Tak-Hyun Kim

Decolorization of disperse and reactive dyes by continuous electrocoagulation process

The electrocoagulation process was developed to overcome the drawbacks of conventional wastewater treatment technologies. This process is very effective in removing organic pollutants including dyestuff wastewater and allows for the reduction of sludge generation. The purposes of this study were to investigate the effects of the operating parameters, such as current density, electrode number, electrolyte concentration, electrode gap, dyestuff concentration, pH of solution and inlet flow rate, on decolorization by continuous electrocoagulation. The dye removal efficiencies and reaction rate constants from the curves following the first-order relationship of electrocoagulation were calculated. In addition, from the points of power consumption, the effects of the operating parameters were also searched. Finally, the behaviors of decolorization according to dyestuff types, i.e., disperse dye and reactive dye, were also examined.

Pilot scale treatment of textile wastewater by combined process (fluidized biofilm process-chemical coagulation- electrochemical oxidation)

The performance of pilot scale combined process of fluidized biofilm process, chemical coagulation and electrochemical oxidation for textile wastewater treatment was studied. In order to enhance biological treatment efficiency, two species of microbes, which can degrade textile wastewater pollutants efficiently, were isolated and applied to the system with supporting media. FeCl3 x 6H2O, pH 6 and 3.25 x 10(-3) mol/l were determined as optimal chemical coagulation condition and 25 mM NaCl of electrolyte concentration, 2.1 mA/cm2 of current density and 0.71/min of flow rate were chosen for the most efficient electrochemical oxidation at pilot scale treatment. The fluidized biofilm process showed 68.8% of chemical oxygen demand (COD) and 54.5% of color removal efficiency, even though using relatively low MLSS concentration and short sludge retention time. COD and color removals of 95.4% and 98.5% were achieved by overall combined process. The contribution of fluidized biofilm process to the overall combined process was increased over 25.7% of COD reduction and 20.5% of color reduction by adopting support media in biological treatment. It can be thought that the fluidized biofilm process was effective, and pollutant loading on post-treatment was pretty much decreased by this system. This combined process was highly competitive in comparison to the other similar combined systems. It was concluded that this combined process was successfully employed and much effectively decreased pollutant loading on post-treatment for textile wastewater treatment at pilot scale.

Decolorization of disperse and reactive dye solutions using ferric chloride

Abstract The composition of wastewater from dyeing and textile processes is highly variable depending on the dyestuff type; typically it has a high chemical oxygen demand. This study examined the decolorization of some of the most commonly used disperse and reactive dyestuffs by destabilization using ferric chloride as a coagulant. Dye removal, distributions of zeta potential, concentration of suspended solids, changes of the SCOD/TCOD ratio and distributions of SV and SVI values were investigated in this work. Compared to reactive dyes, disperse dyes have lower solubility, higher suspended solids concentrations and lower SCOD/TCOD ratios. It was concluded that disperse dye solutions are more easily decolorized by chemical coagulation than reactive dye solutions.

Carbon source recovery from waste activated sludge by alkaline hydrolysis and gamma-ray irradiation for biological denitrification

The recovery of an organic carbon source from a waste activated sludge by using alkaline hydrolysis and radiation treatment was studied, and the feasibility of the solubilized sludge carbon source for a biological denitrification was also investigated. The effects of an alkaline treatment and gamma-ray irradiation on a biodegradability enhancement of the sludge were also studied. A modified continuous bioreactor for a denitrification (MLE reactor) was operated by using a synthetic wastewater for 47 days. Alkaline treatment of pH 10 and gamma-ray irradiation of 20 kGy were found to be the optimum carbon source recovery conditions. COD removal of 84% and T-N removal of 51% could be obtained by using the solubilized sludge carbon source through the MLE denitrification process. It can be concluded that the carbon source recovered from the waste activated sludge was successfully employed as an alternative carbon source for a biological denitrification.

Electrochemical oxidation of polyvinyl alcohol using a RuO2/Ti anode

Abstract Polyvinyl alcohol (PVA), known as the dominant contributor of chemical oxygen demand (COD) in textile wastewater, is very difficult to decompose by conventional treatment technologies. In this study, electrochemical oxidation using a RuO 2 /Ti anode was applied to treat a PVA solution. The mechanisms of PVA degradation and COD destruction were investigated, while the operating parameters affecting the mechanisms were also studied. The parameters investigated included current density, PVA concentration in waste stream, the rate of electrolyte consumption of sodium chloride, and the feed rate of wastewater. The overall mass transport behavior of electrochemical oxidation of PVA was explained by the mathematical relationship of dimensionless numbers such as the Reynolds, Schmidt and Sherwood numbers.

Enhancement of struvite purity by re-dissolution of calcium ions in synthetic wastewaters.

Although it is widely known that the presence of Ca ions inhibits the nucleation and growth of struvite, which consists of NH4(+), PO4(3-), and Mg(2+), there is a lack of knowledge on actual Ca contents in struvite co-precipitates at various N and P concentrations and the corresponding effects on the sizes of the precipitates. Therefore, to address this challenge, this study designed synthetic wastewaters including the variety of N and P concentrations, and conducted batch experimental reactions with each wastewater to investigate Ca precipitation and size distributions of the precipitates. The molar ratio of Mg:P:N was confined to 1:1:7, while the initial Ca(2+) concentrations were chosen to be 30-60 mg/L, which are typical Ca concentrations in real wastewaters. The result of the batch experiments confirmed that the presence of Ca caused smaller solids than struvite as indicated in previous studies, and there was competition between Ca-phosphate and Mg-N- PO4 (struvite) reactions, as expected. At the beginning of the experiment (∼1 min), fast Ca-phosphate precipitation was dominant because free Ca and P ions were quickly removed while Mg and N concentrations gradually reduced. However, as the nucleation and crystal growth processes elapsed, dissolved Mg and N concentrations continuously decreased, but dissolved Ca concentrations could rise again at high N and P concentration conditions. The interesting phenomenon is that such increases of Ca concentrations probably results from the thermodynamic energy differences between struvite and Ca-phosphate formations. A high thermodynamic driving force of struvite precipitation could drive the re-dissolution of Ca-ions from the Ca-phosphate compounds with low saturation states. This result is expected to be applied for increasing the struvite purity by the Ca re-dissolution through the thermodynamic spontaneity without additional energy input.

Effects of Cl-based chemical coagulants on electrochemical oxidation of textile wastewater

As a supporting electrolyte and the source of chloride reactant, NaCl is generally added for the electrochemical oxidation process. In this study, Cl-based chemical coagulation was employed as the pretreatment step for the preremoval of suspended and colloidal solids which impede electrochemical oxidation. It was adopted for the purpose of providing the source of the chloride reactant for the electrochemical oxidation. It was ultimately intended to omit the artificial addition of electrolyte solution and to decrease the pollutant loading efficiently on the post electrochemical oxidation process in order to improve the performance of organics removal. PAC and FeCl3, Cl-based chemical coagulants, were successfully employed as the pretreatment step of electrochemical oxidation. PAC and FeCl3, were able to achieve sufficient removal efficiency of organics as well as to exclude the artificial addition of a supporting electrolyte and the source of a chloride reactant.

Interleukin‐1β and interleukin‐1 receptor antagonist gene polymorphisms in Korean patients with adult‐onset Still's disease

Objective. Interleukin‐1 (IL‐1) has been implicated in the pathogenesis of several rheumatic inflammatory diseases, including adult‐onset Stills disease (AOSD) and systemic‐onset juvenile idiopathic arthritis (SoJIA). Several clinical trials also suggest that anakinra, a human recombinant interleukin‐1 receptor antagonist (IL‐1Ra), is effective in patients with AOSD and SoJIA. We have therefore investigated whether IL‐1β and IL‐1Ra gene polymorphisms are associated with the development and clinical features of AOSD. Methods. Genomic DNA was isolated from 83 AOSD patients and 144 healthy controls. Genotyping of the two IL‐1β gene (IL‐1B+3954 and IL‐1B–511) polymorphisms was performed using polymerase chain reaction restriction fragment length polymorphism (PCR‐RFLP). Genotyping of the IL‐1Ra gene (intron 2, VNTR) polymorphism was performed using PCR‐based analysis. To compare genotype and allele frequencies, the χ2‐test or Fishers exact test was used. Haplotype frequencies and pairwise linkage disequilibrium were also estimated. A p‐value <0.05 was considered significant. Results. There were no significant differences in the genotype and allele frequencies of the IL‐1β and IL‐1Ra gene polymorphisms. No differences were also found in the IL‐1 gene cluster haplotypes between both groups. IL‐1 gene cluster polymorphisms had no effect on the clinical course and joint involvement pattern. Nevertheless, the IL‐1B–511 and IL‐1RN (VNTR) polymorphic sites were in linkage disequilibrium. Conclusion. These results suggest that IL‐1β and IL‐1Ra gene polymorphisms are not associated with the development and clinical features of AOSD in Korean patients.

Swine wastewater treatment using a unique sequence of ion exchange membranes and bioelectrochemical system

An ion exchange biological reactor (IEBR) treated organic matter and nitrogen in swine wastewater at 23 °C. The enhanced IEBR enhanced the ammonium flux by electrochemical attraction. The abiotic ammonium fluxes at the applied voltage of 0, 1, and 3 V were 1.33, 1.79, and 2.73 mg/m(2)/s, respectively. In the meantime, the ammonium fluxes caused by biological nitrification at the applied voltage of 0, 1, and 3 V were 1.54, 2.07, and 3.59 mg/m(2)/s, respectively. Removal of organic matter and nitrogen in swine wastewater was proportional to the applied voltage. The average SCOD removal efficiencies at the applied voltage of 0, 1, and 2V were 59.7%, 60.2%, and 67.0%, respectively. The average total nitrogen removal efficiencies at the applied voltage of 0, 1, and 2V were 39.8%, 49.5%, and 58.7%, respectively.

Syntheses of carboxymethylcellulose/graphene nanocomposite superabsorbent hydrogels with improved gel properties using electron beam radiation

Nanocomposite superabsorbent hydrogels (NCSHs) were prepared via electron beam radiation-assisted polymerization using carboxymethylcellulose (CMC) and carbon materials as a superabsorbent polymer and additive inorganic nanomaterial, respectively. Carbon materials such as graphite oxide (GO), reduced graphene oxide (rGO), and activated carbon (AC) were used as additives. The chemical structure and morphology of the prepared NCSHs and pure superabsorbent hydrogels (SHs) were characterized using Fourier transform infrared spectroscopy and optical microscopy. In the prepared NCSHs, the carbon components were dispersed well in the CMC polymer matrix. The mechanical strength and gel fraction of the prepared materials were measured, and the swelling kinetics were evaluated using distilled water, urea solution, and physiological saline water. The prepared NCSHs using GO and rGO exhibited larger gel fraction and mechanical strength than the corresponding non-composite SHs. Electron beam radiation was more effective than solution polymerization in the syntheses of SHs and NCSHs with large gel fraction and high mechanical strength. The NCSHs prepared by electron beam radiation exhibited comparable swelling capabilities to those prepared by solution polymerization.