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Öğe Arsenic removal by the micellar-enhanced ultrafiltration using response surface methodology(Iwa Publishing, 2020) Gokcek, Oznur Begum; Uzal, NigmetThe present research investigates the removal of arsenic (As) from aqueous solutions using micellar-enhanced ultrafiltration (MEUF) by utilizing two different surfactants: benzethonium chloride and dodecyl pyridinium chloride (BCl and DPCl). The impact of the operating variables and maximum removal efficiency were found under different conditions for BCl and DPCl surfactants. The maximum As rejection efficiency for MEUF with BCl and DPCl surfactants is 92.8% and 84.1%, respectively. In addition to this, a statistics-based experimental design with response surface methodology was used for the purpose of examining the impact of operating conditions, including initial pH, initial As concentration (ppb), and surfactant concentration (BCl, mM) in As-removal from aqueous solutions. In the analysis of the experimental data, a second-order polynomial model that was validated by statistical analysis for the BCl surfactant was used. On the basis of the response model created, the removal of As ions was acquired at optimum operating parameters, including the initial As concentration of 150 ppb, surfactant concentration of 5 mM and pH 10 for the BCl surfactant with 92.8% As-removal efficiency.Öğe Biogas Upgrade Techologies And Biomethane Utulization Oportunities(Mehmet Sinan Bilgili, 2022) Muratcobanoglu, Hamdi; Mert, Ruhullah Ali; Muratcobanoglu, Fatma; Gokcek, Oznur Begum; Demirel, SevgiThe increase at the waste generation and energy demand still remain as a problem to be solved. Anaerobic digestion has a great importance in the term of waste reduction and renewable energy production as a green solution. Methane content of the biogas expresses the energy content and the potential. Removing impurities like CO2 H2S siloxane etc. and increasing the methane content of the biogas is allowing biomethane for further usage. Biomethane can be used as vehicle fuel (diesel replacement), gas grid injection (natural gas replacement), usage as a raw material for ethanol, dimethlyether etc. production other than electricity and heat generation. In this study, biogas upgrade technologies like pressure swing adsorption, membrane processes, scrubbing processes, cryogenic separation and biomethane utilization opportunities in the term of in-situ and ex-situ usage have been reviewed. In addition, the potential utilization areas of biomethane and specific requirements based on biogas quality are investigated comprehensively.Öğe Biomethane enhancement using reduced graphene oxide in anaerobic digestion of municipal solid waste(Elsevier Sci Ltd, 2022) Muratcobanoglu, Hamdi; Gokcek, Oznur Begum; Muratcobanoglu, Fatma; Mert, Ruhullah Ali; Demirel, SevgiThe present research investigated the impact of reduced graphene oxide (rGO) addition on the semi-continuous anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) in the range of 0.5-10 gVolatileSolid(VS)/L(reactor)day organic loading rates (OLR). Adding rGO enhanced the rate and yield of biomethane production, and the maximum biomethane increment rate was obtained as 110% at an OLR of 4.0 gVS/L(reactor)day. However, after increasing the OLR to 6 gVS/L(reactor)day, there was a dramatic decrease in biomethane production because of volatile fatty acid (VFA) accumulation. Methanotrix is the predominant archaeal genus at OLRs lower than 6 gVS/L(reactor)day in reactors (89-97%). An increment in biomethane production was associated with the higher abundance of the Methanothrix genus in the rGO-supported reactor (rG) than in the control reactor (rC).Öğe Investigation of the treatability of pre-coagulated slaughterhouse wastewater using dead-end filtration(Wiley, 2021) Ozdemir, Safiye; Uzal, Nigmet; Gokcek, Oznur BegumBACKGROUND In the present study, the performance of the membrane process, one of the advanced treatment methods that can enable the reuse of slaughterhouse wastewater, was evaluated. The wastewater was treated using ultrafiltration (UF) (10, 50 kDa), nanofiltration (NF) (150-300 DA) and reverse osmosis (RO) (500 kDa) membranes alone, and UF + NF, UF + RO membrane combinations at different pressures. In addition to rejection and permeate flux considerations, it was attempted to select the most effective membrane by performing scanning electron microscopy, Fourier transform infrared, contact angle, and atomic force microscopy analyses of the membranes used. RESULTS As a result of the experiments, the highest flux was observed at 5 bar for the 50 kDa UF membrane. When the performances of the sequential application of 10 and 50 kDa UF membranes followed by NF and RO membranes were evaluated, the highest flux was obtained for the sequential application of the 50 kDa UF membrane with the NF membrane as 19.68 and 9.05 L m(-2) h, respectively. CONCLUSION The highest chemical oxygen demand (COD) removal was obtained for the RO membrane at 20 bar as 88.67%, and for the 50 kDa UF + RO sequential application, the COD removal was increased from 70% to 88.67%. (c) 2021 Society of Chemical Industry (SCI).Öğe LINKAGE OF OPERATIONAL PARAMETERS AND MICROBIOME IN ANAEROBIC CO-DIGESTION WITH GRAPHITE(Yildiz Technical Univ, 2020) Demirel, Sevgi; Gokcek, Oznur Begum; Muratcobanoglu, HamdiIn terms of renewable energy sources, studies on increasing the amount of methane produced per unit feeding materials have attracted attention in recent years. Many different methods like chemical, physical, thermal, and thermochemical processes have been applied to anaerobic digesters for enhancing biogas production efficiency. Recently, besides these processes, supporting anaerobic digestion (AD) system with conductive materials like graphite, magnetite, activated carbon, etc. is one of the trend topics. In this paper, the effect of graphite on biogas/biomethane production potential was investigated for co-digestion of food waste (FW) and cow manure (CM). Additionally, the relationship between the distribution of anaerobic microbial structure and operational conditions is examined using Redundancy analysis (RDA) revealed that Clostridium could enhance to methanogenesis process through conductive materials such as graphite. These findings will improve the understanding of the mutual relationship between operational conditions and community composition in anaerobic digestion of food waste and cow manure mixture. As a result, the analysis of the correlation between microbiome and operational parameters indicated that Clostridium, Methanosaeta, and Methanosarcina, all together could enhance to methanogenesis process with the graphite supplementation.Öğe Optimization of the Coagulation-Flocculation Process for Slaughterhouse Wastewater Using Response Surface Methodology(Wiley, 2020) Gokcek, Oznur Begum; Ozdemir, SafiyeSlaughterhouse wastewater is one of the main sources of environmental pollutants, containing a high amount of organic matter (chemical oxygen demand (COD), biochemical oxygen demand (BOD)), total nitrogen (TN), total suspended solids (TSS), total phosphorus (TP), grease, and oil. The main aim of the present research is optimizing the coagulation-flocculation process and examining the effects of experimental factors with each other, for example, pH, the concentration of two different coagulants (FeCl(3)and alum), rapid mixing rate, and settling time. Therefore, it is aimed to treat slaughterhouse wastewater using the coagulation-flocculation process with the optimization of the response surface methodology (RSM). COD, turbidity, and suspended solids (SS) of the treated wastewater are chosen as the response variables. Furthermore, the optimal conditions for three responses are acquired by employing the desirability function approach. When the experimental results of two coagulants are compared, it is observed that the alum coagulant gave better results for the three responses. The alum coagulant utilized in the present research is able to increase COD, SS, and turbidity removal efficiency by 75.25%, 90.16%, and 91.18%, respectively. It is possible to optimize coagulation-flocculation by utilizing the RSM analysis, which proves that coagulation can pre-treat slaughterhouse wastewater.Öğe RESPONSE SURFACE MODELLING FOR REACTIVE DYE REMOVAL USING BIO-SOLIDS: APPLICATION OF BOX-BEHNKEN EXPERIMENTAL DESIGN(PARLAR SCIENTIFIC PUBLICATIONS (P S P), 2015) Cebeci, Meltem Sarioglu; Gokcek, Oznur BegumThe removal of reactive dyes is rather difficult by chemical coagulation/flocculation because of strong resistance to biodegradation in aerobic environments. The removal of color from textile wastewater using low-cost adsorbents instead of expensive adsorbents is considered to be an important application of adsorption. In this study, powder-activated sludge was studied for the removal of color from aqueous solutions in a batch system using response surface methodology. Effects of initial pH, initial reactive dye concentration (Everzol Yellow 3RS H/C), contact time, and amount of bio-solid dosage (dried activated sludge) was optimized by using a four-factor, three-level Box-Behnken design for response surface modeling. Experiments were carried out in a lab-scale batch study. Four independent variables (initial pH: 2-8, initial concentration of dye ions (Co): 25-200 mg/L, contact time (tc): 10-180 min, and bio-solid amount (m): 1-15 g/L) were labeled as A, B, C, and D at three levels (-1, 0, 1), and a second-order polynomial regression equation was used to predict responses. The variables were tested by using analysis of variance (ANOVA). The optimal conditions were found to be pH = 2, Co = 200 mg/L, tc = 95 min, and m = 0.8 g/100 ml for which EY3RS removal was 92.75%. The results show that dye concentrations, bio-solid amount, and contact time are the most important factors in color removal. All factors showed combined effects on dye removal.Öğe Simultaneous synergistic effects of graphite addition and co-digestion of food waste and cow manure: Biogas production and microbial community(Elsevier Sci Ltd, 2020) Muratcobanoglu, Hamdi; Gokcek, Oznur Begum; Mert, Ruhullah Ali; Zan, Recep; Demirel, SevgiThe effects of graphite on the anaerobic digestion of food waste (FW), cow manure (CM) and its mixture (FW/CM) via batch experiments under mesophilic conditions have been investigated in this study. Maximum biogas production with graphite addition for FW + 1 g/L, CM + 1.5 g/L and FW/CM + 0.75 g/L are 1128.46, 829.6 and 1471.1 mL/gVS respectively. Additionally, this study investigates the link between microbial community structure and biogas production when graphite addition of anaerobic digester was conducted. Based on 16S rRNA gene amplicon sequencing results, Aminiphilus (13-14%), Actinobaculum (13-15%) and Clostridium (12-18%) were the predominant bacterial genera in graphite-added FW, CM and FW/CM reactors, respectively. Comparatively higher biogas production of FW/CM synergistically affected by abundances of Clostridium as well as co-digestion in this anaerobic digestion setup. Methanosaeta was the most abundant methanogen in the graphite added digesters; however, the relative abundance of these genera was different.Öğe Spatial prediction of PM10 concentration using machine learning algorithms in Ankara, Turkey(Elsevier Sci Ltd, 2020) Bozdag, Asli; Dokuz, Yesim; Gokcek, Oznur BegumWith the increase in population and industrialization, air pollution has become one of the global problems nowadays. Therefore, air pollutant parameters should be measured at regular intervals, and the necessary measures should be taken by evaluating the results of measurements. In order to prevent air pollution, pollutant parameters must be evaluated within the framework of a model. Recently, in order to obtain objective and more sensitive results with regard to air pollution nowadays, studies, which use machine learning algorithms in artificial intelligence technologies, have been carried out. In this study, PM10 concentrations, which are obtained from 7 stations in Ankara province in Turkey, were trained with machine learning algorithms (LASSO, SVR, RF, kNN, xGBoost, ANN). The PM10 concentrations of the years 2009-2017 of 6 stations in Ankara were given as input, and the PM10 concentrations of the seventh station for the year 2018 were predicted. The model development stage was repeated for each station, and the performance and error rates of the algorithms were determined by comparing the results produced by the algorithms with the actual results. The best results were provided with ANN (R-2 = 0.58, RMSE = 20.8, MAE = 14.4). The spatial distribution of the estimated concentration results was provided through Geographic Information System (GIS), and spatial strategies for improving air pollution over land use were established. (c) 2020 Elsevier Ltd. All rights reserved.Öğe Technical and economic evaluation of freshwater production from a wind-powered small-scale seawater reverse osmosis system (WP-SWRO)(ELSEVIER SCIENCE BV, 2016) Gokcek, Murat; Gokcek, Oznur BegumWind-powered desalination is an attractive and sustainable method for providing potable water in isolated arid and coastal zones and islands. In this study, a techno-economic analysis of a wind-powered small-scale seawater reverse osmosis system (WP-SWRO) is presented. Levelised unit costs for electricity and water (LCOE and LCOW) were estimated for Gokceada Island, Turkey. The energy requirement of the system showed that water can be produced at a cost between US$2.962 and US$6.457 $/m(3) for all wind turbines (with rated capacities ranging from 6 kW to 30 kW) at various discount rates when considering off-grid operations. For a grid connected-wind turbine system, the levelised cost of water was predicted to be in the range from US$0.866 to US$2.846/m(3). The levelised costs of electricity are predicted to be US$0.077 to US$0.155/kWh for an 8% discount rate using a 30-kW wind turbine based on the turbine-specific cost. According to the results from an emission reduction analysis, using a 30-kW wind turbine for a reverse osmosis system permits a reduction of 80.028 tonnes of CO2 annually. The results show that wind-powered potable water production is economically and technically reasonable for the site. (C) 2015 Elsevier B.V. All rights reserved.Öğe The effect of adding zero-valent iron nanoparticles on biohydrogen production from refectory waste(Pergamon-Elsevier Science Ltd, 2024) Gokcek, Oznur Begum; Erdogmus, Safak NurThe objective of the current research was to increase biogas and biohydrogen production by adding zero-valent iron nanoparticles (Fe0NPs) to refectory waste by the dark fermentation method. Loading was done at 0, 2, 4, 8, and 10 gVS/gVS ratios to determine the highest S/I ratio. The best yield was obtained at the S/I loading ratio of 4 gVS/gVS. Different Fe0NP concentrations (0, 50, 100, 200 and 400 mg/L) were studied at the best loading rate. The highest biogas (86%) and biohydrogen production (140%) occurred at a Fe0NP concentration of 100 mg/L. The highest TS and VS removal were determined as 50% and 37%, respectively, in the reactor with the 100 mg/L Fe0NP concentration added. The highest total VFA concentration was observed at the S/I loading ratio of 4 gVS/gVS and 100 mg/L Fe0NP concentration added. Considering biogas and biohydrogen production, biofilm samples were taken from the S/I = 4 gVS/gVS reactor with the highest efficiency and the best results in the addition of Fe0NP, and as a result of examining their microbial distribution, Lactobacillus, Pseudomonas, and Clostridium were determined as the most dominant species. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe The impact of reduced graphene oxide (rGO) supplementation on cattle manure anaerobic digestion: Focusing on process performance and microbial syntrophy(Elsevier, 2021) Muratcobanoglu, Hamdi; Gokcek, Oznur Begum; Mert, Ruhullah Ali; Zan, Recep; Demirel, SevgiAt a time when there is a surge in demand for increasing renewable energy production, boosting biomethane production per unit organic matter/waste has become a big challenge and necessity. In this study, the effect of rGO addition on biomethane production from cow manure under mesophilic-batch conditions was investigated. Biomethane production was increased via rGO supplementation at appropriate concentrations. The highest biomethane production, which was 335 mL/gVS(ad) (65 % increase), was obtained by adding 20 mg/L rGO (CM20) while rGO addition slightly increased (up to 5.4 %) the CH4 content of biogas. The microbial community analysis indicated that via rGO supplementation, the dominant bacteria changed from Levilinea to Candidatus Cloacamonas and a more diverse archaeal community was formed. According to this study results, rGO supplementation could be used at biogas plants to boost renewable energy production.Öğe Treatment of automotive industry wastewater using anaerobic batch reactors: The influence of substrate/inoculum and molasses/wastewater(INST CHEMICAL ENGINEERS, 2016) Sarioglu (Cebeci), Meltem; Gokcek, Oznur BegumA study of the anaerobic treatment of an automotive-industry wastewater was conducted at mesophilic temperature in batch mode. In this study, molasses was used as a co-substrate. The experiments were carried out with samples prepared in 500 ml bottles using a shaker at 35 degrees C. The concentration of inoculum was prepared to be 5000 mg/L VSS. Substrate-inoculum ratios (SIR) were 0.75 and 1.0. Molasses-wastewater ratios (MWR) were 0.3, 1, and 3. All tests were carried out against controls of inoculum without substrate. A speed of 150 rpm was used for the sample bottles and they were examined daily for chemical oxygen demand (COD), pH, total solids, and total gas. The highest COD removal efficiency, 47%, was at SIR=0.75 and MWR=3. The highest total solid material removal efficiency was at SIR=1 and MWR=0.3. The best result in biogas production was at SIR=1 and MWR=0.3 and SIR=0.75 and MWR=3. Monod-, zero-, first-, and second-order kinetic models were used to calculate and define model constants for organic removal rates. Data show a close fit to the Monod kinetic model based on the verification constants (R-2) and other parameters (K-s, D-max, k(0), k(1), and k(2)). (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
