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ÖgeEnhancing wastewater treatment efficiency through laccase-mediated biodegradation of trace organic contaminants(Graduate School, 2023-09-07)Recently, concerns have been raised about trace organic contaminants (TrOCs) in wastewater and their potential adverse effects on human health and the environment. TrOCs found in wastewater are a cause for concern due to their ability to contaminate drinking water sources and the environment. Consuming contaminated water with TrOCs can pose health risks to humans. It can also harm aquatic life, leading to ecosystem disruptions and potential entry into the food chain. Additionally, certain TrOCs have properties that can disrupt endocrine systems, which can further impact human health and the stability of the environment. Researchers have explored various treatment methods, including fungal treatments and laccase enzymes. However, there needs to be more literature regarding selecting fungal strains and optimizing laccase-based biodegradation mechanisms for efficient TrOC removal. This thesis aims to fill that gap by delving into laccase production, purification, immobilization, and its impact on degrading TrOCs. By exploring various aspects of this process, we can work towards developing more efficient and sustainable methods of reducing the negative impact of TrOCs on our environment. The current study encompasses a comprehensive examination of different fungal strains, including Trametes hirsuta, Pleurotus dryinus, Tramates versicolor, and Coriolopsis polyzona, to evaluate their laccase productivity and response to trace elements. The sorption mechanisms of laccase-mediated fungal treatment on targeted TrOCs were also explored. Furthermore, the study investigated free Laccase's purification and removal efficiency and the potential of laccase mediator systems (LMS) and immobilization techniques for enhanced biodegradation. The findings from this study provided valuable insights into the optimization and cost-effectiveness of laccase-based bioremediation strategies for sustainable wastewater treatment and environmental protection. Throughout experiments, fungal strains have been found to play a crucial role in producing external laccase activities. One of the advantages of using fungi is its high adsorption capacity, thus making it an effective pollutants-removal method. It is interesting to note that the reactions of internal and external enzymes on selected compounds differ from one compound to another. It has been observed that Laccase does not affect all types of TrOCs. It is essential to establish reasonable system control measures to prevent the release of adsorbed contaminants or enhance laccase activities to optimize the fungal treatment. It also highlights the importance of degradation by external enzyme activity and/or adsorption mechanisms as a primary step in removing TrOCs, followed by internal enzyme activities that remove some of the existing compounds after reaching a specific limit of adsorption capacity. Following these experiments, the study focused on the efficiency of laccase-mediator systems in removing recalcitrant organic contaminants. The results showed that laccase-mediator systems efficiently removed recalcitrant organic contaminants such as atrazine (ATZ) and carbamazepine (CBZ) in individual compound solutions, even at environmentally relevant concentrations. The removal efficiency of ATZ and CBZ in single compound solutions sets was observed up to 100% during the first 36h, and no significant difference was observed for all the tested mediators. Regardless of single compound sets, ATZ and CBZ in mixed compound sets removal were less than 65%. Also, the phenolic contaminant acetaminophen (APAP) is examined as a potential mediator candidate for laccase, and the results showed positive results. The study on laccase mediator systems led to a sub-study on "Laccase Catalyzed Iodine Synthesis as Disinfectant." Results showed that acetophenone was a more efficient mediator than APAP for iodine synthesis. Increasing APAP concentration increased iodine synthesis with a maximum of 0.5 mM. High concentrations of KI (>20 mM) inhibited laccase activities. Under 10 U/L, 20 mM KI concentration was most efficient for enzyme activity, chemical consumption, and contaminant removal efficiency. APAP and other phenolic compounds in real wastewater could serve as a mediator and increase the system's efficiency. Laccase-catalyzed iodine demonstrated high disinfection performance in fecal coliform tests, with the optimal concentrations observed at 15 and 20 mM KI. The study examined the effectiveness of laccase immobilization and optimization. The immobilization was achieved by bonding and adsorbing on mesoporous silica-covered packing. The results showed that the immobilized laccase was more efficient and stable in harsh conditions than the free enzyme. It had broader optimal temperature and pH ranges and better storage stability. This study suggests that immobilization can be a promising solution for industries that rely on sensitive biological enzymes. Particularly noteworthy is the use of mesoporous silica-covered packing and laccase-abundant broth instead of pure laccase for the immobilization, which offers substantial financial benefits. This approach facilitates the immobilized enzyme at any desired time, allowing for multiple cycles of re-utilization. Such a strategy holds tremendous potential for enhancing the efficiency and sustainability of enzymatic processes in various industries. The resulting enzyme immobilization yield on the support was between 56-74 %, and the highest immobilization efficiency, 1.8 U/g packing, was achieved in the sets where initial laccase activity was limited (15 U). The unique part of this study was that the silica-covered mesoporous packing was immobilized by contacting with 15000 U laccase-abundant broth without the purifying step, which consumes many chemicals. The immobilization yield was 60%, and the highest activity was 346 U/g packing. The immobilization process remained consistent after 2 days, indicating that most laccase molecules were adsorbed within the pores without undesired lateral interactions. The immobilized laccase exhibited good reusability and retained more than 50 % of its initial activity after being stored at 4ºC for 5 months. It was addressed that the best pH was selected as 7 to condition silica-covered packing with glutaraldehyde, while the optimum pH was 3.5 or 5.5 to immobilize laccase on the silica-covered packing. The optimum glutaraldehyde concentration was also selected as 3%. Unfortunately, it is not enough to immobilize laccase; it requires a high amount of laccase immobilization, so it requires a high amount of laccase production. It examined the potential of non-polar solvent hexane and polar solvents, methanol, and ethanol, as inducers for laccase production and the established inducer copper. Also, the abundant hexane effluent from silica production is tested as an inducer to diminish the ecological footstep of the study. The impact of mesoporous silica-coated plastic packing on free laccase production and concomitant immobilization was evaluated under both sterilized and unsterilized conditions to understand if the costly step-sterilization can be avoided. The study revealed that copper and ethanol were the most effective inducers, with the highest total laccase activity achieved at a copper concentration of 0.5 mM under sterilized conditions. The groups treated with copper and ethanol also showed immobilized laccase activity under unsterilized conditions. Our evaluation of concomitant laccase immobilization showed that the sterilized waste hexane sets had the highest activity of immobilized laccase, with a value of 1.25 U/mg packing. The hexane sets under sterilized conditions had the second-highest immobilized enzyme activity. It was found that even though a small amount of immobilized laccase activity was detected in the packings of the copper and inducer sets in the unsterilized sets, the desired levels of free and immobilized laccase activity were not achieved in comparison to the sterilized sets. These results likely are because the sets were not sterilized, which could have led to other species due to planned -microbial contamination from the laboratory. This presence of several fungal species could have had a significant impact on the reduction of laccase activity. Using pure cultures and ensuring a sterilized system is essential to avoid contamination. This step of the study focuses on one of the most remarkable outcomes of the current research: the successful application of waste hexane as an inducer for concomitant immobilized laccase activity. This innovative approach to laccase production could lead to a promising method for decreasing running costs and improving the cost-efficiency of enzymatic processes in wastewater treatment plants, both industrial and domestic.
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ÖgeConcentrate treatment via membrane distillation/crystallization method(Graduate School, 2023-08-23)Boron is an important semimetal element that is found in water, soil and rocks. Boron is widely used in a variety of industries such as glass, semi-conductors, detergents, cosmetics, drugs and fertilizer. Boron is also an essential nutrient for animals, plants and humans that needs to be found in dietary intake. Although it is beneficial the excessive amount of boron can lead to some health problems for humans and growth problems or death for plants. The boron content in wastewater is increasing due to the increasing industrial activities. Boron can also be found naturally from rocks, salt deposits or rainfalls and approximately 75% of the boron reserves of the world are found in Turkey. In the second chapter of this thesis study a literature review was prepared comprehensively. Boron removal and recovery techniques were reviewed. The increasing demand for clean water resources makes boron removal from water resources much more important. However, the removal is not enough alone in the aspect of sustainability. The removal and recovery techniques both conventional methods like precipitation, adsorption, coagulation, ion exchange and membrane processes are examined to juxtapose the states of the science in these two related—and increasingly important—processes. In the third chapter, the optimization studies of the membrane distillation process used in the thesis study were conducted. 2 different MD configurations, 3 different vacuum pressures, 6 different membranes and 3 different feed water were used to determine the optimum conditions. VAGMD had the higher fluxes since vacuum assistance enhanced fluxes while decreasing specific energy consumption. The boron content in permeate waters was lower than the 0.5 mg/L. In the fourth chapter hydrophobic and superhydrophobic membrane production methods were investigated. Different fabrication techniques as phase inversion and electrospinning were utilized while coating was applied to modify commercial and fabricated membranes. Different coagulation bath mediums for phase inversion method, nanoparticle additives and different coating solutions were compared. It was possible to obtain a superhydrophobic membrane that has a contact angle of 153. A novel hydrophobic blend membrane was fabricated to use in VAGMD within the scope of the fifth chapter. NaCl, synthetic boron solution and real RO concentrate supplied from the boron mining area were tested. A fluoro-containing benzoxazine monomer (Bz) was blended with our base polymer PVDF. The cross-linking of Bz is provided by thermal curing. According to the results, the BisF-Bz membrane showed higher hydrophobicity, more durability and physical stability compared to the pristine membrane. Boron rejection was highest for the BisF-Bz blended and two times thermally cured nanofiber membrane. In chapter six VAGMDC system was utilized to remove and recover boron from the concentrate stream. The concentrate problem is the main drawback of membrane processes so needs additional treatment and management. To address this problem VAGMDC system was tested. Synthetic boron solution was used to optimize process conditions such as concentration, pH and membrane type. Real RO concentrate was tested in the following experiments. Flux values, boron concentration and boron rejections, SEM-EDS analysis and XRF analysis for obtained crystals were conducted. The results showed that VGMDC could be successfully used for the removal and recovery of boron. The pilot scale VAGMDC system was tested in the scope of chapter seven. Different recovery ratios and operating modes were tested. Highly boron-contented raw river water and RO concentrate of that water were fed to the pilot scale MD system. Conductivity, flow rate and vacuum pressure were observed during the experiments. Boron, arsenic, hardness and conductivity removals were analyzed and determined. After VAGMD operation crystallization was applied to the obtained concentrate. 43.9% B2O3 contented crystals could be obtained. In conclusion, the relatively new VAGMDC process is an effective method for boron removal and recovery.
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ÖgeCoupling ozone with GAC, AIX and biochar: Removal of pharmaceuticals from the biologically treated wastewater and fate of their transformation products(Graduate School, 2024-09-24)In order to prevent water pollution in the water bodies, there has been a rising interest in improving cost-efficient quaternary treatment technologies to efficiently remove pharmaceuticals from the effluents of wastewater treatment plants. Various methods, including physical, biological, and chemical processes, are being utilized to eliminate organic micropollutants (OMPs) which include pharmaceuticals and persistent pollutants such as per- and polyfluoroalkyl substances (PFAS). Among these advanced techniques, ozonation and activated carbon adsorption are currently suggested as the most feasible options for substantially decreasing pharmaceutical concentrations in the wastewaters. Carbon-based materials such as activated carbon are notably effective adsorbents used for removing pharmaceuticals. Likewise, ozone is a highly potent oxidizing agent capable of oxidizing micropollutants directly via O3 itself or indirectly through the generation of hydroxyl radicals. However, after ozonation, instead of being mineralized, compounds can be converted into other substances known as transformation products, which may pose greater toxicity than the original compound. Additionally, the reaction between bromide and ozone produces bromate which is a toxic and carcinogenic by-product. To mitigate potential adverse effects from ozonation, it is often recommended to implement post-treatments such as biological or adsorptive systems like granular activated carbon (GAC) to eliminate potential transformation products and by-products. When combined with activated carbon adsorption, ozonation acts as an additional method for removing compounds that are resistant to adsorption. Crucially, activated carbon, with its extensive specific surface area and high concentration of functional groups, has demonstrated its ability to eliminate transformation products and by-products that may be generated during ozonation. While the effectiveness of the O3-GAC pairing is well-documented in literature, less attention has been given to combinations like ozonation with anion exchange (AIX) or other potentially more sustainable sorption materials such as biochar. The O3-AIX combination is particularly intriguing for this study, as many wastewater treatment plants, including the WWTP that provided wastewater for this research, are grappling with the challenge of removing PFAS. The treated wastewater from the aforementioned WWTP is released into the Fyrisån River, which flows into Ekoln Lake, Mälaren Lake, and eventually to the Baltic Sea. Fyrisån River also contributes to replenishing a groundwater source used for the city's drinking water. Consequently, the conventionally treated wastewater, containing untreated micropollutants, is discharged into a river that ultimately serves as a drinking water source. Thus, this study aims to simulate a potential combined advanced treatment step for the wastewater treatment plant. This research is particularly noteworthy as it not only provides guidance for implementing advanced techniques to remove micropollutants in full-scale wastewater treatment plants, but also investigates the fate of transformation products within three different combined systems: ozone and granular activated carbon filtration, ozone and ion exchange, and ozone and biochar. The objective of this thesis was both to examine the effectiveness of removing 24 selected pharmaceuticals and to monitor the fate of 7 of their metabolites, including oxidation transformation products. This investigation utilized a combination of processes, namely O3-GAC, O3-biochar (with two different types of biochar), and O3-AIX, in laboratory-scale experiments using actual effluent from a full-scale WWTP. The entire system was operated with three different O3 dosages, each maintained continuously for two weeks. Various sorption filters, including two types of biochar (one derived from forest biomass and the other from sewage sludge), reactivated GAC, and an AIX resin, were assessed. The evaluation of results focused not only on micropollutant removal but also on the generation of transformation products and by-products. 23 out of the 24 pharmaceuticals examined were detected in the effluent wastewater collected from the Kungsängsverket WWTP in total. The findings revealed that concentrations of sertraline, trimethoprim, fluconazole, atenolol, and sulfamethoxazole were below 500 ng/L, whereas the average concentrations of venlafaxine, desvenlafaxine, fexofenadine, bicalutamide, and lamotrigine were above 5,000 ng/L. According to the study findings, the average removal of selected pharmaceuticals varied between 8.8% and 97% with an O3 dosage of 0.28 g O3/g DOC, while it ranged from 86% to 99% for higher O3 dosages (0.96 and 2.17 g O3/g DOC). Pharmaceuticals such as fluconazole, atenolol, metoprolol, and tramadol exhibited relatively lower removal rates (9-15%) with the specific O3 dosage of 0.28 g O3/g DOC compared to furosemide, propranolol, clindamycin, and clarithromycin, which showed high removal rates (>90%). Tertiary amines like cetirizine and fexofenadine, known for their high reactivity with ozone, achieved removal rates of 79% and 89%, respectively, via 0.28 g O3/g DOC in this study. Furthermore, highly reactive compounds such as carbamazepine, diclofenac, sulfamethoxazole, and trimethoprim were removed by 70%, 85%, 70%, and 88%, respectively, with 0.28 g O3/g DOC, consistent with existing literature. Conversely, fluconazole exhibited a removal rate of 9% with an O3 dosage of 0.28 g O3/g DOC, while atenolol had an average removal rate of 15%. Among all materials tested, GAC emerged as the top-performing sorbent, effectively removing nearly all compounds below the limit of quantification (LOQ) even after continuous operation for two weeks (BV=864). The potential efficacy of biochar 2 for pharmaceutical removal, which was derived from sewage sludge, was particularly significant for the overall sustainability of the WWTP. Although biochar 1 exhibited better performance than biochar 2, both sorption materials showed decreased sorption capacity over the two-week period (BV=864) for most target compounds, including carbamazepine, fexofenadine, tramadol, fluconazole, sulfamethoxazole, and erythromycin. By the end of the continuous two-week operation, biochar 1 achieved removal rates ranging between 30% and 89% (mean 68%), while biochar 2 removed selected compounds at rates of 8.5% to 82% (mean 38%). Conversely, AIX that has been included for PFAS removal, demonstrated lower removal rates as expected after two weeks compared to biochars 1 and 2, ranging between 2% and 55% (average: 20%) for positive removal rates (BV= 3,264). Based on the findings, GAC exhibited the highest performance when paired with ozone (>99%), followed by biochar 1. Generally, the combination of ozone with biochar 1 proved to be more effective (mean=91%, range: 42-99%) than with biochar 2 (mean=79%, range: 29-99%). As anticipated, the combination of ozone with AIX yielded the lowest removal rates for pharmaceuticals (mean=58%, range: 6-98%). Based on the findings, six out of seven metabolites were identified in samples both pre- and post-ozonation. The results suggested that while the concentrations of certain metabolites decreased during ozonation, some metabolites, including oxidation transformation products like citalopram N-oxide, exhibited an increase over the two weeks of continuous operation. On average, citalopram concentration decreased by 81%, whereas the concentration of citalopram N-oxide increased by 19% with an O3 dosage of 0.28 g O3/g DOC. With the system operating at 2.17 g O3/g DOC, citalopram's average removal reached the LOQ, while the increase in citalopram N-oxide exceeded to 33%. Furthermore, all detected metabolites were eliminated to below the LOQ using GAC after two weeks of operation. Concentrations of most metabolites exhibited a linear decrease over time for biochar 1 and biochar 2, while for AIX, concentrations of certain metabolites increased over time. During all three O3 dosages (0.28, 0.96, and 2.17 g O3/g DOC), bromate concentrations remained below 5 µg/L. At the lower O3 dosage of 0.28 g O3/g DOC, the bromide concentration in the utilized WWTP effluent was 1.03 mg/L, whereas at the higher O3 dosages of 0.96 and 2.17 g O3/g DOC, the bromide concentrations were 0.52 and <0.50 mg/L, respectively. This variation resulted in an inability to assess the potential formation of bromate. Removal of DOC via different O3 dosages ranged from 19% to 26%, while GAC removed over 90% of DOC under all operational conditions. Conversely, AIX only removed less than 10% of initial DOC across all operational conditions, while in all cases, biochar 1 and biochar 2 removed within the range of 18-23% and 5-10%, respectively. In summary, ozonation exhibited high removal efficiency of pharmaceuticals and their metabolites at higher O3 dosages (>0.96 g O3/g DOC), while at lower O3 dosages (0.28 g O3/g DOC), a post-treatment became necessary for effective pharmaceutical removal. However, higher O3 dosages entail increased operational costs and pose a risk of transformation product formation. Therefore, employing combined systems for pharmaceutical and metabolites elimination is suggested as a preferable alternative to sole reliance on ozonation as the advanced treatment method. Comparative analysis of different post-treatment filter sorbents indicated that GAC yielded the most favorable results for pharmaceutical and metabolite removal. Conversely, the adsorption capacities of two distinct biochar types diminished over the continuous two-week operation, whereas GAC's performance remained consistent throughout. Biochar 1 outperformed biochar 2 in terms of pharmaceutical removal. AIX exhibited the lowest removal efficiencies, suggesting it may not suffice as a polishing step for ozonation when simultaneous removal of pharmaceuticals and PFAS is targeted. Overall, the combination of O3 with GAC demonstrated the most effective performance for pharmaceutical removal. Biochar holds promise as a more sustainable substitute for GAC, as it can be sourced from renewable materials like wood. However, there is a need for ongoing development to better understand the efficacy of combined O3-filter systems, with a focus on considering long-term operation. Before scaling up to a full-scale WWTP, conducting a life cycle assessment and feasibility analysis would be prudent steps to take.
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ÖgeUnlocking sustainability in wastewater denitrification through waste-derived volatile fatty acids(Graduate School, 2024-08-08)In the studies performed, the effectiveness of food waste-derived VFAs (AD-VFA) was investigated in the post-denitrification process in comparison with synthetic VFA and methanol as carbon sources. Acetic acid had the highest rate of disappearance among single tested VFAs with a denitrification rate of 0.44 g NOx-N removed/m2/day, indicating a preferential utilization pattern. While AD-VFA had a denitrification rate of 0.61 mg NOx-N removed/m2/day, sVFA had a rate of 0.57 mg NOx-N removed/m2/day, indicating that impurities in AD-VFA did not play substantial role in denitrification. AD-VFA proved to be promising carbon source alternative for denitrification in wastewater treatment plants. In the continuation study, although solely added AD-VFAPPL as a carbon source had a slower denitrification capability (0.56 ± 0.13 mg NOx-N removed/m2/day) than methanol (1.04 ± 0.46 mg NOx-N removed/m2/day), up to 50% of the methanol can be replaced by waste-derived AD- VFAPPL and achieve comparable performance (1.08 ± 0.07 mg NOx-N removed/m2/day) with the pure methanol. This proves that the co-addition of VFAs together with methanol can fully compete with pure methanol in performance. This integration emerges as a sustainable approach, attaining parallel denitrification performance while reducing reliance on fossil-derived sources. This proves that the co-addition of VFAs together with methanol can fully compete with pure methanol in performance, providing a promising opportunity for wastewater treatment plants to potentially reduce their carbon footprint and become more sustainable in practice while benefiting from recovered nutrients from waste. xxi In conclusion, this thesis reimagines WWTPs as places that recover valuable resources, going beyond only wastewater treatment. Bridging VFA generation with value-added usage holds the potential to strengthen biorefineries and promote environmentally friendly wastewater solutions.
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ÖgeEnvironmental and economic assessment of zero waste management(Graduate School, 2023-12-08)The waste management (WM) approach for the protection of resources known as "zero waste" (ZW) has become popular in recent years. A number of measures have been taken and facilities have been installed to facilitate improved management of municipal solid waste (MSW). ZW to landfill targets have gained significant traction worldwide, including in Turkiye. The aim of this thesis is to assess the environmental and economic results of WM pathways within the context of an increasingly applied ZW approach.This study evaluates the sustainability of municipal solid WM through the ZW goal on multiple scales (Istanbul and Ayazağa Campus). The thesis provide a framework that enables institutions to develop a goal-oriented WM strategy using material flow analysis (MFA) and life cycle assessment (LCA). In addition to presenting the framework, a case study was conducted on a campus scale by using primary and secondary data. The framework assumes that no prior data is available, and the study will begin by collecting primary data on campus. For providing primary data; waste characterization and recycling potential of the Istanbul Technical University (Turkiye) Ayazağa Campus before (2019) and after (2022) the ZW management strategy the campus was divided into four distinctive groups, which are (i) academic (ii) administrative (iii) residential/dormitory and (iv) cafeteria. First, initial field study was conducted afterwards (for waste characterization and recycling potential), the new containers were placed. Students and campus personnel have been trained in within the scope of ZW management practices through both in-person and online seminars. The final phase of the study, the second field work, was completed. The results demonstrate that the waste generation rate in the pilot areas fluctuates between 0.045-0.190 kg/cap/day, but it decreases to 0.011-0.117 kg/cap/day in the second field study. The first field study had a potential recycling rate of 76.3%, but then it dropped to 68.2% in the second study. The MFA results indicate that landfill diversion ranges between 29.8% to ~99-100%, some residuals or ash from the incineration plant will still be disposed in landfill. Furthermore, simply diverting waste from landfill does not necessarily lead to circularity or directly address sustainable consumption and public attitudes towards ZW goals. The study framework aims to address potential challenges in campus-based, goal-oriented WM studies. Future case studies from other institutions and their campuses could help validate and improve this methodology. Based on the Ayazağa waste characterization results, the efforts to establish a ZW management system also led to a reduction in waste generation and increase in recycling performance. However, further studies are still required to assess the ZW's public awareness activities. In addition, a case example was developed based on ITU Ayazağa campus, Turkiye, with annual separated food waste of 577 tonne per year to provide a more circular and decarbonised economy. A LCA was conducted using the EASETECH software. Four scenarios were evaluated: anaerobic digestion, composting, incineration, and landfill. Of these, incineration resulted in the highest CO2-eq savings (-192 kg CO2-eq/tonne FW), but lacked decoupling and circularity of resources. Conversely, anaerobic digestion demonstrated the highest circularity and lowest toxicity. Based on these findings, anaerobic digestion was selected for further investigation. Economic transactions for the anaerobic digestion system's business models were analysed,including revenues, municipality fees and operating costs. The new economic model is expected to align with circular economy strategies and promote stakeholder collaboration as a significant social outcome.
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