performance was seen at a dilution ratio of 10% raw wastewater, there was a decrease in all parameters including soluble COD removal efficiency, methane yield, activity test results and an increase in total VF A concentration at a dilution ratio of 60% raw phannaceutical wastewater. According to the results of the SMA test indicating poor activity of acetoclastic methanogens, the study was discontinued at this ratio. According to the microbiological studies, there were variations in the dominant species and the ratio of acetoclastic methanogens to total bacteria during the operation. Methanococcus like species and short rods were dominant species after the operation with glucose. Short rods and medium rods were dominant at the end of the operation with 100% pre-aerated wastewater while short rods remained most dominant species until the end of the study. The ratio of acetoclastic methanogens to the total bacteria decreased at the end of the operation with glucose from 38% to 30% when 60% raw phannaceutical wastewater was introduced to the CSTR.
Effect of powered activated carbon addition on substrate removal and sludge characteristics in leachate treatment
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2001., 2001.) Kılıç, Emel.; Çeçen, Ferhan.; Erdinçler, Ayşen.
The performance of activated sludge process depends on substrate removal efficiency and a good separation of biomass from the supernatant. Powdered Activated Carbon (PAC) addition to activated sludge is a promising method in the treatment of wastewater containing non-biodegradable and inhibitory substances. Substrate removal efficiency can be enhanced via addition of PAC to activated sludge systems in the treatment of leachate combined with domestic wastewater. The increase in substrate removal is due to adsorption of non-biodegradable and inhibitory and/or toxic compounds in the leachate. Moreover, addition of PAC has an effect on settling and dewatering characteristics of activated sludge. The purpose of this study was to investigate the effect of powdered activated carbon (PAC) addition on substrate removal and sludge characteristics in the cotreatment of leachate and domestic wastewater. In the first pali of the experimental path of the study, leachate and domestic wastewater were mixed at different ratios and PAC was added at various concentrations to batch reactors. Also, a control reactor was used which was fed under the same conditions as the PAC added reactor. Results showed that leachate could be treated successfully even if the leachate ratios was high (20-25 %) in the activated sludge system. The inert COD in PAC added activated sludge systems was lower than in activated sludge reactors. Results of the study also showed that the Specific Resistance to Filtration (SRF) increased during removal of readily biodegradable COD alld then tended to decline. Moreover, the SRFs of the sludges were higher if the leachate ratio increased. This showed that the dewaterability of the sludge decreased when the leachate ratio in the feed increased. As a general trend, in most of the runs, PAC addition suppressed these SRF increases. In the next step, leachate (diluted) and domestic wastewater were treated alone. The aim was to have an idea about the effect of leachate and domestic wastewater in the case of combined treatment. In the case of diluted leachate, although COD removal was considerable, sludge characteristics were negatively affected. PAC addition to leachate bad a positive effect. The effect of PAC was most obvious in the case of diluted leachate showing that leachate constituents were highly adsorbable onto activated carbon. The presence of domestic wastewater always resulted in a decrease in SRF or an increase in dewaterability. In the treatment of domestic wastewater alone, very high COD removal was observed and PAC addition did not result in additional COD removal. The SRF values of this sludge were much lower compared to leachate and co-treatment.
Effect of radical scavengers on the performance of advanced oxidation processes
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2002., 2002.) Gültekin, Işıl.; İnce, Nilsun.
Advanced Oxidation Processes (AOPs) rely on the generation of short-lived, powerful and non-selective hydroxyl radicals (·OH) that are responsible for the destruction of a wide range of contaminants in wastewaters. The efficiency of AOPs depends on the production of ·OH and utilization of it effectively by the target contaminants. Non-target substances, or radical scavengers that exist in wastewaters reduce the efficiency of AOPs by consuming significant amounts of ·OH.The purpose of this study was to investigate the kinetics of reactive dyestuff degradation by an advanced oxidation system using ultraviolet light (UV) and hydrogen peroxide (H2O2), and the effect of ·OH scavenging species such as bicarbonate, carbonate and chloride on the efficiency of the process.The method involved preparation of synthetic dye solutions using a reactive azo dye, Procion Red HE-7B, which was selected as a model compound for its wide use in the industry. The effectiveness of the employed system was tested by monitoring the degradation of color and organic carbon in the absence and presence of scavengers.It was found that in the absence of scavengers, 15 minutes was sufficient for complete color removal, whereas 1 hour contact time was necessary for 92 per cent organic carbon degradation. In the presence of scavenging species, the rate of color removal was inhibited and the degree of inhibition increased with increasing concentrations of bicarbonate and carbonate species. It was further found that chloride inhibited the degradation of color only at 100-1250 mM chloride, and did not affect the rate at higher concentrations.The rate of color and organic carbon degradation was found to follow first order kinetics with respect to concentration, and second order kinetics with respect to ·OH. The bimolecular color and organic carbon rate constants with ·OH was estimated by using a simplified kinetic model describing the reaction mechanism. The estimated constants were in good agreement with the published data for azo dyes.
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.
Land use change analysis of Erdemli-Kız Kalesi region by using GIS methodology
(Thesis (M.S.) - Bogazici University. Institute of Environmental Sciences, 2002., 2002.) Oral, Hasan Volkan.; Yenigün, Orhan.; Mater, Barış.
According to scientific authorities in the year of 2025, the majority of the world's population around 5 billion people will be living in urban areas. As human settlements expand, prime agricultural land and habitats such as wetlands, forests, and watersheds are transformed into land for housing, roads and industry. In the developing countries the urban poor, searching an alternative place to live, often establish informal settlements in ecologically fragile areas.Changes in land-use and land cover have important consequences for natural resources through their impacts on soil and water quality, biodiversity, and global climatic systems. Land use and changes are particularly related to increase of population and intensive agriculture. With the awareness of the importance of land-use changes at coast sides, the study of regional or global land use change has become the focus of much scientific authorities and international organizations. From past to future remote sensing technology has been recognised as a useful means of supplying up to date information on activities within the urban environment . At the same time, computer based geographic information systems are being used to improve the management and use of information. The aim of the study is : to determine the land use changes through the years in the coast of Erdemli and Kizkalesi by using the Geographical Information System , ARC- VIEW GIS software and ER MAPPER .
Modeling of SO2 emissions from Yatağan power plant
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2003., 2003.) İm, Ulaş.; Yenigün, Orhan.
The meteorological model, CALMET, and its plume dispersion model, CALPUFF, were used in order to simulate the dispersion of SO2 emitted from Yatağan Power Plant and its effect on Yatağan district in the episodic event on December 2 and 3, 2000. CALMET was used to predict the hourly meteorological fields for 96 hours, starting from December 1, 2000, to December 4, 2000, while CALPUFF was used to predict the hourly ground level SO2 concentrations over a region of 15 km x 15 km grid with 1 km resolution. The meteorological data were obtained from two meteorological stations: surface data from Yatağan Meteorological Station, and upper air data from Isparta Meteorological Station. The emission data was taken from Yatağan Power Plant. It is found that south westerly and light winds and the nighttime surface inversion layers lead to accumulation of pollutants over Yatağan district. The results are compared with the measurements done by Local Environmental Authorities of Muğla. The simulation results indicate that the maximum ground level concentrations were found northeast from the source, which agrees with experimental measurement. On the other hand, the magnitude of results obtained with the model shows some differences compared with experimental measurements. The SO2 concentration levels are calculated to be very high in the morning hours of December 2 and 3, 2000. Overall, the results indicate that Yatağan district suffered seriously on these days. The sensitivity analysis showed that the concentrations are directly proportional to the emission rates, but wind speed is the most significant meteorological parameter on air pollution modeling compared to other meteorological parameters.
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.
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.
Effects of ozonation, photocatalystic oxidation, and sequential oxidation on coagulation of humic acids
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2004., 2004.) Şen, Sibel.; Bekbölet, Miray.
In this study, coagulation behavior of untreated and treated humic acids with two different types of metal coagulant and two types of polyelectrolyte as coagulant aid were investigated. The aim of this study was to understand the coagulation efficiencies of different type of coagulant and the mechanisms underlying the contribution of pretreatments to coagulation. Pretreatment were done by ozonation, photocatalytic oxidation and sequential oxidation in which ozonation was applied as pretreatment stage for partial oxidation of humic acids prior to photocatalytic oxidation using TiO2.The coagulation properties of humic acid were evaluated according to Color436 and UV254 values. These parameters were calculated for treated and untreated humic acid samples as well as for alum, ferric chloride, and combination of metal coagulant with anionic and nonionic polyelectrolyte. Coagulation efficiencies decreased with pretreatments regardless of the type of the coagulants used. However, anionic and nonionic polyelectrolytes were effective coagulant aids for the coagulation of humic acid. Especially, polyelectrolyte more effective for untreated humic acid than treated humic acid. Removal percentages of UV254 and Color436 values increased with using metal salts combining with anionic and nonionic polyelectrolyte. Nevertheless, applied high dosage of primary coagulant combining with low synthetic polyelectrolyte led to higher removal percentages of humid acid than applied low dosage of primary coagulant combining with high dosage of synthetic polyelectrolyte. Furthermore, using metal salts combining with anionic and nonionic polyelectrolyte lead to decrease in used primary coagulant.
Mathematical modeling of a biogas recovery system at the İZAYDAŞ, Kocaeli sanitary landfill
(Thesis (M.S.)-Bogazici University. Institute of Environmental Sciences, 2004., 2004.) Cıngır, Alper.; Onay, Turgut T.; Copty, Nadim.
The purpose of this study is to asses the potential of landfill gas generation and recovery from Lot 7 of the İZAYDAŞ solid waste disposal site in Izmit, Turkey. A multi-step model is developed to evaluate the performance and aid in the operation of an active gas collection system for Lot 7. The model consists of three main components: a water balance model, HELP; a gas generation model, LANDGEM; and a gas flow model, MODAIR, based on the MODFLOW computer program. The results of this study indicate that the main factors influencing the efficiency of the gas collection system are: decay rate of the organic component of the solid waste, the mode of operation of the active gas collection system, the air permeability of the soil cover. Specifically, the decay rate controls the duration of the most active gas generation period and the required extraction rates to capture the generated gases. Time-dependent gas extraction rates, as opposed to time-invariant extraction rates, was shown to lead to reduced gas losses into the atmosphere and higher landfill gas concentration in the collected gas. Moreover, the use of low permeability soil cover can also lead to reduced air intrusion into the collection system.
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.
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.

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