Environmental Engineering / Çevre Mühendisliği
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Book Part Arsenic Removal by Electrocoagulation(Wiley, 2022) Gören, Ayşegül Yağmur; Kobya, MehmetBecause of the toxic impacts on human health, the arsenic (As) limit value in drinking water was decreased from 50 to 10 ?g l-1 by the relevant authorities (WHO 1993; US EPA 2001). In this case, the problem of As pollution in natural water resources used for drinking water has grown even more and turned into a global crisis. According to reports in many parts of the world, over about 230 million people appear to be affected by high arsenic concentrations in groundwater. In this case, it turned out that there was a great need for cost-effective and environmentally friendly technologies from drinking water sources. One of the emerging water treatment technologies in recent years is electrocoagulation (EC) and it has been seen that it is effective in treating As (>99%) from water and eliminates some of the disadvantages of other conventional treatment processes. EC method includes electro-oxidation of anode electrode materials (iron and aluminum) and in situ production of coagulant agents. From groundwater resources with As content of 5-1000 ?g l-1, As removal efficiencies and operating costs (OCS) of EC technology using iron (Fe) and aluminum (Al) anodes were 85.0-99.9% and 0.0020-1.04 US$ m-3, respectively. Different types (plate, scrap, rod, and ball) of electrodes were used for As removal with the EC process, and it was observed that Fe electrodes or Fe-Al hybrid electrodes performed better in As removal. In addition, it has been determined that arsenate (As(V)) removal is more effective than arsenite (As(III)). A significant quantity of As(III) is oxidized in the EC process, resulting in precipitation, adsorption, and metal-oxy hydroxylic complex reactions. EC process has a lower OC to achieve As removal below the permissible WHO value compared to conventional treatment processes, accomplishing it as a further applicable option for As removal. © 2023 John Wiley & Sons, Inc.Article Citation - WoS: 8Citation - Scopus: 8Removal of Arsenic in Groundwater From Western Anatolia, Turkey Using an Electrocoagulation Reactor With Different Types of Iron Anodes(Elsevier, 2022) Kobya, Mehmet; Dolaz, Mustafa; Özaydın Şenol, Burcu; Gören, Ayşegül YağmurElectrocoagulation (EC) is a significantly efficient method for As removal from waters and received considerable attention recently. In this study, the natural groundwater (GW) samples containing As concentrations of GW-1: 538.8 μg L−1, GW-2: 1132.1 μg L−1, and GW-3: 52, 000 μg L−1 were obtained from different provinces and treated by EC process using different iron anodes (plate, ball, and scrap). To achieve drinking water As standard (10 μg L−1), the operational time, applied current, and As removal optimization for all anode types were studied. At applied current of 0.025 A, the As removal efficiency, EC time, and operating cost were >99.9%, 180 min and 0.406 $ m−3 for ball anodes, >99.9%, 100 min and 0.0813 $ m−3 for plate anodes, >99.9%, 80 min and 0.0815 $ m−3 for scrap anodes for GW-3, respectively. It was observed that as the As concentration in the GW increased, the EC time and operating cost increased. Overall, it was concluded that Fe scrap anodes are more advantageous than other types of anodes in terms of operating cost in EC reactor for As removal.Book Part Citation - Scopus: 32Language of Response Surface Methodology as an Experimental Strategy for Electrochemical Wastewater Treatment Process Optimization(Elsevier, 2022) Gören, Ayşegül Yağmur; Recepoğlu, Yaşar Kemal; Khataee, AlirezaThe availability and accessibility to safe and secure water resources are the key technological and scientific concerns of global significance. As a result of water scarcity worldwide, wastewater treatment and reuse are considered viable options to replace freshwater resources in agricultural irrigation and domestic and industrial purposes. A significant need for clean water has promoted the invention and/or enhancement of several electrochemical wastewater treatment (EWT) processes. Optimization of the process variables plays a crucial role in wastewater treatment to enhance technology performance, considering removal efficiency, operating cost, and environmental impacts. These processes are fundamentally complex multivariable, and the optimization through conventional methods is unreliable, inflexible, and time- and material-consuming. In this perspective, response surface methodology (RSM) appears to be a beneficial statistical experimental strategy for the performance optimization of the EWT process. This model could be utilized for the optimization and analysis of the individual and/or combined effects of operational variables on the treatment process to improve the system performance. Furthermore, this model provides a number of information from a slight number of experimental trials. In this chapter, a summary and a discussion are presented on the RSM model used in the electrochemical wastewater treatment processes to overcome process crucial challenges toward the optimization and modeling of process parameters. It provides a potential model to enhance the various types of wastewater treatment process performance with effective optimization. Overall, it is described that the RSM model can be used in EWT processes to find the optimum conditions.Article Citation - WoS: 9Citation - Scopus: 9How Does Arsenic Speciation (arsenite and Arsenate) in Groundwater Affect the Performance of an Aerated Electrocoagulation Reactor and Human Health Risk?(Elsevier, 2022) Gören, Ayşegül Yağmur; Kobya, Mehmet; Khataee, AlirezaArsenic (As) occurrence in water resources has become one of the most critical environmental problems worldwide. The detrimental health impacts on humans have been reported due to the consumption of As-contaminated groundwater resources. Consumption of As-containing water over the long term can cause arsenicosis and chronic effects on human health due to its toxicity. Several treatment processes are available for As removals such as coagulation, ion exchange, adsorption, and membrane technologies but they have various major drawbacks. In the present work, therefore, an aerated electrocoagulation (EC) system with aluminum anodes was operated for simultaneous arsenate (As(V)) and arsenite (As(III)) removal to overcome the disadvantages of other processes such as, sludge formation, difficulties in operation, high operating costs, high energy consumption, and the requirement of pre-treatment process and to enhance the conventional EC process. The combined effects of the applied current (0.075–0.3 A), aeration rate (0–6 L/min), pH (6.5–8.5), and As speciation (As(V)-As(III)) were studied on As removal efficiency. The findings revealed that As removal mostly depended on the airflow rate and the applied current in the EC system. The highest As removal efficiency (99.1%) was obtained at an airflow rate of 6 L/min, a pH of 6.5, an initial As (V) concentration of 200 μg/L, and a current of 0.3 A, with an energy consumption of 2.85 kWh/m3 and an operating cost of 0.66 $/m3. The human health risk assessment of treated water was also examined to understand the performance of the EC system. At most of the experimental runs, the chronic toxic risk (CTR) and carcinogenic risk (CR) of As were within the permissible limits except for an airflow rate of 0–2 L/min, an initial pH of 8.5, and a current of 0.075–0.15 A for high initial As (III) concentrations. Overall, the As removal performance and groundwater risk assessment show that the EC process is a promising option for industrial applications.Article Citation - WoS: 10Citation - Scopus: 12Removal of Arsenate by Electrocoagulation Reactor Using Aluminum Ball Anode Electrodes(IWA Publishing, 2018) Gören, Ayşegül Yağmur; Öncel, Mehmet Salim; Demirbaş, Erhan; Şık, Emrah; Kobya, MehmetThe aim of this research was to remove arsenate (As(V)) from groundwater using an air-injected electrocoagulation (EC) reactor with aluminum (Al) ball anodes. The effects of seven operating variables - initial pH, applied current (i), operating time (t(EC)), initial As(V) concentration (C-o), Al ball anode diameter (d(p)), reactor column height (h), and airflow rate (Q(air)) were investigated with a Box-Behnken statistical experimental design. ANOVA results from the quadratic model equations indicated that the model fitted very well with the experimental data for the responses, which were removal efficiency, operating cost (OC), As(V) adsorption capacity, and effluent concentration (R-2 >= 0.87). The most effective parameters were applied current, operating time, and anode height for As(V) removal efficiency in the EC reactor, while initial pH, Al anode diameter, and air flow rate had limited effect on removal. The model predicted a residual As(V) concentration below 10 mu g/L under the optimum operating conditions (pH 7.03, 0.29 A, 10.5 min, d(p) 7.5 mm, 613.4 mu g/L, h 5.1 cm, and Q(air) 6.4 L/min). The maximum As(V) removal efficiency and minimum OC in the EC process were almost 99% and 0.442 $/m(3), respectively.Article Citation - WoS: 26Citation - Scopus: 34Arsenite Removal From Groundwater in a Batch Electrocoagulation Process: Optimization Through Response Surface Methodology(Taylor & Francis, 2019) Şık, Emrah; Gören, Ayşegül Yağmur; Demirbaş, Erhan; Kobya, Mehmet; Öncel, Mehmet SalimIn this study, influences of seven process variables such as initial pH (pH(i)), applied current (i), operating time (t(EC)), initial As(III) concentration (C-o), diameter of Fe ball anode (d(p)), column height in the electrocoagulation (EC) reactor (h) and airflow rate (Q(air)) for removal of As(III) from groundwater by a new air-fed fixed-bed EC reactor were evaluated with a response surface methodology (RSM). The proposed quadratic model fitted very well with the experimental data for the responses. The removal efficiencies and operating costs were determined to be 99% and 0.01 $/m(3) at the optimum operating conditions (a pH(i) of 8.5, 0.05 A, 4.94 min, d(p) of 9.24 mm, h of 7.49 cm, Q(air) of 9.98 L/min for 50 mu g/L). This study clearly showed that the RSM in the EC process was a very suitable method to optimize the operating conditions at the target value of effluent As(III) concentration (10 mu g/L) while keeping the operating cost to minimal and maximize the removal efficiency.Article Citation - WoS: 4Citation - Scopus: 5Combined Influence of Some Cations on Arsenic Removal by an Air-Injection Ec Reactor Using Aluminum Ball Electrodes(Desalination Publications, 2020) Gören, Ayşegül Yağmur; Kobya, Mehmet; Şık, Emrah; Demirbaş, Erhan; Öncel, Mehmet SalimCombined effects of some cations such as calcium (Ca2+), iron (Fe2+), manganese (Mn2+), and magnesium (Mg2+) and operating time on the removal of arsenic by air-injected electrocoagulation (EC) reactor with aluminum (Al) ball electrodes were investigated. The operating conditions were optimized with the Box-Behnken design of response surface methodology (RSM). The response variables were selected from the program as removal efficiency, residual arsenic concentration, energy consumption and operating cost (OC) in the EC process. A total of 46 experimental run was performed. The removal efficiency of arsenic increased with an increase in iron concentration (0.5-4.5 mg/L). The rest of the cations showed no noticeable effect on arsenic removal efficiency. The maximum arsenic removal efficiency and minimum OC at the optimum operating conditions (C-Ca: 305 mg/L, C-Mg: 42 mg/L, C-Fe: 3.3 mg/L, C-Mn: 2.34 mg/L, initial pH of 7.5 applied current of 0.15 A, Al ball size of 7.5 mm, 5.0 cm of Al ball anodes height in the EC reactor, air-fed rate of 6.0 L/min and t(EC): 16.83 min) in the EC process were 99.9% and 0.0332 $/m(3) for initial arsenic concentration of 200 mu g/L, respectively. The removal mechanism of As(III) by EC seems to be oxidation of As(III) to As(V) and subsequent removal by adsorption/complexation with aluminum hydroxides generated in the process. The results showed that the air-injected EC reactor can be used effectively for arsenic and hardness removal simultaneously from real groundwater sources.Article Citation - WoS: 37Citation - Scopus: 40Arsenite Removal From Groundwater by Aerated Electrocoagulation Reactor With Al Ball Electrodes: Human Health Risk Assessment(Elsevier, 2020) Gören, Ayşegül Yağmur; Kobya, Mehmet; Öncel, Mehmet SalimThe application of conventional electrocoagulation (EC) process for removal of As(III) from groundwater suffers from the need of external oxidation agent for oxidation of As(III) to As(V). To tackle this limitation, an aerated EC reactor for the removal of As(III) from groundwater was evaluated in this study. The effect of initial pH(i), air flow rate, applied current, and electrode height in the EC reactor was examined. The experimental results showed that removal of arsenic mostly dependent on the applied current, electrode height in EC reactor, and air flow rate. The As(III) removal efficiency (99.2%) was maximum at pH(i) of 7.5, air flow rate of 6 L min(-1), applied current of 0.30 A, and electrode height in EC reactor of 5 cm, with an total operating cost of 0.583 $ m(-3). Furthermore, the carcinogenic risk (CR) and non-carcinogenic risk of arsenic (As) was in the range of tolerable limits at all operating conditions except applied current of 0.075 A at the end of the aerated EC process to remove As from groundwater. The present EC reactor process is able to remove As(III) from groundwater to below 10 mu g L-1, which is maximum contaminant level of arsenic in drinking water according to the World Health Organization (WHO). (C) 2020 Elsevier Ltd. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 6Optimization of Some Cations for Removal of Arsenic From Groundwater by Electrocoagulation Process(Gheorghe Asachi Technical University of Iasi, 2018) Kobya, Mehmet; Şık, Emrah; Demirbaş, Erhan; Gören, Ayşegül Yağmur; Öncel, Mehmet SalimThis study dealt with investigation of arsenic removal from groundwater using electrocoagulation (EC) method in a batch mode by the Box-Behnken experimental design method. Effects of some cations like Ca, Fe, Mg, Mn and operating time on the removal were explored by an air injected EC reactor. The combined effects of these variables were analyzed by the quadratic model for predicting the highest removal efficiency of arsenic from groundwater. The arsenic removal efficiency was found to be dependent on increase with operating time and concentrations of Ca, Mg, Fe and lower concentration of Mn. When operating variables were considered as minimum operating cost and maximum removal efficiency, the optimum operating parameters were determined to be 132 mg/L of CCa, 55 mg/L of CMg, 4.5 mg /L of CFe, 4.5 mg/L of CMn and operating time of 3 min to meet the target concentration of <10 μg/L. Values of removal efficiency and operating cost at the optimum conditions were 95.1% and 0.041 $/m3.Article Citation - WoS: 28Citation - Scopus: 29Arsenite and Arsenate Removals From Groundwater by Electrocoagulation Using Iron Ball Anodes: Influence of Operating Parameters(Elsevier Ltd., 2017) Şık, E.; Demirbaş, Erhan; Gören, Ayşegül Yağmur; Öncel, Mehmet Salim; Kobya, MehmetRemovals of arsenite (As(III)) and arsenate (As(V)) from groundwater by a cylindrical packed-bed electrocoagulation (EC) reactor using Fe ball anodes were investigated in this study. Effects of some operating parameters such as initial pH (pHi of 6.5–8.5), applied current (i of 0.075–0.30 A), initial concentration (Co of 30–200 μg/L), diameter of iron ball (dp of 5.0–10.0 mm), height of anode balls in the reactor (h of 2–8 cm) and airflow rate (Qair of 0.0–6.0 L/min) on the removal efficiency of arsenic were evaluated. The removal efficiency of arsenic decreased with increase in concentrations of arsenic from 30 to 200 μg/L while its removal efficiency increased with increase in operating time, applied current, height of anode in the reactor, and airflow rate. The optimum operating conditions for effective As(III) and As(V) removals to meet the permissible level of arsenic effluent concentration of <10 μg/L were determined as 0.3 A, 14 min of EC time for As(III) and 12 min for As(V), a pHi of 7.5, Co of 200 μg/L, dp of 7.5 mm, h of 7.5 cm and Qair of 6 L/min, respectively. Arsenic removal efficiency, energy and electrode consumptions, operating cost, charge loading and arsenic removed capacity per amount of electrochemically generated Fe at the optimum conditions were also calculated as 96.0%, 1.442 kWh/m3, 0.0752 kg/m3, 0.612 $/m3, 252 C and 2.55 μg/mg Fe (0.762 μg/C) for As(III) removal and 95.8%, 1.386 kWh/m3, 0.0628 kg/m3, 0.546 $/m3, 216 C and 3.05 μg/mg Fe (0.887 μg/C) for As(V) removal, respectively.