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  • Öğe
    A review on dendrimers in preparation and modification of membranes: progress, applications, and challenges
    (Elsevier, 2021) Karataş, Okan; Keyikoğlu, Ramazan; Gengec, N. Atalay; Vatanpour, V.; Khataee, A.
    Although membrane technologies have been used for different purposes because of their selective permeability and suitability for modifications, fouling is the most important limiting parameter. Intensive research is being conducted to solve the membrane fouling problem, and in this context, dendrimers, as a macromolecule, have attracted wide interest with their unique chemical and structural properties. This review provides a comprehensive overview of the production methods, challenges, and applications of dendrimer-modified membranes. Modification methods include grafting, coating, and addition of dendrimers as a hydrophilic additive. These modifications, especially using polyamidoamine dendrimers, have improved separation performance, selectivity, and antifouling properties in microfiltration, ultrafiltration, reverse osmosis, forward osmosis, nanofiltration, and gas separation membranes. We also highlight the use of various nanomaterials in membrane modifications along with dendrimers because of the different structures and properties they can offer. Finally, the development prospects and key challenges of the dendrimer-modified membranes are briefly discussed.
  • Öğe
    High-performance carbon black electrode for oxygen reduction reaction and oxidation of atrazine by electro-Fenton process
    (Elsevier, 2021) Karataş, Okan; Gengec, Nevin Atalay; Gengec, Erhan; Khataee, Alireza; Kobya, Mehmet
    The aim of this study is to produce an electrode that can be used in H2O2 production and Electro-Fenton (EF) process by an effective, cheap, and easy method. For this reason, a superhydrophobic electrode with a higher PTFE ratio and high thickness was produced with a simple press. The produced electrode was used in the production of H2O2 and mineralization of Atrazine. First, the effect of pH, cathode voltage, and operation time on H2O2 production was evaluated. The maximum H2O2 concentration (409 mg/L), the highest current efficiency (99.80%), and the lowest electrical energy consumption (3.16 kWh/kg) were obtained at 0.8 V, 7.0 of pH, and 120 min, and the stability of the electrode was evaluated up to 720 min. Then, the effects of the operational conditions (pH, cathode voltage, operating time, and catalyst concentration) in electro-Fenton were evaluated. The fastest degradation of Atrazine (>99%) was obtained at 2.0 V, 3.0 of pH, and 0.3 mM of Fe2+ in 15 min. In the final part of the study, the degradation intermediates were identified, and the characterization of the electrode was evaluated by SEM, XRD, FT-IR, tensiometer, potentiostat, and elemental analyzer.
  • Öğe
    Translocation of clothianidin to guttation fluid and its potential impact on honey bee, Apis mellifera anatoliaca Maa, 1953 (Hymenoptera: Apidae)1
    (ENTOMOLOGICAL SOC TURKEY, 2021) Yalcin, Melis; Kapiz, Ilknur; Kosoglu, Mustafa; Koca, Onur; Turgut, Nalan; Topal, Erkan; Kurt Karakuş, Perihan Binnur
    Honey bees, Apis mellifera anatoliaca Maa, 1953 (Hymenoptera: Apidae) forage water from guttation fluid so transported neonicotinoid insecticides in guttation fluid poses a risk to the bees. The first aim of this study was to determine the toxicity and risk of clothianidin to honey bees. In addition, the changes of clothianidin residue in the guttation fluid of maize plants in Turkey were determined in 2018 and 2019. Also, the toxicity of guttation fluid collected from the maize plants to bees was determined in ecotoxicological tests. The acute oral LD50 of clothianidin to honey bees in the first 24 h was 1.80 ng bee-1 and residue analysis demonstrated that honey bees were exposed to clothianidin concentration in guttation fluid ranging from 0.02 to 6.0 mg L-1 with mortality ranging between 80 and 100%. As the measured concentration of clothianidin in guttation fluid can lead to the mortality of honey bees, present study indicates that clothianidin, and possibly related pesticides in treated maize seed poses a risk to honey bees. Future studies are needed to determine the scale and distribution of this risk in Turkey.
  • Öğe
    Different methods applied to remove pollutants from real epoxy paint wastewater: modeling using the response surface method
    (Taylor and Francis Ltd., 2021) Adar, Elanur; Ilhan, Fatih; Aygün, Ahmet
    Comparing between classical and advanced methods for the treatment of industrial wastewater is extremely important to optimize factory operations and cost, and reduce the effects on environment. In the present study, some classical and advanced processes were assessed for chemical oxygen demand (COD) removal, the biggest problem in the wastewater from a factory producing epoxy paints. The response surface methodology was used for optimization. While the chemical coagulation (CC) and classical Fenton (CF) processes were used as the traditional methods, the electrocoagulation (EC) and electro-Fenton (EF) processes were used as the advanced methods to treat wastewater. As a result, the highest COD removal efficiencies were obtained in EF (97.8%) and CF (88.6%), respectively. Low COD removal efficiencies (43.5% and 47.5% respectively) were achieved in coagulation-based processes (CC and EC). Operating cost for CF calculated as 2.15 euro/m(3). Considering in terms of treatment efficiency, sludge volume and operating cost, CF is the most suitable option for the management of epoxy paint wastewater (EPW). These results also show that Fenton-based methods provide higher removal yields for the treatment of EPW. In other words, it is stable wastewater and the presence of hydroxyl radicals is required for its successful management.
  • Öğe
    Organochlorine pesticides and polychlorinated biphenyls from a greenhouse area on the Mediterranean coast of Turkey: Distribution, air-soil exchange, enantiomeric signature, and source implications
    (Dokuz Eylül Üniversitesi, 2021) Can-Guven, Emine; Gedik, Kadir; Kurt Karakuş, Perihan Binnur
    Levels, seasonal variation, and air-soil exchange of 22 organochlorine pesticides (OCPs) and 15 polychlorinated biphenyls (PCBs) were determined in addition to the first insight into the enantiomeric signatures of chiral OCPs in an agricultural region of Turkey. A total of 47 polyurethane foam disk passive air samples and 34 surface/indepth soil samples were analyzed. Sigma OCP and Sigma PCB levels in air samples were 32.6-741 pg/m(3) and nd-2764 pg/m(3), while they were nd-28.1 ng/g dw and nd-0.302 ng/g dw in soil samples, respectively. Dichlorodiphenyl-trichloroethane (DDT) and its metabolites and endosulfan isomers were the most prevalent chemicals along with the light-weighted PCB congeners. During this study, lower or similar contamination levels were observed compared to global studies conducted in agricultural regions. The enantiomer fractions of o,p'-DDT in air samples might be due to re-volatilization of equally depleted enantiomers or fresh input of racemic o,p'-DDT to the air. The fugacity fractions showed that net deposition is the dominant mechanism.
  • Öğe
    Treatment of intermediate landfill leachate using different anode materials in electrooxidation process
    (Wiley, 2021) Can, Orhan Taner; Gazigil, Leyla; Keyikoglu, Ramazan
    This study aims to investigate the performances of widely used anode materials in the treatment of intermediate landfill leachate treatment by electrooxidation (EO) process. The raw leachate was collected from an 8-year-old landfill facility and had a chemical oxygen demand (COD) of 4660 mg/L, biological oxygen demand (BOD5) of 1370 mg/L, and total organic carbon (TOC) of 2260 mg/L. TOC and COD removal efficiencies of Boron-Doped Diamond (BDD), Pt, and four different Ti-based mixed metal oxide (MMO) anodes ((RuO2-TiO2, RuO2-IrO2, PtO2-IrO2, and IrO2-Ta2O5) were compared at the current densities of 25 mA/cm(2), 75 mA/cm(2), and 125 mA/cm(2). At the highest current density, the BDD achieved 100% TOC and COD removal efficiencies in 240 min. BDD was followed by the Pt anode, which achieved 95.53% COD and 92.74% TOC removal efficiencies. The Pt electrode also had the lowest SEC values at all current densities. Although the performances of four MMO electrodes were very close, RuO2-TiO2 achieved a slightly higher performance than the others. It was concluded that Pt anode can be a promising alternative to BDD, which was 18 times more expensive, with its comparable pollutant removal performance and low specific energy consumption.
  • Öğe
    Ecological risk assessment of domestic sewage sludge: a case study
    (Yıldız Teknik Üniversitesi, 2021) Yakamercan, Elif; Aygün, Ahmet
    This study aims to evaluate potential ecological risks and heavy metal pollution in sewage sludge. For these purposes, domestic sewage sludge samples were collected for a period of one year from a wastewater treatment plant in Bursa, Turkey and analyzed for heavy metals. The average heavy metal content of the sewage sludge was wherein decreasing order of Zn>Cu>Ni>Cr>Pb>As>Se>Cd. As a whole, the concentration of heavy metals was below the limit values indicated within the agricultural land application legal standards. Correlation analysis showed a very strong correlation observed between Ni and Cr. Determining to pollution degree and potential ecological risks, some indices such as Enrichment factor (EF), Single-factor pollution index (PI), Geoaccumulation index (Igeo), Nemerow synthetic pollution index (PN), Contamination factor (Cf), Integrated pollution degree (Cd), Pollution Load Index (PLI), Monominal potential ecological risk (ER), Potential ecological risk index (RI), and the Probability of toxicity (mERM-Q) were used in this study. Based on the pollution index calculations, Zn and Se posed the highest contamination while As and Cd posed the lowest contamination. The mERM-Q values indicated that the probability of toxicity varied from 21 to 49%, while ecological indices indicated that ER (2.0-23.7) and RI (67.3-106.2) values were lower than a threshold value for all samples.
  • Öğe
    Sequential sulfur-based denitrification/denitritation and nanofiltration processes for drinking water treatment
    (Academic Press, 2021) Asik, Gulfem; Yilmaz, Tulay; Di Capua, Francesco; Uçar, Deniz; Esposito, Giovanni; Sahinkaya, Erkan
    Efficient and cost-effective solutions for nitrogen removal are necessary to ensure the availability of safe drinking water. This study proposes a combined treatment for nitrogen-contaminated groundwater by sequential autotrophic nitrogen removal in a sulfur-packed bed reactor (SPBR) and excess sulfate rejection via nanofiltration (NF). Autotrophic nitrogen removal in the SPBR was investigated under both denitrification and denitritation conditions under different NO3− and NO2− loading rates (LRs) and feeding strategies (NO3− only, NO2− only, or both NO3− and NO2− in the feed). Batch activity tests were carried out during SPBR operation to evaluate the effect of different feeding conditions on nitrogen removal activity by the SPBR biofilm. Bacteria responsible for nitrogen removal in the bioreactor were identified via Illumina sequencing. Dead-end filtration tests were performed with NF membranes to investigate the elimination of excess sulfate from the SPBR effluent. This study demonstrates that the combined process results in effective groundwater treatment and evidences that an adequately high nitrogen LR should be maintained to avoid the generation of excess sulfide.
  • Öğe
    Novel gas measurement based on pressure triggered release cycles for biochemical methane potential tests
    (De Gruyter Open Ltd, 2021) Bekmezci, Ozan K.; Sapci-Ayas, Zehra; Uçar, Deniz
    This study aims to present a novel gas counter and to demonstrate its suitability for biochemical methane potential tests. In this system, the gas to be measured is collected in a chamber enclosed with two one-way solenoid valves and the absolute pressure is continuously monitored. After a trigger pressure is reached, a portion of the gas is released and the amount of the released gas is calculated according to ideal gas law and recorded. Three iterations of the supervisory control and data acquisition unit were constructed and tested for BMP measurement. Although it can be further improved and variations are possible, the presented final version works with eight reactors simultaneously and the recommended maximum gas flow is 1.24 mL/min. For those reactors, the measured/ theoretical BMP ratio was 65.3% with 4.2% standard uncertainty, which is subjectively acceptable. Therefore, it can be concluded that the concept is valid and applicable to BMP tests.
  • Öğe
    Machine learning for design of thin-film nanocomposite membranes
    (Elsevier B.V., 2021) Fetanat, Masoud; Keshtiara, Mohammadali; Keyikoğlu, Ramazan; Khataee, Alireza; Daiyan, Rahman; Razmjou, Amir
    In this study, a novel machine learning approach is proposed for estimation of the permeate flux and foulant rejection in nanocomposite filtration membranes. Nine independent variables are fed to artificial neural networks (ANNs) including support, nanoparticles concentration, concentration of organic phase trimesoyl chloride (TMC) in-n-hexane (TMC in n-hexane), operation pressure, contact angle, thin layer thickness, location of the nanoparticles (NPs), post-treatment temperature and duration, and permeate flux and foulant rejection were derived as the outputs of the ANNs. The proposed method was evaluated on two datasets across training, validation and test datasets, and an unseen dataset. 2250 different initial weights and number of the neurons in the hidden layer for the proposed ANN models were considered and compared to find the optimized ANN models. The mean squared error (MSE) and coefficient of determination (R2) were employed to select the best 20 ANN models for further analysis. The proposed ANN models resulted in accurate estimates for both permeate flux and foulant rejection with R2 of 0.9958 and 0.9412 in all data included in the training, validation and test datasets and R2 of 0.9938 and 0.9811 in unseen dataset, respectively. In addition, results of sensitivity analysis revealed that post treatment temperature and contact angle were found the most important input variables for estimation of permeate flux and foulant rejection. The proposed method can provide valuable insights for formulating permeate flux and foulant rejection and considering the effects of each experimental condition on nanocomposite filtration membranes without doing real experiments, which is time-consuming and expensive.
  • Öğe
    Machine Learning for Advanced Design of Nanocomposite Ultrafiltration Membranes
    (American Chemical Society, 2021) Fetanat, Masoud; Keshtiara, Mohammadali; Low, Ze-Xian; Keyikoğlu, Ramazan; Khataee, Alireza
    Although the incorporation of nanoparticles into ultrafiltration polymeric membranes has shown promising outcomes, their commercial implementation has yet to be fulfilled due to inconsistency in data, lack of a reliable recipe for the optimum filler content, and reluctance in disrupting the production line which requires significant time and resources. There is a growing demand among membrane communities for a design platform that can accelerate the discovery of new nanocomposite membranes. In this work, a feed-forward ANN (artificial neural network) model that has one hidden layer and the Bayesian regularization training algorithm were chosen for designing a graphical user interface platform to predict the ultrafiltration nanocomposite membrane performance, that is, solute rejection, flux recovery, and pure water flux, thereby saving time and resources used in membrane design. Experimental data (735 samples from 200 reports published between 2006 and 2020) were derived from the literature for training, validation, and testing of the ANN models. The results indicated that the best 30 ANN models produce the most accurate estimation of membrane performance using the seven input variables of polymer concentration, polymer type, filler concentration, average filler size, solvent concentration (in the dope solution), solvent type, and contact angle on the unseen data set. Furthermore, a sensitivity analysis was performed on the achieved models to identify the most effective input variables for each nanocomposite membrane performance. This work has the potential to be extended to other mixed matrix membrane types that are going to be used for microfiltration, nanofiltration, reverse osmosis, and so forth.
  • Öğe
    Land application of municipal sewage sludge: Human health risk assessment of heavy metals
    (Elsevier Ltd, 2021) Yakamercan, Elif; Ari, Akif; Aygün, Ahmet
    Land application of municipal sewage sludge has become an attractive option and disposal method used worldwide. Hence, the suitability of the sludge with regards to toxic and carcinogenic chemicals is crucial to prompt informed decisions regarding its use on agricultural areas. This study aims to assess ecological and human health risks of heavy metals in sewage sludge samples collected from 22 different cities' wastewater treatment plants to determine their agricultural application potential in Turkey. The average metal concentrations of the samples decreased as the following order of Zn > Cu > Cr > Pb > Ni > Mo > As > Cd > Se > Hg without a significant seasonality. To evaluate the carcinogenic and non-carcinogenic health risks, site-specific overall total cancer risk (TCR) and Hazard Index (HI) values were calculated as the sum of all heavy metals’ ingestion, inhalation, and dermal contact exposures for children and adults. Contribution of the inhalation exposure due to the dust re-suspension during agricultural work to the total health risk has seemed be negligible when compared to ingestion and dermal contact. The carcinogenic risk for the adults were within the acceptable range (10−6 to 10−4) proposed by USEPA based on our estimations (2.4 ✕ 10−5), but the risk value was slightly exceeded the safe levels for children (1.6 ✕ 10−4). Similarly, HI values for adult subjects were below the reference value of 1, whereas they were higher for children (up to 2.52). Pb, As, and Cr were the major contributing metals to carcinogenic risks for both children and adults. Although the heavy metal concentration of collected samples was within the agricultural land application legal standards proposed by the Environmental Protection Agency (EPA) and the Ministry of Environment and Urbanization of Turkey (MEU), but the results of human health risk assessments showed that the risks may occur especially for sensitive individuals like children. This study showed that the evaluation of waste materials such as municipal sewage sludge should be applied only if it is proper for both ecological and health-safe, and assessing based on the regulatory limit values would not be enough to protect all population.
  • Öğe
    Effect of nitrogen loading on denitrification, denitritation and filtration performances of membrane bioreactors fed with biogenic and chemical elemental sulfur
    (Elsevier B.V., 2021) Uçar, Deniz
    Autotrophic denitrification with elemental sulfur (S0) as an electron donor is a clean and cost-effective solution for nitrogen removal from contaminated waters poor in organics and has gained increasing interest in the last decades. In contrast, less attention has been driven towards autotrophic denitritation and the effect of nitrogen oxide (N-NOx−) loading and feeding strategy on the process. This study investigates the denitrification and denitritation performances of two membrane bioreactors fed with chemically synthesized S0 (S0chem) and biogenic S0 (S0bio) under different N-NOx− loading rates (50 and 100 mg N-NOx− L−1 d−1) and feeding strategies (nitrate or nitrite only and both nitrate and nitrite) and their influence on the specific nitrogen uptake rate (SNUR) of S0-oxidizing denitrifiers. N-NOx− removal was faster with S0bio compared to S0chem at all tested N-NOx− loading rates and feeding strategies, confirming S0bio as an advantageous electron donor for autotrophic NO3− and NO2− reductions. Influent NO2− levels as high as 100 mg N-NO2− L−1 did not inhibit autotrophic denitrification and denitritation. On the contrary, batch activity tests showed that NO2− feeding resulted in higher SNUR values compared to feeding with both NO3− and NO2− and with NO3− only, confirming NO2− as a more thermodynamically favorable electron acceptor than NO3−. The impact of different operational conditions on membrane filtration performance was also evaluated, showing that S0bio was the main responsible for pressure increase and membrane fouling during bioreactor operation.
  • Öğe
    Electrocoagulation of disperse dyebath wastewater: Optimization of process variables and sludge production
    (Korean Electrochemical Society, 2021) Aygün, Ahmet; Nas B.; Sevimli M.F.
    This study was conducted to investigate the effect of initial pH, current density, and electrolysis time on process performance in terms of decolorization and chemical oxygen demand (COD) removal from disperse dyebath wastewater (DDW) by mono-polar parallel laboratory scale electrocoagulation (EC) process. COD reduction of 51.3% and decolorization of 92.8% were obtained with operating cost of 0.19 €/m treated wastewater for Al-Al electrode pair, while 90.5% of decol-orization and 49.2% of COD reduction were obtained with operating cost of 0.203 €/m treated wastewater for an Fe-Fe electrode pair. The amount of sludge production were highly related to type of the electrode materials. At the3 optimum conditions, the amount of sludge produced were 0.18 kg/m and 0.28 kg/m for Al-Al and Fe-Fe electrode pairs, respec-tively. High decolorization can be explained by the hydrophobic nature of the disperse dye, while limited COD removal3 3 was observed due to the high dissolved organic matter of the DDW based on auxiliary chemicals. Energy, electrode, and chemical consumptions and sludge handling were considered as major cost items to find a cost-effective and sustainable solution for EC. The contribution of each cost items on operating cost were determined as 10.0%, 51.1%, 30.5% and 8.4% for Al-Al, and they were also determined as 9.0%, 38.0%, 40.5% and 12.5% for Fe-Fe, respectively. COD reduction and decolorization were fitted to first-order kinetic rule.
  • Öğe
    Correction to: An environmental risk assessment for a DDX-contaminated agricultural area in Turkey: soil vs. plant or human vs. animal (Environmental Science and Pollution Research, (2021), 28, 36, (50127-50140), 10.1007/s11356-021-14154-4)
    (2021) Korucu, Mahmut Kemal; Elibol P.S.; İşleyen, Mehmet
    A Correction to this paper has been published: https://doi.org/10.1007/s11356-021-14449-6. © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.
  • Öğe
    Anodic oxidation of bisphenol A by different dimensionally stable electrodes
    (IWA Publishing, 2021) Can, Orhan Taner; Tutun M.M.; Keyikoglu R.
    Bisphenol A (BPA) is a known endocrine disrupter and was detected in surface waters. This study investigated the mineralization of BPA by electrochemical oxidation using different anode materials including boron-doped diamond (BDD), platinum, and mixed metal oxide (MMO) electrodes (RuO2-IrO2, RuO2-TiO2, IrO2-Ta2O5, and Pt-IrO2). These electrodes were compared in terms of BPA mineralization efficiencies and electrical energy consumptions. Total organic carbon (TOC) was analyzed to monitor the mineralization efficiency of BPA. BDD achieved 100% BPA mineralization efficiency in 180 min and at a current density of 125 mA/sq cm, whereas the TOC removal efficiency of Pt was 60.9% and the efficiency of MMO electrodes ranged between 48% and 54%. BDD exhibited much lower specific energy consumption, which corresponds to a lower energy cost. The effect of operational parameters showed that the BDD anode was much more affected by the current density, initial BPA concentration, and electrolyte concentration than the other parameters such as the stirring speed and interelectrode distance.
  • Öğe
    An environmental risk assessment for a DDX-contaminated agricultural area in Turkey: soil vs. plant or human vs. animal
    (Springer Science and Business Media Deutschland GmbH, 2021) Korucu, Mahmut Kemal; Elibol P.S.; İşleyen, Mehmet
    This study is the first research attempt to assess the environmental risks of an agricultural area contaminated with the p,p′-DDT and its metabolites (DDX) on human and terrestrial species through exposure to soil and agricultural products, simultaneously. The study was carried out for a DDX-contaminated agricultural area in Turkey. Soil samples obtained in two different harvest applications were analyzed in terms of DDX levels. Similarly, stem, leaf, and fruit samples of an agricultural product grown on the same soils were analyzed. Using the results of these analyses, DDX intake values were calculated for 5 different human receptor groups, 4 different bird species, and 4 different mammal species, and the risk values were calculated by using a stochastic approach based on a Monte Carlo simulation. Findings indicated a substantial level of carcinogenic risk in the human receptor groups. Furthermore, a significant risk of reproductive toxicity was determined for the birds and mammals. The findings prominently showed that these risks can develop not only through exposure to DDX-contaminated soils but also through the consumption of plants grown on these soils.
  • Öğe
    Fate and removal of pentachlorophenol and diethylhexyl phthalate from textile industry wastewater by sequencing batch biofilm reactor: Effects of hydraulic and solid retention times
    (Elsevier Ltd, 2021) Yakamercan, Elif; Aygün, Ahmet
    This study aimed to examine the effects of hydraulic retention time (HRT) and solid retention time (SRT) on the removal of diethylhexyl phthalate (DEHP) and pentachlorophenol (PCP) from real textile wastewater. Experiments were conducted daily and at different SRTs (10 d, 15 d, and 20 d) and HRTs (36 h, 48 h, and 60 h). The results showed that the optimal HRT and SRT for DEHP removal were 48 h and 20 d, respectively, and the removal efficiency reached 83.27%. Meanwhile, the highest removal efficiency was 75.5% for PCP at an HRT of 60 h and an SRT of 15 d. The addition of biocarriers to the reactor system was intended to facilitate microorganism growth and increase the average removal efficiencies of PCP and DEHP. Short HRTs and SRTs resulted in low micropollutant removal efficiencies. Based on the mass balance calculations, it was determined that biodegradation and sorption onto sludge were the main removal mechanisms for PCP and DEHP. The findings also revealed that using the optimal HRT and SRT is critical to achieve the highest growth of the bacteria responsible for the biodegradation of selected micropollutants. In the biocarrier amended system, biodegradation served and sorption onto sludge contributed to PCP removal. Conversely, the major removal mechanism for DEHP varied depending on the operating conditions. In particular, with increasing SRT, biodegradation became the dominant removal mechanism.
  • Öğe
    Optimization of Struvite Precipitation for Landfill Leachate Treatment
    (2018) Doğan, Selim; Aygün, Ahmet; Argun, Mehmet Emin; Esmeray, Ertuğrul
    Sanitary landfill is the most preferred municipal solid waste disposal method. The production of highly polluted leachate is a major disadvantage of sanitary landfills. In this study, optimization of struvite precipitation to remove ammonium from landfill leachate was conducted by using Response Surface Methodology and central composite design. Optimum struvite precipitation conditions were determined based upon 11 runs performed in central composite design. A second-order polynomial functional model was fitted well to the results. The statistical analysis showed that two independent variables which are molar rates of Mg/N and N/P had significant effects on the ammonium removal efficiency. Maximum ammonium removal efficiency was 99.8% at a molar rate of 1.20 for Mg/N and 1.27 for N/P for a constant 9.2 pH value. The obtained results revealed that struvite used as pre-treatment in anaerobic process can be modelled by using response surface methodology. And also, response surface methodology can be used to optimize required ammonium removal efficiency for lower Mg/N and N/P molar ratio which affects the performance of pre-treatment method that designed for an anaerobic process having 300:5:1 ratio for COD/N/P.
  • Öğe
    Elektrokoagülayon Yöntemiyle Reaktif Yellow 160 Boyar Maddesinin Giderimi
    (2017) Aygün, Ahmet; Eren, Beytullah
    Demir ve alüminyum elektrotlar ile donatılmış elektrokoagülasyon prosesinin (EP) kullanıldığı çalışmada Reaktif Yellow 160 (RY160) boyarmaddesi giderimi üzerine başlangıç pH, akım yoğunluğu, iletkenlik ve elektroliz süresinin etkisi incelenmiştir. EP'de elektrot materyalinden bağımsız olarak yüksek renk giderim verimi elde edilmiştir. Optimum işletme şartları alüminyum elektrot kullanılması durumunda, pH = 5, akım yoğunluğu 100 A/m2, elektroliz süresi 10 dakika, iletkenlik 1000 µS/cm iken demir elektrot kullanılması durumunda pH = 7, akım yoğunluğu 200 A/m2, elektroliz süresi 5 dakika, iletkenlik 1000 µS/cm olarak belirlenmiştir. Renk giderim verimi alüminyum elektrot çifti için 2,3 kWsa/m3 enerji sarfiyatı ve 0,52 $/m3 toplam maliyetle %96,4 iken demir elektrot çifti için 1,7 kWsa/m3 enerji sarfiyatı ve 0,28 $/m3 toplam maliyetle %95,8 elde edilmiştir. Sonuçlar, demir elektrot kullanımının alüminyum elektrot ile karşılaştırıldığında RY160 boyarmaddesinin gideriminde daha ekonomik olduğunu göstermiştir.