PURPOSES : Recently, air pollution due to fine particulate matter has been increasing in Korea. Nitrogen oxides (NOx) are particulate matter precursors significantly contributing to air pollution. Increasing efforts have been dedicated to NOx removal from air, since it is particularly harmful. Application of titanium dioxide (TiO2) for concrete road structures is a suitable alternative to remove NOx. As the photocatalytic reaction of TiO2 is the mechanism that eliminates NOx, the ultraviolet rays in sunlight and TiO2 in existing concrete structures need to be contacted for the reaction process. For the application of vertical concrete road structures such as retaining walls, side ditches, and barriers, a pressurized TiO2 fixation method has been developed considering the pressure and pressurization time. In this study, longterm serviceability and repeatability were investigated on concrete specimens applying the dynamic pressurized TiO2 fixation method. Additionally, the environmental hazards of nitrate adsorbed on TiO2 particles were evaluated. METHODS : Concrete specimens to simulate roadside vertical concrete structures were manufactured and used to evaluate the long-term serviceability and repeatability of the dynamic pressurized TiO2 fixation method. The NOx removal efficiency was measured using NOx evaluation equipment based on ISO 22197-1. In addition, the nitrate concentration was measured using a comprehensive water quality analyzer for evaluating environmental hazards. RESULTS : As the experiment to evaluate the NOx removal efficiency of the dynamic pressurized TiO2 fixation method progressed from one to seven cycles, the nitrate concentration increased from 2.35 mg/L to 3.06 mg/L, and the NOx removal efficiency decreased from 53% to 25%. After seven cycles of NOx removal efficiency evaluation, the average nitrate concentration was 3.06 mg/L. The nitrate concentration collected immediately after the NOx removal efficiency test for each cycle was in the range of 2.51 to 2.57 mg/L. By contrast, it was confirmed that the nitrate concentration was lowered to approximately 2.1 mg/L when the surface was washed with water. CONCLUSIONS : The NOx removal efficiency was maintained at over 25% even after seven cycles of NOx removal efficiency evaluation, securing long-term serviceability. In addition, the harmful effects on the environment and human health are insignificant, since the nitrate concentration was less than 10 mg/L, in accordance with domestic and foreign standards. Practical applicability of the pressurized TiO2 fixation method was established by evaluating the long-term serviceability, repeatability, and environmental hazards.

The binary oxide adsorbent using Fe and Mn (Fe-Mn) has been prepared by precipitation method to enhance the removal of phosphate. Different amounts of chitosan, a natural organic polymer, were used during preparation of Fe-Mn as a stabilizer to protect an aggregation of Fe-Mn particles. The optimal amount of chitosan has been determined considering the separation of the Fe-Mn particles by gravity from solution and highest removal efficiency of phosphate (Fe-Mn10). The application of Fe-Mn10 increased removal efficiency at least 15% compared to bare Fe-Mn. According to the Langmuir isotherm model, the maximum uptake (qm) and affinity coefficient (b) were calculated to be 184 and 240 mg/g, and 4.28 and 7.30 L/mg for Fe-Mn and Fe-Mn10, respectively, indicating 30% and 70% increase. The effect of pH showed that the removal efficiency of phosphate was decrease with increase of pH regardless of type of adsorbent. The enhanced removal efficiency for Fe-Mn10 was maintained in entire range of pH. In the kinetics, both adsorbents obtained 70% removal efficiency within 5 min and 90% removal efficiency was achieved at 1 h. Pseudo second order (PSO) kinetic model showed higher correlation of determination (R2), suggesting chemisorption was the primary phosphate adsorption for both Fe-Mn and Fe-Mn10.

PURPOSES : The increase in particulate matter due to increased air pollutant emissions has become a significant social issue. According to the Ministry of Environment, air pollutants emitted from large-scale businesses in 2022 increased by 12.2% compared to the previous year, indicating that air pollution is accelerating owing to excessive industrialization. In this study, TiO2, which is used to reduce airborne particulate, was used. The TiO2 coating fixation and dynamic pressure coating-type TiO2 fixation methods were used to solve the material peeling phenomenon caused by gravity, which is a limitation when the TiO2 penetration method is applied to a vertical concrete structure along the road. The long-term durability and performance were analyzed through environmental resistance and NOx removal efficiency evaluation experiments. These analyses were then assessed by comparing the NOx removal efficiency with the dynamic pressure permeationtype TiO2 fixation method used in previous studies. METHODS : To evaluate the long-term durability and performance of the TiO2 coating fixation method and dynamic pressure coating TiO2 fixation method for vertical concrete structures, specimens were manufactured based on roadside vertical concrete structures. Environmental resistance tests such as the surface peeling resistance test (ASTM C 672) and freeze-thaw resistance test (KS F 2456) were conducted to evaluate the long-term durability. To evaluate the long-term performance, the NOx removal efficiency of TiO2 concrete owing to road surface deterioration during the environmental resistance test was evaluated using the NOx removal efficiency evaluation equipment based on the ISO 22197-1 standard. This evaluation was compared and analyzed using the dynamic pressure infiltration TiO2 fixation method. RESULTS : The long-term durability of the TiO2 coating fixation and dynamic pressure coating TiO2 fixation methods were evaluated using environmental resistance tests. During the surface peeling resistance test, the TiO2 material degraded and partially detached from the concrete. However, the NOx removal efficiency was ensured by the non-deteriorated and fixed TiO2 material. The long-term performance was confirmed through a freeze-thaw resistance test to evaluate the NOx removal efficiency after 300 cycles of surface deterioration. The results showed that when the TiO2 coating fixation and dynamic pressure infiltration TiO2 fixation methods were applied to vertical concrete structures, the durability of the structure was not compromised. In comparison to the dynamic pressure infiltration TiO2 fixation method, the NOx removal efficiency observed during the surface peeling resistance test was lower, while the freeze-thaw test exhibited notably higher removal efficiency. CONCLUSIONS : To solve the material peeling phenomenon caused by gravity, the long-term durability and performance were evaluated by applying the TiO2 coating fixation and dynamic pressurized coating TiO2 fixation methods to vertical concrete specimens. Long-term durability was confirmed through environmental resistance tests, and long-term utility was secured by measuring the NOx removal efficiency according to surface degradation. These findings show that implementing the TiO2 coating fixation method and dynamic pressure coating TiO2 fixation methods on-site effectively reduce NOx.

This study focused on using indirect filtration through riverbeds to produce high-quality drinking water. Data on water quality from a water intake facility(capacity 10,000 m3/day) and nearby rivers were collected over a three-year period. The average intake facility specifications were found to be a specific surface area of 58 balls/m2, a mean particle size of 24 mm, an inflow velocity of 2.2 cm/sec, and a burial depth of 5 m. The water quality improvement rate was assessed as grade Ia, surpassing the adjacent river’s water quality. Correlation analysis showed a weak correlation between opening ratio, Suspended Solid (SS), and Biochemical Oxygen Demand (BOD) compared to total coliforms and fecal coliforms. The correlation coefficient R value of SS was -0.614, BOD was –0.588, total coliforms -0.870, and fecal coliforms -0.958. The R value shows a negative value, which showed that the larger the opening rate, the lower the removal rate of water pollutants. The correlation coefficient R values according to the depth of burial were found to be BOD 0.914, SS-0.124, total coliforms 1.000, and fecal coliforms 0.866. The deeper the burial depth, the higher the removal rate of BOD and microbial groups.

Daechung Reservoir has been suffering from severe cyanobacterial blooming periodically due to the water pollutants from the watershed, especially nutrients from nonpoint sources. As a countermeasure, an artificial wetland was constructed to mitigate the pollutant load from the watershed by utilizing the vegetation. We investigated the water quality of the influent and outflow of the wetland during years 2014~2020 to evaluate the performance of pollutant removal through the wetland. Major pollutants (e.g. BOD, COD, SS, T-N, and T-P) were largely reduced during the retention in the wetland while nutrients removal was more efficient than that of organic matters. Pollutant removal efficiency for different inflow concentrations was also investigated to estimate the wetland’s capability as a way of managing nonpoint sources. The efficiency of water treatment was significantly higher when inflow concentrations were above 75th percentile for all pollutant, implying the wetland can be applied to the pre-treatment of high pollution load including initial rainfall runoff. Furthermore, the yearly variation of removal efficiency for seven years was analyzed to better understand long-term trends in water treatment of the wetland. The annual treatment efficiency of T-P was very high in the early stages of vegetation growth with high concentration of inflow water. However, it was confirmed that the concentration of inflow water decreased, vegetation stabilized, and the treatment efficiency gradually decreased as the soil was saturated. The findings of the study suggest that artificial wetlands can be an effective method for controlling harmful algal blooms by alleviating pollutant load from the tributaries of Daechung Reservoir.

PURPOSES : Advancements in science and technology caused by industrialization have led to an increase in particulate matter emissions and, consequently, severity of air pollution. Nitrogen oxide (NOx), which accounts for 58% of road transport pollutants, adversely affects both human health and the environment. A test-bed was constructed to determine NOx removal efficiency at the roadside. TiO2, a material used to reduce particulate matter, was used to remove NOx. It was applied to a vertical concrete structure using the dynamic pressurized penetration TiO2 fixation method, which can be easily applied to vertical concrete structures. This study was conducted to evaluate the NOx removal efficiency of the dynamic pressurized-penetration TiO2 fixation method in a test-bed under real roadside conditions. METHODS : A test-bed was constructed in order to determine the NOx removal efficiency using the dynamic pressurized penetration TiO2 fixation method on the roadside. The dynamic pressurized-penetration TiO2 fixation method was applied by installing a vertical concrete structure. NOx was injected into the test-bed using an exhaust gas generator. By installing a shading screen, the photocatalytic reaction of TiO2 was suppressed to a maximum concentration of 1000 ppb along the roadside. The removal efficiency was evaluated by measuring NOx concentrations. In addition, illuminance was measured using an illuminance meter. RESULTS : From the results of the analysis of the NOx removal efficiency in the test-bed which the dynamic pressurized type TiO2 fixation method was applied to, an average removal efficiency ranging from 18% to 40% was achieved, depending on the illuminance. Similarly, according to the results of the evaluation of the NO removal efficiency, an average of removal efficiency ranging from 20% to 62% was achieved. Thus, the NOx removal efficiency increased when the illuminance was high. CONCLUSIONS : From the results of the experiment conducted, the efficiency of NOx removal per unit volume was obtained according to the illuminance of TiO2 concrete along an actual road. Field applicability of the dynamic pressurized-penetration-type TiO2 fixation method to vertical concrete structures along roads was confirmed.

Most of the white fumes from the tenter process of a textile plant in an industrial complex are generated by water vapor and oil mist. While general water vapor disappears when the humidity is lowered, the white fume generated in the tenter process does not disappear and is continuously maintained, resulting in environmental problems and complaints. Efforts to reduce white fume are being conducted, but it is vitally important to develop a performance index that quantitatively calculates and deduces the degree by which white fume has been reduced, so that a tangible and visible result can be obtained in the performance evaluation of prevention facilities. In this study, the removal efficiency or performance of a general wet scrubber and a wet electrostatic precipitator (electrical fume collector, EFC) installed in the actual textile tenter process was analyzed by the light scattering method that can measure the concentration of particles up to a high level. The white fume removal efficiency of the EFC was 92%, much higher than the 17% removal efficiency of the general scrubber. In addition, the EFC was more effective in removing toluene, 1,1'- [oxybis(methylene)]bis- Benzene, and benzothiazole, which are the major substances generated from the textile tenter process, as well as complex odors. From these results, it was found that the light scattering method is one of the useful tools to evaluate the performance of white fume prevention facilities in the industrial field in terms of satisfying the urgent need for measurement and the ability to obtain a clear and precise result on site. This approach is meaningful in that real-time quantification is applicable more intuitively than the gravimetric method in assessing the fume removal performance as it can be observed with the naked eye.

PURPOSES : Recently, air pollution caused by particulate matter has been worsening. Among the substances generating particulate matter, NOx is the main precursor of particulate matter and is widely distributed in areas with a high volume of traffic. TiO2 has been used as a material for removing NOx through a chemical reaction as a photocatalyst. In this context, the reduction of NOx through TiO2 concrete is proposed. However, the research on the surface deterioration on the performance of TiO2 concrete is not documented yet. Therefore, the objective of this study was to evaluate the long-term durability and NOx removal efficiency of TiO2 concrete by considering the concrete surface deterioration. METHODS : Freezing–thawing resistance test (KS F 2456) and scaling test (ASTM C 672) were performed to investigate the variation in the TiO2 penetration distribution and NOx removal efficiency of TiO2 concrete corresponding to surface deterioration. The long-term durability of TiO2 concrete was evaluated through an environmental resistance test and changes in TiO2 penetration depth and distribution characteristics. In addition, the NOx removal efficiency of TiO2 concrete was evaluated as surface deterioration occurs. RESULTS : As a result of the freeze–thawing resistance test, a relative dynamic elastic modulus of more than 80 % was detected. In addition, a TiO2 penetration depth of 0.3 mm, NOx removal efficiency of 11.2 %, and a 30 % of TiO2 surface prediction mass ratio were achieved after 300 cycles. As a result of visual observation of the scaling test, “0, no scaling” was secured. After 50 cycles of scaling test, the TiO2 penetration depth, NOx removal efficiency, and TiO2 surface prediction mass ratio were 0.3 mm, 36.3 %, and 63 %, respectively. Through the results of the environmental resistance test, the excellent long-term durability and NOx removal efficiency of TiO2 concrete were confirmed. CONCLUSIONS : As a result of the experiment, long-term durability and NOx removal efficiency of TiO2 concrete were secured. The application of TiO2 concrete can be a good alternative with long-term performance and durability.

The adsorption process using GAC is one of the most secured methods to remove of phosphate from solution. This study was conducted by impregnating Cu(II) to GAC(GAC-Cu) to enhance phosphate adsorption for GAC. In the preparation of GAC-Cu, increasing the concentration of Cu(II) increased the phosphate uptake, confirming the effect of Cu(II) on phosphate uptake. A pH experiment was conducted at pH 4-8 to investigate the effect of the solution pH. Decrease of phosphate removal efficiency was found with increase of pH for both adsorbents, but the reduction rate of GAC-Cu slowed, indicating electrostatic interaction and coordinating bonding were simultaneously involved in phosphate removal. The adsorption was analyzed by Langmuir and Freundlich isotherm to determine the maximum phosphate uptake(qm) and adsorption mechanism. According to correlation of determination(R2), Freundlich isotherm model showed a better fit than Langmuir isotherm model. Based on the negative values of qm, Langmuir adsorption constant(b), and the value of 1/n, phosphate adsorption was shown to be unfavorable and favorable for GAC and GAC-Cu, respectively. The attempt of the linearization of each isotherm obtained very poor R2. Batch kinetic tests verified that ~30% and ~90 phosphate adsorptions were completed within 1 h and 24 h, respectively. Pseudo second order(PSO) model showed more suitable than pseudo first order(PFO) because of higher R2. Regardless of type of kinetic model, GAC-Cu obtained higher constant of reaction(K) than GAC.

PURPOSES : NOx is a particle matter precursor that is harmful to humans. Various methods of removing NOx from the air have been developed. TiO2 and activated carbon are particularly useful materials for removing NOx, and the method is known as particulate matter precursor reduction. The removal of NOx using TiO2 requires sunlight for the photocatalytic reaction, whereas activated carbon absorbs NOx particles into its pores after contact with the atmosphere. The purpose of this study is to evaluate the NOx removal efficiency of TiO2 and activated carbon applied to concrete surfaces using the penetration method. METHODS : Surface penetration agents, such as silane-siloxane and silicate, were used. Photocatalyst TiO2 and adsorbent activated carbons were selected as the materials for NOx removal. TiO2 used in this study was formed by crystal structures of anatase and rutile, and plant-type and coal-type materials were used for the activated carbon. Each surface penetration agent was mixed with each particulate matter sealer at a concentration ratio of 8:2, and the mixtures were sprayed onto the surface. The NOx removal efficiency was evaluated using NOx removal efficiency equipment fabricated in compliance with the ISO 22197-1 standard. RESULTS : Anatase TiO2 showed a maximum NOx removal efficiency of 48% when 500 g/m² was applied. However, 500 g/m² of rutile TiO2 showed a NOx removal efficiency of up to 10%. When 700 g/m² of coal-based activated carbon and plant-based activated carbon was used, NOx removal efficiencies of up to 11% and 14%, respectively, were obtained. CONCLUSIONS : Rutile TiO2, a coal-based activated carbon, and plant-based activated carbon have lower NOx removal efficiencies than anatase TiO2. A lower amount of anatase TiO2 (500 g/m²), compared to the other spraying volumes, yielded the most significant NOx removal efficiency under optimal conditions. Therefore, it is recommended that 500 g/m² of anatase TiO2 should be sprayed onto concrete structures to improve the economic and long-term performance of these structures.

우리나라 영해 밖 EEZ내 침몰한 외국선박의 잔존유 제거작업이 국내 최초로 2019년 5월 이행되었다. 우리 관할수역이지만 기 름 제거작업은 홍콩 선주 측 P&I 보험사와 계약을 맺은 일본업체가 수행하고 국내 업무 대행은 S법무법인과 J해운이 맡았다. 해당 선박은 총톤수 4,433톤의 일반화물선으로 2015년 4월 제주도 남동방 약 48마일 해상에서 침몰하였다. 침몰 후 기름 제거 작업 개시까지 만 4년이 넘는 기간이 소요되었지만 잔존유 제거작업은 단 22일 만에 끝났다. 대형선박이고 잔존유량이 많았던 Erika호나 Prestige호 등 외국사례 등과 비교하면 기름 제거 결정까지 긴 시간이 걸렸다. 그 원인을 파악하고자 해당선박 침몰 시부터 잔존유 제거까지 생산된 모든 문서 93건을 확보하여 분석하였다. 그 결과, 가장 우선적으로 이루어져야 할 행정적 절차 즉, 잔존유 제거에 대한 관할 행정기관의 의사결정이 지연 되었음이 확인되었다. 관할청에서 긴 시간 동안 많은 검토를 하였지만 최종 결과는 초기방안과 별로 달라지지 않았다. 4년의 시간이 흐르는 동안 선내 잔존유 상당량이 유출되고 화물 전체가 유실되었다. 의사결정 지연에 영향을 미친 원인으로 관할청의 사고 관련 기본 사실 이나 자료 확인 소홀부터 법률적, 기술적, 환경적 그리고 인적 측면 등 여러 문제점이 식별되었다. 연구 마지막에 식별된 문제점에 대한 개선안, 즉 의사결정 효율화 방안을 제시한다. 이 연구는 국내 최초 EEZ내 외국 침몰선박 잔존유 제거 사례를 고찰하여 향후 유사한 작업 계획이나 정책수립 등에 도움이 될 것으로 기대한다.

The purpose of this study was to analyze water treatment characteristics, including the efficiency of removing algae from water purification plants, by installing a demonstration facility for decontamination of algae, including natural algae remover injection equipment, in the water purification plant. Jar-test showed that the optimum injection of natural decontaminant was 20 mg/L. Of the water contaminant treatment efficiency of the intake and water purification plants, Chl-a averaged 74.0% elimination efficiency from 5.0 mg/m3 to 1.3 mg/m3 and the maximum treatment efficiency was 91.5% removal efficiency when the inflow concentration of Chl-a was 11.8 mg/m3. In addition, 51.2% and 47.1% of the taste and odor indicator items, geosmin and 2-MIB, resulted from the overgrowth and decaying of algae, respectively, to identify toxic substances and odor reduction effects. In addition, elimination efficiencies of SS and Turbidity materials were higher than 70.0%. In the injection of natural algae remover, no effects such as sudden changes in water quality due to secondary reactions were found, and appropriate levels were maintained under water treatment conditions.

This study was performed to assess particulate matter removal efficiency of domestic air cleaner products in a field condition. The assessment also included air cleaners with different air removal mechanisms. The particulate matter (PM2.5) removal test with a different air removal mechanism using air cleaners showed that the electrostatic precipitation technique showed better performance compared with HEPA filters and other types of systems. Its removal efficiency was almost 95% in one of our operation times in the given test condition. It was assumed that not only the type of removal system but also the individual design, supply and exhaust system, and the automatically controlled air volume are involved in the removal efficiency. With respect to the area of application, tests with air cleaners for 40 m2, 60 m2, and 80 m2 areas revealed that particulate matter removal efficiency increased with the air cleaner that had a broad area of application. However, particulate matter removal efficiency by air cleaners did not correspondingly increase with the increase of the area of application. Moreover, the installation location did not influence particulate matter removal efficiency. Our results are expected to be used as the basic information for indoor air quality improvement and prediction using air cleaners.