Young Min Wie

This study analyzed environmental impacts and economic feasibility to evaluate whether recycling fly ash, which has rarely been addressed in previous studies, as a raw material for lightweight aggregates can be a sustainable waste management alternative. This study presents a comparative analysis of three disposal scenarios: landfill disposal, recycling as cement raw material, and recycling as lightweight aggregate raw material. Nine environmental impacts were assessed through life cycle assessment (LCA): acidification, global warming, eutrophication, photochemical oxidation, stratospheric ozone depletion, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, and terrestrial ecotoxicity. The results showed that the landfill disposal scenario posed the greatest threat to global warming, eutrophication, and marine aquatic ecotoxicity, while the cement scenario had the greatest impact on stratospheric ozone depletion, human toxicity, and other ecotoxicity items while recycling as lightweight aggregate showed the lowest environmental impacts in most items except acidification and photochemical oxidation. Life cycle costing (LCC) analysis was also performed to compare the economic aspects of each scenario. The lightweight aggregate scenario is more energy-intensive and costly, but it has significant economic benefits due to the significant revenues from the products produced. Therefore, even though the cost is high, this scenario is considered economically advantageous. This study highlights that recycling fly ash into lightweight aggregate reduces environmental impacts, provides economic benefits, and is a better alternative to landfilling and recycling cement raw materials. It will also contribute to promoting sustainable practices of fly ash recycling.

This study validates the attributes of the mineral carbonation process employing circulating fluidized bed combustion (CFBC) ash, which is generated from thermal power plants, as a medium for carbon storage. Furthermore, an examination was conducted on the properties of construction materials produced through the recycling of carbonated circulating fluidized bed combustion (CFBC) ash. The carbonation characteristics of circulating fluidized bed combustion (CFBC) ash were investigated by analyzing the impact of CO₂ flow rate and solid content. Experiments were conducted to investigate the use of it as a concrete admixture by replacing cement at varying percentages ranging from 0% to 20% by weight. The stability and setting time were subsequently measured. To produce foam concrete, specimens were fabricated by substituting 0 to 30 wt% of the cement. Characteristics of the unhardened slurry, such as density, flow, and settlement depth, were measured, while characteristics after hardening, including density, compressive strength, and thermal conductivity, were also assessed. The findings of our research study validated that the carbonation rate of CFBC ash in the slurry exhibited distinct characteristics compared to the reaction in the solid–gas system. Manufactured carbonated circulating fluidized bed combustion (CFBC) ash, when used as a recycled concrete mixture, improved the initial strength of cement mortar by 5 to 12% based on the 7-day strength. In addition, it replaced 25 wt% of cement in the production of foam concrete, showing a density of 0.58 g/cm³, and the 28-day strength was 2.1 MPa, meeting the density standard of 0.6 grade foam concrete.

This study evaluated the environmental impact of landfill, incineration, and lightweight aggregate production for sewage sludge management techniques and compared the utilization of sewage-produced lightweight aggregates with natural aggregates in terms of building material production. Two scenarios were established for the life cycle assessment (LCA) of the sludge and associated product that was carried out after sludge generation. Sludge incineration and landfill deposition includes emissions from the drying, transportation, incineration of sludge, and landfill, and the production of lightweight aggregates and natural aggregates includes transportation to manufacturing facilities, the manufacturing processes themselves, and transportation of the produced aggregates to construction sites. We calculated the amount of pollutant emissions for each process in each scenario and analyzed the environmental impact index considering the environmental impact of each pollutant using the Open LCA program. The parameters used for the environmental impact index analysis for sludge management are potential acidification, climate change, eutrophication potential, human toxicity, photochemical oxidation, and stratospheric ozone depletion. The environmental impact values of lightweight aggregates (LWA) are GWP 100 441 kg CO₂_Eq, AP 2.73 × 10⁻² kg SO_{2_}Eq, EP 4.46 × 10⁻³ kg PO₄⁻_Eq, HTP 4.15 × 10⁻² kg, 1,4-DCB_Eq, POCP 1.64 × 10⁻³ kg CH₄_Eq, and ODP 3.41 × 10⁻⁷ kg CFC-11_Eq. We found that these values were low compared to landfill and incineration as a sewage sludge disposal method and compared to natural aggregate as a construction material production method. The environmental impact index analysis during LCA of lightweight aggregates produced from the sludge verified its positive environmental impact compared to the other potential methods of sludge management.

Marine glaciers play a significant role in shaping landforms due to their erosive nature coupled with their surrounding environment. During this process, they pose a natural hazard threat to man-made infrastructure. The dynamic nature of these glaciers poses a particular threat, especially to railway infrastructure constructed in remote areas with glacial activity. Substantial research has been undertaken on the role of threats posed by marine glaciers to railway infrastructure. However, a detailed study of favorable glacier landforms prior to railway construction has yet to be explored. In this study, we propose a geospatial analysis-based method to determine the favorable most landforms shaped by marine glaciers for railway network route selection. This study provides a novel approach by first analyzing the availability of four major favorable landforms shaped by marine glaciers (glacier canyons, valley shoulders, moraine terraces, and ancient dammed lake basins), then proposes a railway route selection method for marine glacier distribution areas involving three steps. First, it is necessary to understand the basic situation of regional glaciers; then, to determine a feasible location for the railway based on judgment of the direct and indirect action areas of glaciers; and finally, through a thematic study of glacial geomorphology, to devise corresponding strategies for using glacial landforms to optimize the railway route. In order to verify the feasibility of the proposed method, it was implemented in the Palong Zangbo watershed of the Sichuan–Tibet railway network. Utilizing the power function method, the glacier basin areas of 22 glacier canyons along the Sichuan–Tibet railway line were identified and the maximum annual average velocity of 75 glaciers over the past ten years was calculated by offset tracking technology. The results indicate that the proposed optimization strategies utilizing glacier canyons for a short and straight route scheme and leveraging moraine terraces for a high-line scheme can provide comprehensive guidance for railway route selection in marine glacial areas.

Earthworms have been commonly used for solid waste management by employing the process of vermicomposting. In this study, we used two different types of earthworm for vermicomposting and analyzed their efficacy for plant production in comparison to chemical fertilizer. The worms used for vermicomposting included Eisenia fetida (EF) and Lumbricus rubellus (LR), and we studied compost efficiency for the harvesting of spinach and turnips. The parameters we used to evaluate the performance of the produced compost on crops were variations in sprouting time, harvesting time, plant height, and plant yield. For the production of compost, the waste was collected and degraded in an environment where various parameters, including pH, moisture content, temperature, carbon, and nitrogen, were measured regularly throughout the experiment. The compost obtained from these three setups was used as a fertilizer to grow spinach and turnip. Compost efficiency was compared based on plant yield, plant height, sprouting, and harvesting time. In the case of turnip, the combination worm compost yielded 38% and 58% more than the compost obtained using EF and LR, respectively. For spinach, the EF–LR combined compost gave similar results, 17.4% and 37.9% more yield than the above two worms individually. The study’s results showed that the compost obtained by the combination of worms is more promising than the compost obtained from a single species and applied as fertilizer. Moreover, the comparative evaluation by statistical analysis confirmed that growing spinach by combined compost would be a better option compared to growing turnip, due to higher significant difference in outcome parameters.

The goal of this study was to evaluate the biodegradation of 1,4–dioxane using a mixed biological culture grown in textile wastewater sludge with 1,4–dioxane as the sole carbon source. The conditions for the long-term evaluation of 1,4–dioxane degradation were determined and optimized by batch scale analysis. Moreover, Monod’s model was used to determine the biomass decay rate and unknown parameters. The soluble chemical oxygen demand (sCOD) was used to determine the concentration of 1,4–dioxane in the batch test, and gas chromatography/mass spectrometry (GC/MS) was used to measure the concentrations via long-term wastewater analysis. Two types of reactors (continuous stirred reactor (CSTR) and plug flow reactor (PFR)) for the treatment of 1,4–dioxane from textile wastewater were operated for more than 120 days under optimized conditions. These used the mixed microbial culture grown in textile wastewater sludge and 1,4–dioxane as the sole carbon source. The results indicated efficient degradation of 1,4–dioxane by the mixed culture in the presence of a competitive inhibitor, with an increase in degradation time from 13.37 h to 55 h. A specific substrate utilization rate of 0.0096 mg 1,4–dioxane/mg MLVSS/h was observed at a hydraulic retention time of 20 h for 20 days of operation in a biomass concentration of 3000 mg/L produced by the mixed microbial culturing process. In the long-term analysis, effluent concentrations of 3 mg/L and <1 mg/L of 1,4–dioxane were observed for CSTR and PFR, respectively. The higher removal efficacy of PFR was due to the production of more MLVSS at 4000 mg/L compared to the outcome of 3000 mg/L in CSTR in a competitive environment.

The presence of inorganic and organic substances may alter the physicochemical properties of iron (Fe) salt precipitates, thereby stabilizing the antimony (Sb) oxyanions in potable water during the chemical treatment process. Therefore, the present study aimed to examine the surface characteristics, size of Fe flocs and coagulation performance of Sb oxyanions under different aqueous matrices. The results showed that surface properties of Fe flocs significantly varies with pH in both Sb(III, V) suspensions, thereby increasing the mobility of Sb(V) ions in alkaline conditions. The negligible change in surface characteristics of Fe flocs was observed in pure water and Sb(III, V) suspension at pH 7. The key role of Van der Waals forces of attraction as well as hydration force in the aggregation of early formed flocs were found, with greater agglomeration capability at higher more ferric chloride dosage. The higher Sb(V) loading decreased the size of Fe flocs and reversed the surface charge of precipitates, resulting in a significant reduction in Sb(V) removal efficiency. The competitive inhibition effect on Sb(III, V) removal was noticed in the presence of phosphate anions, owing to lowering of ζ-potential values towards more negative trajectory. The presence of hydrophobic organic matter (humic acid) significantly altered the surface characteristics of Fe flocs, thereby affecting the coagulation behavior of Sb in water as compared to the hydrophilic (salicylic acid). Overall, the findings of this research may provide a new insight into the variation in physicochemical characteristics of Fe flocs and Sb removal behavior in the presence of inorganic and organic compounds during the drinking water treatment process.

Arsenic (As)-laden wastewater may pose a threat to biodiversity when released into soil and water bodies without treatment. The current study investigated the sorption properties of both As(III, V) oxyanions onto iron hydroxide (FHO) by chemical coagulation. The potential mechanisms were identified using the adsorption models, ζ-potential, X-ray diffraction (XRD) and Fourier Transform Infrared Spectrometry (FT-IR) analysis. The results indicate that the sorption kinetics of pentavalent and trivalent As species closely followed the pseudo-second-order model, and the adsorption rates of both toxicants were remarkably governed by pH as well as the quantity of FHO in suspension. Notably, the FHO formation was directly related to the amount of ferric chloride (FC) coagulant added in the solution. The sorption isotherm results show a better maximum sorption capacity for pentavalent As ions than trivalent species, with the same amount of FHO in the suspensions. The thermodynamic study suggests that the sorption process was spontaneously exothermic with increased randomness. The ζ-potential, FT-IR and XRD analyses confirm that a strong Fe-O bond with As(V) and the closeness of the surface potential of the bonded complex to the point of zero charge (pH_zpc) resulted in the higher adsorption affinity of pentavalent As species than trivalent ions in most aquatic conditions. Moreover, the presence of sulfates, phosphates, and humic and salicylic acid significantly affected the As(III, V) sorption performance by altering the surface properties of Fe precipitates. The combined effect of charge neutralization, complexation, oxidation and multilayer chemisorption was identified as a major removal mechanism. These findings may provide some understanding regarding the fate, transport and adsorption properties onto FHO of As oxyanions in a complex water environment.