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Öğe Coupling Pyrite-Fenton Process with Aerobic Biodegradation for the Treatment of 2-Chlorophenol(Springer International Publishing Ag, 2020) Kayan, Iremsu; Oz, Nilgun Ayman; Kantar, CetinThis study investigates the performance of a sequential pyrite-Fenton and biological process for the treatment of 2-chlorophenol (2-CP) containing wastewater using pyrite-Fenton process as a pretreatment stage. Pyrite was tested as a catalyst material in Fenton reaction due to its low cost and high abundance in the environment. All experiments were run in batch mode. The biodegradation experiments were performed under aerobic conditions using glucose as the co-substrate with untreated or Fenton-pretreated 2-CP. Despite the 100% removal of 2-CP in batch pyrite-Fenton reactors, the total organic carbon (TOC) removal only approached 70%, implying the transformation of 2-CP into some chemically stable intermediate reaction by products during pyrite-Fenton oxidation. In systems with no pyrite-Fenton pretreatment, a combined effect of biotic and abiotic processes including biological degradation, sorption, and volatilization played a significant role on 2-CP removal. The pyrite-Fenton pretreatment of 2-CP significantly improved the performance of aerobic biological reactor relative to system with no pyrite-Fenton pretreatment by (1) reducing the toxicity of 2-CP on aerobic microbial cells and (2) enhancing cell growth. Overall, this study shows that pyrite-Fenton pretreatment coupled with aerobic biological degradation could provide a cost-effective solution for the treatment of wastewater containing low-biodegradable toxic compounds such as chlorophenols.Öğe Hydrogen production from municipal wastewaters via electrohydrolysis process(Pergamon-Elsevier Science Ltd, 2019) Yarimtepe, Canan Can; Turen, Busra; Oz, Nilgun AymanNowadays, studies investigating alternative treatment processes for domestic wastewater have gained momentum. Rather than using conventional treatment plants which require energy and high amount of chemicals in order to treat the wastewaters, it is a viable option to use effective methods and to get clean energy in the form of hydrogen with alternative methods. Therefore, the aim of this study is to investigate the effect of electrohydrolysis process on domestic wastewater treatability at different DC voltages (4, 6, 8 and 10 V). Maximum hydrogen production was obtained from 8 V DC for 4 h reaction time. Under optimum conditions (8 V DC and 4 h operation time), 82% turbidity, 75% color, 86% TSS, 84% COD, 82% sCOD, 75% BOD, 38% oil and 40% total coliform removal efficiencies were achieved, respectively. It is a huge advantage to use this method which meets effluent discharge standards in such a short time without biological sludge production requiring additional operating cost. It has been shown that with the electrohydrolysis method, sustainable clean energy production and simultaneous pollution reduction can be achieved for domestic wastewater. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Individual and combined inhibitory effects of methanol and toluene on acetyl-CoA synthetase expression level of acetoclastic methanogen, Methanosaeta concilii(Elsevier Sci Ltd, 2015) Akyol, Cagri; Ince, Orhan; Coban, Halil; Koksel, Gozde; Cetecioglu, Zeynep; Oz, Nilgun Ayman; Ince, BaharOrganic solvents found in waste streams can be inhibitory to microbial communities in wastewater treatment plants. In this study, possible inhibitory effects of commonly used organic solvents, methanol and toluene, were investigated in batch anaerobic digestion tests. Anaerobic sludges were fed with acetate repeatedly and exposed to various concentrations of toluene, methanol and mixture of them. Expression level of the key enzyme of acetoclastic methanogenesis, acetyl-CoA synthetase 1 (Acs1), was determined by reverse transcriptase real time PCR. Additionally, active populations of Methanosaeta spp. were monitored and quantified by fluorescent in situ hybridization (FISH). Transcript abundance of Acs1 was 1.31 x 10(6) mRNAs ml(-1) in the control reactors; whereas, singular methanol exposure of 0.1 M, 0.3 M, 0.5 M and 1.0 M and methanol + toluene combination of 1.0 M + 0.5 mM and 1.0 M + 1.5 mM did not cause any significant effect on the acetyl-CoA expression level. However, singular toluene-exposed serum bottle reactors were completely inhibited after 3rd exposure at all concentrations from 0.5 mM to 4.0 mM. FISH results for singular methanol and toluene additions as well as their combination in the ranges studied showed no particular effect on the relative abundance of Methanosaeta spp. cells. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Inhibition effect of isopropanol on acetyl-CoA synthetase expression level of acetoclastic methanogen, Methanosaeta concilii(Elsevier Science Bv, 2011) Ince, Bahar; Koksel, Gozde; Cetecioglu, Zeynep; Oz, Nilgun Ayman; Coban, Halil; Ince, OrhanIsopropanol is a widely found solvent in industrial wastewaters, which have commonly been treated using anaerobic systems. In this study, inhibitory effect of isopropanol on the key microbial group in anaerobic bioreactors, acetoclastic methanogens, was investigated. Anaerobic sludges in serum bottles were repeatedly fed with acetate and isopropanol; and quantitative real-time PCR was used for determining effect of isopropanol on the expression level of a key enzyme in acetoclastic methane production, acetyl-CoA synthetase of Methanosaeta concilii. Active Methanosaeta spp. cells were also quantified using Fluorescent in situ hybridization (FISH). Transcript abundance of acetyl-CoA synthetase was 1.23 +/- 0.62 x 10(6) mRNAs/mL in the uninhibited reactors with 222 mL cumulative methane production. First exposure to isopropanol resulted in 71.2%, 84.7%, 89.2% and 94.6% decrease in mRNA level and 35.0%, 65.0%, 91.5% and 100.0% reduction in methane production for isopropanol concentrations of 0.1 M, 0.5 M, 1.0 M and 2.0 M, respectively. Repeated exposures resulted in higher inhibitions; and at the end of test, fluorescent intensities of active Methanosaeta cells were significantly decreased due to isopropanol. The overall results indicated that isopropanol has an inhibitory effect on acetoclastic methanogenesis; and the inhibition can be detected by monitoring level of acetyl-CoA transcripts and rRNA level. (C) 2011 Elsevier B. V. All rights reserved.Öğe INVESTIGATION OF THE PRETREATMENT EFFECT OF ULTRASOUND ON ANAEROBIC SEQUENCING BATCH REACTOR TREATING LANDFILL LEACHATE(Wit Press, 2018) Yarimtepe, Canan Can; Oz, Nilgun AymanLandfill leachate is one of the most complex wastewaters. Anaerobic treatment has environmental benefits such as low sludge production and biogas production. However, studies have been continuing to achieve better reactor performance. In recent years, ultrasound treatment has been used for different purposes. The aim of this study is to determine the ultrasound effects on anaerobic sequencing batch reactors (ASBR) to increase COD removal efficiency and biogas production for landfill leachate. During operation of ASBRs, in biogas production and methane content, there is an increase of 10% and 7% in pretreated leachate, respectively. This increase in reactor performance is directly related to the transition of landfill leachate's organic matter to dissolved phase by ultrasound pretreatment.Öğe Ligand enhanced pharmaceutical wastewater treatment with Fenton process using pyrite as the catalyst: Column experiments(Pergamon-Elsevier Science Ltd, 2019) Kantar, Cetin; Oral, Ozlem; Oz, Nilgun AymanAdvanced oxidation processes offer practical and cost effective solutions for the treatment of poorly biodegradable industrial wastewaters. Here, column experiments were performed to understand the role of a complexing agent, citrate, on Fenton-treatment of an actual pharmaceutical wastewater with pyrite as the catalyst under dynamic flow conditions. Our results suggest that the pharmaceutical wastewater treatment with Fenton reaction using pyrite as the catalyst was mainly regulated by the extent of Fe dissolution from pyrite, which, in turn, resulted in formation of hydroxyl radicals in solution. The Fenton treatment efficiency was much lower in the absence of citrate compared to citric acid containing systems due to clogging of column pores with oxidized Fe species. On the other hand, the addition of citrate to wastewater significantly improved Fenton process efficacy, and prolonged the lifecycle of pyrite-packed columns depending on solution pH. Low pH values were favorable for better Fenton efficiency in systems containing citrate due to combined effect of proton and ligand promoted dissolution and mobilization of oxidized Fe species. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Oxidative degradation of chlorophenolic compounds with pyrite-Fenton process(Elsevier Sci Ltd, 2019) Kantar, Cetin; Oral, Ozlem; Urken, Ozge; Oz, Nilgun Ayman; Keskin, SeldaBatch experiments, in conjunction with chromatographic and spectroscopic measurements, were performed to comparatively investigate the degradation of various chlorophenolic (CP) compounds (e.g., 2-CP, 4-CP, 2,3-DCP, 2,4-DCP, 2,4,6-TCP, 2,3,4,6-TeCP) by a modified Fenton process using pyrite as the catalyst The batch results show that the CP removal by pyrite-Fenton process was highly dependent on chemical conditions (e.g., pH, CP and pyrite concentration), CP type, number and location of chlorine atoms on the aromatic ring. With the exception of 2,3,4,6-TeCP and 2,3-DCP, the CP removal decreased with increasing the number of chlorine constituents. While the main mechanism responsible for monochlorophenol removal (e.g., 2-CP and 4-CP) was the hydroxyl radical attack on aromatic rings, the CP removal for multichlorophenolic compounds (e.g., 2,3,4,6-TeCP) was driven by both: (1) hydroxyl radical attack on aromatic rings by both solution and surface-bound hydroxyl radicals and (2) adsorption onto pyrite surface sites. The adsorption affinity increased with increasing the number of Cl atoms on the aromatic ring due to enhanced hydrophobic effect. The TOC removal was not 100% complete for all CPs investigated due to formation of chemically less degradable chlorinated intermediate organic compounds as well as low molecular weight organic acids such as formic and acetic acid. Spectroscopic measurements with SEM-EDS, zeta potential and XPS provided evidence for the partial oxidation of pyrite surface Fe(II) and disulfide groups under acidic conditions. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Role of complexing agents on oxidative degradation of chlorophenolic compounds by pyrite-Fenton process: Batch and column experiments(Elsevier Science Bv, 2019) Kantar, Cetin; Oral, Ozlem; Urken, Ozge; Oz, Nilgun AymanThis study involves batch reactor and fixed-bed continuous flow experiments to determine the effects of complexing agents (e.g., tartrate and citrate) on the treatment of chlorophenolic (CP) compounds using heterogeneous Fenton system with pyrite mineral as the iron source. While the addition of organic ligands to the batch systems adversely affected CP removal, organic ligands had a beneficial effect on CP removal in column systems. Although the ligands extended the life span of pyrite-packed columns by removing surface oxidation products through the formation of soluble Fe-ligand complexes, the ligands competed against CPs for hydroxyl radicals (HO*). The competitive effect was much higher in batch systems since pyrite loading was very low in order to generate sufficient hydroxyl radicals. On the other hand, at much higher pyrite loading of column experiments, the H* radicals generated during Fenton process were sufficient to overcome the competitive effect exerted by organic ligands. In spite of much higher Fe solubility in the presence of citrate, citrate was less effective in enhancing CP removal in column systems compared to tartrate since the competitive effect caused by citrate for HO* radicals was more than that exerted by tartrate.Öğe Simultaneous hydrogen production and pollutant removal from olive mill wastewaters using electrohydrolysis process(Pergamon-Elsevier Science Ltd, 2019) Oz, Nilgun Ayman; Eker, Alev Cagla UzunManagement of olive mill wastewaters is one of the most challenging environmental issue in Mediterranean countries due to its high organic load, color, presence of phenolic compounds and need for high energy cost. Performance of electrohydrolysis (EH) process in terms of removal of organic compounds, detoxification and discoloration of olive mill wastewater (OMW) with simultaneous energy production in the hydrogen gas form has been investigated using aluminum electrodes. Different reaction times and electric potential gradients have been tested in order to determine the most effective conditions for removal of pollutants. The optimum reaction time and current were determined as 8 h and 8 V, respectively. Under these conditions, removal efficiencies for tCOD, suspended solids, color and phenol were obtained as 73%, 84%, 91% and 75%, respectively. At the end of the operating period of 8 h, 1037 ml hydrogen gas was obtained. The results show that electrohydrolysis process can be used as an alternative solution for the management of OMW and the process can be upgraded with a better reactor design or combined with different treatment processes to achieve a better effluent quality to meet discharge standards. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Ultrasound assisted biogas production from landfill leachate(Pergamon-Elsevier Science Ltd, 2014) Oz, Nilgun Ayman; Yarimtepe, Canan CanThe aim of this study is to increase biogas production and methane yield from landfill leachate in anaerobic batch reactors by using low frequency ultrasound as a pretreatment step. In the first part of the study, optimum conditions for solubilization of organic matter in leachate samples were investigated using various sonication durations at an ultrasound frequency of 20 kHz. The level of organic matter solubilization during ultrasonic pretreatment experiments was determined by calculating the ratio of soluble chemical oxygen demand (sCOD) to total chemical oxygen demand (tCOD). The sCOD/tCOD ratio was increased from 47% in raw leachate to 63% after 45 min sonication at 600 W/I. Non-parametric Friedman's test indicated that ultrasonic pretreatment has a significant effect on sCOD parameter for leachate (p < 0.05). In the second part of the study, anaerobic batch reactors were operated for both ultrasonically pretreated and untreated landfill leachate samples in order to assess the effect of sonication on biogas and methane production rate. In anaerobic batch reactor feed with ultrasonically pretreated leachate, 40% more biogas was obtained compared to the control reactor. For statistical analysis, Mann-Whitney U test was performed to compare biogas and methane production rates for raw and pretreated leachate samples and it has been found that ultrasonic pretreatment significantly enhanced biogas and methane production rates from leachate (p < 0.05) in anaerobic batch reactors. The overall results showed that low frequency ultrasound pretreatment can be potentially used for wastewater management especially with integration of anaerobic processes. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Ultrasound pretreatment for enhanced biogas production from olive mill wastewater(Elsevier, 2015) Oz, Nilgun Ayman; Uzun, Alev CaglaThis study investigates applicability of low frequency ultrasound technology to olive mill wastewaters (OMWs) as a pretreatment step prior to anaerobic batch reactors to improve biogas production and methane yield. OMWs originating from three phase processes are characterized with high organic content and complex nature. The treatment of the wastewater is problematic and alternative treatment options should be investigated. In the first part of the study, OMW samples were subjected to ultrasound at a frequency of 20 kHz with applied powers varying between 50 and 100W under temperature controlled conditions for different time periods in order to determine the most effective sonication conditions. The level of organic matter solubilization at ultrasound experiments was assessed by calculating the ratio of soluble chemical oxygen demand/total chemical oxygen demand (SCOD/TCOD). The results revealed that the optimum ultrasonic condition for diluted OMW is 20 kHz, 0.4 W/mL for 10 min. The application of ultrasound to OMW increased SCOD/TCOD ratio from 0.59 to 0.79. Statistical analysis (Friedman's tests) show that ultrasound was significantly effective on diluted OMW (p < 0.05) in terms of SCOD parameter, but not for raw OMW (p > 0.05). For raw OMW, this increase has been found to be limited due to high concentration of suspended solids (SS). In the second part of the study, biogas and methane production rates of anaerobic batch reactor fed with the ultrasound pretreated OMW samples were compared with the results of control reactor fed with untreated OMW in order to determine the effect of sonication. A nonparametric statistical procedure, Mann-Whitney U test, was used to compare biogas and methane production from anaerobic batch reactors for control and ultrasound pretreated samples. Results showed that application of low frequency ultrasound to OMW significantly improved both biogas and methane production in anaerobic batch reactor fed with the wastewater (p < 0.05). Anaerobic batch reactor fed with ultrasound pretreated diluted OMW produced approximately 20% more biogas and methane compared with the untreated one (control reactor). The overall results indicated that low frequency ultrasound pretreatment increased soluble COD in OMW and subsequently biogas production. (C) 2014 Elsevier B.V. All rights reserved.Öğe Volatile fatty acid production dynamics during the acidification of pretreated olive mill wastewater(Elsevier Sci Ltd, 2017) Yarimtepe, Canan Can; Oz, Nilgun Ayman; Ince, OrhanThis study focuses on the dynamics of VFA production from pretreated olive mill wastewater (OMW). Acidogenic anaerobic sequencing batch reactors (AcASBR) were operated with the pretreated OMW at hydraulic retention time (HRT) of 2 days and pH of 5,5 for different organic loading rates (OLRs) ranging from 5 g COD/L. d to 40 g COD/L. d. VFA production reached to the highest value of about 27,000 mg/L with the increase in the organic load applied (20 g COD/L. d). The highest acidification rate was calculated as 68%. Acetic acid was found to be as the dominant VFA compound for all stage of the study. At steady state, VFA production during a day-cycle period (24th hour) in AcASBR is also monitored, VFA production gradually increased after the 3rd and 6th hours (about 20%) and a rapid increase (about 40%) was observed reaching the maximum at the end of the cycle (24th hour). (C) 2017 Elsevier Ltd. All rights reserved.
