Occurrence, removal, and prioritization of organic micropollutants in four full-scale wastewater treatment plants in Korea.

This study investigated the occurrence, removal rate, and potential risks of 43 organic micropollutants (OMPs) in four municipal wastewater treatment plants (WWTPs) in Korea. Results from two-year intensive monitoring confirmed the presence of various OMPs in the influents, including pharmaceuticals such as acetaminophen (pain relief), caffeine (stimulants), cimetidine (H2-blockers), ibuprofen (non-steroidal anti-inflammatory drugs- NSAIDs), metformin (antidiabetics), and naproxen (NSAIDs) with median concentrations of >1 µg/L. Some pharmaceuticals (carbamazepine-anticonvulsants, diclofenac-NSAIDs, propranolol-ß-blockers), corrosion inhibitors (1H-benzotriazole-BTR, 4-methyl-1H-benzotriazole-4-TTR), and perfluorinated compounds (PFCs) were negligibly removed during WWTP treatment. The OMP concentrations in the influents and effluents were mostly lower in August than those of other months (p-value <0.05) possibly due to wastewater dilution by high precipitation or enhanced biodegradation under high-temperature conditions. The anaerobic-anoxic-oxic process (A2O) with a membrane bioreactor exhibited higher OMP removal than other processes, such as A2O with sedimentation or the conventional activated sludge process (p-value <0.05). Pesticides (DEET and atrazine), corrosion inhibitors (4-TTR and BTR), and metformin were selected as priority OMPs in toxicity-driven prioritization, whereas PFCs were determined as priority OMPs given their persistence and bioaccumulation properties. Overall, our results contribute to an important database on the occurrence, removal, and potential risks of OMPs in Korean WWTPs.

Loss of micropollutants on syringe filters during sample filtration: Machine learning approach for selecting appropriate filters.

Prefiltration before chromatographic analysis is critical in the monitoring of environmental micropollutants (MPs). However, in an aqueous matrix, such monitoring often leads to out-of-specification results owing to the loss of MPs on syringe filters. Therefore, this study investigated the loss of seventy MPs on eight different syringe filters by employing Random Forest, a machine learning algorithm. The results indicate that the loss of MPs during filtration is filter specific, with glass microfiber and polytetrafluoroethylene filters being the most effective (<20%) compared with nylon (>90%) and others (regenerated-cellulose, polyethersulfone, polyvinylidene difluoride, cellulose acetate, and polypropylene). The Random Forest classifier showed outstanding performance (accuracy range 0.81-0.95) for determining whether the loss of MPs on filters exceeded 20%. Important factors in this classification were analyzed using the SHapley Additive exPlanation value and Kruskal-Wallis test. The results show that the physicochemical properties (LogKow/LogD, pKa, functional groups, and charges) of MPs are more important than the operational parameters (sample volume, filter pore size, diameter, and flow rate) in determining the loss of most MPs on syringe filters. However, other important factors such as the implications of the roles of pH for nylon and pre-rinsing for PTFE syringe filters should not be ignored. Overall, this study provides a systematic framework for understanding the behavior of various MP classes and their potential losses on syringe filters.

Predicting micropollutant fate during wastewater treatment using refined classical kinetic model based on quantitative monitoring in multi-metropolitan regions of South Korea.

This study aimed to implement an extensive prediction model for the fate of micropollutants (MPs) in wastewater treatment plants (WWTPs). Five WWTPs equipped with seven different biological treatment processes were monitored from 2020 to 2022 with three to four sampling events in each year, and 27 datasets for 20 MPs were collected. Among these datasets, 12 were used to investigate the behavior and fate of MPs in WWTPs in South Korea. Metformin, acetaminophen, caffeine, naproxen, and ibuprofen were the MPs with the highest influent concentrations (ranging from 3,933.3-187,637.0 ng L-1) at all WWTPs. More than 90% of MPs were removed by biological treatment processes in all WWTPs. The Kruskal-Wallis test verified that their efficacy did not differ statistically (p-value > 0.05). Meanwhile, to refine the performance of the prediction model, this study optimized the biodegradation rate constants (kbio) of each MP according to the variation of seasonal water temperature. As a result, compared to the original prediction model, the mean difference between the actual data and predicted results (MEAN) decreased by 6.77%, while the Nash-Sutcliffe efficiency (NSE) increased by 0.226. The final MEAN and NSE for the refined prediction model were calculated to be 5.09% and 0.964, respectively. The prediction model made accurate predictions, even for MPs exhibiting behaviors different from other cases, such as estriol and atrazine. Consequently, the optimization strategy proposed in this study was determined to be effective because the overall removal efficiencies of MPs were successfully predicted even with limited reference datasets.

Cr-Doped FeC2O4 Microrods Formed Directly on AISI 420 Stainless Steel to Enhance Electrochemical NO3- Reduction to N2 at Circumneutral pH.

We synthesized low-cost cathodes for use in the electrochemical NO3- reduction reaction (NO3RR) via the simple reconstruction of AISI 420 stainless steel (SS). Thermochemical treatment of the SS in oxalic acid generated iron oxalate (FeC2O4) microrods (BL-SS), with further anodization affording Cr-doped Fe2O3 (R-SS) or FeC2O4 (G-SS). G-SS displayed supreme N2 selectivity during galvanostatic electrolysis at circumneutral pH. Electroanalysis and descriptor/scavenger analysis indicated that Fe sites were the primary active sites of NO3- adsorption, with C2O42- as the H-binding sites. The C2O42- ligands and Cr dopants altered the electronic structures of the Fe sites. A parametric study of the current density, pH, [NO3-]0, and [Cl-]0 indicated an Eley-Rideal N2 generation mechanism, with NO2- as an intermediate. Cl- elevated the N2 selectivity but reduced the NO3RR efficiency. To demonstrate the practical applicability of G-SS with a proposed regeneration strategy, its durability was examined in synthetic and real wastewater matrices. Compared with that in synthetic wastewater, G-SS displayed more stable performance in real wastewater owing to the natural buffering capacity at the cathode, which reduced the corrosion rate. Cr-doped FeC2O4 is viable for use in the low-cost, efficient electrochemical treatment of wastewater containing NO3-.

Opportunities and challenges of machine learning in bioprocesses: Categorization from different perspectives and future direction.

Recent advances in machine learning (ML) have revolutionized an extensive range of research and industry fields by successfully addressing intricate problems that cannot be resolved with conventional approaches. However, low interpretability and incompatibility make it challenging to apply ML to complicated bioprocesses, which rely on the delicate metabolic interplay among living cells. This overview attempts to delineate ML applications to bioprocess from different perspectives, and their inherent limitations (i.e., uncertainties in prediction) were then discussed with unique attempts to supplement the ML models. A clear classification can be made depending on the purpose of the ML (supervised vs unsupervised) per application, as well as on their system boundaries (engineered vs natural). Although a limited number of hybrid approaches with meaningful outcomes (e.g., improved accuracy) are available, there is still a need to further enhance the interpretability, compatibility, and user-friendliness of ML models.

A multi-scale framework for modeling transport of microplastics during sand filtration: Bridging from pore to continuum.

The fate and transport of microplastics (MPs) during deep bed filtration were investigated using combined laboratory experiments and numerical modeling. A series of column experiments were conducted within the designated ranges of six operating parameters (i.e., size of the MP and collector, seepage velocity, porosity, temperature, and ionic strength). A variance-based sensitivity analysis, the Fourier amplitude sensitivity test, was conducted to determine the priority in affecting both the attachment coefficient at the pore scale, and the subsequent stabilized height of the breakthrough curve at the continuum scale, which follows non-monotonic trends with singularity in the size of MP (i.e., 1 µm). Finally, Damkohler numbers were introduced to analyze the dominant mechanisms (e.g., attachment, detachment, or straining) in the coupled hydro-chemical process. The robustness of conceptual frameworks bridges the gap between pore-scale interactions and the explicit MPs removal in the continuum scale, which could support decision-making in determining the priority of parameters to retain MPs during deep bed filtration.

Optimization of the Design Configuration and Operation Strategy of Single-Pass Seawater Reverse Osmosis.

The numerical study was conducted to compare process performance depending on the pump type and process configuration. The daily monitoring data of seawater temperature and salinity offshore from Daesan, Republic of Korea was used to reflect the site-specific seawater conditions. An algorithm for reverse osmosis in constant permeate mode was developed to simulate the process in time-variant conditions. Two types of pumps with different maximum leachable efficiencies were employed to organize pump-train configuration: separated feed lines and common pressure center design. The results showed pump type and design configuration did not have a significant effect on process performance. The annual means of specific energy consumption (SEC) for every design configuration were under 2 kWh/m3, except for a worst-case. The worst-case was decided when the pump was operated out of the best operation range. The two operation strategies were evaluated to determine the optimal configuration. The permeate flow rate was reduced to 80% of the designed permeate flow rate with two approaches: feed flow rate reduction in every train and pump shutdown in a specific train. The operation mode with feed flow rate reduction was more efficient than the other. The operating pressure reduction led to a decrease in SEC.

Sex-specific role of education on the associations of socioeconomic status indicators with obesity risk: A population-based study in South Korea.

BACKGROUND: No study of obesity risk for people in developed countries has conducted a multi-dimensional analysis of the association of socioeconomic status with obesity. In this paper, we investigated if education functions as either a confounder or an effect modifier in the association of another socioeconomic status indicator with obesity. METHODS: This cross-sectional study analyzed data of an adult population sample (10,905 men and 14,580 women) from the Korea National Health and Nutrition Examination Survey (2010-2014). The study performed multivariate logistic regression analyses for three education levels and four indicators of socioeconomic status (i.e., marital status, residential area, occupation, and income). RESULTS: The overall prevalence of obesity was 38.1% in men and 29.1% in women (p < 0.001). In men, while education functioned as an effect modifier in the association between marital status and obesity (p for interaction = 0.006), it functioned as both a confounder (p < 0.001) and an effect modifier (p for interaction < 0.001) in the association between residential area and obesity. In contrast, in women, education functioned as a confounder in the association of residential area with obesity (p = 0.010). However, it functioned as both a confounder (p < 0.001) and an effect modifier (p for interaction = 0.012) in the association between income and obesity. A prediction showed that unlike in women, education was positively associated with obesity risk for some socioeconomic indicator groups in men; for example, in a rural resident group, a higher level of education increased the probability of being obese by 19.7%. CONCLUSIONS: The present study suggests the need to examine sex-specific studies regarding the role of education on the association between other socioeconomic status indicators and obesity. This should be considered in planning education policies to reduce the risk of obesity.

Gender-specific interactions between education and income in relation to obesity: a cross-sectional analysis of the Fifth Korea National Health and Nutrition Examination Survey (KNHANES V).

OBJECTIVES: To identify gender-specific associations between education and income in relation to obesity in developed countries by considering both the interaction-effect terms of the independent variables and their main-effect terms. DESIGN: A cross-sectional study. Education and income levels were chosen as socioeconomic status indicators. Sociodemographics, lifestyles and medical conditions were used as covariates in multivariable logistic regression models. Adjusted ORs and predicted probabilities of being obese were computed and adjusted for a complex survey design. SETTING: Data were obtained from the Fifth Korea National Health and Nutrition Examination Survey (2010-2012). PARTICIPANTS: The sample included 7337 male and 9908 female participants aged ≥19 years. OUTCOME MEASURE: Obesity was defined as body mass index of ≥25, according to a guideline for Asians. RESULTS: In models with no interaction-effect terms of independent variables, education was significantly associated with obesity in both men and women, but income was significant only in women. However, in models with the interaction-effect terms, education was significant only in women, but income was significant only in men. The interaction effect between income and education was significant in men but not in women. Participants having the highest predicted probability of being obese over educational and income levels differed between the two types of models, and between men and women. A prediction using the models with the interaction-effect terms demonstrated that for all men, the highest level of formal education was associated with an increase in their probability of being obese by as much as 26%. CONCLUSIONS: The well-known, negative association between socioeconomic status and obesity in developed countries may not be valid when interaction effects are included. Ignoring these effects and their gender differences may result in the targeting of wrong populations for reducing obesity prevalence and its resultant socioeconomic gradients.

Modifying effects of education on the association between lifestyle behaviors and the risk of obesity: evidence from South Korea.

BACKGROUND: No previous study has explored the interactions between education and lifestyle in relation to obesity. This study hypothesized that education may be obesogenic through its interplay with lifestyle behaviors. METHODS: Data for a nationally representative sample (6937 men and 9333 women) from the Korea National Health and Nutrition Examination Survey (2010-2012) were analyzed. Multivariate logistic regressions were performed for three education levels and six lifestyle behaviors, each of which comprised two groups. RESULTS: Interactions between education and lifestyle behaviors in relation to obesity were observed for all lifestyle behaviors in women (p for interaction <0.001) and for three lifestyle behaviors in men. Education appeared obesogenic for three groups of lifestyle behaviors in men (p for trend <0.05), but was protective against obesity for 11 groups in women. Each one-unit increase in education level in men increased the odds of obesity by 1.29-fold among under-reported energy intake groups (95 % confidence interval: 1.16, 1.44). CONCLUSIONS: Education may be a risk factor for obesity through its interplay with lifestyle behaviors. Further research is required to examine these findings in different socio-cultural settings.

Gender-specific combined effects of smoking and hypertension on cardiovascular disease mortality in elderly Koreans: THe Kangwha Cohort Study.

OBJECTIVE: We examined gender-specific combined effects of smoking and hypertension on risk of mortality from cardiovascular disease in elderly Korean men and women. STUDY DESIGN: This study followed a cohort of 6097 residents (2593 men, 3504 women) in the general population of Kangwha County, aged ≥55 years in March 1985 and examined their cause-specific mortality for 20.8 years, up to December 31, 2005. All participants were followed up more than once after the 1985 survey. MAIN OUTCOME MEASURES: We calculated hazard ratios for mortality for the combined sets of smoking habits and blood pressure levels using the Cox proportional-hazard model. The set of non-smokers with normal blood pressure served as a reference group. RESULTS: During the 20.8 years of follow-up, 759 people died from cardiovascular disease. The risk of mortality from cardiovascular disease and stroke according to smoking or hypertension was not different between men and women. However, the risk among smokers combined with hypertension was higher in men than in women; the multivariable-adjusted hazard ratios (95% CI) for mortality from cardiovascular disease and stroke were 4.52 (1.67-12.21) and 6.37 (1.57-25.85) in men and 2.11 (1.37-3.24) and 2.41 (1.44-4.01) in women, respectively. CONCLUSIONS: The magnitude of the joint effects of smoking and hypertension on cardiovascular disease and stroke mortality was different between men and women. This study suggests that combining quitting smoking with lowering blood pressure could contribute to preventing cardiovascular disease and stroke, especially in men.

The socioeconomic burden of coronary heart disease in Korea.

OBJECTIVES: We aimed to estimate the annual socioeconomic burden of coronary heart disease (CHD) in Korea in 2005, using the National Health Insurance (NHI) claims data. METHODS: A prevalence-based, top-down, cost-of-treatment method was used to assess the direct and indirect costs of CHD (International Classification of Diseases, 10th revision codes of I20-I25), angina pectoris (I20), and myocardial infarction (MI, I21-I23) from a societal perspective. RESULTS: Estimated national spending on CHD in 2005 was $2.52 billion. The majority of the spending was attributable to medical costs (53.3%), followed by productivity loss due to morbidity and premature death (33.6%), transportation (8.1%), and informal caregiver costs (4.9%). While medical cost was the predominant cost attribute in treating angina (74.3% of the total cost), premature death was the largest cost attribute for patients with MI (66.9%). Annual per-capita cost of treating MI, excluding premature death cost, was $3183, which is about 2 times higher than the cost for angina ($1556). CONCLUSIONS: The total insurance-covered medical cost ($1.13 billion) of CHD accounted for approximately 6.02% of the total annual NHI expenditure. These findings suggest that the current burden of CHD on society is tremendous and that more effective prevention strategies are required in Korea.

Estimating the lifetime economic burden of stroke according to the age of onset in South Korea: a cost of illness study.

BACKGROUND: The recently-observed trend towards younger stroke patients in Korea raises economic concerns, including erosion of the workforce. We compared per-person lifetime costs of stroke according to the age of stroke onset from the Korean societal perspective. METHODS: A state-transition Markov model consisted of three health states ('post primary stroke event', 'alive post stroke', and 'dead') was developed to simulate the natural history of stroke. The transition probabilities for fatal and non-fatal recurrent stroke by age and gender and for non-stroke causes of death were derived from the national epidemiologic data of the Korean Health Insurance Review and Assessment Services and data from the Danish Monitoring Trends in Cardiovascular Disease study. We used an incidence-based approach to estimate the long-term costs of stroke. The model captured stroke-related costs including costs within the health sector, patients' out-of-pocket costs outside the health sector, and costs resulting from loss of productivity due to morbidity and premature death using a human capital approach. Average insurance-covered costs occurring within the health sector were estimated from the National Health Insurance claims database. Other costs were estimated based on the national epidemiologic data and literature. All costs are presented in 2008 Korean currency values (Korean won = KRW). RESULTS: The lifetime costs of stroke were estimated to be: 200.7, 81.9, and 16.4 million Korean won (1,200 KRW is approximately equal to one US dollar) for men who suffered a first stroke at age 45, 55 and 65 years, respectively, and 75.7, 39.2, and 19.3 million KRW for women at the same age. While stroke occurring among Koreans aged 45 to 64 years accounted for only 30% of the total disease incidence, this age group incurred 75% of the total national lifetime costs of stroke. CONCLUSIONS: A higher lifetime burden and increasing incidence of stroke among younger Koreans highlight the need for more effective strategies for the prevention and management of stroke especially for people between 40 and 60 years of ages.

Economic burden of injuries in South Korea.

UNLABELLED: BACKGROUND STUDIES: on the cost of injury are useful in setting research and policy priorities and it is valuable to observe differences in the economic burden of injuries across countries. OBJECTIVE: To estimate the treated prevalence rate, economic burden and gender- and age-specific costs of injuries in Korea in 2006. DESIGN: Annual direct healthcare costs associated with injuries were estimated from the National Health Insurance, Medical Aid and Automobile Insurance databases. Annual direct non-health costs were estimated for transport and caregiver's costs. Indirect costs were estimated for premature death, absence from work and disability. Costs were adjusted to 2006 levels using the healthcare component of the Consumer Price Index. MAIN OUTCOME MEASURES: Prevalence-based direct costs, incidence-based indirect costs and total costs for injuries, stratified by gender, age group and type of injury. RESULTS: The treated prevalence rate of injury in 2006 of the Korean population was 26.5 per 100, resulting in an annual economic burden of $39837 million ($4703 million in direct and $35134 million in indirect costs). The cost of medical treatment associated with injuries accounted for 9.5% of the total health expenditure in Korea. The cost of premature death was the largest contributor to the total and automobile-related injuries accounted for 30.3% of total costs. CONCLUSIONS: The estimates were considerably understated because they did not include losses in household production and quality of life. Nevertheless, the size and main components of the injury burden were identified; this information should aid decision-making about research priorities and improve monitoring of the effects of policy initiatives.

[Socioeconomic costs of stroke in Korea: estimated from the Korea national health insurance claims database].

OBJECTIVES: To estimate the annual socioeconomic costs of stroke in Korea in 2005 from a societal perspective. METHODS: We identified those 20 years or older who had at least one national health insurance (NHI) claims record with a primary or a secondary diagnosis of stroke (ICD-10 codes: I60-I69, G45) in 2005. Direct medical costs of the stroke were measured from the NHI claims records. Direct non-medical costs were estimated as transportation costs incurred when visiting the hospitals. Indirect costs were defined as patients' and caregivers' productivity loss associated with office visits or hospitalization. Also, the costs of productivity loss due to premature death from stroke were calculated. RESULTS: A total of 882,143 stroke patients were identified with prevalence for treatment of stroke at 2.44%. The total cost for the treatment of stroke in the nation was estimated to be 3,737 billion Korean won (KRW) which included direct costs at 1,130 billion KRW and indirect costs at 2,606 billion KRW. The per-capita cost of stroke was 3 million KRW for men and 2 million KRW for women. The total national spending for hemorrhagic and ischemic stroke was 1,323 billion KRW and 1,553 billion KRW, respectively, which together consisted of 77.0% of the total cost for stroke. Costs per patient for hemorrhagic and ischemic stroke were estimated at 6 million KRW and 2 million KRW, respectively. CONCLUSIONS: Stroke is a leading public health problem in Korea in terms of the economic burden. The indirect costs were identified as the largest component of the overall cost.