LEE- Çevre Bilimleri Mühendisliği ve Yönetimi- Yüksek Lisans
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Sustainable Development Goal "Goal 9: Industry, Innovation and Infrastructure" ile LEE- Çevre Bilimleri Mühendisliği ve Yönetimi- Yüksek Lisans'a göz atma
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ÖgeCritical evaluation for nitrogen removal performance of a stereotype activated sludge system under dynamic process conditions(Graduate School, 2021-12-28) Bodur, Minel ; İnsel, Güçlü Hayrettin ; 501181724 ; Environmental Sciences Engineering and ManagementIn recent years, with the increasing population and the effects of global warming, the design, construction, and operation of domestic and urban wastewater treatment plants are carried out considering the treatment steps that provide nutrient removal. The most suitable treatment alternative to remove nutrients from wastewater in terms of applicability and cost are determined to be Biological Nutrient Removal processes. Because of the need for biological nutrient removal, stress caused by the nutrients and organic matter on receiving water environments are reduced and active sludge systems gain more and more attention moving forward. As widely known, highly complex biological reactions occur in activated sludge systems and although stable state conditions are generally used to simplify design calculations, active sludge systems operate under dynamic conditions. This indicates that input wastewater characterization as well as the inlet flow, various environmental factors (temperature, precipitation, etc.) and operating conditions vary depending on time. Therefore, various modeling tools are used to understand the treatment system more efficiently. With the modelling tools, it is possible to comprehend system dynamics and determine the rehabilitation, refurbishment and expansion requirements of existing treatment plants, while for the new plants, plant design can be optimized considering modeling outputs. Additionally, data from pilot-scale reactors can be evaluated through models and used to predict full-scale plant performance. To reflect the actual conditions at wastewater treatment plants, process simulators which provide guidance on determining the design principles of wastewater treatment plants, creating automation scenarios, choosing equipment, and evaluating process performance for both wastewater and sludge units, are used. The main purpose of this thesis is to evaluate the use of oxidation ditch reactors in series in terms of nitrification and denitrification processes and to model the actual behavior of an Oxidation Ditch (OD) system operated by following the pre-denitrification principles using input wastewater data collected from an urban wastewater treatment plant in the Marmara Region (Istanbul, Turkey) under dynamic conditions. Sumo software was used to model and simulate the wastewater treatment plant under dynamic conditions and the treatment efficiency of the plant in terms of nitrogen removal was examined. This thesis mainly focuses on nitrogen removal under dynamic conditions in a municipal wastewater treatment plant that employs four oxidation ditches located upstream of Bio-P tanks and operated in series. Although simultaneous nitriding denitrification principles apply to plant configuration due to oxidation ditches, the treatment plant is operated as a conventional active sludge system and considers pre-denitrification principles, which the first oxidation ditch is operated under anoxic conditions. The second oxidation ditch in the plant is operated under anoxic and aerobic conditions by controlling the diffusers (on/off), while the remaining two oxidation ditches are continuously aerated by the diffusers located at the bottom of the tanks and operated under aerobic conditions. In this context, a dynamic simulation was carried out using Sumo software for the entire oxidation ditch system. Bio-P tanks and final sedimentation tanks were included in the model to ensure system integrity, but only the nitrogen removal efficiency of oxidation ditch reactors was examined within the scope of this thesis. Modeling and simulation results confirmed that the minimum nitrate production rate occurred in the first oxidation ditch due to lack of aerobic environment. It was also examined that the nitrate recirculated from the fourth oxidation ditch to the first oxidation ditch was consumed within this first reactor. Hence, transfer of recirculated nitrate to the second reactor does not occur. Additionally, it was confirmed by the modelling studies that nitrate is consumed within the first reactor only at rates of the recirculated nitrate. Even if the second OD reactor is operated under anoxic conditions to provide denitrification for the recirculated nitrate, the volume of the first oxidation ditch cannot be used efficiently, because the recirculated nitrate from the fourth OD to the first OD is very low due to simultaneous nitrification denitrification occurs in the remaining reactors. In addition, results confirmed that the highest nitrate consumption rate was achieved within the first reactor, while this is followed by the second, third and fourth reactors, respectively. Nitrate production and utilization rates were determined through model outputs, which were very close in the second oxidation ditch due to operating conditions and creating both anoxic and aerobic zones, while in the third and fourth reactors, the difference between these rates increases due to decreased anoxic volume. Considering the information obtained from the modeling studies, it can be stated that the system is divided into two parts as the first oxidation ditch reactor and the remaining tanks (OD-2, OD-3 and OD-4). This is because nitrate can be removed from wastewater in OD-1 reactor only at a rate and an amount of the recirculated nitrate, which is determined to be low due to simultaneous nitrification denitrification occurred within the remaining OD reactors. Hence, the first oxidation ditch reactor volume, operated under anoxic conditions to provide denitrification, is not used effectively, and does not fit for purpose. Therefore, it was recommended that the optimization of the system could be achieved by operating four oxidation ditches in parallel with the principles of simultaneous denitrification nitrification. In addition, it is envisaged that this will also provide flexibility to plant operators in case of maintenance works etc., and the treatment system can be operated without interruption even if one of the tanks is out of operation. It may also be beneficial to select simpler and more efficient treatment systems for the plant configurations to prevent such treatment complications in the future.
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ÖgeNutrient recovery from source separated human urine and the treatment of the residual urine with anaerobic processing and ion exchange/adsorption(Graduate School, 2022-05-11) Akdağ, Yasemin ; Baykal Beler, Bilsen ; 501181734 ; Environmental Sciences Engineering and ManagementGlobal population is continuously increasing with a predicted increase to 9.7 billion by 2050. On the other hand, resources are facing with extinction. Sustainable food production greatly depends upon fertilizer production, which has nitrogen, phosphorus and potassium as key elements. Nitrogen, which is abundant in the air, is fixated by Haber-Bosch process, which consumes enormous amounts of energy, to be used in the fertilizer production. Phosphorus, which is a vital element, has limited resources, which is distributed unevenly around the world. The current domestic wastewater management, which adopts mixed collection of wastewater, is based on "treat" and "discard". Valuable materials in wastewater cannot be recovered with the current management practices. Therefore, an alternative way is needed to be generated. Segregation of domestic wastewater into different streams at the source of generation is suggested to get benefit from each stream. ECOSAN is an alternative sanitation concept that claims wastewater is not waste to be discarded but a source to be revaluated. Within this context, each stream is separately collected at the source and is processed for the recovery/reuse of valuable materials. ECOSAN is based on the separation of different domestic wastewater streams into three streams as yellow water, grey water and brown water. Yellow water, which is mainly source separated human urine, is a valuable waste stream in terms of macro plant nutrients (N, P, K). Yellow water constitutes only 1 % of conventional domestic wastewater by volume; however, it contains over 80% of nitrogen, over 50% of phosphorus and over 50% of potassium. This rich nutrient content makes urine a potential source of fertilizers. There are two routes to use source separated human urine as fertilizer in agriculture; (i) direct application and (ii) indirect application. Direct application of human urine as fertilizer is based on the collection of human urine, followed by transport (if required), storage of human urine to destruct pathogens and direct application of stored urine onto soil as fertilizer. Indirect use of human urine as fertilizer necessitates processing urine before intended use. Urine is frequently processed to produce urine-based fertilizers through struvite precipitation, ammonia stripping/absorption and ion exchange/adsorption. Nutrient removal/recovery from source separated human urine was widely investigated in literature. After nutrient removal, the residual liquid phase needs to be handled in an appropriate way as it still contains appreciable amounts of organic matter and nutrients. However, studies on the handling of residual urine are scarce. This study aims the investigation of nutrient recovery from source separated human urine by ion exchange/adsorption on one hand, while investigating organic matter and nitrogen removal from the residual urine by anaerobic processing and ion exchange/adsorption. The behavior of organic matter was closely monitored during different phases of the investigation. Within the scope, urine was collected from two urine diverting toilets and a urinal, and then it was stored for the conversion of urea to ammonium, which is the desired form of nitrogen for ion exchange. Ion exchange/adsorption was employed for nutrient removal from stored urine. The residual urine was processed with anerobic processing and second stage ion exchange/adsorption. Anaerobic processing was suggested to reduce organic matter content of the residual urine and to investigate possible production of biogas. Second stage ion exchange/adsorption was employed to reduce organic matter content of the residual urine and to maximize nutrient removal from the residue. The results of this study revealed that storage was a crucial step not only for urea hydrolysis but also for organic matter removal as between 25% to 39% of COD in urine was removed during storage. Through ion exchange/adsorption for nutrient removal/recovery with the initial loading of 15 mg NH4+/g clinoptilolite, 82% of ammonium and 28% of COD were removed from stored urine. The residual urine still contained appreciable amounts of COD and ammonium, and a high level of salinity for which a special care should be taken. During nutrient recovery, 99% of ammonium and 94% of phosphorus were recovered from the surface of nutrient enriched clinoptilolite upon contact with tap water with the contact time of 5 min in 16 days. 63% of ammonium and 100% of phosphorus were recovered with the contact time of 300 min in 35 days. The COD release from the surface was not considerable for both contact times, indicating that organic matter is not released appreciably from the surface of the clinoptilolite upon contact with water. This is beneficial from the standpoint of pollution prevention when nutrient enriched clinoptilolite is applied as fertilizer in agriculture. Anaerobic granular sludge from a confectionery industry was adapted to highly saline human urine using synthetic urine as feed in attempt to control adaptation conditions. During adaptation the effect of salinity and COD concentration on the removal of organic matter were investigated. During adaptation to high salinity levels at constant COD, organic matter removal efficiency was decreased from 90% to 85% when electrical conductivity was gradually increased from 14000 to 32000 µs/cm, indicating that organic matter removal was not considerably affected by salinity. For different COD concentrations at constant salinity, organic matter removal efficiency was decreased from 83% to 53% when COD was reduced from 2000 mg/L to 750 mg/L, indicating that organic matter removal efficiency was greatly affected by COD concentration. The results showed that selection of the treatment process for residual urine was case specific. Anaerobic processing seems to be a better option for organic matter removal in case of higher COD in residual urine. However, second stage ion exchange/adsorption seems to be a better choice for the treatment of residual urine in case of lower COD concentrations. Anaerobic processing has a potential of a calculated biogas production between 0.2 to 0.46 L CH4/L urine. However, not all of this could be collected under the conditions of the experiments in this work. Second stage ion exchange/adsorption, on the other hand, was advantageous in terms of complete removal of ammonium from residual urine. This study showed that the suggested processing layout was applicable for simultaneous recovery of nutrients and treatment of residual urine. For residual urine, process selection should be evaluated based on the conditions of specific cases to be handled.