Lee-Hyung Kim

Multiple linear regression models of urban runoff pollutant load and event mean concentration considering rainfall variables.

Rainfall is an important factor in estimating the event mean concentration (EMC) which is used to quantify the washed-off pollutant concentrations from non-point sources (NPSs). Pollutant loads could also be calculated using rainfall, catchment area and runoff coefficient. In this study, runoff quantity and quality data gathered from a 28-month monitoring conducted on the road and parking lot sites in Korea were evaluated using multiple linear regression (MLR) to develop equations for estimating pollutant loads and EMCs as a function of rainfall variables. The results revealed that total event rainfall and average rainfall intensity are possible predictors of pollutant loads. Overall, the models are indicators of the high uncertainties of NPSs; perhaps estimation of EMCs and loads could be accurately obtained by means of water quality sampling or a long-term monitoring is needed to gather more data that can be used for the development of estimation models.

Characteristics of contaminants in water and sediment of a constructed wetland treating piggery wastewater effluent.

Constructed wetland (CW) is the preferred means of controlling water quality because of its natural treatment mechanisms and function as a secondary or tertiary treatment unit. CW is increasingly applied in Korea for secondary effluent of livestock wastewater treatment. This study was conducted to recognize the characteristics of contaminants in the accumulated sediment at the bottom soil layer and to reduce the phosphorus release from sediments of the free water surface CW for the treatment of secondary piggery wastewater effluent from a livestock wastewater treatment facility. The results revealed that the dominant phosphorus existence types at near the inlet of the CW were non-apatite phosphorus (59%) and residual phosphorus (32%) suggesting that most of the particles of the influent are made up of inorganic materials and dead cells. Sediment accumulation is important when determining the long-term maintenance requirements over the lifetime of CW. Continuous monitoring will be performed for a further assessment of the CW system and design.

Fractionation of heavy metals in runoff and discharge of a stormwater management system and its implications for treatment

A stormwater management system utilizing the mechanisms of sedimentation and filtration/infiltration was developed and constructed for the immobilization of suspended solids and heavy metal constituents (Fe, Zn, Pb, Cr, Cu, Cd, Ni) in runoff. Monitoring took place between May 2010 and November 2012 on a total of 24 storm events. This research on the fractionation of heavy metals in runoff and discharge of a stormwater system provided insight on the actual efficiency of the system and determined the implications for treatment of the particulate-bound and dissolved heavy metals in runoff. Results revealed that the partitioning of heavy metal load in runoff in either dissolved or particulate-bound were influenced by flow rate and total suspended solids load, and evident in high-intensity storm (rainfall-runoff event). On the other hand, the partitioning of heavy metal load discharge from the stormwater system was more apparent during the early period of discharge having higher variability in dissolved than particulate-bound heavy metal. Findings revealed that fractionation of heavy metals played an important role in the performance of the stormwater system; thus, must be considered in designing stormwater systems. For the stormwater system to be effective, it is recommended to design the system treating not only the early period of a storm (first flush criteria) rather until the peak part of the hydrograph (high flow rate where partitioning was greatest) from a load basis.

Evaluation of the capability of low-impact development practices for the removal of heavy metal from urban stormwater runoff.

ABSTRACT Low-impact development (LID) and green infrastructure (GI) have recently become well-known methods to capture, collect, retain, and remove pollutants in stormwater runoff. The research was conducted to assess the efficiency of LID/GI systems applied in removing the particulate and dissolved heavy metals (Zn, Pb, Cu, Ni, Cr, Cd, and Fe) from urban stormwater runoff. A total of 82 storm events were monitored over a four-year period (2010–2014) on six LID/GI systems including infiltration trenches, tree box filter, rain garden, and hybrid constructed wetlands employed for the management of road, parking lot, and roof runoff. It was observed that the heavy metal concentration increased proportionally with the total suspended solids concentration. Among the heavy metal constituents, Fe appeared to be highly particulate-bound and was the easiest to remove followed by Zn and Pb; while metals such as Cr, Ni, Cu, and Cd were mostly dissolved and more difficult to remove. The mass fraction ratios of metal constituents at the effluent were increased relative to the influent. All the systems performed well in the removal of particulate-bound metals and were more efficient for larger storms greater than 15 mm wherein more particulate-bound metals were generated compared to smaller storms less than 5 mm that produced more dissolved metals. The efficiency of the systems in removing the particulate-bound metals was restricted during high average/peak flows; that is, high-intensity storms events and when heavy metals have low concentration levels.

First Flush Stormwater Runoff from Highways

Stormwater is now receiving attention from regulatory agencies and has become an important component in watershed planning. In many cases, pollutant mass emissions from stormwater exceed those from wastewater treatment plants. Land use has been identified as an important parameter in predicting stormwater quality. Land uses associated with vehicular activity, such as parking lots, are thought to be high contributors of stormwater pollutants. Other factors, such as greater pollutant concentrations or mass emissions at the onset of rainfall, usually called a “first flush,” or higher emissions from the first storm of the season, usually called a “seasonal first flush,” have been identified. In order to determine the magnitude of the first flush from freeway runoff, three sites in the west Los Angeles area were sampled for 14 storms during the 1999-2000 rainy season. Samples were collected very early in the storm in order to compare water quality from the first runoff to water quality from the middle of the storm. A large range of water quality parameters and metals were analyzed. The data show large first flushes in concentration profiles and moderate first flushes in mass emission rates.

Appropriate determination method of removal efficiency for nonpoint source best management practices

Abstract In Korea, best management practice (BMP) pilot facilities were installed to manage nonpoint source (NPS) pollution from the watershed areas. These BMPs are consistently monitored to determine the accurate pollutant removal efficiencies. However, the difficulty of removal efficiency determination in NPS BMPs is generally caused by uncertainties of site and storm characteristics. For that reason, removal efficiency determination has to apply appropriate method to eliminate uncertainties. In this study, the monitoring program was performed during 3 years in order to verify the efficiency of the infiltration trench during storm events. The pollutant removal efficiency was determined by four different methods namely the efficiency ratio (ER), summation of loads (SOL), regression of loads (ROL) and rainfall of frequency (ROF) methods. In comparison to other methods, the ROF method uses the rainfall frequency which is practical to eliminate uncertainties of NPS. Therefore, the ROF method is suggested as...

Unit soil loss rate from various construction sites during a storm

The Korean Ministry of Environment (MOE) opts to establish an ordinance having a standard specifying an allowable soil loss rate applicable to construction projects. The predicted amount of soil loss from a construction site exceeding the standard can be used to calculate the percent reduction necessary to comply with the ordinance. This research was conducted to provide a basis to establish a standard by investigating the unit soil loss rates in the three phases of development: pre-construction, active construction and post construction based from 1,036 Environmental Impact Assessment (EIA) reports within the six-year period (2000-2005). Based on the findings, several factors affect the magnitude of soil loss rates particularly storm characteristics, site slope, soil type, location from rivers, as well as the type of construction activity. In general, the unit soil loss rates during the active construction phase are extremely higher in comparison to undisturbed areas; in magnitude of 7 to 80 times larger in urban areas and 18 to 585 times in rural areas. Only between 20 to 40 percent of the soil loss rates was contributed at pre- and post- construction phases indicating that the active construction phase is the most important phase to control.

Evaluation of a hybrid constructed wetland system for treating urban stormwater runoff

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 o...

Fate and removal of nutrients in bioretention systems

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 indicum Linnaeus 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 th...

Determination of the number of storm events representing the pollutant mean concentration in urban runoff

Abstract Urban storm water quality monitoring is usually limited due to time and cost constraints, and thus, the determination of the minimum number of storm events that should be sampled necessary to estimate the pollutant mean concentration relative to the landuse is valuable. In this research, the minimum number of storm events was derived by considering both the variability of event mean concentration (EMC) values and the associated degree of uncertainty for a given set of measured storm events using monitored storm event data during a three-year period from 2009 to 2011 on five urban sites. Based on the findings, the required number of storm events could be determined using the propose method but representing only the 99 and 95% confidence limits of the site mean concentration (SMC) and differed depending on the pollutant. Results showed that a minimum of six to eight storm events were adequate to estimate the SMC of total suspended solids at low levels of uncertainties with relative standard error o...