An improved method of removal for high concentrations of NO by electro-scrubbing process

In the Ag(II)/Ag(I) redox mediator integrated scrubber system, NO reacts with the Ag(II) ions produced by the electrochemical oxidation of Ag(I) in an electrochemical cell present in the scrubbing solution (aqueous HNO₃ acid) to form NO₂. This NO₂ is then absorbed into the scrubbing solution and degraded to nitrate. Numerous experimental runs were carried out to evaluate the feasibility of the integrated system to treat industrial waste gases containing high NO_x levels. The results showed that the levels of NO and NO_x removal increased with increasing Ag(II) loading and contact time. Under optimized conditions, 93.5% and 73.3% of the NO and NO_x, respectively, were removed by a single stage gas scrubber with 1.62 g L^?1 Ag(II) operating at 25 °C and atmospheric pressure.     

A New Flood Index for Use in Evaluation of Local Flood Severity: A Case Study of Small Ungauged Catchments in Korea1

Ahn, Jae Hyun and Hyun Il Choi, 2013. A New Flood Index for Use in Evaluation of Local Flood Severity: A Case Study of Small Ungauged Catchments in Korea. Journal of the American Water Resources Association (JAWRA) 49(1): 1‐14. DOI: 10.1111/jawr.12025 Abstract: The aim of this article is to develop a new index measuring the severity of floods in small ungauged catchments for initial local flood information by the regression analysis between the new flooding index and rainfall patterns. Although a rapid local flood caused by heavy storm in a short period of time is now one of common natural disasters worldwide, such a sudden and violent hydrologic event is difficult to forecast. As local flooding rises rapidly with little or no advance warning, the key to local flood forecasting is to quickly identify when and where local flooding above a threshold is likely to occur. The new flooding index to characterize local floods is measured by the three normalized relative severity factors for the flood magnitude ratio, the rising curve gradient, and the flooding duration time, quantifying characteristics of flood runoff hydrographs. The new flooding index implemented for the two selected small ungauged catchments in the Korean Peninsula shows a very high correlation with logarithm of the 2‐h maximum rainfall depth. This study proposes 30 mm of rainfall in a 2‐h period as a basin‐specific guidance of precaution for the incipient local flooding in the two study catchments. It is expected that the best‐fit regression equation between the new flooding index and a certain rainfall rate can provide preliminary observations, the flood threshold, and severity information, for use in a local flood alert system in small ungauged catchments. Editor's note: This paper is part of a featured series on Korean Hydrology. The series addresses the need for a new paradigm of river and watershed management for Korea due to climate and land use changes.     

Combination of ion exchange system and biological reactors for simultaneous removal of ammonia and organics

A novel process for a simultaneous removal of ammonia and organics was developed on the basis of ion exchange and biological reactions. From batch experiments, it was found out that NH₄⁺ could be removed effectively by combining cation exchange and biological nitrification showing 0.98 mg N/m²?s of a maximum flux. On the other hand, the removal of NO₃⁻ was 3.5 times faster than NH₄⁺ and the maximum flux was calculated to be 3.4 mg N/m²?s. The systems for NH₄⁺ and NO₃⁻ removal were combined for establishing the IEBR process. When the process was operated in a continuous mode, approximately 95.8% of NH₄⁺ was removed showing an average flux of 0.22 mg N/m²·s. The removal efficiency of total nitrogen was calculated as 94.5% whereas that of organics was 99.5%. It was concluded that the IEBR process would be effectively used for a simultaneous removal of NH₄⁺ and organics.     

Distribution and early life history of <Emphasis Type="Italic">Kaupichthys</Emphasis> leptocephali (family Chlopsidae) in the central Indonesian Seas

Leptocephali of the widely distributed tropical marine eels of the genus Kaupichthys (family Chlopsidae) were collected around Sulawesi Island during a sampling survey in the Indonesian Seas in late September and early October 2002, and the otolith microstructure of 24 of the 59 specimens captured was examined to learn about the larval growth rates and spawning times of these small sized eels. Leptocephali ranging in size from 25 to 60 mm were collected in Makassar Strait and the Celebes Sea, but they were most abundant in the semi-enclosed Tomini Bay of northeast Sulawesi Island. The Kaupichthys leptocephali examined had 39–161 otolith growth increments. Their back-calculated hatching dates indicated that five age groups were present and each group appeared to have been spawned around the full moon of previous months. Average growth rate estimates of the first two age groups were 0.65 and 0.54 mm/day for the 27.4–30.4 and 37.6–45.6 mm age classes. The growth rates of the oldest three age groups (52.0–60.8 mm) appeared to have slowed down after they reached their approximate maximum size. An increase in increment widths at the outer margin of the otoliths of those larger than 53 mm suggested that the process of metamorphosis had begun even though there were few external morphological changes indicating metamorphosis. It is hypothesized that chlopsid leptocephali have an unusually short gut that may not need to move forward during early metamorphosis. The presence of four age classes in Tomini Bay suggests that the Togian Islands region may be productive habitats for Kaupichthys juveniles and adults.     

Distribution and hydrodynamic model of the Keumdong oil spill in Kwangyang Bay, Korea

Oil concentrations in the seawater, seabed sediments, and shoreline sediments were measured from the samples collected 165 days after the Keumdong oil spill accident, which had occurred in Kwangyang Bay of the South Sea, Korea in September 1993. Distribution patterns of the concentrations in the seabed and shoreline sediments have allowed us to hindcast the transport and fate of the spilled oil. Overall, the patterns agree better with the southward (seaward) surface water circulation than with the northward (landward) bottom water circulation over the region. Rapid, initial dispersal of the spilled oil to the south and its subsequent grounding onto the intertidal seabed sediments, as well as onto the shorelines, appear to have made ineffective the subsurface oil transport by the bottom current.     

Occurrence of organic pollutants in recovered soil fines from construction and demolition waste

The objective of this study was to characterize recovered soil fines from construction and demolition (C&D) waste recycling facilities for trace organic pollutants. Over a period of 18 months, five sampling trips were made to 14 C&D waste recycling facilities in Florida. Screened soil fines were collected from older stockpiles and newly generated piles at the sites. The samples were analyzed for the total concentration (mg/kg) of a series of volatile organic compound (VOCs) and semi-volatile organic compounds (semi-VOCs). The synthetic precipitation leaching procedure (SPLP) test was also performed to evaluate the leachability of the trace organic chemicals. During the total analysis only a few volatile organic compounds were commonly found in the samples (trichlorofluoromethane, toluene, 4-isopropyltoluene, trimethylbenzene, xylenes, and methylene chloride). A total of nine VOCs were detected in the leaching test. Toluene showed the highest leachability among the compounds (61.3-92.0%), while trichlorofluoromethane, the most commonly detected compound from both the total and leaching tests, resulted in the lowest leachability (1.4-39.9%). For the semi-VOC analysis, three base-neutral semi-VOC compounds (bis(2-ethylhexyl)phthalate, butyl benzyl phthalate, and di-n-butyl phthalate) and several PAHs (acenaphthene, pyrene, fluoranthene, and phenanthrene) were commonly detected in C&D fines samples. These compounds also leached during the SPLP leaching test (0.1-25%). No acid extractable compounds, pesticides, or PCBs were detected. The results of this study were further investigated to assess risk from land applied recovered soil fines by comparing total and leaching concentrations of recovered soil fines samples to risk-based standards. The results of this indicate that the organic chemicals in recovered soil fines from C&D debris recycling facilities were not of a major concern in terms of human risk and leaching risk to groundwater under reuse and contact scenarios.     

Trans-boundary air pollution over remote islands in Japan: observed data and estimates from a numerical model

Observations of air pollutants were conducted in remote Japanese islands (Oki Island and Okinawa Island) in early spring to clarify the extent of trans-boundary air pollution from the Asian continent. A three-dimensional Eulerian model calculation, which included parameters on emission, transport and transformation of sulfur oxides, nitrogen oxides and ammonia, was performed to compile sulfate isosurface concentrations over the observational sites. Concentrations of non-sea-salt sulfate (nss-SO₄²⁻) of greater than 10 μg m⁻³ were observed at Oki after the northeastward passage of low-pressure systems in the Sea of Japan. At these times, the weather showed a typical winter pattern and air pollutants over China were transported southeastward to Japan with the northwesterly wind. The model calculation reproduced the observed variations of nss-SO₄²⁻ concentration well, except for one case in which the model calculation could not reproduce the extremely low nss-SO₄²⁻ concentration observed on 8 March. In Hedo (Okinawa Island), we observed long-lasting (3 days) medium concentrations of nss-SO₄²⁻ (approximately 5 μg m⁻³). Although the model reproduced these observed medium concentrations well, in general the observed results were reproduced better for Oki than for Hedo. Under the synoptic weather conditions of early spring, high concentrations of nss-sulfate were sometimes transported to these remote Japanese islands from areas of continental Asia with a strong outflow of air pollutants.     

A comparison of refrigerant management policies and suggestions for improvement in South Korea

HFCs (hydrofluorocarbons) emerged as alternative refrigerants after the production of chlorofluorocarbons was banned and hydrochlorofluorocarbons were phased out, under the Montreal Protocol on Substances that Deplete the Ozone Layer. However, because the Kyoto Protocol considered HFCs as greenhouse gases, and their impact on climate change has been increasing, major developed countries have been strengthening existing regulations on the use of HFCs as refrigerants. South Korea has also passed various legislations related to refrigerant management. However, reports indicate that implementation of these regulations has been ineffective, due to the absence of a specific system for managing the production, use, and disposal phases of refrigerants. To identify and resolve these issues, this study investigates the current state of refrigerant management in South Korea for those three phases. Refrigerant management policies are compared between different legislatures, using the examples of the European Union, United States, and Japan. Based on the findings, five types of measures are suggested to reduce the production and consumption of refrigerants, and to improve refrigerant management regulations in ways that are most appropriate to the South Korean context.     

Fate and behavior of selected heavy metals with mercury mass distribution in a fluidized bed sewage sludge incinerator

In this paper, emission and distribution behavior of six heavy metals (As, Cd, Cr, Ni, Pb, and Hg), particulate matter and mass distribution of mercury within the different streams of a fluidized bed sewage sludge incinerator are presented. At the inlet of air pollution control devices (APCDs); Cd, Cr, Ni and Pb were mainly enriched in coarse particles; comparatively As content was higher in fine particles (<PM_2.5). The concentration of heavy metals in total particulate matter and PM_2.5, at the inlet of APCDs, were in the order of Cr > Ni > Pb > As > Cd. Mercury was almost always distributed in flue gas. Metals, other than mercury, were efficiently removed in APCDs and their concentrations in bottom ash, with fly ash being higher, whereas for that in wastewater, then waste sand was lesser. Overall mercury removal efficiency of APCDs was 98.6 %. More than 83.3 % of mercury was speciated into oxidized form at the inlet of APCDs, attributed by higher chlorine content in sludge. Mercury was mainly distributed in wastewater (78.4 %), wastewater from a spray dry reactor (16.8 %), fly ash in a hopper (3.4 %) and flue gas (1.4 %). This result is one of the first for data to be obtained; more experiments are required to control emission from such sources.