Papers by Author: Ree Ho Kim

Abstract: The recent abnormal climate and extreme weather events have frequently given unexpected casualties and damages. In particular, in cases accompanying with heavy rainfall or extremely hot weather in a short period of time, there increases possibility leading financial damage by flooding, heat island phenomenon etc.. One of the main factors that are caused these problems is impermeable area including asphalt and concrete pavement which is increased by urbanization. So, it is interested in porous pavement to solve the environmental problems in Korea. In this study, a block pavement system for sidewalk to control surface temperature of pavement and rainwater runoff was developed. The block pavement system is composed of permeable or water-retentive block and rainwater storage which can harvest and supply rainwater. Surface temperature of permeable block pavement is reduced about 10°C compare with it of impermeable block pavement. Also, rainwater runoff was not happened during the period of rainfall.

Abstract: Recently, increasing of impervious surface as concrete or asphalt pavement with urban development brought increasing of air temperature in city. So many researchers have explored ways to reduce the urban heat island effect and water-retentive or water absorbing pavements have been found to be very effective. In this study, to evaluate the reduction effects of urban heat reduction of water-retentive pavement, surface temperature of pavement, air temperature, wind speed and albedo were measured for 3 years (2008~2010, summer period). And the intensity of sensible heat flux was calculated to estimate a influence on air temperature. Experimental results indicated that water-retentive was effective to reduction of air temperature by decreasing of surface temperature of pavement compare to other pavements. This is showed that water-retentive pavement can be contributed to mitigation of urban heat island.

Abstract: Recently the interest on rainwater harvesting has been increasing and the installation of rainwater harvesting system (RWHS) has been spread. However, little information is available about influences of catchment materials and system configurations on rainwater quality. This study was performed to examine the rainwater quality according to catchment conditions and system configurations in a roof RWHS. The catchment area of the building #39 in Seoul National University, Seoul, South Korea is 3,652 m² and consists of the concrete roof, roof garden and marble terrace. RWHS provides water for toilet flushing through the supply facilities. Water quality was analyzed at each catchment area and facilities of the system during rainfall. The pH, EC, turbidity and SS of runoff from the marble terrace showed higher than those of runoff from roof and roof garden. As influences of runoff from terrace and roof garden, turbidity, SS and EC showed high concentration in early part of the RWHS, but those were lower as passing through the system. Catchment conditions should be considered carefully in design of RWHS. Furthermore, the change of water quality due to the arrangement and configurations of the system should be reflected to evaluate water quality in RWHS.

Abstract: Urban areas consume huge amounts of water and produce much wastewater, which deteriorate the aquatic environment and exhaust the country’s freshwater resources. Water reuse from sewage and wastewater is recognized as a good option for securing water. There are several kinds of processes for improving the water quality. Nutrient removal is very important for water reuse, especially in water supply for outdoor use, to prevent water quality deterioration via eutrophication. Moreover, low cost and easy maintenance should be considered for nutrient removal. In this study, red mud and Bauxsol^TM, a mixed mineral powder made of physicochemically modified red mud residue generated by the Bayer process for alumina refineries, was used for the removal of nitrate and heavy metals in artificial solution, and of phosphate in final effluent, from a sewage treatment plant in Dae-gu, Republic of Korea. Nitrate removal by red mud showed little efficiency while heavy metal removal showed high efficiency. The concentrations of the total phosphate in the effluent and treated water were 1.51 and 0.14 mg/L, respectively, which represent about 90.7% removal. Before and after the treatment, the pH was maintained at a neutral range of 6.5-7.2. Bauxsol^TM also showed a high heavy metal removal capacity. Therefore, Bauxsol^TM in powder and pellet form can be applied individually or mixed with soil to improve water quality for water reuse.

Abstract: Rainwater collection and use is usually considered for runoff from building roofs. Runoff from impervious layers such as roads and pavements, however, has hardly been used as water supply due to its high pollutant concentration. If runoff from roads will be treated and used properly, though, it can be a good water resource and will contribute minimally to a non-point source. In this study, a multistage soil filter system (MSFS) composed of a gravel layer, a functional-media layer with zeolite, a sand layer, and a lawn layer, was developed to treat the runoff from roads and green areas. To evaluate the performance of MSFS, its removal rate of total suspended solids (TSS) was investigated based on the rainfall intensity and the thickness of each layer. The experiment results were compared with the predicted values using the Minitab^TM program. The TSS removal rates ranged from 82 to 96%, with various combinations of experiment conditions. The predicted removal rates well fitted with the removal rates obtained from the experiment. An equation was formulated for predicting the TSS removal rate based on the rainfall intensity and the thickness of each layer. The optimum design factors for MSFS considering its TSS removal rate could be derived based on such equation. Based on the study results, it is expected that MSFS can contribute to securing water resources and to controlling non-point sources.

Abstract: Pollutants in rainwater often cause problems such as non-point source pollutant and deterioration of collected water quality in rainwater harvesting systems. Fiber filter media have been developed to resolve these problems by removing pollutants in rainwater by filtration and ion-exchange mechanisms. They have been also successfully applied for the treatment of first-flush rainwater. However, little information is available on the long-term efficiency and the lifetime of the fiber filter media. In this study, new and used fiber filter media were compared in terms of their filterability and ion-exchange capability. The used filter media samples were taken from a first flush filter in a rainwater harvesting system located in an elementary school in Kyonggi-Do. They were used from 2005 to 2010 without any replacement or cleaning. Water quality parameters of an inflow and outflow in the first flush filter were analyzed to quantify the on-site treatment efficiency of the used media. It was shown that the turbidity was removed by approximately 60% and COD was partly removed. The removal efficiency of particles by the used media was similar to that by the new media. Nevertheless, the removal efficiencies of nitrogen and phosphorous by the used media were substantially reduced when compared with the new media. This suggests that the fiber filter media should be periodically replaced to maintain high removals of nutrients. On the other hand, they can be used for more than 6 years if their primary purpose is to removal particles.

Abstract: First-flush rainwater is of great interest in the research on urban environmental protection and rainwater harvesting. It deteriorates the chemical, physical, and microbiological quality of the collected/stored water as well as the water body in an urban area. Accordingly, effective and economic treatment of first-flush rainwater is highly required. This study aimed to develop a technology for the treatment of first-flush rainwater using new filters made of wood fiber mat, dental cotton, and feldspar. The removal of pollutants in first-flush rainwater with each filter material was evaluated. Experiments were carried out using an artificial rainwater solution made of road dust particles (less than 200 um small) and D.I. water that contained ionic species. The SS concentration of the solution was set between 30 and 150 mg/L. Prior to the experiments, the fiber materials were pretreated with NaOH, FeCl₃, and Al₂O₃. The batch test results indicated that the phosphate removal efficiency of the wood fiber mat was 8.6%; of the dental cotton, 34.7%; and of the feldspar, 1.7%. On the other hand, the heavy metal removal efficiency of the wood fiber mat was 91%; of the dental cotton, 26%; and of the feldspar, 0%. The highest cation exchange capacity of the wood fiber mat that was pretreated with NaOH was attributed to the existence of carboxyl and hydroxyl functional groups in the wooden polymers. Combinations of filter materials were found to have been effective in removing particles in the rainwater. The combination of the wood fiber mat with polyethylene beads resulted in 97-98% particle removal. Other combinations such as DP (dental cotton and polyethylene beads), MF (wood fiber mat and feldspar), and DF (dental cotton and feldspar) showed particle removal rates of 90-95%, 84-96%, and 87-94%, respectively. After 30 minutes, all the combinations had a particle removal rate of over 90%.

Abstract: Urbanization together with increased population and industrialization has increased impermeable areas including asphalt and concrete pavement, leading to potential dangers of environmental disasters in urban area. While environmental pavements have been investigated to mitigate these problems in some countries such as Germany and Japan, little work has been done in Korea. Furthermore, most studies on environmental pavements have focused on permeable asphalt pavements. This study was intended to develop new materials for water-absorbing pavement blocks to control pavement temperature and storm water runoff. Bottom ash, which is a coal combustion by-products, was used as a composing material for these blocks. A polymer with water absorption ratio of 76% was used as a water-retention material for the pavement blocks. The effect of block compositions on mechanical characteristics, compressive strength and porosity were examined as well as thermal characteristics. This water-absorbing polymer is likely to be suitable to be used with the bottom ash blocks. The time required to fill the pores of the blocks with the polymer ranged from 9 to 14 sec, indication that the polymer can be readily applied to the blocks. The final products with optimum compositions satisfied the Korean Standard for blocks and possessed an excellent water-retentive ability. Experiments are ongoing to measure the properties of the blocks for further application as a new construction material.

Abstract: Urban area may be warmer than surrounding regions due to asphalt and concrete for roads, buildings, and other artificial structures. Especially, pavements have become an important contributor to this effect by altering land-cover over significant portions of an urban area. Therefore, researchers have studied ways to reduce the heat island effect such as cooling pavement, porous pavements such as water-retentive or water absorbing pavements. Accordingly, this study aims at the development of water-retention asphalt pavement for urban areas in order to solve problems related to the distortion of water cycle and the heat island phenomena. Experimental results indicated that asphalt pavement using developed water retaining material was effective to decrease its surface temperature compare to other pavements. A correlation between air temperature and surface temperature of the pavement was obtained to estimate the efficiency of the developed pavement materials.

Abstract: The creation of large impervious surface in urban and urbanizing areas have led to significant impacts on local climate, which is commonly known as urban heat island (UHI). In this study, porous pavements made of recycled sludge were examined as a way to control UHI by lowering the surface temperature. A novel image analysis technique was applied to quantify cooling effect of porous pavement materials without and with water. Although the porous pavement itself has smaller heat capacity than the natural soil, supplying water to the pavement decreased its surface temperature. At its highest point, the difference in surface temperatures without and with water was more than 10 oC. The water was supplied either from the top of the pavement or from the bottom of the pavement using the capillary effects. In both cases, pavement temperature was effectively lowered. The cooling effect of pavement by surface coating using epoxy-based polymers was negligible because surface pores were blocked. Field tests also confirmed the cooling potential of porous pavements.