Tschungil Kim

Quantitative analysis on the urban flood mitigation effect by the extensive green roof system

Extensive green-roof systems are expected to have a synergetic effect in mitigating urban runoff, decreasing temperature and supplying water to a building. Mitigation of runoff through rainwater retention requires the effective design of a green-roof catchment. This study identified how to improve building runoff mitigation through quantitative analysis of an extensive green-roof system. Quantitative analysis of green-roof runoff characteristics indicated that the extensive green roof has a high water-retaining capacity response to rainfall of less than 20 mm/h. As the rainfall intensity increased, the water-retaining capacity decreased. The catchment efficiency of an extensive green roof ranged from 0.44 to 0.52, indicating reduced runoff comparing with efficiency of 0.9 for a concrete roof. Therefore, extensive green roofs are an effective storm water best-management practice and the proposed parameters can be applied to an algorithm for rainwater-harvesting tank design.

Micro and nanobubble technologies as a new horizon for water-treatment techniques: A review

This review article organizes the studies conducted on the areas of microbubbles and nanobubbles with a special emphasis on water treatment. The basic definitions of bubble types and their size ranges are also presented based on the explanations of different researchers. The characterization parameters with state-of-the-art measuring and analysis techniques of microbubble and nanobubble technologies are summarized. Some major applications of these technologies in water-treatment processes are reviewed and briefly discussed. Based on the reviews, various potential areas for research and bubble application gaps in water and wastewater treatment technologies are identified for further study. The article is prepared in such a way that it provides a step-by-step acquaintance to the subject matter with the objective of focusing on the application of microbubbles and nanobubbles in water-treatment technology.

Optimization of fertilization characteristics of urine by addition of Nitrosomonas europaea bio-seed.

BACKGROUND Because of the high concentration of nutrients in human urine, its utilization as an organic fertilizer has been notable throughout history. However, the nitrogen compounds in urine are not stable. Therefore, to convert urine into a suitable fertilizer, it is important to stabilize and adjust unstable nitrogen compounds such as ammonia. Because nitrification can influence the nitrogen profile, the use of nitrifying microorganisms can be useful for stabilizing the nitrogen profile of urine. This study investigated the changes in nitrogen compounds in pure urine and examined the effect of adding Nitrosomonas europaea bio-seed solution on these changes. RESULTS It was found that the addition of bio-seed could reduce nitrogen loss as well as the time required to stabilize the nitrogen profile. Furthermore, the optimum concentration of bio-seed (6 × 10(5) N. europaea cells L(-1) ) that not only leads to the least nutrient loss but also results in an adequate nitrate/ammonium ratio and regulates the amount of nitrate produced, thereby preventing over-fertilization, was determined. CONCLUSION At this concentration, no dilution or dewatering is required, thus minimizing water and energy consumption. Usage of the optimum of concentration of bio-seed will also eliminate the need for inorganic chemical additives.

The Waterless Portable Private Toilet: An Innovative Sanitation Solution in Disaster Zones.

Catastrophes can occur without warning and inevitably cause short-term and long-term problems. In disaster zones, having an action plan to alleviate difficulties can reduce or prevent many long-lasting complications. One of the most critical and urgent issues is sanitation. Water, energy, personnel, transportation, and the allocation of resources in disaster areas tend to become very limited during emergencies. Sanitation systems suffer in the process, potentially leading to crises due to unsafe and unhygienic surroundings. This article explores the problems of current sanitation practices in disaster areas and identifies the essential characteristics of sustainable sanitation systems. This study also presents a plan for an innovative and sustainable sanitation system using a waterless, portable, private toilet, in addition to a procedure for collecting and disposing waste. The system is agronomic, is socially acceptable, prevents contact with human waste, and can be used for individuals or families. Environmental pollution and social problems (such as sexual harassment) can be reduced both during and after restoration.

Determinant Factor Analysis for the Spread of Water Reuse

The purpose of this study was to survey Suwon citizens over the age of 20 in order to provide basic data on the extent of coverage of the city’s water reclamation system and to set guidelines for a policy on water reuse. The survey used a questionnaire with two fields, rainwater use and wastewater recycling, for analyzing factors that influenced water reuse. A factor analysis of 19 questionnaires gave a Cronbachs alpha coefficient greater than 0.4. Factors that influenced rainwater use were environmental protection, water charges, and the risk of climate change. Of the total explanatory power, the share of rainwater use and environmental protection was 39.7% and 28.1% respectively. Environmental protection (explanatory power 24.2%) had an effect on the explanatory power of wastewater reuse. When factors influencing wastewater recycling, like cost of recycling, water management policy, climate change, and suspension of tap water supply were included, the explanatory power of each of these factors went up by 4.3%, 2.8%, 3.3%, and 1.1%, respectively. For more effective wastewater recycling, a water management policy that factors in the above is required, along with a campaign to educate citizens on water management and environment conservation. Additionally, it may be necessary to improve the reliability and the quality of water supply.

Development of novel oil washing process using bubble potential energy.

Oil contaminants attached to soils were separated using the bubble energies from the bursting and coalescence. The separation efficiency increased when the rotary kilns were combined. Wastewater containing separated oil contaminants was treated with the buoyant energy of bubbles and with positively charged bubbles. The water quality of the treated wastewater was good enough for the latter to be used as recycled water for bubble generation. The separation and treatment efficiencies of the novel oil washing process developed in this study was found to be similar to that of the existing oil washing process operated under high-temperature and high-pressure conditions and with dosage of chemicals.

The effect of material and flushing water type on urine scale formation.

One of the important challenges with current sanitation practices is pipe blockage in urinals caused by urine scale formation. Urinal material and flushing water type are the two most important factors affecting scale formation. This paper examines the scale formation process on different materials which are commonly used in urinal manufacturing and exposed to different urine-based aqua cultures. This study shows that urine scale formation is the greatest for carbon steel material, and the least for PVC. Additionally, material exposure to the urine-rainwater mixture resulted in the smallest amount of scale formation. Based on these results, two new methods for improving sanitation practices are proposed: (1) using PVC as production material for urinals and pipelines; and (2) using rainwater for flushing systems.

Adaptive impedance control of a cleaning unit for a novel wall-climbing mobile robotic platform (ROPE RIDE)

This paper presents a new position-based adaptive impedance control (PAIC) scheme of a cleaning unit for a novel wall-climbing mobile robotic platform (ROPE RIDE), which can climb up a high-rise building with the help of a rope ascender and two propellers thrusters. To guarantee the cleaning performance of proposed ROPE RIDE, it is crucial to maintain a constant contact force between a cleaning unit and various types of walls. Compared to existing impedance control methods, the proposed PAIC method is not only simple to implement but also robust against external disturbances such as the varying wall positions and materials. Therefore, it can promise the zero steady state force tracking error even for a step-type wall. The extensive experiments in addition to simulations are performed to validate the cleaning performance as well as the stability of proposed adaptive impedance control scheme.

Design parameter estimations for adjustable bubble size in bubble generating system

In this study, we developed a customized low cost and low energy bubble generator that can control bubble size. Hence, it can be used not only in the water treatment process but also in various other processes. This device was able to generate bubbles with a very simple system using only a general pump and a mixing chamber. Increasing the number of partition walls in the mixing chamber reduced the bubble size. Furthermore, bubbles of a few hundred nanometers were produced by the shear stress caused by increasing the thickness of the partition wall. Although the generated sub-micron bubbles were too small for their exact size to be measured using an image analysis and particle counting method, it was possible to confirm their existence indirectly through the coalescence arising from ultrasonic irradiation. The device used in this research is simple and allows bubble size to be adjusted easily by controlling the design of the mixing chamber. Therefore, it can be applied to a water treatment process, as well as a variety of other processes.

Policies and Strategies to Overcome Barriers to Rainwater Harvesting for Urban Use in Ethiopia

The Ethiopian government has been working on rainwater harvesting (RWH) for more than three decades. Despite its efforts, the results are not as expected. Different barriers have posed challenges to promoting RWH in Ethiopia. This study was done to identify the main problems and obstacles, and reflect on potential solutions. As a result, absence of clear policy definitions, lack of sustainably implemented projects, poor societal perceptions of RWH, local professionals lacking proper knowledge, and initial investment costs are found to be major causes of poor outcomes. Considering the site-specific nature of water issues, the authors propose various management strategies such as policy-oriented promotion, formulation of design guidelines, proactive planning, collaborative research, and integration of RWH with cost covering practices.