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AbstractA hybrid BMP (best management practice) is a technology that incorporates several functions, such as infiltration, filtration, and retention in a single system. Nevertheless, such functions are still prone to clogging and may require frequent maintenance. Clogging due to the deposition of sediments over time reduces the porosity and infiltration rate during monitoring despite being a well-designed system. The objective of this study was to determine the clogging potential of a hybrid BMP. The clogging tests using filter media columns were undertaken to determine the physical clogging processes and the factors that affect clogging. Based on the results, hydraulic loading and sediment mass loading influenced the generation and duration of clogging in the filter media. Early development of premature clogging was observed at the initial 25% of the depth due to the retention of sediment particle sizes ranging between 50 and 250 μm. It was suggested that scraping of the first 25% depth of the media can be performed to maintain the hydraulic capacity of the stormwater filters. Although laboratory studies do not entirely demonstrate the actual field conditions, insights from this study can provide valuable understanding on how such system would perform over time.

AbstractThis study presents an application of stormwater management model in predicting the optimal physical characteristics and rainfall design criteria of an established low impact development (LID) treating urban stormwater runoff. The optimization of this LID was performed for the purpose of enhancing the treatment performance and serve as future guidelines in designing treatment systems. The values of different calibration parameters used in the model were obtained from the 10 monitored storm events conducted from July 2010 to July 2013. Based on the findings, the runoff volume reduction of the system was found out to be directly proportional with storage volume/surface area (SV/SA) ratio. However, it was also dependent on the amount of rainfall during a storm event. For the total suspended solids load reduction of the system, it has no significant relationship with the rainfall but found to be directly proportional with SV/SA ratio as well. Lastly, the physical dimensions of the system were also analyzed with respect to the SA/SV ratio.

AbstractThis study investigated the applicability of bottom ash as filter media for a stormwater treatment facility. Filtration test experiments were conducted in a 30 × 15 × 15 cm transparent acrylic test reactor using a synthetic run-off, prepared from run-off collected from a wetted impervious road. The reactor designed as a stormwater treatment system and incorporated bottom ash as filter media was tested for three flow regimes (i.e. 200, 400, and 800 mL/min) to investigate the treatment performance of the system at various intensities during rainfall events. Based on the findings, the bottom ash media was able to reduce 70% of total suspended solids and more than 50% of iron, zinc, and lead from the synthetic run-off. A design guideline was developed which recommended a facility surface area to catchment area ratio of 0.007–0.015 for the effective treatment of 5, 7.5, and 10 mm design rainfall.

AbstractThe continuous increase in water demand is primarily caused by the explosive population growth rate due to urbanization and industrialization, and thus, is accelerated in both agricultural and residential parts. Drought adversely affects the quality of life and the whole economic situation of the country, and therefore, an accurate assessment of the incidence of water shortage is required. The existing researches for calculating drought indices do not consider the water demand and the water supply from irrigation facilities, streams, and water storages; thus, existing hydrological drought indices have many limitations in determining actual drought situations in the country. Only water supply without water demand is considered on the existing hydrological drought index therefore, water shortage cannot be calculated. On the other hand, real-time drought index (RDI) evaluates drought on a daily basis in real-time and calculate water shortage according to residential, agricultural, and industrial water. In this study, the water shortage based on real-time water supply and demand is calculated and a new drought index corresponding to such shortage is developed. The drought assessment is performed using the proposed drought index during national drought events from year 2008 to 2009. Based on the results of this study, it turns out that the regions supplied by small reservoirs and streams are more vulnerable in drought as compared with regions supplied by large-scale dams and rivers. The applicability of the proposed drought index is proved to be appropriate, from the comparison results between major historical drought situations and the corresponding situation modeled by this study.

AbstractThis study developed hybrid constructed wetlands (CWs) for treatment of urban stormwater runoff pollutants. Hybrid CWs applied at narrow sections in urban areas are typically small and modular in type. Several treatment mechanisms were occurring in the hybrid system to treat high level of pollutant mass loading from urban stormwater runoff. A small scale hybrid CW comprised of a sedimentation tank, free water surface (FWS) CW, and horizontal sub-surface flow (HSSF) CW, was studied. A total of 10 test runs were simulated in the hybrid CW since July 2011–November 2012. Based on the results, almost 51–78% reduction in pollutants such as TSS, COD, TN, TP, and total heavy metals (Fe, Cu, and Zn) was achieved after passing the first and second units of the hybrid CW (i.e. sedimentation tank and FWS CW). Finally, additional 9–25% reduction of these pollutants was obtained as they went through the HSSF CW. Using normalized pollutant concentration with respect to the facility length, the appropriate size of hybrid CWs was determined to be at least 2 m. Comparing the removal efficiencies of the two types of hybrid CW system (i.e. reed and iris combination in Type A; and reed and cattail combination in Type B) similar results were obtained.

AbstractPhosphorus and nitrogen in different forms are the primary concern in surface water bodies nowadays since it causes eutrophication. A bioretention system, an example of green stormwater infrastructures reduces nutrients through biological processes such as plant uptake and microbial conversion of nitrogen known as bioremediation. In this study, the performance of two types of bioretention system in managing nutrients from urban stormwater runoff was investigated. Total phosphorus (TP) was reduced by 85% up to 86% in both bioretention types while total nitrogen (TN) was reduced by 49 and 55% in type A and type B bioretention, respectively. Among the plants species used in the study, Rhododendron indicumLinnaeus was identified as the most appropriate plant that should be used in bioretention systems considering factors such as number of flower per plants, plant decay rate, cost of plant, number of plant per reactor, and TN and TP uptake by plants. Based on the results, 25–32% of TN and 47–59% of the TP load were absorbed by the soil medium. This finding signified that filtration was the main removal mechanism for nutrients in bioretention.

Recently, the frequency of severe torrential rain storms has been continuously increasing as an effect of abnormal climate. Annual flood damages and water quality degradation continuously worsen despite the imposition of flood and water quality managements. Hence, suitable analyses should be made to mitigate future flood damages and water quality degradation in riverine systems. In this study, two major analyses were done: analysis on the variation of the flood frequency and water quality. The principal method used to analyze variation of the flood frequency is through the application of flood-frequency analysis in time series on flood discharges. For the flood-frequency analysis, the stream flow data used were gathered from 25 gauging stations located in Geum River Basin. The Log Pearson Type III distribution was used to determine the probability of the flood discharges. The annual maximum series of the flood discharge data from stations was divided into two parts: the historical data and the present data. Flood-frequency analysis was performed to determine the influence of the effects of abnormal climate to the flood discharge in Bugil and Seokhwa stations. For the second part of this study, the water quality data such as BOD, COD, and SS for 24 years were also collected for the analysis of variation patterns of water quality induced by abnormal climate. This study showed that the flood frequency by flood-frequency analysis using the present data was higher compared with the historical data. Further findings showed that, both COD and SS consistently increase while BOD decreases in a yearly basis.