Kyoohong Park

With increasing environmental and economic concerns surrounding food waste, this study assesses the feasibility of three food waste management (FWM) scenarios integrating food waste disposers (FWDs). A social cost–benefit analysis (Social CBA) evaluates their economic and environmental impacts while incorporating a multi-criteria decision-making (MCDM) approach using the analytic hierarchy process (AHP) to consider technical, economic, socio-cultural, and environmental factors. Scenario 1 involves shredding household food waste with FWDs, fully discharging it into the sewer system, treated in the public sewage treatment facilities (PSTFs), and converting it into biogas at sewage sludge and organic waste co-digestion facilities (SSECRFs). Scenario 2 also utilizes FWDs but separates food waste into solid and liquid fractions at communal collection and pre-treatment facilities (CCPF), with the solid portion transported to bio-gasification facilities via pressurized pipelines for transporting waste (PPTW). Scenario 3 follows the same separation process as Scenario 2, but the solid fraction is transported using vehicles instead of PPTW. The results indicate that while all scenarios have costs exceeding their respective benefits (BCR < 1), Scenario 1 demonstrates the best economic outlook (BCR = 0.7359) due to lower collection and transportation costs, though its feasibility depends on a separate sewer system. Sensitivity analysis shows Scenario 1 becomes economically viable (BCR > 1) if the value of convenience in life increases by 50%. This study provides a structured evaluation framework to guide policymakers in optimizing sustainable food waste management strategies. Graphical Abstract

The aim of this study is to present criteria to evaluate the resilience of sewer networks related to ground collapse and urban flooding likely to occur in a specific region and then to determine the ranks of the sewer networks resilience of the selected regions to show the applicability of the analytic hierarchy process (AHP) and the Preference Ranking Organization Method for Enriching Evaluations (PROMETHEE II) method. Fourteen evaluation criteria representing resistance, reliability, redundancy, and response and recovery are presented and their weights are estimated by the AHP by asking questionnaires to 10 sewer experts, leading to the result that the sub-criteria of reliability showed the highest importance, followed by the length ratio of good pipelines (under resistance) and adequacy of the flow capacity of the bypass pipelines (under redundancy). Four separate small blocks of drainage areas (total area of 3.57 km2; sewer length of 50.6 km) in Seoul are chosen for the case study. Using appropriate preference functions and thresholds for each evaluation criterion for PROMETHEE II application yields the resilience rankings of four blocks as Block III > Block IV > Block I > Block II. A sensitivity analysis was also carried out by changing the weights.

Old wastewater treatment plants (WWTPs) must be upgraded to alleviate the problems associated with aging and reduce their total environmental impacts. To enhance the environmental sustainability in retrofitting large and old WWTPs, the decision-making process for selecting the most appropriate alternative is complicated. In this study, evaluation criteria were proposed to select the most sustainable alternatives for mid- to long-term retrofitting plans for a large WWTP with the treatment capacity of 1.6 M m3/d, which is initially built in 1987. An analytic hierarchy process was applied to estimate the weights of each criterion. Fourteen experts evaluated the relative importance of criteria through pairwise comparisons. In order to assess the current retrofitting opinions, three retrofitting alternatives were constructed: A focused on energy sufficiency; B expanded the bioreactor capacity and enhancement of the facility for incinerating the sludge leaving the anaerobic digestor; C emphasized the treatment of contaminants of emerging concerns (CECs). A achieved the highest score (0.623) owing to the environmental benefits associated with recycling and first flush stormwater treatment. C exhibited the second highest score (0.612) as the focus on CECs removal. B corresponded to the lowest sustainability (0.426), with the lowest scores pertaining to effective land use and first flush stormwater treatment.

Generally, when evaluating the resilience of infrastructure, the four properties of resilience (robustness, rapidity, resources, and redundancy, 4Rs) are widely considered. However, there is little research on the resilience assessment of sewer networks. Therefore, to establish a framework to evaluate sewer network resilience under the perspective of urban ground collapse prevention, this study considers the 13 second-level detailed indicators corresponding to the four first-level indicators (4Rs) based on literature reviews and experts' opinions. An analytic hierarchy process (AHP) is used to obtain relative weights of each indicator and a weighted sum method (WSM) is used to evaluate the sewer network resilience index (SRI). The evaluation system is applied to eight small blocks of selected drainage areas in Seoul, South Korea, and the SRI of eight small blocks are computed. This study could help the sewer management department to make decisions and manage sewer network assets that enhance the resilience of the sewer networks.

This paper proposes a novel hybrid method for flood susceptibility mapping using a geographic information system (ArcGIS) and satellite images based on the analytical hierarchy process (AHP). Here, the following nine multisource environmental controlling factors influencing flood susceptibility were considered for relative weight estimation in AHP: elevation, land use, slope, topographic wetness index, curvature, river distance, flow accumulation, drainage density, and rainfall. The weight for each factor was determined from AHP and analyzed to investigate critical regions that are more vulnerable to floods using the overlay weighted sum technique to integrate the nine layers. As a case study, the ArcGIS-based framework was applied in Seoul to obtain a flood susceptibility map, which was categorized into six regions (very high risk, high risk, medium risk, low risk, very low risk, and out of risk). Finally, the flood map was verified using real flood maps from the previous five years to test the model’s effectiveness. The flood map indicated that 40% of the area shows high flood risk and thus requires urgent attention, which was confirmed by the validation results. Planners and regulatory bodies can use flood maps to control and mitigate flood incidents along rivers. Even though the methodology used in this study is simple, it has a high level of accuracy and can be applied for flood mapping in most regions where the required datasets are available. This is the first study to apply high-resolution basic maps (12.5 m) to extract the nine controlling factors using only satellite images and ArcGIS to produce a suitable flood map in Seoul for better management in the near future.

Displacement is crucial for structural health monitoring, although it is very challenging to measure under field conditions. Most existing displacement measurement methods are costly, labor-intensive, and insufficiently accurate for measuring small dynamic displacements. Computer vision (CV)-based methods incorporate optical devices with advanced image processing algorithms to accurately, cost-effectively, and remotely measure structural displacement with easy installation. However, non-target-based CV methods are still limited by insufficient feature points, incorrect feature point detection, occlusion, and drift induced by tracking error accumulation. This paper presents a reference frame-based Deepflow algorithm integrated with masking and signal filtering for non-target-based displacement measurements. The proposed method allows the user to select points of interest for images with a low gradient for displacement tracking and directly calculate displacement without drift accumulated by measurement error. The proposed method is experimentally validated on a cantilevered beam under ambient and occluded test conditions. The accuracy of the proposed method is compared with that of a reference laser displacement sensor for validation. The significant advantage of the proposed method is its flexibility in extracting structural displacement in any region on structures that do not have distinct natural features.