FBE- Çevre Mühendisliği Lisansüstü Programı - Doktora
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ÖgeThe prevention of biofilm formation and prohibiting of the antibiotic resistance development(Lisansüstü Eğitim Enstitüsü, 2021)Membrane bioreactors (MBRs) are powerful systems for wastewater treatment, especially for the removal of toxic compounds such as antibiotics. To address the inadequate removal of antibiotics and spread of resistance genes in wastewater treatment plants, this study investigated the impact of bioaugmentation with dried Eichhornia crassipes roots, Trichocladium canadense and Penicillium restrictum on MBR systems. Performance of the reactors in terms of pollutant removal, including antibiotics sulfamethoxazole (SMX), tetracycline (TET) and erythromycin (ERY) were investigated, while anaerobic reactors were optimized for potential for reclaiming value through biogas production. For deeper insight, the shift in microbial communities in sludge and biofilm were analyzed through Illumina sequencing. MBRs and AnMBRs were set up for the experiment, aerobic sets consisted of C1 (inoculum), C2 (inoculum + antibiotics), EC (inoculum + antibiotics + E. crassipes) and PR (inoculum + antibiotics + P. restrictum), and anaerobic sets consisted of A.C1 (inoculum), A.C2 (inoculum + antibiotics), A.EC (inoculum + antibiotics + E. crassipes), A.TC (inoculum + antibiotics + T. canadense). In the aerobic sets, the addition of E. crassipes into the MBR increased the COD (by 6%), antibiotics and transformation products removal efficiency. Removal efficiencies of 97%, 98% and 84% were obtained for removal of ERY, SMX and TET in E. crassipes added reactor, respectively. Furthermore, E. crassipes reconstructed indigenous and microbial communities. It modified the biodegradation network, increased the relative abundances of Chloroflexi, Proteobacteria and Nitrospirae and decreased Firmicutes, compared to control with antibiotics. The addition of E. crassipes also enriched Actinobacteria and Bacteroidetes while decreasing Chloroflexi and Saccharibacteria phyla in biofilm. Addition of P. restrictum alleviated membrane fouling, increased removal of the antibiotics while decreasing sorption onto solid phase. The results showed a shift in bacterial composition toward shaping an antibiotic resistant profile in bioreactor after bioaugmentation with P. restrictum, mostly because of phenotypic expression via quorum quenching activity of secreted metabolites from P. restrictum. In the anaerobic bioreactor, E. crassipes biomass mitigated some of the toxic effects of antibiotics on the microbial community and prevented negative impact on the archaeal community, and significantly increased average biogas production (by 37% compared to control without antibiotics and 42% compared to control with antibiotics) as well as antibiotics removal at anaerobic membrane bioreactor. Furthermore, bioaugmented reactors showed significant reduction of ERY (97%) and TET (83%) concentrations in effluent. Microbial community analysis revealed that the structure, which was shifted in the presence of antibiotics, was restored to a similar composition as control without antibiotics in the presence of dried E. crassipes roots. This was especially notable for the archaeal population, allowing a more balanced distribution of acetoclastic and hydrogenotrophic methanogens. Results for T. canadense anaerobic reactors indicated that with bioaugmentation with 20% T. canadense, membrane biofouling was slowed by 25%, chemical oxygen demand (COD) removal increased by 16% and higher efficiency removal of ERY and SMX was achieved. Furthermore, the bioaugmented T. canadense significantly increased the abundance and diversity of the archaeal community on the biofilm and bacterial phylum Firmicutes, a known bio-foulant, decreased by 14%, which indicated apparent impact on biofilm formation. Utilization of these biological agents in MBR systems offers simple yet powerful tools for preventing the emergence of antimicrobial resistance and dissemination of such pollutants into the environment while increasing performance of the reactors and producing biogas. Bioaugmentation of such agents can lead to efficient and self-sustaining wastewater treatment facilities in the future.
ÖgeMicroalgae growth in anaerobic digestate for high-value product recovery(Fen Bilimleri Enstitüsü, 2020)As a result of diminished fossil fuel reserves and increased prices of petrochemical fuels, and the simultaneous result of fossil fuels on extreme greenhouse gas emissions leading global warming, the world is searching for an alternative renewable energy sources. Renewable energy sources such as solar, wind, hydro, geothermal and biomass have been successfully developed but research shows that biomass energy has the highest capability among other renewable sources. Microalgae has the highest attention in the field of bioenergy by not requiring arable land, their higher productivity and higher biofuel yield compared to terrestrial plants. Not only for bioenergy aspect, bu also for the environmental aspect, microalgae has too many advantages such as mitigation of CO2 through photosynthesis and treatment of wastewater. Anaerobic digestion is another and the most conventional methods used to generate energy from renewable sources. However, untreated anaerobic liquid digestate may cause eutrophication if directly discharges into the water sources due to its high nutrient content. Cultivating microalgae in digested effluents offers significant advantages in terms of wastewater treatment, the production of valuable biomass which can be further valorized, and a major decrease in the upstream cost of the process. Microalgae can assimilate nutrients especially nitrogen and phosphorous from wastewater for their growth and produce valuable biomass. Digestates include all essential macro/micro nutrients and can be recovered as cultivation media for microalgal biomass production. However, some of the main physicochemical characteristics of the digestates, such as high content of inhibitory compounds, turbidity, and colored dissolved compounds might negatively influence microalgal growth, and therefore they need to be adjusted by using one or a combination of pretreating methods (e.g., dilution, solid/ liquid separation, filtration, etc.) in order to provide suitable medium for cell growth. The main objective of this thesis was to investigate the applicability of recovery of nutrients from digestate with mixed microalgae and observe positive effect on algal biomass resulting in enhanced high value product content. High-value products such as pigments, proteins, lipids, and carbohydrates that are obtained from microalgae grown in digestate can used as fuel, fertilizer and animal feed contributing to a substantial saving in the overall cost of microalgae biomass production. In this scope, the Anaerobic Liquid Digestate (ALD) obtained from real full scale plant to demonstrate and to show the applicability of succesful growth on digestate, instead of treating with advanced treatment methods and to recover high value products from the wild type algal biomass isolated from near-by water bodies in ITU to examine its dominancy change and positive effect. To promote the sustainability of microalgae–bacteria-based systems that treat wastewater, the examination of multiple products in the form of high value products and biomass were detailly monitored. In the first part of the study, batch experiments were carried out to investigate the biokinetic coefficients for nutrient removal of mixed microalgae grown on anaerobic liquid digestate by Michaelis–Menten rate expression. The initial NH3-N concentration was varied between 18.6–87.1 mg L-1 while initial PO4-P concentration was between 1.85–6.88 mg L-1, which corresponds to 2%, 5%, 7% and 10% dilution ratio of anaerobic digestate. According to the yield results (mg chl a mg-1 nutrient), mixed microalgae uptake 10 times more nitrogen than phosphorus. Biokinetic coefficients were determined as kN = 2.48 mg NH3-N mg−1 chl a d−1, KmN = 29.3 mg L-1, YN = 0.45 mg chl a mg-1 NH3-N for nitrogen; and kP = 0.21 mg PO4-P mg−1 chl a d−1, KmP = 2.94 mg L-1, YP = 5.03 mg chl a mg−1 PO4-P for phosphorus. The highest chlorophyll production (39 mg L-1 or 3.31 mg L-1 d-1 ) was observed at the highest dilution ratio of 10%. Moreover, the highest dilution resulted in highest biomass (1.25 g L-1) despite of dark, high ammonicial and particulate rich wastewater. In the second stage of the study, mixed microalgal culture dominated by Chlorella vulgaris and Scenedesmus armatus were grown in Anaerobic Liquid Digestate (ALD) under different NaCl concentrations ranging between 0 to 100 mM. Highest lipid and carbohydrate amount were observed as 38% and 36%, respectively, when the salinity was 50 mM NaCl. However, the protein content was drastically decreased to 13% with increased NaCl concentration. Furthermore, the algal biomass was subsequently decreased along with total chlorophyll amount with increased NaCl concentration. Algal species showed diverse response to salinity stress and demonstrated a cost-effective approach towards the cultivation of mixed microalgae within digestate and provided insight that ALD and/or other wastewaters can be diluted with seawater instead of tap water in the future studies. This study could be further converted into biofuels due to high lipid increase along with the digestate treatment, which will help to valorize ALD and bring into economy. In the third stage of the study, FeSO4 supplementation ranging from 0 to 4.5 mM, and MgSO4 supplementation ranging from 0 to 5.1 mM were investigated to observe the effect on the population dynamics, biochemical composition and fatty acid content of mixed microalgae grown in Anaerobic Liquid Digestate (ALD). Overall, 3.1 mM FeSO4 addition into ALD increased the total protein content 60% and led to highest biomass (1.56 g L-1) and chlorophyll-a amount (18.7 mg L-1) produced. Meanwhile, 0.4 mM MgSO4 addition increased the total carotenoid amount 2.2 folds and slightly increased the biomass amount. According to the microbial community analysis, Diphylleia rotans, Synechocystis PCC-6803 and Chlorella sorokiniana were identified as mostly detected species after confirmation with 4 different markers. The abundance of Chlorella sorokiniana and Synechocystis PCC-6803 increased almost 2 folds both in iron and magnesium addition. On the other hand, the dominancy of Diphylleia rotans was not affected by iron addition while drastically decreased (95%) with magnesium addition. This study helps to understand how the dynamics of symbiotic life changes if macro elements are added to the ALD and reveal that microalgae can adapt to adverse environmental conditions by fostering the diversity with a positive effect on high value product. In conclusion, in this thesis, the production of microalgae biomass have been successfully carried out, and the macronutrients needed in the production of microalgae have been provided from the digestate effluent obtained from a real-scale anaerobic digester using a mixture of domestic organic solid waste, industrial treatment sludge and animal feces. Moreover, it helped to understand how the dynamics of symbiotic life changes if macro elements are added to the ALD and reveal that microalgae can adapt to adverse environmental conditions by fostering the diversity with a positive effect on high value product. This thesis might help to be a answer for aiming both reducing adverse effect of anaerobic liquid digestate by mixed microalgae and increasing product values by valorization and give an idea that digestate can be diluted with sea water instead of tap water in the future studies. Moreover, by this thesis, it was proves that digestate cultivated algae are rich source of primary (carbohydrates, proteins, lipids) and secondary (pigments) metabolites that could be exploited to produce biofuels, bio-polymers, biofertilizers, nutraceuticals, food/health grade compounds, enzymes, feed supplements etc. and the treated digestate can be reutilized for the agricultural or industrial purposes according to the high removal rates by mixed culture.
ÖgeReinforced hollow fiber nanofiltration membrane production for the removal of natural organic matter(Institute of Science And Technology, 2019-05-30)Hollow fiber membranes are used in water and wastewater treatment; wastewater reuse for a long time. Hollow fiber membrane configuration offers high packing density, have small footprints and filtration efficiency is high. Fouling is a problem in hollow fiber membranes like all types of membranes. Ideal membrane properties should include high permeability with enough mechanical strength and excellent stability to chemical attacks. Chemical composition of membrane solutions defines chemical properties of membranes. Permeability and mechanical strength of membranes strongly depend on membrane structure, which is primarily determined by phase inversion method used to fabricate membranes. Currently, two most commonly employed membrane module geometries are spiral-wound and tubular. The advantages of spiral wound modules are low cost and large specific surface area (m2/m3). Yet, they are highly susceptible to fouling by suspended matter, have high energy losses caused by headloss in spacer-filled channels and cannot be back-flushed. Tubular modules do not require as extensive pre-treatment and allow for back- flushing; however, they have low packing density and are expensive. In 2000s, researches focused on developing capillary nanofiltration modules to combine advantages of the two module types. These capillary membranes have been used at the pretreatment stage to decrease fouling in downstream spiral wound modules. A hollow fiber (HF) NF module is a viable alternative to both spiral wound and tubular membranes for treatment of low quality water sources. It has been estimated that an optimized HF NF module would give a one hundred percent increase in module performance compared to an optimized spiral-wound module configuration. The aim of this thesis to carry out a comprehensive study on the development of reinforced hollow fiber nanofiltration membranes. For this objective, reinforced membrane production made optimized and tried different support layers. Braided textile support made from PET is used to reach high mechanical strength in hollow fiber membranes. In this study, we evaluated PET and glass fiber supports. We noticed that glass fiber support layer is broken in time because of the material. Thus, support layer made with PET was found that it is more suitable for production of reinforced hollow fiber membranes. Hollow fiber membranes have the advantage of higher packing density compared to flat sheet and spiral wound configurations. However, low pressure tolerance of hollow fiber (HF) membranes limits their applications in nanofiltration. In this work, reinforced thin film composite (r-TFC) hollow fiber nanofiltration membranes were fabricated and evaluated in tests with water containing different salts and organic matter. Reinforced polysulfone ultrafiltration membranes were used as a support for the polyamide layer prepared from piperazine and trimesoyl chloride monomers. Interfacial polymerization conditions were optimized by selecting the trimesoyl chloride reaction time that gives the highest membrane performance. Specific permeate flux of 5.1 L/(m2∙h∙bar), MgSO4 rejection of 69 % and NaCl rejection of 26 % at the transmembrane pressure of 6 bars were obtained with optimized r-TFC membranes. Performance studies with water characterized by synthetic solution demonstrated removals of TOC, UV254, and turbidity in exceedance of 65 %, 80%, and 90 %, respectively. This work illustrates the feasibility of manufacturing r-TFC hollow fibers and using them in water treatment applications.
Ögeİstanbul metropoliten alanından boşalan drenaj suları atık yüklerinin model kullanarak hesabı(Fen Bilimleri Enstitüsü, 1998-07-06)Son 20 - 25 senedir Dünya'da gelişmiş ülkelerin pek çoğu alıcı ortam olarak kullanılan yüzeysel su kaynaklarının kirliliğinin önlenmesi için büyük çaba sarf etmektedirler. Bu çabaların çoğu noktasal kaynaklardan ileri gelen kirlenmenin önlenmesine veya etkisinin azaltılmasına yönelik olmaktadır. Ancak özellikle son on yıldır yoğunlaşan araştırmalar, yayılı kaynaklardan ileri gelen kirlenmelerin kontrolünde herhangi bir iyileşme olmaksızın, sadece noktasal kaynakların kontrolüyle alıcı ortam kalitesinde ancak sınırlı iyileşme sağlanabildiğini göstermiştir. Bu durum özellikle yağışların akışa geçerek büyük miktarlarda drenaj suları debi ve yüklerinin oluştuğu kentlerde son derece önemlidir ve bu nedenle dünyanın pek çok kentinde drenaj suları kontrolü için önemli yatırımlar yapılmaktadır. İstanbul Mertopolitan alanında atık suların toplanması ve uzaklaştırılması için gerçekleştirilecek projelerin yaklaşık 4 milyar $ mertebesinde olacağı (IMC, 1995) tahmin edilmektedir. Buna göre, bu yatırımların gerekçesini oluşturan Marmara Denizi'ni koruma hedefinin yalnızca noktasal kaynakların kontrolü ile sağlanıp sağlanamayacağının bilimsel olarak cevabının verilmesi ve doğrulanması büyük önem taşımaktadır. Ancak yapılan çalışmaların bu cevabı vermekten çok uzak olduğu saptanmıştır. Bu çalışmanın kapsamını; İstanbul Metropolitan alanına düşen yağışlardan kaynaklanan drenaj suları debi ve atık yüklerinin bu suları toplayan ve taşıyan derelerin drenaj havzaları bazında hesabı için bir modelin geliştirilmesi ve geliştirilen model için bir bilgisayar programının hazırlanması; modelin gerektirdiği meteorolojik, hidrolojik ve arazi kullanımlarına ait bilgi ve verilerin elde edilmesi ve bunların analizi, son olarak modelle hesap edilen yüklerin drenaj havzaları bazında noktasal kaynak yükleriyle karşılaştırılması ve değerlendirilmesi oluşturmaktadır. Bu değerlendirmeler, Marmara Denizi'nde beklenen kalitenin sağlanması için, drenaj suları kontrolünün gerekliliğini ortaya çıkaracaktır. Çalışmada geliştirilen modelin yurdumuzun diğer kentleri içinde uygulanmasını temin etmek üzere, tezin ilgili bölümlerinde modelin kullanımı ve verilere analiz yöntemleri hakkında gerekli bilgiler verilmiştir.
ÖgeBiyolojik film reaktörlerinin kinetiği üzerine bir araştırma(Fen Bilimleri Enstitüsü, 1978)Bu çalışmada biyolojik filtrelerin verimlerinin hesabı ile ilgili olan teoriler incelenmiş, özel olarak düzlemsel yüzeyli biyof ilmlerde besi maddesi tüketimini karakter ize eden kısmî türevli diferansiyel denklemin, boyutsuz değişkenlerle ifade edildikten sonra, bazı sı nır şartlar: altında bilgisayar yardımı ile nümerik çö zümü yapılarak bu modelin küresel yüzeyli biyofilmlere tatbik şekli gösterilmiştir. Düzlemsel yüzeyli biyof ilmlerle ilgili teorilerin taneli filtrelere aktarılabilmesi için literatürde bu tip filtreler, özgül yüzeyleri gözönünde tutularak, aynı de rinlikte düzlemsel yüzeyli filtrelere dönüştürülmek sure tiyle hesaplanmakta ise de, her iki tip malzemenin fizik sel özellikleri ve meydana gelen akımın şekli bakımından aralarında büyük farklar vardır. Bu itibarla bu çalışmada, küresel yüzeyli biyofilmlerde besi maddesi tüketimi ve kon santrasyon darılımı hesaplanarak yukardaki kabulün netice leri ile bir karşılaştırma yapılmak amacı güdülmüştür. Olayın son derece karmaşık karakteri sebebi ile hesap kolaylığı ve karşılaştırma imkânı bakımından kübik dizilişli bir filtre seçilmiş ve nümerik bir metodla çö züme gidilmiştir. - VI - Bu filtrenin matematik modeli düşey küre zincir erinden oluştuğundan, kürelerin temas noktalarında tam bir karışım meydana geldiği kabul edilmiş, sistemin biyo lojik verimi bir küre üzerindeki konsantrasyon değişini yardımı ile hesaplanmıştır. Elde edilen sonuçlar, düzlemsel yüzeyli bir filt re gibi hesaplanan kübik dizilişli küresel filtrelerin biyolojik verimi ile kıyaslanmış ve geliştirilen teori nin deney neticeleri ile uygunluğu gösterilmiştir.