Browsing by Author "Lohwacharin J."
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Item Metadata only Bromate abatement with ultraviolet light-emitting diode/thiosulfate advanced reduction processes: Mechanisms, affecting parameters and applications(2026-03-01) Phan K.A.; Pornsuwan S.; Oguma K.; Lohwacharin J.; Phan K.A.; Mahidol UniversityBromate, a possible carcinogenic byproduct of ozonation, is potentially removed by the ultraviolet (UV)/sulfite advanced reduction process (ARP), with hydrated electrons playing a major role. However, this process becomes less efficient under acidic to neutral pHs and remains limited to the use of conventional mercury UV lamps. To address these issues, a UV-light emitting diode (UV-LED)-based ARP was studied for bromate removal using thiosulfate as an alternative reducing agent and UV-LEDs emitting at 265 nm and 280 nm as a radiation source. The UV-LED265/thiosulfate process effectively reduced 100 ± 0.0% of the initial bromate concentration (4.0 μM) at pH 6.4 ± 0.1, following the pseudo first-order rate constant of 1.3 × 10−2 min−1. Meanwhile, the UV-LED265/sulfite process attained only 11.6 ± 1.4% bromate degradation efficiency. Results of electron paramagnetic resonance and scavenging experiments indicate that hydrated electrons and sulfite radicals derived from the UV-LED265/thiosulfate process played a significant role in bromate degradation. The process demonstrated optimal performance within a pH range of 5.8–6.4, with higher thiosulfate doses accelerating the bromate removal efficiency. Furthermore, excessive chloride and bicarbonate concentrations interfered with the bromate removal. Comparable energy consumption (electrical energy per order of 27.4 kWh/m3) with UV/sulfite processes has demonstrated the potential of UV-LED265/thiosulfate ARPs for effective bromate degradation, using a sustainable UV radiation source and compatible with acidic ozone-treated water.Item Metadata only Building a Resilient City through Sustainable Flood Risk Management: The Flood-Prone Area of Phra Nakhon Sri Ayutthaya, Thailand(2024-08-01) Munpa P.; Dubsok A.; Phetrak A.; Sirichokchatchawan W.; Taneepanichskul N.; Lohwacharin J.; Kittipongvises S.; Polprasert C.; Munpa P.; Mahidol UniversityResilience has gained significant prominence in the management of climate-related shocks and the minimization of disaster risks. Assessing flood resilience is, therefore, crucial in identifying areas lacking support and opportunities for development. Comprehensive risk assessments are urgently required, especially in areas prone to floods. By applying the Analytical Hierarchy Process (AHP), stakeholder meetings, and keyword analysis, this study aims to assess the flood resilience of Phra Nakhon Sri Ayutthaya Province (PNSAP) in Thailand, an area at high risk of flooding and home to a UNESCO World Heritage Site. According to the Arup and Rockefeller Foundation’s City Resilience indicators, the key elements for building resilience in PNSAP include effective emergency response services, comprehensive hazard monitoring and risk assessment, and emergency medical care. In addition, the focus group discussions and keyword analysis identified the following critical components for strengthening flood resilience: “financial aspects”, “community awareness and preparedness”, “multi-stakeholder collaboration”, “citizen engagement”, and “urban flood monitoring and data management.” Moreover, to gain insight into the perceptions of people in local communities, the results of a household survey (n = 552) indicated that approximately one-third of the respondents had never engaged in flood preparedness activities. Neither the gender nor the education level of the respondents significantly influenced their engagement in flood preparedness. The respondents also perceived that infrastructure flexibility, affordable transport networks, flood monitoring and data management, the adequate provision of critical services, and reliable communication systems in building resilience were important during a flood disaster. These results provide valuable insight into the community’s perception of the effectiveness of disaster risk reduction mechanisms for building flood resilience in PNSAP and can serve as a useful guide for future resilience-building initiatives. By addressing these factors, PNSAP could enhance its resilience to the impacts of flooding and contribute to the global field of flood management and resilience building.Item Metadata only Climatic and Hydrological Factors Affecting the Assessment of Flood Hazards and Resilience Using Modified UNDRR Indicators: Ayutthaya, Thailand(2022-05-01) Munpa P.; Kittipongvises S.; Phetrak A.; Sirichokchatchawan W.; Taneepanichskul N.; Lohwacharin J.; Polprasert C.; Mahidol UniversityThis research aims to investigate the effect of climatic and hydrological factors on flood hazards and assess flood resilience in Ayutthaya, Thailand, using the 10 essentials for making cities resilient modified by the United Nations Office for Disaster Risk Reduction (UNDRR). Flood resilience assessment was performed based on a multi-criteria decision-making approach or the analytical hierarchy process (AHP) of pairwise comparison. The results indicate that runoff is considered the most influential factor in flood hazards, followed by land use, rainfall, and historical flood events, sequentially. Regarding the flood incident management concept, a questionnaire survey (n = 552) was conducted to understand the impacts of flood on local communities. The findings reveal that 50% of respondents had never received any flood information or participated in training sessions on flood preparedness. Most reported their concerns about the inadequate supply of drinking water during a flood. Spearman’s correlation coefficient shows positive correlations between flood disaster relief payments, preparedness training, access to flood hazard mapping, emergency health services, and their flood preparation actions. According to the modified UNDRR indicators, the top three highest AHP values in building community resilience to flood hazards in Ayutthaya are flood risk scenario identification, the effectiveness of emergency flood disaster response, integrated urban planning, and disaster risk reduction. The policy implications of this research include the need for national authorities to better understand the role cities can play a vital role in supporting both national and international climate resilience frameworks, especially Thailand’s National Disaster Management Plan, the Sendai Framework for Disaster Risk Reduction (SFDRR), and the global Sustainable Development Goals (SDGs).Item Metadata only Delineating multi-phase performance of ozone-enhanced ceramic filter–microfiltration system for treating polluted surface water(2024-11-01) Rerkrungchariya N.; Suyamud B.; Phetrak A.; Lohwacharin J.; Rerkrungchariya N.; Mahidol UniversityPre-ozonation may affect microorganisms in the biofilter and impact the removals of organics and nutrients. This study investigated the effect of pre-ozonation on biofilter-membrane filtration for removing organic matter and subsequent membrane fouling to treat polluted surface water. To mimic seasonal variation on water quality, one-year experiments were divided into five phases, having different organic loadings. A ceramic bead was used as the media in the packed-bed filter. The ozone-treated system achieved the maximum total organic carbon (TOC) removal by 53 ± 7 %, greater than without ozone for the initial TOC of 15–20 mg/L. The effect of pre-ozonation on the removal of organics was more pronounced during the first month (phase I), but gradually diminished in time, probably due to developing refined bioactivities in the media filter. Pre-ozonation substantially reduced the suspended aerobic bacteria count, but thereafter, 4-fold increase in the bacterial count was observed in the ceramic-media filter. The system without pre-ozonation suffered from a rapid increase (ca. 20 kPa within 14 days) in the transmembrane pressure, which required chemical cleaning. Contrarily, pre-ozonation offered relatively stable filtration until 300 days. The difference is attributable to eliminating cake resistance, which is composed primarily of aromatic proteins, by pre-ozonation.Item Metadata only Effects of relative microplastic–biochar sizes and biofilm formation on fragmental microplastic retention in biochar filters(2025-03-01) Changlor N.; Inchana C.; Sabar M.A.; Suyamud B.; Lohwacharin J.; Changlor N.; Mahidol UniversityMicroplastics (MPs) pose significant risks to aquatic life and human health. Conventional water treatment is ineffective in removing MPs, demanding alternative technologies. Biochar exhibits a potential for removing MPs through adsorption and filtration. The efficiency of biochar derived from macadamia (Macadamia Integrifolia) nutshells on MP removal from contaminated water was assessed in fixed-bed column tests at environmentally relevant MP concentrations in upward flowing regime. Fragmental polyethylene MPs (50–100 and 100–300 μm) were tested on the effects of the operating conditions, the relative MP–biochar size ratios (0.05–0.14 and 0.13–0.36 for small and large MPs), and biofilm formation on their retention in the biochar bed. The interactions between MPs and biochar are apparently electrostatically repulsive. Small biochar demonstrated >78% removal of the MPs at flow rates of 2.78 × 10−5, 2.78 × 10−4, or 1.39 × 10−3 m/s. Increasing the MP influent concentrations significantly increased the MP removal by the filter. The lower flow rates increase the MP removal with both MP influent concentrations and MP sizes, showing a maximum of 96% removal of small MP. The removal of large MPs by biochar filters (i.e. MP–biochar size ratio: 0.13–0.36) is significantly different when the highest flow rate is used. This difference moderates as the flow rates and MP size decline. Biofilm formation at its early stage altered the porous characteristics and surface morphology of the biochar and enhanced the MP removal. Overall, this study provides insights into the application of biochar filters in tertiary wastewater treatment.Item Metadata only Elucidating of the metabolic impact of risperidone on brain microvascular endothelial cells using untargeted metabolomics-based LC-MS(2024-12-01) Ngamratanapaiboon S.; Srikornvit N.; Hongthawonsiri P.; Pornchokchai K.; Wongpitoonmanachai S.; Mo J.; Pholkla P.; Yambangyang P.; Duchda P.; Lohwacharin J.; Ayutthaya W.D.N.; Ngamratanapaiboon S.; Mahidol UniversityRisperidone is useful for the treatment of schizophrenia symptoms; however, it also has side effects, and an overdose can be harmful. The metabolic effects of risperidone at high therapeutic doses and its metabolites have not been elucidated. Endogenous cellular metabolites may be comprehensively analyzed using untargeted metabolomics-based liquid chromatography-mass spectrometry (LC-MS), which can reveal changes in cell regulation and metabolic pathways. By identifying the metabolites and pathway changes using a nontargeted metabolomics-based LC-MS approach, we aimed to shed light on the potential toxicological effects of high-dose risperidone on brain microvascular endothelial cells (MVECs) associated with the human blood brain barrier. A total of 42 metabolites were selected as significant putative metabolites of the toxicological response of high-dose risperidone in MVECs. Six highly correlated pathways were identified, including those involving diacylglycerol, fatty acid, ceramide, glycerophospholipid, amino acid, and tricarboxylic acid metabolism. We demonstrated that methods focused on metabolomics are useful for identifying metabolites that may be used to clarify the mechanism of drug-induced toxicity.Item Metadata only Evaluation of drinking water quality and health risk assessment in rural primary schools along the Thai Myanmar border(2025-07-01) Choda K.; Sangkarak S.; Maneekan P.; Prangthip P.; Ittisupornrat S.; Eaktasang N.; Kittipongvises S.; Lohwacharin J.; Phetrak A.; Choda K.; Mahidol UniversitySafe drinking water in schools is important for students' health. Despite the presence of water treatment systems in rural schools, systematic monitoring and evaluation of drinking water quality are often insufficiently integrated into risk assessment frameworks, potentially compromising student health. In this study, a cross-sectional survey was conducted using drinking water samples from rural primary schools along the Thai-Myanmar border in Kanchanaburi, Thailand, aiming to evaluate the quality of drinking water in terms of physicochemical and bacteriological parameters and assess the health risks to students. A total of 52 drinking water samples were collected for water quality analysis. Among these, approximately 42% (n = 22) of these collected samples did not comply with Thailand's recommended limits of drinking water quality. Among the noncompliant samples, total coliform bacteria were detected in 59% (n = 13), fluoride concentrations exceeded the permissible limit of 0.70 mg/L in 18% (n = 4), and arsenic levels surpassed the recommended limit of 10 µg/L in 9% (n = 2). These contaminants may pose a potential health risk to students. Health risk assessments indicated that, although the majority of hazard index (HI) and cancer risk (CR) values were within acceptable limits (HI < 1; CR between 1 × 10⁻6 and 1 × 10⁻4), the 95th percentile values exceeded these thresholds, suggesting potential health risks for students consuming the contaminated water. To mitigate health risks associated with contaminated drinking water in rural primary schools, the implementation of effective water treatment systems, coupled with routine monitoring of drinking water quality and proper maintenance, is recommended. However, this study has some limitations, including a restricted geographic coverage and reliance on generalized exposure parameters, which constrain causal inferences between contaminant exposure and health outcomes. Future research should expand the study area and incorporate region-specific behavioral data to more comprehensively assess chronic exposure risks and the effectiveness of intervention strategies.Item Metadata only Influence of the iron-oxide mass fractions of magnetic powdered activated carbon on its hexavalent chromium adsorption performance in water(2024-09-01) Sangkarak S.; Kittipongvises S.; Kitkaew D.; Chaveanghong S.; Ittisupornrat S.; Phetrak A.; Lohwacharin J.; Sangkarak S.; Mahidol UniversityMagnetic powdered activated carbon (Mag-PAC) is an effective adsorbent to remove hexavalent chromium (Cr(VI)) from water and can be recovered for reuse. However, the tradeoff between the adsorption performance of Cr(VI) and magnetic properties of Mag-PAC remains unclear. Herein, we prepared a series of Mag-PAC adsorbents containing various iron-oxide mass fractions with FeSO4·7H2O as the precursor, using a facile wet-chemical precipitation route and conducted batch experiments to evaluate the Cr(VI) adsorption performance. Results revealed that Mag-PAC was functionalized by magnetic iron oxide comprising crystalline goethite and magnetite structures. Furthermore, its adsorption performance was highly dependent on pH and was most effective at an initial solution pH of 2. Both the sorption rate constant and Cr(VI) adsorption capacity were greatly influenced by magnetization, and they gradually decreased as the iron-oxide mass fraction increased. Among the prepared adsorbents, Mag-PAC-75 (∼32% wt iron) exhibited not only an excellent Cr(VI) adsorption performance (Langmuir adsorption capacity: 75.76 mg/g) but also effective magnetic properties (saturation magnetization: 9.66 emu/g). Coexisting anions had a negligible competitive effect on Cr(VI) removal by Mag-PAC-75 at an initial pH of 2, whereas the presence of tannic acid markedly improved the Cr(VI) elimination. The presence of trivalent chromium on the surface of Mag-PAC-75 confirmed via X-ray photoelectron spectroscopy indicated that some synergistic redox reactions may occur during the sorption process. After five regeneration cycles using NaOH, Mag-PAC-75 continued to exhibit a high Cr(VI) removal efficiency and magnetic stability. These findings indicate that optimizing the adsorption performance and magnetic properties is a key factor for realizing the practical application of Mag-PAC for Cr(VI) removal. Overall, Mag-PAC may have been a promising application prospect for Cr(VI) removal from water due to its high adsorption capacity and magnetic properties, coupled with its good reusability and magnetic stability after regeneration cycles.Item Metadata only Investigating the impact of organic matter on Vibrio parahaemolyticus inactivation in aquaculture water by UV-LED system(2025-05-01) Thanajiradech P.; Suyamud B.; Duchda P.; Lohwacharin J.; Larpparisudthi O.a.; Thanajiradech P.; Mahidol UniversityUltraviolet (UV) irradiation becomes a promising technology in inactivating pathogenic microbes, but the compositional change of organics and its consequence of inactivation need further study in raw water during UV light-emitting diode (UV-LED) irradiation. Herein, the bench-scale study aimed at evaluating the effect of organic fractions isolated from shrimp-farming water on the inactivation efficiency of Vibrio parahaemolyticus using UV-LED process at wavelengths of 265 nm, 280 nm, and combined wavelengths. The lowest required UV fluence (4.06 mJ/cm2) for 3-log inactivation was attained with UV-LED 280 nm. After UV irradiation the changes in elemental compositions of organic compounds, based on H/C and O/C ratios, were small. This is probably due to low UV exposure and UV resistant structure of organic constituents, predominantly lipid-like compounds. Contrarily, fluorescent spectroscopic analysis that showed degradation of protein-like substances by UV irradiation. In addition, the significant declines in the number of chemical formulas in organic compounds were identified through non-target screening using orbitrap mass spectrometry, suggesting degradation and amalgamation into new compounds. The presence of organic compounds did not profoundly affect inactivation efficiency at applying a minimum required fluence or greater. This study highlights the potential of UV-LED irradiation, particularly at 280 nm, for efficient inactivation of V. parahaemolyticus and subsequent molecular structure alteration of organic matter after UV irradiation.Item Metadata only Investigating the impacts of pre-treatment and alternative disinfection on pollutant elimination and byproduct formation in an emergency water supply system(2026-06-01) Bunditboondee C.; Phetrak A.; Larpparisudthi O.a.; Lohwacharin J.; Bunditboondee C.; Mahidol UniversityExtreme weather events have significantly increased the risk of microbial contamination in water sources, necessitating the evaluation of alternative disinfectants whose reactivity and byproduct formation in real water matrices remain insufficiently explored. This study investigates an integrated treatment system combining carbon adsorption and ion exchange pretreatment with ultra-low pressure reverse osmosis (ULRO) for purifying both synthetic and real contaminated source waters. Three disinfectants—peracetic acid (PAA), performic acid (PFA), and sodium hypochlorite—were evaluated for their impact on water purification performance and disinfection byproduct (DBP) formation. The integrated system demonstrated high efficiency in meeting national drinking water standards, achieving 60–90% removal of total organic carbon and 65–80% of total nitrogen. Furthermore, UV254 absorbing organic matter (1560–3800 Da) was reduced by 50–90%, and all coliform bacteria were eliminated. Regarding DBPs, bromoform was the dominant trihalomethane, while monochloroacetic and trichloroacetic acids were the primary haloacetic acids. PFA treatment resulted in the highest bromoform concentrations, and increased haloacetic acid formation compared to chlorine, correlating with an increase in humic-like organics within the hydrophilic fraction. Biological dissolved organic carbon (BDOC) assays revealed that while RO achieved peak biological stability under chlorination, applying PAA compromises water biostability. Crucially, a low-dose chlorination–PAA mixture significantly enhanced the biological stability of feed water, compared to chlorination alone. Strategic optimization of disinfectant mixtures is essential to balance biological stability and control the BDOC formation across diverse water treatment units.Item Metadata only METABOLIC PROFILING OF HALOPERIDOL: INSIGHTS INTO POTENTIAL TOXICOLOGICAL EFFECTS ON BRAIN MICROVASCULAR ENDOTHELIAL CELLS(2024-01-01) Ngamratanapaiboon S.; Yambangyang P.; Duchda P.; Lohwacharin J.; Ayutthaya W.D.N.; Ngamratanapaiboon S.; Mahidol UniversityHaloperidol is effective in the treatment of schizophrenia symptoms, but the adverse effects and overdose risks are significant. The metabolic consequences of haloperidol at high therapeutic doses, including the metabolites produced, remain only partially understood. To analyse endogenous cellular metabolites thoroughly, researchers can use untargeted metabolomics-based liquid chromatography-mass spectrometry. The aim of this approach is to reveal the potential toxic effects of high-dose haloperidol on brain microvascular endothelial cells (BMVECs) integral to the human blood-brain barrier. We identified 62 significant metabolites linked to the toxic response in BMVECs and pinpointed four haloperidol-related processes: the pentose phosphate pathway; the citrate cycle; glutamine and glutamate metabolism; and alanine, aspartate and glutamate metabolism. Our findings clarify the metabolic effects of high-dose haloperidol, thereby providing insights for refining its clinical application and for further studies, personalized medicine and the development of novel therapeutic strategies.Item Metadata only Metabolomic insights into rotenone-induced dysregulation of purine metabolism and impaired insulin secretion in murine pancreatic beta cells(2025-01-01) Ngamratanapaiboon S.; Yambangyang P.; Duchda P.; Lohwacharin J.; Devakul Na Ayutthaya W.; Ngamratanapaiboon S.; Mahidol UniversityRotenone, an insecticide, and herbicide has been associated with various environmental and health concerns. This study investigates the molecular alterations in rotenone-treated murine pancreatic beta cells, using untargeted metabolomics based on liquid chromatography-mass spectrometry. We established a model mimicking rotenone toxicity in MIN6 cells and observed decreased insulin secretion despite no significant loss of cellular viability. Our untargeted metabolomics analysis revealed a decrease in 19 metabolites and an increase in 62 metabolites following exposure to rotenone. Mapping these changes onto metabolic pathways, we found that purine metabolism underwent significant alterations. Critical metabolites in this pathway, including adenine, adenosine monophosphate, guanine, and others, exhibited a substantial increase upon rotenone treatment. This study underscores the utility of untargeted metabolomics for investigating molecular alterations due to rotenone exposure. It further highlights rotenone’s significant impact on purine metabolism, providing potential insights into the mechanisms of rotenone-associated diabetes risk.Item Metadata only New insights into the adsorptive characteristics of trihalomethane precursors from surface water using magnetic powdered activated carbon(2024-01-01) Sangkarak S.; Phetrak A.; Kittipongvises S.; Denpetkul T.; Ittisupornrat S.; Lohwacharin J.; Mahidol UniversityPowdered activated carbon (PAC) can effectively eliminate dissolved organic matter (DOM) as a precursor of trihalomethane (THM), but its application has raised concerns regarding its separation and the overelevated formation of brominate THM species in treated water after chlorination. Although magnetic PAC (Mag-PAC) has been proposed as an easily separable adsorbent for water treatment, its removal by Mag-PAC remains unknown. In this study, a novel Mag-PAC adsorbent for removing DOM and controlling THM formation from surface water was fabricated, evaluated using batch experiments, and compared with PAC. Our results found that Mag-PAC blended the advantages of PAC and magnetic particles, having an efficient removal performance toward DOM with an adsorption capacity of 2.84–3.69 mg-C/g and good magnetic separability of 10.15 emu/g. The iron oxide coating on the carbon matrices was predominantly distributed in the presence of crystalline goethite and magnetite structures. Chemisorption was the dominant mechanism of DOM adsorption by Mag-PAC. The sorption rate of DOM was influenced by the impregnation of iron oxide, but such impregnation did not significantly affect the DOM adsorption capacity. Aromatic DOM, humic-acid and fulvic-acid like compounds were efficiently adsorbed by the Mag-PAC. Compared with PAC, Mag-PAC exhibited a higher reduction in lifetime cancer risks from THMs through the ingestion pathway by decreasing the formation potential of trichloromethane and bromodichloromethane, which generated high unit risks among various THM species. These findings highlight the potential of Mag-PAC as an effective sorbent for DOM removal to control the formation of THM in surface water.Item Metadata only The Emergence of blaNDM-Encoding Plasmids in Enterobacteriaceae Isolated from Shared Water Resources for Livestock and Human Utilization in Central Thailand(2026-01-01) Songsaeng W.; Kurilung A.; Prapasarakul N.; Wongsurawat T.; Am-In N.; Lugsomya K.; Lohwacharin J.; Damrongsiri S.; Shein H.Z.; Sirichokchatchawan W.; Songsaeng W.; Mahidol UniversityBackground/Objectives: The environmental dissemination of antimicrobial-resistant Enterobacteriaceae poses a remarkable threat to public health. This study investigates the environmental presence and dissemination of carbapenemase-producing Enterobacteriaceae (CPE) in 30 important water bodies selected according to their interconnection with and utilization by livestock and community people in central Thailand. Methods: Water samples were collected from 30 selected water bodies. Enterobacteriaceae were isolated and screened for CPE and multidrug resistance. Carbapenemase genes (blaNDM-5, blaNDM-1 and blaIMI-1) were detected and their locations (plasmid and chromosome) determined. Plasmid types were further characterized, and conjugation experiments were performed to assess transferability among bacterial species. Results: From all selected samples, six isolates (20%) were identified as multidrug-resistant CPE including one Escherichia coli, one Klebsiella pneumoniae and four Enterobacter roggenkampii carrying blaNDM-5, blaNDM-1 and blaIMI-1 genes, respectively. The blaNDM-5 and blaNDM-1 genes were located on phage-like pO111 type plasmid and IncC plasmid, while blaIMI-1 was located on chromosomes. The plasmids also consisted of components that closely resembled those found in resistance plasmids obtained from clinical and environmental isolates worldwide. Additionally, through plasmid conjugation experiment, carbapenemase genes were transferable with a high rate among bacterial species. Conclusions: These findings indicated that water bodies are polluted and there is an urgent need for integrated strategies to monitor and mitigate the spread of antibiotic resistance across human, animal and environmental health domains in aquatic environments.Item Metadata only Unravelling capability of municipal wastewater treatment plant in Thailand for microplastics: Effects of seasonality on detection, fate and transport(2022-01-15) Kittipongvises S.; Phetrak A.; Hongprasith N.; Lohwacharin J.; Mahidol UniversityMany factors can affect microplastics (MPs) behaviors in aquatic environments. The effects of seasonal and meteorological conditions on MPs are not well understood. This study demonstrates the impacts of seasonality on the fate and transport, and the efficacy of MPs removal by a wastewater treatment plant. The fate and transport of MPs at a WWTP in Nonthaburi, Thailand were tracked during the dry and wet seasons of 2019–2020. Polypropylene (PP), polyethylene (PE), and toothpaste formulations were the most abundant MP types observed. Total detected MP quantities ranged between 76 and 192 particles L−1 during the dry season, and only 36–68 particles L−1 during the wet season, indicating runoff dilution effects. T-test analysis found a statistically significant difference between MP concentrations between the dry and wet seasons of 2019–2020. Spearman's correlation showed statistically strong negative relationships between MP concentrations versus wastewater flow, and MP concentrations versus precipitation; a positive correlation between MP abundance versus temperature in the treatment system was observed. During the dry seasons, MPs were mostly found in the aeration process, and were mostly rayon or polyester particles in the shape of fibers. Contrarily, in the wet seasons, MPs were detected in both the raw influent and aeration process, with PE, polyacrylate, and polyethylene terephthalate fragments dominating the make-up. MPs were also detected in the return activated sludge, thus calling for proper sludge age and drainage management. No MPs were detected in the plant's effluent during the wet season, suggesting that the plant had sufficient MPs removal capability during normal wet-season conditions. Overall, this study suggests that municipalities should focus on increasing MPs removal efficiency of wastewater treatment plants for dry seasons, while properly managing the water flows of combined sewage systems to prevent overflows that may inevitably become point-sources of MPs release into water bodies during wet seasons.Item Metadata only Upcycling spent activated carbon blocks via chemical surface modification for enhanced hexavalent chromium removal from electroplating wastewater(2025-09-01) Sangkarak S.; Kittipongvises S.; Kitkaew D.; Panyacharoen B.; Ittisupornrat S.; Phetrak A.; Lohwacharin J.; Sangkarak S.; Mahidol UniversityThe widespread adoption of point-of-use water treatment technologies has resulted in significant waste accumulation from activated carbon block (ACB) filters. Although ACBs are effective at removing organic pollutants, their capacity to adsorb hexavalent chromium (Cr(VI)) remains limited. This study addresses this limitation by upcycling spent ACBs through chemical surface modifications to enhance Cr(VI) removal from the electroplating wastewater, which aligns with the circular economy principles. Five modified sorbents were developed using acid (r-PAC-HNO3), alkaline (r-PAC-NaOH), oxidation (r-PAC-H2O2), permanganate (r-PAC-KMnO4), and iron-oxide (r-PAC-Mag) treatments. Batch adsorption experiments demonstrated that r-PAC-H2O2 exhibited the highest adsorption capacity (11.94 ± 0.03 mg/g), attributed to its increased surface area, larger pore volume, and abundant oxygen-containing functional groups. Optimal Cr(VI) removal was achieved at pH 3, with equilibrium reached within 360 min. The adsorption data conformed to the Freundlich isotherm and pseudo-second-order kinetic models, indicating a chemisorption-driven multilayer mechanism on heterogeneous surfaces. X-ray photoelectron spectroscopy confirmed the reduction of Cr(VI) to trivalent chromium, which subsequently complexed with the surface oxygenic functional groups, reinforcing a synergistic adsorption-reduction mechanism. The addition of a high sulfate and phosphate concentration at 0.1 M further enhanced Cr(VI) removal. Regeneration with 0.001 M NaOH preserved the adsorbent stability, maintaining Cr(VI) removal efficiency at approximately 55 %–85 % over three cycles. This study provides a practical and effective strategy for converting ACB waste into high-performance sorbents for Cr(VI) remediation, supporting sustainable wastewater treatment and resource recovery. The findings offer valuable insights for developing next-generation adsorbents suitable for industrial-scale applications.