• Clean Technology
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• 제7권2호
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• pp.89-97
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• 2001

The purpose of this study was to find the optimum condition of the high removal efficiency of water pollutant as sewage treatment technology using a filtering bed charged with porous sintering-pellet which was planted with hydrophytes. Experiment was carried out by changing concentration of water pollutants(COD, T-N, T-P), kind of hydrophyte, kinds of filtering material and size, and HRT. The result of removal efficiency was obtained as following: COD removal 73.8~87.1% for input concentration range of 50~450mg/L, T-N removal 61.3~77.3% for input concentration range of 7~124mg/L, T-P removal 89.5~99.1% for input concentration ranger of 3~27mg/L. In a comparative experiment of three kinds of hydrophyte(Iris pseudoacorus, Phragmites communis $T_{RIN}$., Oenanthe javanica Dc.), the best removal efficiency of COD and T-N was gained with Iris pse-udoacorus, and Phragmites communis $T_{RIN}$ showed better result than two hydrophytes for the removal efficiency of T-P. In a comparative experiment of four kinds of filtering-materials, the removal efficiencies were in the order of porous sintering-pellet, gravel, nonused-tire and nonused-concrete. It was found that for the porous sintering-pellet, the smaller its diameter, the better its result. In the filtering bed in which was charged with porous sintering-pellets of 5mm diameter and planted with Iris pseudoacorus, the removal efficiency of COD, T-N and T-P were over 80%, 70% and 90% under the concentration of COD 250mg/L, T-N 70mg/L and T-P 15mg/L for 24hrs treatment. Thus, we concluded that a filtering bed charged with porous sintering-pellet and planted with hydrophytes will be suitable for treatment of sewage water as a pro-natural treatment technology.

• Clean Technology
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• 제23권3호
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• pp.302-307
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• 2017

This study was conducted to evaluate the feasibility of in situ soil flushing for TPH-contaminated soil remediation with column test. The soil texture of the soil was sand and the initial TPH concentration was $9,369mg\; kg^{-1}$. 0.1% Tween-80 was selected as surfactant solution. And the acrylic and the glass syringe columns were used as reactors. In the acrylic column test, 35% of the initial TPH was removed in 1 PV of flushing and approximately 40% in 5 PV and finally 7 PV showed about 60%. The glass column test showed 3 ~ 12% higher removal efficiency than that of acrylic test until 5 PV of flushing. However, there was no difference in TPH removal efficiency when 7 PV of surfactant was finally flushed. Both of alum only and alum+polymer mixed surfactants showed also the best coagulation efficiency in $150mg\;L^{-1}$ of concentraion. When Tween 80 was newly dissolved in 0.1% to the recovered solution after the coagulation treatment, the removal efficiency was increased from 32.0% to 41.0% in comparison to the new 0.1% Tween 80 solution without reuse by coagulation treatment.

• Clean Technology
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• 제24권2호
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• pp.87-98
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• 2018

Phosphorus (P) is an essential and irreplaceable element for all living organisms, and it is widely used as a fertilizer. Unfortunately, it is estimated that phosphate reservoir is depleted within about 100 years. Sewage sludge ash (SSA) is an alternative resource for P recovery because of its high P content. However, SSA cannot be directly used as a fertilizer due to heavy metals in it and low P bioavailability. Thermochemical treatment with Cl donor is known to reduce heavy metal contents and increase P bioavailability of SSA. Literature review on thermochemical technologies of SSA for the reduction of heavy metals and bioavailability enhancement has been carried out to estimate the status of current P recovery technology and to develop strategic future research plan for P recovery. The review showed that $CaCl_2$ and $MgCl_2$ were the most effective Cl donors and reaction temperature (< $1000^{\circ}C$) was the critical operation condition for the reduction. The removal efficiency depends on the species of heavy metals. Thermochemical technology of SSA for P recovery showed the possibility of commercial application in the near future to overcome the coming crisis of human sustainability by P depletion, but it needs cost effectiveness and more ecofriendly process to reduce energy consumption.

• Clean Technology
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• 제12권4호
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• pp.250-258
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• 2006

CFC compounds such as CFC-113 and 1,1,1-TCE, etc. have been used in various industries due to their excellent chemical stability, thermodynamic characteristics, non-inflammability and anti-corrosiveness. However, in oder to protect the earth environment, "the Montreal Protocol on substances that deplete the ozone layer" was adopted in 1989 for prevention of production and utilization of these CFC compounds and alternative cleaning agent have been required in the industry. The objective of this study is to develop non-aqueous cleaning agents that do not require major change of cleaning system, have excellent cleaning efficiency, are favorable to the environment, are harmless to the human body, and are not generated corrosive materials. In this work, non-aqueous cleaning agents have been formulated with glycol ether series and paraffinic hydrocarbon series with siloxane, and their physical properties and cleaning efficiencies were analyzed and compared with those of regulated materials. As a result of physical properties measurement of the formulated cleaning agents, it is expected that they may have good penetration ability into contaminated materials due to their properties with low density and low surface tension. Measurement of flash point and vapor pressure of the cleaning agents will be helpful for evaluation of their safety and working environment. The experimental results of cleaning flux, solder and grease by the formulated cleaning agents show that their cleaning abilities of soils were good and that there were no residues on the substance after cleaning. Therefore, alternative cleaning agents which have equivalent cleaning ability to regulating materials, good penetration ability and low hazard to human body, have been developed in this work.

• Clean Technology
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• 제14권2호
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• pp.123-128
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• 2008

The waste solution, which was discharged from the recovery process of LCD etching solution, consists of 15 wt% nitric acid and 20 wt% acetic acid. In this study, it was conducted to separate acid individually from the mixed acid by vacuum evaporation under -760 mmHg gauge and at $40^{\circ}C$. We have investigated evaporation behavior of acid as a function of temperature. There have been problems that tiny amount of nitric acid were evaporated simultaneously above $33^{\circ}C$. Thus, efforts were conducted to recover acetic acid by vacuum evaporation with adding $H_2O$, waste mixed acid and 20 g/L NaOH for a curb on evaporation of nitric acid. By adding $H_2O$, evaporation of nitric acid was reduced from 7% to 0.78%. However, it was reduced from 7% to 0.25% by adding mixed acid. In view of the results achieved so far, we may expect to separate the etching solution individually by controlling vacuum conditions.

• Clean Technology
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• 제25권2호
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• pp.153-160
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• 2019

As air pollution becomes more serious due to the increased number of diesel vessel operations, ship regulations on harmful emissions strengthen. Therefore, the development of a diesel exhaust after-treatment system for ships is required, and the higher the flow uniformity of the exhaust treatment system, the higher the treatment efficiency. With the computer software ANSYS Fluent, pressure drop and flow uniformity were used in this study to simulate flow rate with and without a baffle in both a Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) system. The system pressure drop was found to be 38 to 40 mbar in the existing system condition, and the flow uniformity was approximately 84 to 92% at the inlet and outlet of the DOC. When the baffle was installed inside the system, the pressure increased and the flow uniformity was lowered due to an increase in flow rate. When the exhaust gas flow was reduced by 50% from $7,548kg\;h^{-1}$ to $3,772kg\;h^{-1}$, the flow uniformity at the inlet and outlet of the DOC increased by approximately 1 to 3% due to the low flow rate. In the case of DPF, the flow uniformity of exhaust gas was 98 to 99% because the uneven flow proceeded after uniformly flowing from the DOC.

• Clean Technology
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• 제28권2호
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• pp.193-200
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• 2022

The term environmental, social and governance (ESG) was first used in the 2003 United Nations Environmental Programme Finance Initiative (UNEP FI). Among the three areas of ESG, environment refers to the impact of companies on the environment. Environmental factors address climate change policies and attempts to reduce emissions, waste and natural resource consumption. Social factors refer to the direction in which a company can improve the social impact of stakeholder includes employees, customers, communities, and governments involved in direct or indirect interaction with the organization itself and the company. Governance factors refer to stakeholders who make major decisions, the composition of the board of directors, their diversity and independence, and the internal policies that set limits and expectations for decision-making. Research related to ESG management is part of corporate social responsibility, sustainability, corporate or financial performance, and social responsibility investment. Through case studies and data-based empirical studies, it was confirmed that ESG management companies had positive results for most of the ESG related fields. Through literature analysis of domestic and international ESG history, introduction background, and management performance, this paper presents theoretical, practical implications by confirming that ESG's introduction and operation strategies are strong competitive strategies that directly affect corporate growth by creating attractive factors.

• Clean Technology
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• 제29권3호
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• pp.227-234
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• 2023

Recently, local governments have recognized river zones as leisure spaces and local festival venues, and hence, the pressure for developing these zones has increased significantly. However, given the unique functionalities of river zones and the time and costs associated with maintaining facilities and restoring damaged areas, a development plan must be selected carefully. To preserve river zones and to facilitate nature-friendly space utilization, this study focused on improving environmental impact assessment (EIA), which is an institutional implementation procedure for project plans. This study prepared a draft guide for EIA by providing an overview of the research background and survey outcomes, including the status of laws and regulations on river zones, development plans, and opinions on EIA. The results showed that because strategic EIA of basic river plans is important for district designation of river zones and the scope and direction of space utilization, it is necessary to establish a more meticulous business plan before reviewing and evaluating the mini EIA linked to the future implementation of a plan to derive a reasonable assessment. Additionally, this study provides a draft guide for EIA to evaluate the suitability of water-friendly facility construction plans considering the location characteristics and to reflect the factors that can reduce the environmental impacts during the mini EIA stage. In the future, we expect that the results of this study will serve as a foundation for establishing instructions and guides for the development of nature-friendly and water-friendly facilities in river zones during the establishment of plans.

• Korean Chemical Engineering Research
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• 제61권1호
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• pp.8-18
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• 2023

Increasing of energy demand due to the rapid growth of global population and the development of world economy has inevitably resulted in the continuously increase of fossil fuel usage in the world. However, highly dependence on fossil fuels has necessarily brought about critical environmental issues and challenges such as severe air pollutions and rapid global warming. In order to settle these environmental and energy problems, clean energy generations in the conventional combustion processes have widely adapted in the world. In particular, novel thermochemical conversion processes such as pyrolysis and gasification have rapidly been applied for generating clean energy. Fluidized bed technologies having advantages such as various fuel use, easy continuous operation, high heat and material transfer, isothermal operation, and lower operation temperature are widely adopted and used because they are suitable for thermochemical energy conversion. The latest research trends and important findings in the thermo-chemical conversion process with fluidized bed technologies are summarized in this review. Also, the need for research such as layered materials and substances to reduce fine dust (biomass, natural resource waste, etc.) was suggested. Through this, it is intended to increase interest and understanding in fluidized bed technology and to present directions for solving future challenges in fluidized bed process technology development.

• Clean Technology
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• 제29권2호
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• pp.151-159
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• 2023

The realization of carbon neutrality requires cooperation from various stakeholders and the utilization of a governance system. The criteria for participating members are crucial for the successful operation of governance, and it is especially necessary for experts who can provide scientific advice for policy implementation to share a framework for successful consensus. In this study, governance model theory and model structure, governance common success factors by case, and the application of governance cases in the climate and environmental sector of Seoul, were investigated and analyzed to derive common success factors in order to present the activity standards of the science and technology experts participating in governance. The study of the model theory suggested that the model structure is commonly composed of a basic condition-process-result structure, and it was confirmed that common success factors can be derived at the process stage which is the activity period of members. Through the case study of common success factors, overlapping factors were found to be reliability, accountability, transparency, networks, and related factors. The validity of the common success factors was verified using the analysis results of satisfaction survey data from Seoul Governance Committee participants. The results confirmed that reliability was the most valuable factor followed by networks, transparency, and responsibility, and it was found that the related factors were appropriately derived. The findings of this study are expected to be used as an activity factor for science and technology experts to increase the acceptability and effectiveness of carbon-neutral policies in the future.