Browsing by Author "Phetrak A."
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Item Metadata only A Review on Water Security in Dhaka City, Bangladesh: Calling for Ensuring Sustainability(2024-04-03) Akram W.; Niyommaneerat W.; Phetrak A.; Kittipongvises S.; Akram W.; Mahidol UniversityDhaka is currently facing a number of significant challenges, and one of them is the protection of water resources. The city is experiencing rapid depletion of groundwater as well as substantial pollution of its surface water. This article aims to highlight a review of the literature on the challenges of water security in Dhaka. The sustainability issues of water resources were elaborated in terms of management, quantity, and quality aspects. Having reviewed, it has been found that groundwater is depleting drastically over the years, which may have environmental, economic, and social consequences in the near future. Due to the rapid depletion of ground-water, land subsidence, increased cost of groundwater abstraction, shortage of drinking water, and social unrest were categorized as high-risk factors. In addition, the water quality of the surrounding rivers has been mostly categorized as ‘poor’ and ‘very poor’ according to the Weighted Arithmetic Index (WAI) and the Canadian Council of Ministers of the Environment (CCME) techniques. Therefore, ensuring the sustainability of water resources is an urgent call.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 Corrigendum: Handwashing among caregivers of young children in a protracted and complex refugee and immigration context: a mixed methods study on the Thai–Myanmar border (Frontiers in Public Health, (2023), 11, (1099831), 10.3389/fpubh.2023.1099831)(2023-01-01) Pooseesod K.; Umezaki M.; Phetrak A.; Phuanukoonnon S.; Mahidol UniversityIn the published article, there was an error in affiliation(s) [Athit Phetrak1]. Instead of “Athit Phetrak1”, it should be “Athit Phetrak3”. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.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 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 Evaluation of Greenhouse Gases Emission from Municipal Solid Waste Disposal Treatment: A Case of Nairobi City, Kenya(2025-09-01) Owino M.G.; Thitanuwat B.; Phetrak A.; Suma Y.; Eaktasang N.; Owino M.G.; Mahidol UniversityMunicipal solid waste (MSW) generation has increased in Nairobi City, Kenya, creating significant challenges for waste management and disposal. Most of MSW ended up at uncontrolled landfill dumpsite which is one cause of greenhouse gases (GHGs) emission from waste sector. This study aimed to investigate the composition of MSW at the Dandora dumpsite in Nairobi in 2023 and to evaluate GHGs emission from different waste treatment methods under three scenarios: (1) landfilling as the business-as-usual (BAU) approach, (2) composting of food waste, and (3) anaerobic digestion of food waste, following the guidelines provided by the Intergovernmental Panel on Climate Change (IPCC). For GHG estimation, 65% (1,560 t/d) of the total MSW generated was used, based on the waste composition categorized at the Dandora dumpsite. The organic waste composition, including food waste, paper and cardboard and other organic materials, was used to estimate GHGs emission under the different scenarios in order to compare the treatment methods. The results showed that food waste had the highest composition at 45.7%, followed by other organic material at 25.5%, plastic at 11.0%, paper and cardboard at 10.0%, and inorganic material at 7.8%. GHGs emissions from the current landfilling method were estimated at 125,777.98 tCO2-e/y. Whereas alternative treatment methods– composting and anaerobic digestion of food waste–resulted in lower emissions of 84,140.26 tCO2-e/y and 44,608.28 tCO2-e/y, respectively. The major proportion of GHG emission contributed from food waste treatment by three scenarios. The findings suggest that GHG emissions from MSW in Nairobi City could be significantly reduced through the composting and anaerobic digestion processes.Item Metadata only Factors influencing secondary school students’ nutrition, mindfulness, and academic performance in Nan Province, Thailand(2025-01-01) Lwin E.Z.; Watthanakulpanich D.; Phetrak A.; Soonthornworasiri N.; Prangthip P.; Lwin E.Z.; Mahidol UniversityAcademic performance is crucial for future educational endeavors of students. However, there has been a concerning decline over time. This study aimed to investigate the association between nutritional status, environmental factors, mindfulness, and academic performance among students at Bo Kluea School in Nan province, Thailand. A cross-sectional study was conducted involving 350 students in grades 8–11 using questionnaires, measurements, and academic records. Results showed that female students performed significantly better academically compared to males(71.9% vs 56.4% achieving good grades; compared to p < 0.001, OR = 3.583, 95%CI = 1.663–7.719). Age, junk food consumption, BMI, and mindfulness were identified as factors influencing academic performance. Students aged 16–18 years were 2.224 times more likely to achieve good academic performance compared to younger students (p = 0.015, OR = 2.224, 95%CI = 1.164–4.247). Significant associations were found between gender, age, waist circumference, mindfulness, and nutritional status. Female students and those with normal waist circumference or good mindfulness were more likely to have a normal BMI (p = 0.019, OR = 1.794, 95%CI = 1.101–2.922). Positive attitudes towards nutrition were associated with better academic performance (60.1% achieving good grades;p = 0.044, AOR = 1.543, 95%CI = 1.010–2.356). This study highlights the interconnectedness of these factors and their importance in in improving academic results. Further research is need to confirm these findings and overcome study limitations.Item Metadata only Handwashing among caregivers of young children in a protracted and complex refugee and immigration context: a mixed methods study on the Thai–Myanmar border(2023-01-01) Pooseesod K.; Umezaki M.; Phetrak A.; Phuanukoonnon S.; Mahidol UniversityIntroduction: Protracted refugee situations create complex contexts that present significant health risks for young children. Effective hand hygiene practices by caregivers can reduce respiratory infections and diarrhoeal disease, the two largest contributors to mortality among children between 1 month and 5 years of age. This study documented handwashing patterns and access to water, sanitation and hygiene (WASH) infrastructure among caregivers of young children living along the Thai–Myanmar border, one of the world’s most protracted and complex refugee and immigration contexts. It also examined the association between handwashing and socio-demographic variables and captured participants’ explanations for when and how hands are washed. The study broadened the scope of previous research by also including the large number of caregivers living outside formal camps. Methods: Caregivers of children attending 11 preschools in Tak province, Thailand participated in a mixed-methods cross-sectional study. Quantitative questionnaire data (n = 384) were supplemented by a thematic analysis of data from in-depth interviews (n = 9). Results: Fewer than half the caregivers reported routinely washing their hands before preparing meals or after using the latrine/toilet. Fewer than one-in-five routinely used soap in these situations. Interviewees explained that handwashing was only necessary when a substance could be felt or seen, in which case wiping with a cloth or a rinsing with water were sufficient to clean hands. However, their explanations also suggested some potential avenues for culturally appropriate and feasible interventions to improve hand hygiene. Conclusion: The results confirmed previous research on the multi-dimensional barriers to good hand hygiene in protracted refugee situations and other low-resource settings. Additional investment to overcome shortages in the infrastructure necessary to support good hand hygiene and creative means of drawing on and developing human capital will be necessary to realize the potential hand hygiene holds for reducing ill-health and mortality among young children living in these contexts.Item Metadata only Impact of saline valorization in contaminated municipal wastewater on the treatment performance and bacterial community dynamics of a membrane bioreactor(2023-03-01) Ittisupornrat S.; Theepharaksapan S.; Krasaesueb N.; Phetrak A.; Mahidol UniversityBackground: Due to salt intrusion and the improper use of seawater for cleaning and flushing in food shops along coastal regions, the aerobic biological wastewater treatment process may have an adverse effect on treatment performance. This study demonstrates membrane bioreactor (MBR) performance for treating saline-contaminated municipal wastewater. The aim of this study is to determine how much salt affects the efficiency of the process and how the functional bacterial community evolves in an MBR for treating actual municipal wastewater. Results: An MBR was applied for actual municipal wastewater treatment by increasing the NaCl concentration from 0 to 20 g L−1 with a hydraulic retention time of 12 h and complete sludge retention. High removal efficiencies of chemical oxygen demand (COD) (ranging from 80.3 to 82.8 mgL−1) and ammonium-N (ranging from 40.8 to 44.4 mgL−1) were found at salinity concentrations of up to 7.8 ± 0.8 g L−1. However, the removal efficiency of COD was below 50% at high salinity concentrations of 17.9 ± 1.3 g L−1, whereas the removal rate of ammonium-N had slightly changed with the value of 90%. In terms of bacterial composition, the largest dominant bacterial communities were Proteobacteria and Planctomycetota, both of which may be the predominant halotolerant/halophilic bacteria group. Additionally, Rhizobiales, Planctomycetales, Pirellulales, and Gemmatales (all of which are members of these phyla) were increased, suggesting that they played an important role in the biodegradation process. Conclusion: The MBR operation showed a good performance for treating municipal wastewater with high salinity concentrations, with a salt tolerance threshold of 7.8 g L−1. The experimental results indicate that the MBR system can be applied for treating municipal wastewater that is occasionally contaminated with seawater. © 2022 Society of Chemical Industry (SCI).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 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 Microplastic contamination and removal efficiency in greywater treatment using a membrane bioreactor(2025-01-01) Ittisupornrat S.; Namyuang C.; Phetrak A.; Sriromreun P.; Theepharaksapan S.; Ittisupornrat S.; Mahidol UniversityMicroplastic (MP) contamination in aquatic environments is a critical concern due to its potential effects on aquatic ecosystems. MP contamination is often unsatisfactorily eliminated using conventional wastewater treatment systems. Membrane bioreactor (MBR) is a modern solution for wastewater treatment offering significant advantages over traditional activated sludge systems, such as a smaller footprint and the ability to produce high-quality effluent. In this study, a pilot-scale MBR was conducted to evaluate MP removal from real greywater. The overall treatment performance for MP removal reached up to 90%, with the MP concentration in the permeate effluent being 0.02 MP L−1. The major MP size distribution was 101–300 μm, with polypropylene as the predominant MP type. Remarkably, polyester fibers were highly predominant in the suspended sludge. Furthermore, Alphaproteobacteria, Bacteroidetes, and Actinobacteria were the predominant communities in the MBR sludge, which preferably formed a biofilm associated with MP accumulation. This study underscores the potential of MBR technology for efficient MP removal in household buildings, contributing to the mitigation of MP discharge into the environment. Implementing MBR systems is a crucial step toward safeguarding aquatic ecosystems and preserving environmental integrity with respect to the corresponding increase in MP pollution.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 Occurrence of Microplastics in Inland and Island Wastewater Treatment Plants and the Role of Suspended Solids as Monitoring Indicators(2025-11-01) Theepharaksapan S.; Sriromreun P.; Kiattisaksiri P.; Phetrak A.; Molee C.; Ittisupornrat S.; Theepharaksapan S.; Mahidol UniversityMicroplastics (MPs) are increasingly recognized as emerging contaminants in aquatic environments; however, their occurrence and fate in tropical wastewater treatment systems remain poorly understood. This study provides the first inland–island comparison of MP removal in wastewater treatment plants (WWTPs) across Thailand’s Eastern Economic Corridor. Influent and effluent samples were collected from six WWTPs, encompassing five treatment types: oxidation ditch, aerated lagoon, stabilization pond, aerated tank, and sand filtration combined with reverse osmosis. Polymeric composition and size distribution were examined in parallel with conventional water quality indicators. Across all sites, polyethylene (PE) and polypropylene dominated influent MPs, together accounting for 57–92% of total abundance. Inland plants received heterogeneous municipal wastewater, including domestic inputs and agricultural runoff. In contrast, island facilities consistently showed PE-enriched influents (45–60%) in site F, reflecting tourism-driven reliance on single-use plastics and personal care products. In addition, several minor polymers were identified, including poly (vinyl stearate) (up to 26%), polyamide, polytetrafluoroethylene and ethylene–butyl acrylate, highlighting overlooked pathways of MP entry into WWTPs. Fine MPs (100–300 μm) comprised over two-thirds of influent particles, with stabilization ponds reaching 16,000 MP m−3. Removal efficiency ranged from 86.0% to 98.5%. Spearman’s correlation and multiple linear regression analyses revealed strong positive relationships between MPs and both total suspended solids (TSS) and turbidity. Suspended solids parameters emerged as the most reliable predictor of MP abundance (adjusted R2 = 0.91, p = 0.001). This finding highlights TSS coupled with turbidity as a practical, cost-effective indicator for monitoring MPs in tropical WWTPs. To achieve greater accuracy, a larger dataset should be built and further analyzed.Item Metadata only Performance in full-scale MBRs treating domestic and industrial wastewaters and bacterial community structure dynamics(2026-01-01) Theepharaksapan S.; Lerkmahalikit Y.; Mhuantong W.; Phetrak A.; Jutagate A.; Ittisupornrat S.; Theepharaksapan S.; Mahidol UniversityMembrane bioreactors (MBRs) are increasingly applied for domestic and industrial wastewater treatment. However, information linking treatment performance and microbial community dynamics in full-scale MBRs operating under tropical climate conditions remains limited. This study investigates bacterial community structures and treatment performance in four full-scale MBRs located in Thailand. The systems treated domestic wastewater and industrial process wastewater. Treatment performance and bacterial communities were evaluated using next generation sequencing. All MBRs operated stably under tropical conditions and complied with regulatory discharge standards. High BOD5 removal efficiencies ranging from 85 to 99% were observed. TKN removal ranged from 62 to 94% depending on wastewater characteristics. The distinct bacterial community structures were identified among the systems. The core bacterial communities across all systems shared dominant phyla, including Proteobacteria, followed by Actinobacteria, Planctomycetes, Acidobacteria, Bacteroidetes, and Chloroflexi. However, some phyla, such as Gemmatimonadetes, Armatimonadetes, Verrucomicrobia, and Latescibacteria, were detected and attributed to differences in influent characteristics and pH conditions. Interestingly, the predominant bacterial genera under low pH condition were Mizugakibacter and Acidobacterium. Furthermore, the significant bacterial members which were responsible for TKN removal in domestic wastewater were Nitrosomonas and Nitrospira, whereas inindustrial wastewater were Candidatus Alysiosphaera and Haliangium. Overall, the results demonstrate that wastewater types driven pH variation strongly influence bacterial community dynamics in full-scale MBRs. This study provides field scale evidence and highlights the value of bacterial indicators for optimizing MBR performance and supporting non-potable water reuse.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.