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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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ÖgeEffect of different precursors and disinfection processes on the formation of nitrosamines(Graduate School, 2023-07-18)In drinking water treatment, it is important to focus on public health and ensure the quality of the treated water. Disinfection is a must-process which is applied before supply of drinking water to the water supply system. Disinfection byproducts such as Trihalomethanes (THM), Haloacetic acids (HAA), and Nitrosodimethylamine (NDMA) are present in different water media, i.e., drinking water in treatment facilities, rivers, and wastewaters. The effect of NDMA on human health has become an important issue in recent years, and investigations are planned to define NDMA precursors and the conditions that lead to the formation of NDMA. Nitrosamines, the group of compounds NDMA belongs to, are carcinogenic and toxic compounds with negative effects even at low concentrations. Peter Magee's discovery led to investigations to determine their carcinogenic properties. Nitrosamines are found in industrial products and food industry, and can also form during disinfection of potable water. Although the MCL in drinking water are usually set as the concentration that increases cancer risk one in a million, the concentration of NDMA at which the public has to be warned is set to be 10 ng/L by California Department of Public Health (CDPH, 2022) since the concentration of NDMA causing a one in a million increase in cancer risk 0.7 ng/L (EPA IRIS 1993) is hard to measure properly. NDMA is a disinfection by-product of chlorination, chloramination and ozonation processes, with chloramination producing the highest amount. Precursors are organic nitrogen containing compounds that are converted to nitrosamines during these processes. This thesis aims to reveal the formation potential of NDMA at the end of disinfection processes from selected precursors in different types of water media. It is also aimed to compare the disinfection processes based on the NDMA concentration formed from the potential of precursors in different water matrices. The main steps of this thesis are NDMA method optimization, precursors potential determination, swimming pool monitoring, and surface water monitoring. Optimization of method used for NDMA includes the change of parameters such as mobile phase content and the gradient of them, and LC-MS/MS parameters such as tube lens offset, collision energy. Pharmaceuticals, swimming pool, and surface water were investigated to determine their potential to form NDMA. In addition to target analysis measuring NDMA, non-target analysis was also performed. Transformation products that formed during chloramination of Doxylamine were investigated and the compounds that lead to formation of other products and not NDMA were determined using LC-Q Exactive Hybrid Quadropole-Orbitrap MS and Compound Discoverer Programme version 2.1. NDMA formation in presence of pharmaceuticals which are known precursors resulted with a concentration of 1380 ng/L for Ranitidine, 344 ng/L for Sumatriptan, 156 ng/L for Doxylamine and 4 ng/L for Metformin. The mixture of all four pharmaceuticals resulted in formation of 1896 ng/L NDMA. The highest amount of NDMA was formed by Ranitidine as it was expected from the previous studies in the literature. In order to research the possibility of synergistic or antagonistic effects of the pharmaceuticals in terms of NDMA formation, binary combinations were also examined under formation potential test conditions and 1841 ng/L, 1623 ng/L, 1548 ng/L, 513 ng/L and 322 ng/L NDMA was formed respectively for the couples of Ranitidine-Sumatriptan, Ranitidine-Doxylamine, Ranitidine-Metformin, Sumatriptan-Doxylamine and Metformin-Doxylamine. Ranitidine dominated the formation of NDMA as it was the same with the single formation potential test. To simulate real conditions in the water treatment plants and water supply networks, chloramination was performed in lower concentrations of chlorine than formation potential test. As expected, the NDMA concentration formed during chloramination (Cl2/N ratio of 4:1; Cl2: 2 mg/L) was lower than the NDMA concentration obtained during the formation potential test. The time dependent change of NDMA concentration for each single pharmaceutical was observed and 3 different time intervals were chosen; 30 min, 2 h and 6 h. At the end of the 6h- period the highest amount of NDMA was formed for each of every pharmaceutical except Metformin. Metformin behaved differently and NDMA formed at the second hour decreased at the end of 6 h. In ozonation, the same behavioural trend for Metformin was observed and the concentration of the NDMA formed during ozonation was decreased after a while. Also for the ozonation process the other pharmaceuticals behaved same with Metformin and NDMA was degraded in the second period of application time. The possible effects between pharmaceuticals during formation of NDMA was also investigated under formation potential test conditions. The results from the tests conducted with binary combinations of pharmaceuticals suggested that the relationship between Doxylamine and Metformin was synergistic as they formed higher amount of NDMA when they were together. Other binary combinations of pharmaceuticals did not have synergistic or antogonistic effect when they were together during formation potential test. Sakarya river was investigated as an example of a surface water for the existence of NDMA and its precursors.
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ÖgeHigh-rate activated sludge process for energy efficient wastewater treatment(Graduate School, 2023-10-25)The conventional activated sludge (CAS) process used in wastewater treatment is inefficient in terms of energy and requires a large space. CAS plants can only recover around 33% of the energy in wastewater, which is a significant drawback. The growing urban population and wastewater volume pose a challenge in land-constrained areas like Istanbul. Therefore, it is important to adopt innovative treatment processes that minimize land requirements, maximize organic matter capture, and reduce carbon dioxide (CO2) losses. This approach, known as carbon capture, redirection, or harvesting, focuses on diverting carbon from wastewater to the sludge line for biogas production in anaerobic digesters. High-rate activated sludge (HRAS) systems, developed in the 1980s, aim to redirect carbon from wastewater to anaerobic digesters for energy production, offering an alternative to primary sedimentation in wastewater treatment plants (WWTPs). They are operated at high organic loading rates and have short sludge retention times (SRTs) and hydraulic retention times (HRTs). In the B-stage, pollutant removal primarily occurs through biological oxidation at lower organic loading rates. The HRAS process has proven to be superior to CAS and primary sedimentation units with regard to carbon redirection and methane generation during anaerobic digestion. However, several areas for improvement have been identified based on existing literature. Firstly, there is a lack of information regarding the performance of HRAS systems when equipped with lamella clarifiers, which can enhance the performance of solid-liquid separation in WWTPs. Secondly, existing mathematical modeling studies of the HRAS process are either overly complex or overly simplistic, often overlooking important processes like adsorption and focusing primarily on carbon removal. Furthermore, sensitivity and uncertainty analyses, commonly employed to assess the robustness of models, have not been extensively applied to HRAS system models. Thirdly, despite its potential, there is a scarcity of literature on integrating the HRAS process into water reclamation practices, which could benefit from its smaller spatial footprint, lower energy consumption, and nutrient-rich effluent. Lastly, it is essential to address the fact that the use of coagulants in the HRAS process improves phosphorus removal efficiency while increasing operational costs. Limited research has been conducted on the impact of using water treatment plant (WTP) sludge on the anaerobic digestion of waste sludge in WWTPs and its influence on HRAS process performance and energy recovery. This thesis explores the potential of the HRAS process in sustainable wastewater treatment and investigates the following research topics: Study 1, optimum operational conditions for the HRAS process with a lamella clarifier, Study 2, mathematical modelling of the HRAS process to provide a practical tool for future implementations of HRAS plants, Study 3, integration of membrane filtration for reclaimed water production for industries, Study 4, post-treatment alternatives for HRAS process effluent for irrigation purposes, and Study 5, the reuse of WTP sludge to enhance treatment performance and resource circularity. These topics were investigated through pilot and laboratory scale studies using real municipal wastewater. A pilot-scale HRAS plant with a lamella clarifier was constructed in a full-scale preliminary WWTP (PWWTP) in Istanbul. The plant was operated under various conditions for two years to address the research topics. Laboratory-scale experiments involving membrane filtration and chemical precipitation were conducted using real municipal wastewater collected from the same PWWTP. Study 1 focused on determining the optimal operational conditions for the pilot-scale HRAS system coupled with a lamella clarifier. The study found that using a lamella clarifier resulted in lower total suspended solids (TSS) concentrations in the effluent and required a smaller footprint compared to a conventional clarifier. The optimum operational condition was identified as Stage 1, with an HRT of 75 minutes and a dissolved oxygen (DO) concentration of 0.5 mg/L. This condition demonstrated the best effluent quality, highest carbon capture, and highest production of extracellular polymeric substance (EPS). The study also found that reducing the HRT increased biosorption but led to increased chemical oxygen demand (COD) loss through the effluent. Lower DO concentrations promoted carbon redirection but resulted in weak floc formation and increased particulate COD (xCOD) loss. Meanwhile, higher DO concentrations enhanced COD oxidation but allowed more particles to escape through the effluent. Overall, the HRAS process with a lamella clarifier showed promising particulate matter removal efficiency and the potential for reclaimed water production. Studies 3 and 4 further investigated the inclusion of the HRAS process in reclaimed water production systems. Study 2 developed and calibrated a mathematical model for HRAS systems by integrating Activated Sludge Models No. 1 and 3 (ASM1 and ASM3), accounting for substrate adsorption and storage. The calibration utilized dynamic data from the pilot-scale HRAS plant and identified influential parameters like maximum specific growth rate (µ), growth yield (YH), storage yield (YSTO), storage rate (kSTO), decay rate (b), and readily biodegradable substrate half-saturation coefficient (KS1). The calibrated model demonstrated satisfactory efficiencies for mixed liquor suspended solids (MLSS), total COD (tCOD), soluble COD (sCOD), xCOD, total nitrogen (TN), ammonia nitrogen (SNH), total phosphorus (TP), soluble TP (sTP), and particulate TP (xTP), all above 70%. However, an uncertainty analysis exposed discrepancies in sCOD. The study also highlighted the potential to enhance sTP dynamic behavior estimation. The low model efficiency is likely due to variations in wastewater characteristics, especially the phosphorus (P) fractions, which were not dynamically considered in the model. Another reason could be the precipitation of phosphate salts, which was not included in the model. Overall, the study offers valuable insights into influential parameters and opportunities for refining the HRAS process modeling. Study 3 encompassed both experimental and cost analyses to evaluate different treatment configurations for water reclamation. Six configurations were examined, incorporating pre-treatment options like direct membrane filtration (DMF) via microfiltration (MF) and ultrafiltration (UF) membranes, and HRAS, and final treatment alternatives such as nanofiltration (NF) and reverse osmosis (RO). The performance of NF and RO membranes ensured that the reclaimed water from each scenario met the required quality standards for cooling tower makeup water. Despite HRAS producing effluent with higher turbidity compared to MF and UF membranes, the cost analysis revealed that the HRAS+NF configuration (C3) offered the most cost-effective treatment, with a cost of 0.38 €/m3 of wastewater. This cost advantage was due to the lower expenses associated with the HRAS process compared to MF and UF membranes.
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