Papers by Author: Sang Ho Lee

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: 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: Permeable pavement systems are suitable for a variety of residential, commercial and industrial applications because pavements such as water-retentive or water absorbing pavements are helpful to alleviate urban heat island phenomena by reducing pavement temperature, yet are confined to light duty and infrequent usage. And most of study for the permeable pavement is limited to asphalt pavement. Also, immense quantities of coal combustion by-products are produced every year, but only a small fraction of them are currently utilized, particularly bottom ash which is used in this study. So, in this study, it was intended to develop new permeable and water-absorbing pavement blocks to control pavement temperature and storm water runoff. And mechanical characteristics-compressive strength, porosity etc were carried out. Also, Experiments for thermal environment characteristics and pollution control were carried out in laboratory scale using modified pavement samples. Experimental results indicated that blocks with bottom ash were suited to standard and possessed excellent water-retentive and water purification ability.

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.

Abstract: This study focuses on the development of novel catalysts for simultaneous adsorption and oxidation of micropollutants in aqueous phase. Molecular catalysts were physically immobilized on the surface or pore of amberlite IRA-400 or powdered activated carbon (PAC). Comparison of different combinations of catalysts and adsorbents showed that the Fe(III)-TsPc combined with amberlite had the highest removal efficiency for target compounds. Although the catalyst was immobilized by electrical attraction, no dissociation of catalyst from adsorbent occurred during the tests. Amberlite-supported Fe(III)-TsPc shows more than 98% removal efficiency in 40 min. In homogenous system (suspension of Fe(III)-TsPc in aqueous solution), the oxidation reaction occurred only in acidic conditions (pH ~ 4.5) and the catalyst deactivation rate was fast. On the contrary, the reaction was fast in neutral pH and catalytic deactivation was negligible using the amberlite-supported Fe(III)-TsPc.

Abstract: Enormous use of ground for various purposes in urban areas has led to disappearance of green-planted surfaces. Considering space constraints, planted roofs become one promising and stabilizing choice to improve amenity and reduce the thermal loads on the building’s shell. However, a critical issue for rooftop garden is the release of pollutants in urban runoff. Not only particles but also dissolved pollutants should be removed from building drainage because of their potential impact on water environment. To add functions for the control of pollutant outflow, bauxsite minerals made of red waste from alumina refineries were incorporated in the rooftop garden as a special soil. The minerals have high trapping capacities for trace metals and other soluble species. Moreover, they are easy to integrate with rooftop garden systems. Based on their equilibrium capacity for removing pollutants, an optimum amount of bauxsite minerals is suggested. The characteristics of rainwater runoff and pollutants release were compared for normal and modified rooftop garden in laboratory scale. As expected, the green roof system with the bauxsite layer reduces the concentration of heavy metals. The technique used in this study is also likely to be implemented in other green surfaces in housing complexes.

Abstract: The pollutants in urban stormwater runoff, which lead to non-point source contamination of water environment around cities, are of great concern. Lignocellulose fiber filters have potential to treat urban stormwater runoff because they are cheap and environmentally friendly, and can effectively remove particulate pollutants. However, the fiber filters alone cannot sufficiently remove soluble pollutants including heavy metals, nitrogen compounds, and phosphate. In this study, techniques for chemical modification of lignocellulose fiber filter were implemented to enhance the treatment efficiency of soluble pollutants in urban stormwater runoff. Using these chemically modified fiber filters together with polymer filter media, a new treatment device was examined to control the pollutants in first flush of stormwater. The results indicated that the filters incorporated into the treatment unit allow the control of urban stormwater runoff with minimal cost and high efficiency.

Abstract: The creation of large impervious surface in urban and urbanizing areas commonly leads to multiple impacts on the stream systems including higher peak runoff, reduced infiltration, and increased pollutant loads to streams. Permeable pavements made up of a matrix of concrete blocks with voids offer one solution to the problem of increased stormwater runoff and decreased stream water quality. Experiment results indicate that lower pore size pavement showed a higher runoff reduction rate compared with other pavement. Also, water absorption capability of pavement will drop the surface temperature of pavement. Compared to runoff, the turbidity and phosphorus concentration were lower than 27 [NTU] and 0.5 [mg/L], respectively. It appears that turbidity and hosphorus are concentrated in the pavement void.