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ÖgeCombination of ozonation with GAC, AIX and biochar post-treatment for removal of pharmaceuticals and transformation products from municipal WWTP effluent(Royal Society of Chemistry, 2024)Pharmaceuticals have been detected in water and wastewater, resulting in increasing research attention towards the elimination of these substances from aqueous environments. Due to the limitations of conventional processes in wastewater treatment plants (WWTPs) to fully eliminate these compounds, more research is needed on complementary advanced treatment technologies. This study aims to examine the removal efficiency for 24 selected pharmaceuticals and the fate of their 7 main metabolites including several oxidation transformation products by various technique combinations applied on the effluent from a full-scale WWTP. Investigated treatment options include ozonation (O3) combined with either granular activated carbon (GAC), two different types of biochar, and anion exchange (AIX) in a continuously operated laboratory-scale system. The average removal of analyzed pharmaceuticals ranged between 8.8–97% with an O3 dose of 0.28 g O3/g DOC (dissolved organic carbon), whereas it ranged from 86–99% for higher O3 dosages (0.96 and 2.17 g O3/g DOC). Overall, the investigated metabolites of pharmaceuticals exhibited lower removal efficiency (between −33 and 99%) with ozone compared to the parent compounds at all O3-dosages. Concentrations of oxidation transformation products such as citalopram N-oxide were increased after ozone treatment, whereas it was decreased after the columns at different rates. The bromate concentrations during all three O3-dosages (0.28, 0.96 and 2.17 g O3/g DOC) were below 5 μg L−1. GAC was the best performing sorbent among all materials, where even after two weeks of continuous operation, nearly all compounds were removed below quantification levels. Although biochar 1 showed better performance (30–89%, mean = 68%) than biochar 2 (8.5–82%, mean = 38%), both sorption materials showed reduced sorption capacity over the time period of two weeks for most of the target compounds. On the other hand, AIX had lower removal rates ranging between 2–55% (mean = 20%). Regarding the combination of O3 with the individual sorbent materials, GAC was the most successful combination with O3 for the removal of pharmaceuticals (>99%) and oxidation transformation products (>60%). The combination of O3 with biochar 1 was more successful (mean = 91%) than the combination with biochar 2 (mean = 79%), where the combination of O3 with AIX showed the lowest removal rates (mean = 58%).
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ÖgeSpecific ammonium oxidation and denitrification rates in an MBR treating real textile wastewater for simultaneous carbon and nitrogen removal(Wiley, 2023)BACKGROUND Dissolved oxygen (DO) and aeration on/off time are the determining parameters for simultaneous carbon and nitrogen removal in biological treatment processes. The most effective way to decide the optimum operational conditions, e.g. aeration on/off time or DO concentration during the aeration period, is to determine specific nitrification/denitrification rates. For this purpose, the effects of DO (6 and 3 mg L−1) and aeration on/off time (from 2/2 to 90/360 min) on the specific ammonium oxidation and denitritation/denitrification rates in a membrane bioreactor (MBR) treating real textile wastewater were deeply investigated. RESULTS The highest specific ammonium oxidation, denitritation and denitrification rates were obtained as 5.4, 3.8, and 5.3 mg N g−1 volatile suspended solids h−1, respectively, at an aeration on/off time of 90/360 min, which corresponded to the increase in specific ammonium oxidation rates by 1.8 and 2.1 times compared to continuous aeration conditions where DO was 6 and 3 mg L−1, respectively. CONCLUSION Higher specific ammonium oxidation and denitrification rates can be achieved with the intermittent aeration compared to continuous aeration. Hence existing treatment plants can be retrofitted for higher performance with reduced energy requirements. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).
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ÖgeAnalysis of particle size distribution of organic carbon for landfill leachate : implications for sustainable treatment(Wiley, 2023)BACKGROUND Landfill leachate has a complex composition requiring experimental support to formulate a sustainable treatment strategy. This study utilized the particle size distribution (PSD) of the chemical oxygen demand (COD) content to assess the profile of biodegradable and inert COD fractions; it also emphasized the functions and benefits of ultrafiltration and nanofiltration modules coupled to an activated sludge process. The evaluation profited from the field data of a landfill site in Istanbul, where the leachate was actually treated in a membrane bioreactor (MBR) plant. RESULTS COD and total nitrogen levels fluctuated between 10 100–31 200 mg L−1 and 1150–2800 mg L−1, respectively. PSD analysis for COD, conducted at two extremes, displayed similar results, where the majority of the COD was observed to accumulate at the low extremity of the particle size, 70–72% below 2 nm. Therefore, direct membrane filtration of leachate yielded low COD removals that were limited to 9% with ultrafiltration and to 31–35% with nanofiltration. COD fractionation indicated a ratio of 5% for the inert COD in leachate. The permeate COD of ultrafiltration in the existing plant was 2000 mg L−1, much higher than the inert fraction ratio, which was further reduced to 266 mg L−1 by nanofiltration. CONCLUSION PSD analysis was an integral complement of respirometry for establishing the size-biodegradation relationships of different COD fractions. It located the majority of soluble COD fractions below 0.55 nm, thus implying the necessity of a biological process. PSD also identified the generation of soluble residual metabolic products, indicating that residual COD escaping treatment would be equally significant to the removal potential of the biodegradable substrate.
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ÖgeImproving light availability and creating high-frequency light–dark cycles in raceway ponds through vortex-induced vibrations for microalgae cultivation: a fluid dynamic study(Springer, 2024)Limited light availability due to insufficient vertical mixing strongly reduces the applicability of raceway ponds (RWPs). To overcome this and create light–dark (L/D) cycles for enhanced biomass production through improved vertical mixing, vortex-induced vibration (VIV) system was implemented by the authors in a previous study to an existing pilot-scale RWP. In this study, experimental characterization of fluid dynamics for VIV-implemented RWP is carried out. Particle image velocimetry (PIV) technique is applied to visualize the flow. The extents of the vertical mixing due to VIV and the characteristics of L/D cycles were examined by tracking selected particles. Pond depth was hypothetically divided into three zones, namely dark, light Iimited and light saturated for detailed analysis of cell trajectories. It has been observed that VIV cylinder oscillation can efficiently facilitate the transfer of cells from light-limited to light-saturated zones. Among the cells that were tracked, 44% initially at dark zone entered the light-limited zone and 100% of initially at light-limited zone entered the light-saturated zone. 33% of all tracked cells experienced high-frequency L/D cycles with an average frequency of 35.69 s−1 and 0.49 light fraction. The impact of VIV was not discernible in the deeper sections of the pond, due to constrained oscillation amplitudes. Our findings suggest that the approximately 20% increase in biomass production reported in our previous study can be attributed to the synergistic effects of enhanced L/D cycle frequencies and improved light availability resulting from the transfer of cells from dark to light-limited zones. To further enhance the effectiveness of VIV, design improvements were developed. It was concluded that light availability could be significantly improved with the presented method for more effective use of RWPs.