Effect of reservoir flushing on downstream river water quality

The effect of short-term reservoir flushing on downstream water quality in the Geum River, Korea was studied using field experiments and computer simulations. The reservoir release was increased from 30 to 200 m(3)/s within 6 h for the purpose of this experiment. The flushing discharge decreased the concentrations of soluble nitrogen and phosphorus species considerably, but the experimental results revealed a negative impact on organic forms of nutrients and biochemical oxygen demand (BOD). A dynamic river water quality model was applied to simulate the river hydraulics and water quality variations during the event. The model showed very good performance in predicting the travel time of flushing flow and the variations of dissolved forms of nitrogen and phosphorus constituents. However, it revealed a limited capability in simulating organic forms of nutrients and BOD because it does not consider the re-suspension mechanism of these constituents from sediment during the wave front passage.     

Quantification of ammonia and hydrogen sulfide emitted from pig buildings in Korea

The aim of this field study was to determine the concentrations and emissions of ammonia and hydrogen sulfide in different types of pig buildings in Korea to allow objective comparison between pig housing types in Korea and other countries. Concentrations of ammonia and hydrogen sulfide in the pig buildings averaged 7.5ppm and 286.5ppb and ranged from 0.8 to 21.4ppm and from 45.8 to 1235ppb, respectively. The mean emissions of ammonia and hydrogen sulfide per pig (normalized to 75kg liveweight) and area (m2) from pig buildings were 250.2 and 37.8mg/h/pig and 336.3 and 50.9mg/h/m2, respectively. Ammonia and hydrogen sulfide concentrations and emissions were higher in the pig buildings managed with deep-pit manure systems with slats and mechanical ventilation than in other housing types.     

Removal of anthelmintic drugs and their photodegradation products from water with RO/NF membranes

Photolytic reactions are often complex, involving various competing or parallel pathways and leading to multiple reaction products. Removal of anthelmintic drugs (AD) – levamisole (LEV), albendazole (ABZ), praziquantel (PZQ), febantel (FEBA) from water and their photodegradation products with reverse osmosis (RO) and nanofiltration (NF) membranes were investigated in this work. Simulation of photodegradation of ADs was carried out under laboratory conditions with UV lamp at a wavelength of 254 nm for 4 h.Reverse osmosis (LFC–1 and XLE) and tight nanofiltration (NF90) membranes showed good removal (>83%) of anthelmintic drugs in binary solutions and in mixture. Other nanofiltration (NF270, NF and DK) membranes had rejection between 22 and 45% for smaller drugs (LEV and ALB) and >90% for PZQ and FEBA. These results show that main rejection mechanism in binary solutions was size exclusion and in mixture additional physico-chemical interactions had influence.After the UV treatment anthelmintic drugs were degraded into several photodegradation products (5 for LEV, 2 for ABZ, 1 for PZQ and 8 for FEBA). Reverse osmosis and NF90 membranes removed >95% of all photodegradation products (except FEBA₁ around 70%) and other nanofiltration membranes between 33 and 99.99%.     

The kinetic of the catalytic decomposition of methyl isobutyl ketone over a Pt/gamma-Al2O3 catalyst

Environmental catalysis also can refer to catalytic technologies for reducing emission of environmentally unacceptable compounds. Catalytic decomposition also is one of the cost-effective technologies to solve the troublesome volatile organic compounds. This study treated methyl isobutyl ketone (MIBK) by a commercial catalyst, Pt/gamma-Al(2)O(3), in an isothermal fixed bed differential reactor. The effects of O(2) and MIBK content in carrier gas on the catalysis's reaction rate are also observed. Three kinetic models, i.e. the Mars and van Krevelen model, Langmuir-Hinshelwood model and power-rate law were applied to best fit the experimental results. The results indicate that the kinetic behavior of MIBK oxidation with catalysis can be accounted for by using the rate expression of the Mars and van Krevelen model and Langmuir-Hinshelwood model. Kinetic parameters are also determined on the basis of the differential reactor data. The experimental results are compared with those of the model predicted.     

Enhanced desorption of phenanthrene from soils using hydroxypropyl-beta-cyclodextrin: experimental results and model predictions

Objective of this study was to evaluate the effects of hydroxypropyl-beta-cyclodextrin (HPCD) on the removal of phenanthrene from solid phase. Batch tests for the phenanthrene distribution between aqueous and solid phase were conducted in the presence of HPCD. Column tests and numerical simulations were conducted to evaluate the roles of HPCD cavities and interaction rates between water, HPCD, and solid phase in the enhanced removal of phenanthrene. Experimental results showed that HPCD was effective in removing sorbed phenanthrene from subsurface environment, primarily due to its negligible sorption to the solid phase and the partitioning of phenanthrene into HPCD cavities. From the numerical simulations, it was found that rate-limited partitioning of phenanthrene into HPCD cavities was most influential factor in the enhanced elution of phenanthrene. Sorption and desorption rate of phenanthrene between aqueous and solid phase was very fast or near equilibrium state. Interaction rates of contaminant between water, HPCD, and solid phase could be affected by other factors such as soil types and organic matter contents. Results from this study implied that HPCD flushing could be effectively applied for the removal of hydrophobic organic pollutants existing in the soils as sorbed or NAPL state.     

Stabilization of the As-contaminated soil from the metal mining areas in Korea

Phytoextraction is a remediation technology with a promising application for removing arsenic (As) from soils and waters. Several plant species were evaluated for their As accumulation capacity in hydroponic culture amended with As. Cucumis sativus (cucumber) displayed the highest tolerance against As among 4 plants tested in this study (corn, wheat, sorghum and cucumber). The germination ratio of Cucumis sativus was more than 50% at the high concentration of 5,000 mg-As/l. In Cucumis sativus grown in a solution contaminated with 25 mg-As/l, the accumulated As concentrations in the shoot and root were 675.5 ± 11.5 and 312.0 ± 163.4 mg/kg, respectively, and the corresponding values of the translocation and bioaccumulation factors for As were 1.9 ± 0.9 and 21.1 ± 8.4, respectively. These results indicate Cucumis sativus is to be a candidate plant for phytoextraction of As from soils and water.     

Application of Zn-contaminated soil: Feasibility study on the removal of H2S from hot coal-derived gas

In this study, zinc-contaminated soils were chosen as a candidate material for the removal of hydrogen sulfide (H₂S) from hot coal-derived gas. Laboratory experiments showed that H₂S was decreased to less than 10 ppm when the zinc-contaminated soils were reacted with H₂S. The best removal temperature of H₂S was found to be at 550°C in the operating conditions. In addition to zinc species, free iron oxides in contaminated soils also performed an active species to react with H₂S and enhanced the sulfur capacity. Through the XPS analysis, iron sulfide (FeS) and zinc sulfide (ZnS) were the major products after removal experiments. Regeneration experimental results indicated that the zinc-contaminated soils can be regenerated by pass diluted air and thus be reused on the removal of H₂S for many times.     

Effects of ozonation and coagulation on effluent organic matter characteristics and ultrafiltration membrane fouling

Effluent organic matter （EfOM） is the major cause of fouling in the low pressure membranes process for wastewater reuse. Coagulation and oxidation of biological wastewater treatment effluent have been applied for the fouling control of microfiltration membranes. However, the change in EfOM structure by pre-treatments has not been clearly identified. The changes of EfOM characteristics induced by coagulation and ozonation were investigated through size exclusion chromatography, UV/Vis spectrophotometry, fluorescence spectrophotometry and titrimetric analysis to identify the mechanisms in the reduction of ultrafiltration （UF） membrane fouling. The results indicated that reduction of flux decline by coagulation was due to modified characteristics of dissolved organic carbon （DOC） content. Total concentration of DOC was not reduced by ozonation. However, the mass fraction of the molecules with molecular weight larger than 5 kDa, fluorescence intensity, aromaticity, highly condensed chromophores, average molecular weight and soluble microbial byproducts decreased greatly after ozonation. These results indicated that EfOM was partially oxidized by ozonation to low molecular weight, highly charged compounds with abundant electron- withdrawing functional groups, which are favourable for alleviating UF membrane flux decline.