Hyunook Kim

Decolorization of Wastewater

The public demand for color-free waste discharge to receiving waters and tougher color standards have made decolorization of a variety of industrial wastes a top priority. Unfortunately, with the complicated color-causing compounds, the decolorization of these wastes is a difficult and challenging task. This article first describes the background information of dye molecules and dye waste characteristics. The methods for color measurements and standards are then discussed. Different techniques including almost all the known physical, chemical and biological techniques are described for decolorization. Each process alone may not be able to meet the requirements. A combination of these processes, for example, chemical-biological, biological-chemical, chemical-physical, chemical-chemical, etc. is often used. The formation of intermediates during the decolorization process is emphasized. These byproducts may be more toxic than the parent compounds. Thus, the extent of the mineralization in waste decolorization should be evaluated.

A review of the influence of treatment strategies on antibiotic resistant bacteria and antibiotic resistance genes.

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG) in the aquatic environment have become an emerging contaminant issue, which has implications for human and ecological health. This review begins with an introduction to the occurrence of ARB and ARG in different environmental systems such as natural environments and drinking water resources. For example, ARG or ARB with resistance to ciprofloxacin, sulfamethoxazole, trimethoprim, quinolone, vancomycin, or tetracycline (e.g., tet(A), tet(B), tet(C), tet(G), tet(O), tet(M), tet(W), sul I, and sul II) have been detected in the environment. The development of resistance may be intrinsic, may be acquired through spontaneous mutations (de novo), or may occur due to horizontal gene transfer from donor bacteria, phages, or free DNA to recipient bacteria. An overview is also provided of the current knowledge regarding inactivation of ARB and ARG, and the mechanism of the effects of different disinfection processes in water and wastewater (chlorination, UV irradiation, Fenton reaction, ozonation, and photocatalytic oxidation). The effects of constructed wetlands and nanotechnology on ARB and ARG are also summarized.

Risk factors for and clinical outcomes of bloodstream infections caused by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae.

OBJECTIVE To evaluate risk factors and treatment outcomes of bloodstream infections caused by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP). DESIGN Retrospective case-control study. Stored blood isolates of K. pneumoniae were tested for ESBL production by NCCLS guidelines, double-disk synergy test, or both. SETTING A 1,500-bed, tertiary-care university hospital and referral center. PATIENTS Sixty case-patients with bacteremia due to ESB-KP were compared with 60 matched control-patients with non-ESBL-KP. RESULTS There were no significant differences in age, gender, APACHE II score, or underlying diseases between the groups. Independent risk factors for infections caused by ESBL-KP were urinary catheterization, invasive procedure within the previous 72 hours, and an increasing number of antibiotics administered within the previous 30 days. Complete response rate, evaluated 72 hours after initial antimicrobial therapy, was higher among control-patients (13.3% vs 36.7%; P = .003). Treatment failure rate was higher among case-patients (35.0% vs 15%; P = .011). Overall 30-day mortality rate was 30% for case-patients and 28.3% for control-patients (P = .841). Case-patients who received imipenem or ciprofloxacin as a definitive antibiotic had 10.5% mortality. The mortality rate for initially ineffective therapy was no higher than that for initially effective therapy (9.1% vs 11.1%; P = 1.000), but statistical power was low for evaluating mortality in the absence of septic shock. CONCLUSION For K. pneumoniae bacteremia, patients with ESBL-KP had a higher initial treatment failure rate but did not have higher mortality if antimicrobial therapy was appropriately adjusted in this study with limited statistical power.

Ferrate(VI) oxidation of propranolol: Kinetics and products

The oxidation of propranolol (PPL), a β-blocker by ferrate(VI) (Fe(VI)) was studied by performing kinetics, stoichiometry, and analysis of the reaction products. The rate law for the oxidation of PPL by Fe(VI) was first-order with respect to each reactant. The dependence of second-order rate constants of the reaction of Fe(VI) and PPL on pH was explained using acid-base equilibrium of Fe(VI) and PPL. The required molar stoichiometry for the complete removal of PPL was determined to be 6:1 ([Fe(VI)]:[PPL]). The identified products using liquid chromatography-tandem mass spectrometry were oxidized product (OP)-292, OP-308, and OP-282. The formed OPs could possibly compete with the parent molecule to react with Fe(VI) and thus resulted in a non-linear relationship between degradation of PPL and the added amount of Fe(VI). Rate and removal studies indicate the Fe(VI) is able to oxidize PPL and hence can also oxidize other β-blockers, e.g., atenolol and metoprolol.

Magnetic graphene-carbon nanotube iron nanocomposites as adsorbents and antibacterial agents for water purification.

One of the biggest challenges of the 21st century is to provide clean and affordable water through protecting source and purifying polluted waters. This review presents advances made in the synthesis of carbon- and iron-based nanomaterials, graphene-carbon nanotubes-iron oxides, which can remove pollutants and inactivate virus and bacteria efficiently in water. The three-dimensional graphene and graphene oxide based nanostructures exhibit large surface area and sorption sites that provide higher adsorption capacity to remove pollutants than two-dimensional graphene-based adsorbents and other conventional adsorbents. Examples are presented to demonstrate removal of metals (e.g., Cu, Pb, Cr(VI), and As) and organics (e.g., dyes and oil) by grapheme-based nanostructures. Inactivation of Gram-positive and Gram-negative bacterial species (e.g., Escherichia coli and Staphylococcus aureus) is also shown. A mechanism involving the interaction of adsorbents and pollutants is briefly discussed. Magnetic graphene-based nanomaterials can easily be separated from the treated water using an external magnet; however, there are challenges in implementing the graphene-based nanotechnology in treating real water.

In situ extractive fermentation for the production of hexanoic acid from galactitol by Clostridium sp. BS-1.

Clostridium sp. BS-1 produces hexanoic acid as a metabolite using galactitol and enhanced hexanoic acid production was obtained by in situ extractive fermentation with Clostridium sp. BS-1 under an optimized medium composition. For medium optimization, five ingredients were selected as variables, and among them yeast extract, tryptone, and sodium butyrate were selected as significant variables according to a fractional factorial experimental design, a steepest ascent experimental design, and a Box-Behnken experimental design. The optimized medium had the following compositions in modified Clostridium acetobutyricum (mCAB) medium: 15.5gL(-1) of yeast extract, 10.13gL(-1) of tryptone, 0.04gL(-1) of FeSO4·7H2O, 0.85gL(-1) of sodium acetate, and 6.47gL(-1) of sodium butyrate. The predicted concentration of hexanoic acid with the optimized medium was 6.98gL(-1), and this was validated experimentally by producing 6.96gL(-1) of hexanoic acid with Clostridium sp. BS-1 under the optimized conditions. In situ extractive fermentation for hexanoic acid removal was then applied in a batch culture system with the optimized medium and 10% (v/v) alamine 336 in oleyl alcohol as an extractive solvent. The pH of the culture in the extractive fermentation was maintained at 5.4-5.6 by an acid balance between production and retrieval by extraction. During a 16 day culture, the hexanoic acid concentration in the solvent increased to 32gL(-1) while it was maintained in a range of 1-2gL(-1) in the medium. The maximum rate of hexanoic acid production was 0.34gL(-1)h(-1) in in situ extractive fermentation.

Control of an alternating aerobic–anoxic activated sludge system — Part 1: development of a linearization-based modeling approach

Abstract A two-phase model (linear in each phase) is developed for an alternating aerobic–anoxic completely mixed activated sludge process for the removal of carbonaceous substrates, nitrification, and denitrification. The linearized model is adapted from the activated sludge model No. 1 (ASM1) originally developed by the International Association on Water Pollution Research and Control. The modified dynamic model captures the essential process features of ASM1 while dramatically reducing demand on computational resources. Simulations may be conducted in such short times that the simplified model is suitable for inclusion in on-line optimization-based process control schemes. Calibrated model parameters are within the ranges specified in ASM1. Comparison of model predictions with experimental measurements from two different sets of bench-scale alternating aerobic–anoxic reactors indicates reasonable prediction accuracy of the model; further compensation for inaccuracy is achievable by introducing a feedback loop.

Sulfonamides and tetracyclines in livestock wastewater

Antibiotics (sulfonamides and tetracyclines) have attractive increasing attention due to their persistence for a long time, which lead to concern of widespread antibiotic resistant bacteria and resistance genes in the aquatic environment. Investigation of the occurrence and elimination of antibiotics in the wastewater treatment plant (WWTP) effluent is thus imperative. This paper presents the method development of the liquid chromatography-ion-trap mass spectrometer (IT-MS)-time-of-flight mass spectrometer in series (LC-IT-ToF/MS) hybrid technique to determine concentrations of sulfonamides and tetracyclines in the effluent of animal WWTP. Detection limits of the developed method were 22.8, 23.0, 25.8, 23.6, and 9.8ngL(-1) for sulfathiazole, sulfamethazine, sulfamethoxazole, oxytetracycline, and chlortetracycline, respectively. Average recovery efficiencies of the method for sulfonamides fortified in effluent samples of ananimal WWTP at 1.0, and 4.0μgL(-1) were 73-95%, and 89-104%, respectively, while that of the method for tetracyclines fortified at 0.4 and 4.0μgL(-1) was 76-104%, and 101-107%, respectively. The analysis of effluent of the WWTP showed that more than 90% of analyzed antibiotics were removed by the treatment consisted of biological, a UF membrane, and a coagulation process. The maximum concentrations of sulfonamide and tetracycline in the WWTP were 49.5 and 4.1μgL(-1), respectively.

Outcomes of Hickman catheter salvage in febrile neutropenic cancer patients with Staphylococcus aureus bacteremia

OBJECTIVE To evaluate the outcome of attempted Hickman catheter salvage in neutropenic cancer patients with Staphylococcus aureus bacteremia who were not using antibiotic lock therapy. DESIGN Retrospective cohort study. SETTING A university-affiliated, tertiary-care hospital with 1,500 beds for adult patients. PATIENTS All neutropenic cancer patients who had a Hickman catheter and S. aureus bacteremia (32 episodes in 29 patients) between January 1998 and March 2002. METHODS Salvage attempts were defined as cases where the Hickman catheter was not removed until we obtained the results of follow-up blood cultures performed 48 to 72 hours after starting treatment with antistaphylococcal antibiotics. Salvage was considered to be successful if the Hickman catheter was still in place 3 months later without recurrent bacteremia or death. RESULTS Catheter salvage was attempted in 24 (75%) of the 32 episodes. Of the salvage attempts, the success rate was 50% (12 of 24). Salvage attempts were successful in 14% (1 of 7) of the episodes with positive follow-up blood cultures, and in 65% (11 of 17) of those with negative follow-up blood cultures (P = .07). If the analysis is confined to cases with no external signs of catheter infection, salvage attempts were successful in 14% (1 of 7) of the episodes with positive follow-up blood cultures and in 80% (8 of 10) of those with negative follow-up blood cultures (P = .02). CONCLUSION In neutropenic cancer patients with S. aureus bacteremia, attempted catheter salvage without antibiotic lock therapy was successful in 50% of the cases.

Comparison of Fe(VI) (FeO4(2-)) and Ozone in Inactivating Bacillus Subtilis Spores

The protozoan parasites such as Cryptosporidiumparvum and Giardialamblia have been recognized as a frequent cause of recent waterborne disease outbreaks because of their strong resistance against chlorine disinfection. In this study, ozone and Fe(VI) (i.e., FeO(4)(2-)) were compared in terms of inactivation efficiency for Bacillus subtilis spores which are commonly utilized as an indicator of protozoan pathogens. Both oxidants highly depended on water pH and temperature in the spore inactivation. Since redox potential of Fe(VI) is almost the same as that of ozone, spore inactivation efficiency of Fe(VI) was expected to be similar with that of ozone. However, it was found that ozone was definitely superior over Fe(VI): at pH 7 and 20°C, ozone with the product of concentration×contact time (C¯T) of 10mgL(-1)min inactivate the spores more than 99.9% within 10min, while Fe(VI) with C¯T of 30mgL(-1) min could inactivate 90% spores. The large difference between ozone and Fe(VI) in spore inactivation was attributed mainly to Fe(III) produced from Fe(VI) decomposition at the spore coat layer which might coagulate spores and make it difficult for free Fe(VI) to attack live spores.