LEE- Çevre Bilimleri Mühendisliği ve Yönetimi-Doktora
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Sustainable Development Goal "Goal 6: Clean Water and Sanitation" ile LEE- Çevre Bilimleri Mühendisliği ve Yönetimi-Doktora'a göz atma
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ÖgeApplication of different strategies to improve aerobic granular sludge process performance for treatment of municipal wastewater(Graduate School, 2022-09-29) Koşar, Şadiye ; Erşahin, Mustafa Evren ; 501162714 ; Environmental Sciences, Engineering and ManagementAerobic granular sludge (AGS) process is an energy-efficient alternative biological wastewater treatment process to the conventional activated sludge (CAS) process which requires high energy and big space. In CAS systems, flocs sized above 0.2 mm are referred as granule. So far flocs and granules could be easily differentiated by size clustering as well as their capabilities of removal for organic matter and nutrients. Surface of the granule has porous morphology, and this allows the substrate penetration and as well as oxygen diffusion into the inner layers of the granule. The diffusion of oxygen is somehow can be a limiting factor for the simultaneous carbon and nutrient removal due to structure of the granule. In many cases, granule has a compact and dense structure that limits the oxygen transfer to the inner core layers of the granule which improves the denitrification and allows better phosphorus (P) removal within the granule. Whereas in some situations, granules have amorphous structure which do not improve any core inside the granule so affects the removal of substrate. Aerobic granules are heavier than flocs formed in waste sludge, so they settle faster, and this improves the settleability of the sludge which further allows to operate in one reactor. For this reason, large sedimentation tanks are not required in AGS systems. Since aerobic, anoxic and anaerobic biological activities take place inside the granule, AGS process offers 25-75% less space and consumes 20-50% less energy compared to conventional activated sludge plants. Nitrification takes place on the surface of the granule during aeration phase and denitrification occurs in the inner layers of the granule under anoxic conditions. P removal is maintained by polyphosphate accumulating organisms (PAOs) that are located in the core part of the granule. PAOs and denitrifiers which are responsible for the denitrification are both heterotrophic organisms and compete for the carbon sources as substrate. For this reason, it is important to have sufficient amount of organic matter for nitrogen (N) and P removal. Since PAOs are located in the inner layer of the granule they are only capable of using organic that are in dissolved form. In municipal wastewater, organic matter is particulate and dissolved forms. Particulate matter reduces N and P removal up to 40% and 46% respectively. Particulate organic matter is turned into dissolved form in the presence of extracellular polymeric substances (EPS) which are hydrolyzing them further. Hydrolysis ends up in anaerobic phase when the attached particulate matter on the surface of the granules hydrolyzed and it is uptaken by PAOs and denitrifiers. If dissolved organic matter cannot be consumed by these species, then it would be consumed by the aerobic heterotrophic bacteria on the surface of the granule which further causes filamentous microorganisms' overgrowth. This leads to amorphous structure and disintegration of the granule. In this thesis, the treatability municipal wastewater by AGS process was investigated under different circumstances. Four separate studies were conducted within the scope of this study. In the first study, two different sludge were comparatively investigated as inoculum: (a) waste activated sludge (WAS) taken from the return activated sludge line of an advanced biological wastewater treatment plant (WWTP), (b) WAS taken from the return activated sludge line of a pilot scale high-rate activated sludge (HRAS) system. This study was conducted in two stages: AGS system was seeded with the WAS taken from the return activated sludge line of an advanced biological wastewater treatment plant in the first stage; in the second stage, AGS system was seeded with the mixture of WAS taken from the return activated sludge line of an advanced biological WWTP and WAS of pilot scale HRAS process as volume in proportion of 1:1. This study was performed to reveal the contribution of microorganisms found in the flocculent sludge to the granulation process. Since HRAS process sludge has high settleability and the mixture of WAS with HRAS process as inoculum was expected to enhance the settling properties of granular sludge as well as achieving good treatment performance. Although at the start-up period sludge wash-out occurred and mainly fluffy waste sludge wasted, HRAS process sludge settles faster, and it remained in the reactor. So, in this case especially denitrifiers were mostly washed out of the system which deteriorated system performance compared to the AGS system operated solely with WAS. At the end of this study, WAS waste sludge was chosen as seed sludge for the further studies to obtain aerobic granulation based upon AGS system treatment performance. In the second study, WAS taken from the return activated sludge line of an advanced biological WWTP was used as seed sludge. Study was conducted in two stages: (a) AGS system was fed directly with the synthetic municipal wastewater, (b) AGS system was fed with the pre-settled synthetic municipal wastewater (30 min of settling) to simulate pre-sedimentation tanks in the full-scale wastewater treatment plants (WWTPs). With pre-settling application, it was proposed that particulate matter would settle so mainly dissolved organic matter could be introduced to the AGS system. Since AGS system is anaerobically fed, this would improve the nutrient removal by allowing the uptake of organic matter easily by PAOs and denitrifiers. It was shown that up to 60% of particulate matter was removed by settling and as a result carbon/nitrogen (C/N) ratio decreased 20% lead deterioration of the AGS system treatment performance. It was apparent that a combination of pre-sedimentation in AGS process didn't improve the system. In the third study, AGS system was operated in three different stages continuously following each other without having different start-up periods: (a) AGS system was fed directly with raw municipal wastewater, (b) AGS system was fed with the pilot scale HRAS system's effluent (treated wastewater), (c) AGS system was fed with the mixture these two flows: raw municipal wastewater (20%) and HRAS process effluent (80%). Waste sludge taken from the return activated sludge line of an advanced biological wastewater treatment plant was used as inoculum. Firstly, aerobic granulation was maintained by introducing municipal wastewater than HRAS process effluent fed to the system and AGS system performance was followed thoroughly. It was shown that the granule stability remained somehow same, but AGS system performance was affected by decreased C/N ratio. AGS system was fed with the mixture the raw municipal wastewater and HRAS process effluent to improve the system performance. As a result, AGS system performance was improved with the increase in C/N ratio (20% increase compared to feeding with only HRAS process effluent). Thus, HRAS process integration with AGS process was found to be energy efficient configuration. Both systems comparably occupy less space than conventional treatment systems and their integration will definitely improve the effluent quality. In the fourth study, digestibility of AGS which was obtained from the third study was compared to the WAS taken from the return activated sludge line of an advanced biological wastewater treatment plant. It is known that AGS process sludge has low digestibility than WAS. Thus, ultrasonication was applied to improve the solubilization of organic matter for increasing sludge digestibility. Since aerobic granules are clusters of microorganisms that are attached together, they are bigger in size and more compact than WAS flocs. Therefore, relying on their physical differences, it was assumed that ultrasonication would enhance digestibility of the AGS. It was shown that ultrasonication as pre-treatment method led to solubilization for both sludge sources in terms of volatile fatty acids (VFAs), protein and carbohydrates besides causing decrease in particle size. A direct relation found between the release of organic compounds, ammonium, phosphorus and heavy metals with the increase in ultrasonication intensity. Overall results obtained from this thesis showed a comprehensive approach to treat municipal wastewater by AGS process while improving the treatment performance by focusing on inoculum source as well as feeding strategy. Besides, sludge from AGS process was evaluated in terms of soluble products release by applying ultrasonication process compared to the WAS. This thesis would enhance the knowledge on AGS technology in terms of seeding and feeding regimes beneath giving clues for full-scale AGS process applications.
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ÖgeDynamic membranes in aerobic membrane bioreactor systems for municipal wastewater treatment(Graduate School, 2021-06-08) Işık, Onur ; Demir, İbrahim ; Özgün, Hale ; 501142704 ; Environmental Sciences Engineering and Management ; Çevre Bilimleri Mühendisliği ve YönetimiThe amount of municipal wastewater produced around the world is expected to increase parallel to the increase in population. Therefore, the treatment of municipal wastewater is very crucial for public health. Conventional activated sludge systems have been used for the treatment of municipal wastewater for a long time. Due to limited area availability and stringent discharge standards in most cases, compact treatment systems enabling high effluent quality have become attractive recently. Membrane bioreactor (MBR) technology is a good alternative to conventional activated sludge systems. There are several advantages of MBR technology over conventional biological treatment systems. Low footprint and high permeate quality can be considered as the most distinguishing features of the MBRs. Due to the retention of high suspended solids concentration in the bioreactor, smaller reactor volume and low sludge production can be achieved by the MBR process. However, some constraints have been observed during the operation of MBRs including membrane fouling and membrane costs. Dynamic membrane (DM) technology is a promising solution for problems encountered during the operation of MBRs for wastewater treatment. Membranes can be substituted with coarse-pore filters made of low-cost materials such as meshes or fabrics in dynamic membrane applications for cake (DM) layer formation. DM is a secondary layer formed on a low-coast porous support material. DM layer acts like a Microfiltration (MF) or Ultrafiltration (UF) membrane and keeps the sludge particles inside the bioreactor providing high permeate quality. Besides, physical cleaning, without using chemical reagents, may be enough for cleaning in dynamic membrane bioreactors (DMBRs), thus, the operational costs can be reduced. Flat sheet submerged module configurations were mostly used for aerobic DMBR studies for municipal wastewater treatment in the literature. Also, few studies used tubular modules in DMBRs. However, no studies reported using hollow fiber modules in the literature. The main aim of this thesis was to investigate the applicability of hollow fiber DM for municipal wastewater treatment in an aerobic DMBR. This thesis was conducted in 6 Stages. In stage 1, a hollow fiber polyester fabric support material was used for DM formation and compared with a commercial hollow fiber UF membrane. The system was fed with medium strength synthetic municipal wastewater to keep the characteristics of the wastewater same, and to evaluate the treatment and filtration performances of both membranes clearly. Morphological analyses were also carried out for DM and UF surfaces. The system was operated continuously at a flux of 5 L/m2·h for 85 days. High chemical oxygen demand (COD) removal efficiency and total suspended solids (TSS) rejection were achieved by the DM. Transmembrane pressure (TMP) of the DM was higher in comparison to the UF membrane, which was related to the formation of the cake layer in DM. In Stage 2, impact of support material type on DMBR performance was investigated for municipal wastewater treatment. A hollow fiber polyester support material was compared with a glass fiber support material in terms of treatment and filtration performances. Medium strength synthetic municipal wastewater was used for a stable feed characteristics. Similar treatment performances were obtained with each membrane achieving high removal efficiencies for COD(>97%) and TSS (>99%) parameters. Higher TMP was observed for glass fiber material in comparison to polyester material. Based on morphological analyses, dynamic layers formed on both support materials had similar compositions, organic and inorganic materials. A homogeneous layer was formed on a polyester support material, while fine particles were deposited between the filaments of glass fiber support material, which caused clogging. In Stage 3, a hollow fiber polyester fabric support material was used for DM formation for raw municipal wastewater treatment. The wastewater had average COD concentration of 413 mg/L, sCOD concentration of 208 mg/L and TSS concentration of 259 mg/L. Treatment and filtration performances were evaluated. High treatment performance was obtained in the permeate achieving over 93% of COD removal efficiency and low TSS concentration (<10 mg/L) in the permeate. The average TMP value was observed as around 598 mbar after the system reached stable conditions. In Stage 4, effect of different TSS concentrations on the DM layer was evaluated in terms of biological treatment and filtration performances. Hollow fiber polyester support material was used for DM layer formation. Treatment and filtration performances of the DMBR were investigated at two different TSS concentrations (5 g/L; 10 g/L). The DMBR was operated at a flux of 18 L/m2·h at each condition. High treatment performance and permeate quality were achieved at each sludge concentration. However, a shift to a relatively higher range in particle size distribution of permeate was observed at high sludge concentration. Furthermore, higher TMP was observed at the sludge concentration of 10 g/L, resulting in a rapid clogging. Overall, results indicated that selection of the optimum sludge concentration played a significant role in achieving homogeneous and stable DM layer in DMBRs. In stage 5, hollow fiber polyester support material was used for DM formation and compared with a commercial UF membrane in terms of micropollutant and heavy metal treatment performance from raw municipal wastewater, also biological treatment and filtration performances were evaluated. The removal of different micropollutants; sulfamethoxazole, ciprofloxacin, trimethoprim, caffeine and acetaminophen, was assessed for both membranes. The membranes were operated at a flux of 10 L/m2·h. High TSS (>99%) and COD (> 91%) removal efficiencies were achieved with both membranes. Similar high removal efficiencies of micropollutants (>68.3->99.7%) were achieved with both membranes. DM was operated at higher TMP compared to UF membrane, since DM layer was formed on the support material. Morphological analyses were conducted for both membranes to get insight to the DM layers which accumulated on the membranes. In Stage 6, effect of using different inoculum on DMBRs performance was investigated. Excess sludge from HRAS and conventional activated sludge system retuned activated sludge were used as inoculums. Conventional UF membrane was used in parallel with a dynamic membrane (DM) in the same reactor to be operated at the same conditions. Both sludges were characterized to understand the changes during the operational period. Biological treatment and filtration performances of both membranes were investigated. High TSS (>99%) and COD (> 86%) removal efficiencies were achieved with both membranes for both inoculum sludge. Because of the inoculum sludge characteristics, lower TMP values were observed for DM at Phase-2. Morphological analys (ESEM measurement) was conducted to understand the effect of different inoculum on the sludge cake on the surface of the membranes.
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ÖgeProfile of priority substances and toxicity assessments of wastewater treatment plants in Istanbul(Graduate School, 2023-05-31) Birtek, Rahime İclal ; Öztürk, İzzet ; 501122704 ; Environmental Sciences, Engineering and ManagementWastewaters formed due to anthropogenic activities around urban areas pose a threat to aquatic environments. The growth in industrial activity along with the worldwide urban migration, as well as the threat posed by climate change, increase the extent of pollution. The discharge of the treated or untreated wastewaters is reported to cause a threat to their receiving water environments. Conventional wastewater treatment plants (WWTPs) are constructed to minimize the nutrient loads of macropollutants (C, N, and P) entering the receiving water bodies. As, removal of some of the emerging contaminants (ECs) or micropollutants present in wastewaters is found to be incomplete in conventional wastewater treatment processes, traces of those non-biodegradable ECs were reported to be found in the receiving environments. The presence of ECs, even in very low concentrations (pg/L - ng/L) in the water environments could cause adverse effects on humans and the ecosystem. In addition to industrial emissions, domestic discharges along with urban runoffs are main contributors of ECs in WWTPs. Understanding the presence, sources and transport of the micropollutants and ECs in wastewaters is important for assessing their impacts, and hence can help their reduction and management in the receiving environment. Micropollutants that have shown toxic, persistent, bioaccumulative, and ubiquitous properties and have been identified in aquatic environments, are designated as priority substances (PSs) by the EU Water Framework Directive (WFD). EU Member States are required to identify the presence of PSs in surface waters, in order not to exceed threshold levels specified by the Environmental Quality Standards (EQS) dictated by WFD. The Turkish Ministry of Forestry and Water Affairs adopted the aforementioned quality standards for the PSs in surface waters in 2012, and updated them in 2016. Since WWTPs are known to be main point sources of ECs entering the receiving water bodies, investigating the occurrence of PSs in wastewaters of Istanbul has generated valuable information. This thesis aims at understanding the occurrences of PSs in the wastewaters of the megacity of Istanbul as well as assessing WWTP effluents as sources of PSs in receiving environments. The thesis also includes the acute toxicity assessment of the same wastewaters. The scope of the study includes the wastewaters of the seven largest WWTPs, a hospital wastewater and leachate of a landfill treatment plant in Istanbul. The results of the PSs analyses allowed estimation of risks posed by the PSs in the WWTP effluents. Lists were formed to PSs showing sufficient risk (RQ>1), and their inclusions are recommended in the surveillance monitoring programs for the effluents of advanced treatment, as well as mechanical treatment. The regulators undertaking environmental risk assessments in the initiation of monitoring programs for the protection of the Sea of Marmara, Bosphorus and the Black Sea may utilize the findings of this study. Chapter 2 provides general information on the background of the study that is related to the aim and objective of the study. Chapter 3 comprises of information regarding the study area as well as methods on the description of all the experiments conducted through this study, namely analyses of PSs, toxicity analyses and physiochemical analyses. Chapter 4 Results and Discussion, provides information on the results of the experiments conducted through this study (PSs analyses, toxicity analyses and physiochemical analyses), as well as discussion of those results. Chapter 5 provides a summary of the whole thesis. The References section includes the complete bibliography. The Appendix includes tables, figures and pictures.
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ÖgeTarım kaynaklı pestisitlerin SWAT ile havza ölçeğinde modellenmesi(Lisansüstü Eğitim Enstitüsü, 2022-06-28) Doğan, Fatma Nihan ; Karpuzcu, Mahmut Ekrem ; 501152702 ; Çevre Bilimleri Mühendisliği ve YönetimiTarımsal kaynaklı yayılı kirleticiler özellikle tarım ilaçları, kontrolsüz ve aşırı kullanımlarından ötürü su kaynakları, doğa, insan ve diğer canlılar için tehlike oluşturmaktadır. Nüfus artışları ile birlikte tarım alanlarından maksimum verim alabilmek amacıyla gübre ve pestisitlerin kullanımı kaçınılmaz olmuştur. Piyasada farklı etken maddeli birçok pestisit çeşidinin olması ve bu pestisitlerin herhangi bir sınırlama olmaksızın satın alınıp kullanılabiliyor olması çevre için en büyük riski oluşturmaktadır. Bu çalışmada, İstanbul'da tarımsal faaliyetlerin yoğun yapıldığı Terkos Havzası ve drenaj alanındaki pestisit kirliliği karar destek sistemleri ile değerlendirilmiş, bu kirliliğin kontrolü ve giderimi için uygulanacak yöntemler belirlenmiştir. Terkos Havzası, İstanbul için en önemli ve görece en temiz içme suyu kaynaklarındandır. Diğer İstanbul havzalarına göre Terkos Havzası, yoğun orman alanları ve az şehirleşmesi ile daha bakir alanlara sahiptir. Fakat havzadaki Terkos Gölü rezervuarı ve gölü besleyen nehir ağlarının çok yakınında tarımsal faaliyetlerin yapılması, tarım alanlarından nehre ve dolayısıyla rezervuara pestisit taşınımına yol açmaktadır. Pestisit endüstrisinin gelişmesiyle, bitki zararlılarına karşı çok çeşitli yeni ilaçların üretilip kullanıması su kaynaklarındaki pestisit kirliliğinin kontrolünü zorlaştırmaktadır. Ayrıca şu an kullanımı yasak fakat geçmişte kullanılmış, tarım alanlarında depolanan bozunmaya karşı dirençli pestisitler de su kaynakları için büyük risk oluşturmaktadır. Tarımsal sürdürülebilirliği sağlayacak şekilde tarım ilaçlarının kullanımın kontrol altına alınması sadece su kaynaklarını korumak için değil gıdalardaki kalıntı pestisit miktarını azaltarak gıda güvenliğini sağlamak, sucul ekosistemin iyileştirmek ve insan sağlığına yönelik tehditlerin azaltmak için de gereklidir. Türkiye, Bütünleşik Havza Yönetimi anlayışını benimsemiş olup bu anlayış tarımsal kaynaklı kirleticilerin kontrolünü ve yönetimini içermektedir. Bu amaçla havza bazlı pestisit kullanımının ilk aşamasından su kaynaklarına ulaşana kadar tüm aşamalarında pestisit kirliliğinin yönetimine dair stratejiler geliştirilmelidir. Tarım ilaçlarının aşırı ve gereksiz kullanımını engelleyecek Entegre Pestisit Yönetimi, Zararlılarla Entegre Mücadele, Entegre Ürün Yönetimi, İyi Tarım Uygulamaları gibi yöntemlerin uygulanması pestisit kirliliğini kaynağında önlemeye yönelik faaliyetlerdir. Kullanılması muhtemel pestisitlerin izleme çalışmaları ile tespitinin yapılması ve bu kirleticilerin su ortamına ulaşana kadar uğradıkları dönüşümler ve izledikleri yolların karar destek sistemleri ile belirlenmesi ve En İyi Yönetim Uygulamaları (EİYU) olarak adlandırılan doğal arıtma yöntemleri ile pestisit kirliliğinin su kaynaklarına ulaşmadan kontrolünde önemli adımlardır. Bu çalışmanın amacı, Terkos Havzası'nda tarımsal kaynaklı pestisitlerin su kaynaklarına etkisini tespit edebilmek, mevcut arazi kullanım şartlarında nasıl bir yol izlediklerini ve çevreye etkilerini bir karar destek sistemi olan SWAT (Soil Water Assessment Tool) modeli ile değerlendirmektir. Bu amaçla, öncelikle SWAT modeli yardımı ile havzanın su dengesi oluşturulmuş, hidrolojik modellemesi yapılmıştır. Hidrolojik modellemede havzaya ait topografik, arazi kullanımı ve iklimsel verilerin kullanılmasıyla havzanın su bütçesini çıkarılmış ve suyun havzadaki çevrimi tespit edilmiştir Hidrolojik modelleme, daha sonraki taşınım ve su kalitesi modellemesi için bir altlık görevi görmektedir. Hidrolojik modelin kalibrasyonu ve validasyonu sonunda, sediment ve pestisit taşınım ve akıbeti modellemesi gerçekleştirilmiştir. Pestisit taşınım ve akıbeti modelinin kalibrasyonu için havzadaki çeltik ve kuru tarımın yoğun olarak yapıldığı Karamandere'den numuneler alınmıştır. Pestisit modellemesi sonucunda, havzadaki kritik alanlar belirlenerek, bu bölgelere pestisit yükünü azaltmak amacıyla EİYU'lar eklenmiştir. EİYU'lar ile birlikte havzadaki pestisit kirliliğinin yönetimine dair yapılması gerekenler belirlenmiştir. Havzaya yapılan saha gezilerinde uzun yıllardır havzada tarım yapan çiftçiler, ziraii bayiler ve kalkınma kooperatifleri ile görüşülmüş, çeltik ve kuru tarım hakkında bilgiler edinilmiştir. Havzadaki durum su kaynakları, tarımsal faaliyet, orman habitatı, toprak korunumu, sosyal-ekonomik boyutuyla birlikte ele alınarak havzanın geleceğine dair görüş ve önerilerde bulunulmuştur.