Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
Browse
4 results
Search Results
Article Citation - WoS: 32Citation - Scopus: 35Distribution of Geothermal Arsenic in Relation To Geothermal Play Types: a Global Review and Case Study From the Anatolian Plate (turkey)(Elsevier, 2021) Baba, Alper; Uzelli, Taygun; Sözbilir, HasanArsenic has a natural cycle as it travels underground. It can mix with geothermal fluid in different ways under the control of magmatic and tectonic processes. Geogenic arsenic is present in many geothermal fields in the world at concentrations above the limits set for human health. The arsenic content of geothermal fluids is also related to the concept of geothermal play type, which forms geothermal systems, because the natural processes that form the geothermal system also control the arsenic cycle. In this study, an attempt is made to explain the relationship between the geothermal play type concept and geothermal arsenic circulation. For this purpose, geothermal field examples are given from around the world and Turkey. The result shows that arsenic concentrations can reach significant levels along with plate tectonic boundaries in the world. When arsenic concentrations were evaluated, the effect of major faults on the Anatolian Plate was clearly seen. Also, in the Anatolian plate where volcanosedimentary units are common, geothermal fluids caused more effective alteration along with structural control and increased arsenic concentrations in geothermal systems. This interaction between structural elements, geothermal fluid, and the arsenic cycle shows that the concept of play type in geothermal systems should also be taken into consideration. It was determined that the places with high arsenic values are located within the convective-non-magmatic extensional geothermal play types such as Western Anatolian Extensional System and the North Anatolian Fault. The concept of play type in geothermal systems includes all systematic and external factors that make up these processes. For this reason, it is very important to evaluate the play type classification together with the arsenic cycle.Article Citation - WoS: 58Citation - Scopus: 59Assessment of Different Nanofiltration and Reverse Osmosis Membranes for Simultaneous Removal of Arsenic and Boron From Spent Geothermal Water(Elsevier, 2021) Jarma, Yakubu A.; Karaoğlu, Aslı; Tekin, Özge; Baba, Alper; Ökten, H.Eser; Tomaszewska, Barbara; Kabay, NalanOne of the factors that determine agricultural crops’ yield is the quality of water used during irrigation. In this study, we assessed the usability of spent geothermal water for agricultural irrigation after membrane treatment. Preliminary membrane tests were conducted on a laboratory-scale set up followed by mini-pilot scale tests in a geothermal heating center. In part I, three commercially available membranes (XLE BWRO, NF90, and Osmonics CK- NF) were tested using a cross-flow flat-sheet membrane testing unit (Sepa CF II, GE-Osmonics) under constant applied pressure of 20 bar. In part II, different spiral wound membranes (TR-NE90-NF, TR-BE-BW, and BW30) other than the ones used in laboratory tests were employed for the mini-pilot scale studies in a continuous mode. Water recovery and applied pressure were maintained constant at 60% and 12 bar, respectively. Performances of the membranes were assessed in terms of the permeate flux, boron and arsenic removals. In laboratory tests, the permeate fluxes were measured as 94.3, 87.9, and 64.3 L m?2 h?1 for XLE BWRO, CK-NF and NF90 membranes, respectively. The arsenic removals were found as 99.0%, 87.5% and 83.6% while the boron removals were 56.8%, 54.2%, and 26.1% for XLE BWRO, NF90 and CK-NF membranes, respectively. In field tests, permeate fluxes were 49.9, 26.8 and 24.0 L m?2 h?1 for TR-NE90-NF, BW30-RO and TR-BE-BW membranes, respectively. Boron removals were calculated as 49.9%, 44.1% and 40.7% for TR-BE-BW, TR-NE90-NF and BW30-RO membranes, respectively. Removal efficiencies of arsenic in mini-pilot scale membrane tests were all over 90%. Quality of the permeate water produced was suitable for irrigation in terms of the electrical conductivity (EC) and the total dissolved solids (TDS) for all tested membranes with respect to guidelines set by the Turkish Ministry of Environment and Urbanisation (TMEU). However, XLE BWRO, CK-NF and NF90 membranes failed to meet the required limits for irrigation in terms of boron and arsenic concentrations in the product water. The permeate streams of TR-BE-BW, TR-NE90-NF and BW30-RO membranes complied with the irrigation water standards in terms of EC, TDS and arsenic concentration while boron concentration remained above the allowable limit. © 2020 Elsevier B.V.Article Citation - WoS: 28Citation - Scopus: 31Sustainable Recovery of Waste Vegetable Cooking Oil and Aged Bitumen: Optimized Modification for Short and Long Term Aging Cases(Elsevier, 2020) Uz, Volkan Emre; Gökalp, İslamBitumen ages in the short and long-term due to environmental conditions. As the bitumen ages, it loses its original properties and flexibility. Hardened bitumen causes certain distresses in pavement that may endanger traffic safety and reduce travel comfort. Bitumen is one of recoverable material, however some techniques may not be ecological due to considerable energy, time, and cost. On the other hand, recovering of aged bitumen might be eco-friendlier, energy-efficient, and economic by using bio-based waste materials such as waste vegetable cooking oils (WVCO). In this perspective, this paper was established on the idea of sustainable recovery of aged bitumen and WVCO. Base bitumen was aged in case of short-term (ST) and long-term (LT) in laboratory condition and modified with WVCO ranging from 2 to 10% by weight of bitumen. To determine the effect of WVCO modification on aged bitumen conventional and rheological test methods were utilized. To find the optimum rate of WVCO for full recovery of aged bitumen, an index called Pure Rejuvenation Index (PRI) was specified and applied for each test results. It can be concluded from PRI analyses that WVCO can be used as rejuvenator to recover aged bitumen and approximately 3% and 6% of WVCO are required for ST and LT aged bitumen cases, respectively. However, different test methods yield different optimum rates of WVCO for ST and LT aged bitumen. Recovering of WVCO and aged bitumen by using together may provide environmental protection and conservation of resources.Article Citation - WoS: 72Citation - Scopus: 90Naturally Occurring Arsenic in Terrestrial Geothermal Systems of Western Anatolia, Turkey: Potential Role in Contamination of Freshwater Resources(Elsevier Ltd., 2013) Bundschuh, Jochen; Maity, Jyoti Prakash; Nath, B.; Baba, Alper; Gündüz, Orhan; Kulp, Thomas R.; Jean, Jiin-Shuh; Kar, Sandeep; Yang, Huai-Jen; Tseng, Yujung; Bhattacharya, Prosun; Chen, ChienyenArsenic (As) contamination in terrestrial geothermal systems has been identified in many countries worldwide. Concentrations higher than 0.01mg/L are detrimental to human health. We examined potential consequences for As contamination of freshwater resources based on hydrogeochemical investigations of geothermal waters in deep wells and hot springs collected from western Anatolia, Turkey. We analyzed samples for major ions and trace element concentrations. Temperature of geothermal waters in deep wells showed extreme ranges (40 and 230°C), while, temperature of hot spring fluids was up to 90°C. The Piper plot illustrated two dominant water types: Na-HCO3 - type for geothermal waters in deep wells and Ca-HCO3 - type for hot spring fluids. Arsenic concentration ranged from 0.03 to 1.5mg/L. Dominance of reduced As species, i.e., As(III), was observed in our samples. The Eh value ranged between -250 and 119mV, which suggests diverse geochemical conditions. Some of the measured trace elements were found above the World Health Organization guidelines and Turkish national safe drinking water limits. The variation in pH (range: 6.4-9.3) and As in geothermal waters suggest mixing with groundwater. Mixing of geothermal waters is primarily responsible for contamination of freshwater resources and making them unsuitable for drinking or irrigation.