Uyak, Vedat | Soylu, Senay | Topal, Tufan | Karapınar, Nazan | Özdemir, Kadir | Özaydın, Şahin | Avşar, Edip

Article | 2014 | Environmental Forensics15 ( 2 ) , pp.190 - 205

This study presents the seasonal and spatial variations of trihalomethanes (THMs) and haloacetic acids (HAAs) in 30 sampling points within three water distribution systems of Istanbul City, Turkey. The effects of surface water quality, seasonal variation, and species differences were examined. The occurrence of chlorinated THMs and HAAs levels was considerably lower in the system in which raw water is subjected to pre-ozonation versus pre-chlorination. Seasonal analysis of the data indicated that the median concentration of four THMs (THM4) was higher than nine HAAs (HAA9) concentrations in all three distribution systems sampling po . . .ints. For all distribution systems monitored, the highest median THM4 and HAA9 concentrations were observed in the spring and summer season, while the lowest concentrations of these disinfection byproduct (DBP) compounds were obtained in the fall and winter period. Due to the higher level of bromide in supplying waters of these two systems, moderate levels of brominated DBP species have been observed in the Kagithane and Buyukcekmece distribution systems districts. In fact, Spearman partial correlations (Spearman rank correlation coefficients [rs]) tend to be higher among analogues in terms of number and types of substituent, especially TCAA with TCM (rs 0.91), and DBAA with DBCM (rs 0.90). In contrast, the hydraulic (residence time and flow rate) and chemical mechanisms (hydrolysis, volatilization, and adsorption) affect the fate and transport of DBPs in distribution systems. Seasonal and spatial variations of DBPs presented in this study have important implications on regulatory issues and from an epidemiological point of view. © 2014 Taylor & Francis Group, LLC Daha fazlası Daha az

Özdemir, Kadir | Toröz, İsmail | Uyak, Vedat

Article | 2014 | Asian Journal of Chemistry26 ( 20 ) , pp.6935 - 6939

We investigate the effects of factors such as chlorine dose, reaction time and bromide ions on the formation and speciation of trihalomethanes during the chlorination of Istanbul reservoirs such as Terkos lake water, Büyükçekmece lake water and Ömerli lake water. The experimental results showed that approximately 50% of trihalomethane formation was observed in the first 4 h of reaction time in chlorinated Terkos lake water, Büyükçekmece lake water and Ömerli lake water, respectively. Trihalomethane concentrations increased with increasing chlorine dosage and reaction time. Chloroform was the major trihalomethane species forming as a . . . result of the chlorinated raw water samples. On the other hand, bromide ions play a great significant role in the distribution of trihalomethane species. The bromine and chlorine incorporation ratios were strongly related to natural organic matter precursors and bromide levels in Terkos lake water, Büyükçekmece lake water and Ömerli lake water. The percentage of bromine incorporation was much higher than that of chlorine in all chlorinated water samples Daha fazlası Daha az

Kılıç, Muhammet Samet | Korkut, Şeyda | Hazer, Baki

Article | 2014 | WIT Transactions on Ecology and the Environment181 , pp.213 - 224

Enzymatic biofuel cells (EFCs), which employ enzymes as a catalyst, convert the chemical energy released from the enzymatic oxidation of fuel into electrical energy. While chemical energy is being generated by the oxidation of fuel with enzymes, electricity is generated simultaneously by the movement of electrons released as a consequence of this chemical reaction from anode through cathode in enzymatic fuel cells. The major problem encountered in EFC studies is the difficult/slow electron transfer between the enzyme and the electrode. To mediate the electron transfer between the enzyme and the electrode's surface, low molecular wei . . .ght redox compounds called mediators are used in EFC. Higher power generation and minimal interference effects at a lower cell potential are achieved by using a mediator in EFC. The scope of this study is for the development of an enhanced electron transferred EFC with a proper mediator for the generation of electrical energy by the oxidation of glucose in domestic wastewater. Therefore, glucose in domestic wastewater is utilised for energy generation. In this study, Polypyrrole-2-carboxyclic acid was modified with various mediators such as, ferrocene, neutral red and p-benzoquinone, which were tested for this purpose. The maximum power density (100 nW/cm2) was observed for the ferrocene modified electrodes including glucose oxidase and laccase as anodic and cathodic enzyme, respectively. The electrode fabrication step was optimized with respect to the electrode material, its operational potential and the thickness of the polymeric film. The highest current values were obtained from the addition of 10 mM of glucose for the EFC system designed with the gold electrode material and operated with a working potential of 0.45 V. The most suitable polymeric film thickness was achieved in the cyclic voltammetry parameters set up with a scan rate of 50 mV/s and 25 cycles. The optimized EFC was tested in the domestic wastewater of Zonguldak City in Turkey. Ferrocene mediated EFC yielded a power density of 50-200 nW/cm2 for the domestic wastewater. © 2014 WIT Press Daha fazlası Daha az

Kılıç, Muhammet Samet | Korkut, Şeyda | Hazer, Baki | Erhan, Elif

Article | 2014 | Biosensors and Bioelectronics61 , pp.500 - 505

Newly synthesized gold and cobalt oxide nanoparticle embedded Polypropylene-g-Polyethylene glycol was used for a compartment-less enzymatic fuel cell. Glucose oxidase and bilirubin oxidase were selected as anodic and cathodic enzymes, respectively. Electrode fabrication and EFC operation parameters were optimized to achieve high power output. Maximum power density of 23.5µWcm-2 was generated at a cell voltage of +560mV vs Ag/AgCl, in 100mM PBS pH 7.4 with the addition of 20mM of synthetic glucose solution. 20µg of polymer amount with 185µg of glucose oxidase and 356µg of bilirubin oxidase was sufficient to get maximum performance. T . . .he working electrodes could harvest glucose, produced during photosynthesis reaction of Carpobrotus Acinaciformis plant, and readily found in real domestic wastewater of Zonguldak City in Turkey. © 2014 Elsevier B.V Daha fazlası Daha az

Kılıç, Muhammet Samet | Korkut, Şeyda | Hazer, Baki

Article | 2014 | Analytical Letters47 ( 6 ) , pp.983 - 995

A recently synthesized polypropylene-g-polyethylene glycol polymer was used for the first time as the working electrode of a fuel cell. Electrodes were prepared for unmediated and mediated enzymatic reactions including ferrocene as the mediator. Glucose oxidase and bilirubin oxidase was used as the anodic and cathodic enzymes for the working electrodes, respectively. The biofuel cell was operated using glucose as the fuel in a single-compartment and membrane-less cell. Electrochemical results demonstrated that the catalytic efficiency of the ferrocene based cathode was approximately 100-fold higher than that of an unmediated cathode . . .. The mediated fuel cell electrodes yielded a power density of 65 nW/cm2 at a cell potential of +560 mV. © 2014 Copyright Taylor & Francis Group, LLC Daha fazlası Daha az

Özdemir, Kadir

Article | 2014 | The Scientific World Journal2014 , pp.983 - 995

This study investigates the fractions of natural organic matter (NOM) and trihalomethane (THM) formation after chlorination in samples of raw water and the outputs from ozonation, coagulation-flocculation, and conventional filtration treatment units. All the water samples are passed through various ultrafiltration (UF) membranes. UF membranes with different molecular size ranges based on apparent molecular weight (AMW), such as 1000, 3000, 10,000, and 30,000 Daltons (Da), are commonly used. The NOM fraction with AMW < 1000 Da (1 K) is the dominant fraction within all the fractionated water samples. Its maximum percentage is 85.86% a . . .fter the filtration process and the minimum percentage is 65.01% in raw water samples. The total THM (TTHM) yield coefficients range from 22.5 to 42 g-TTHM/mg-DOC in all fractionated samples, which is related to their specific ultraviolet Absorbance (SUVA) levels. As the molecular weight of the fractions decreased, the TTHM yield coefficients increased. The NOM fractions with AMW values less than 1 K had lower SUVA values Daha fazlası Daha az