Jung-Seok Yang

Comparison of the microbiological and chemical characterization of harvested rainwater and reservoir water as alternative water resources.

Rainwater harvesting (RWH) offers considerable potential as an alternative water supply. In this study, all of the harvested rainwater samples met the requirements for grey water but not for drinking water. In terms of microbiological parameters, total coliform (TC) and Escherichia coli (EC) were measured in 91.6% and 72%, respectively, of harvested rainwater samples at levels exceeding the guidelines for drinking water, consistent with rainfall events. In the case of the reservoir water samples, TC and EC were detected in 94.4% and 85.2%, respectively, of the samples at levels exceeding the guidelines for drinking water. Both indicators gradually increased in summer and fall. The highest median values of both TC and EC were detected during the fall. Chemical parameters such as common anions and major cations as well as metal ions in harvested rainwater were within the acceptable ranges for drinking water. By contrast, Al shows a notable increase to over 200mugL(-1) in the spring due to the intense periodic dust storms that can pass over the Gobi Desert in northern China. In terms of statistical analysis, the harvested rainwater quality showed that TC and EC exhibit high positive correlations with NO(3)(-) (rho(TC)=0.786 and rho(EC)=0.42) and PO(4)(-) (rho(TC)=0.646 and rho(EC)=0.653), which originally derive from catchment contamination, but strong negative correlations with Cl(-) (rho(TC)=-0.688 and rho(EC)=-0.484) and Na(+) (rho(TC)=-0.469 and rho(EC)=-0.418), which originate from seawater.

Adsorption of Cr(VI) onto cationic surfactant-modified activated carbon

Highly toxic oxyanions, such as hexavalent chromium (Cr(VI)), have caused adverse effects on human health. This study evaluated the feasibility of using cationic surfactant-modified activated carbon (AC) to remove Cr(VI). To modify activated carbon using a cationic surfactant, AC was mixed with a surfactant solution of 0.5 critical micelle concentration (CMC), at which concentration the surfactant molecules exist as mono-molecules. Adsorption kinetics and an isotherm model were used to study the adsorption characteristics of Cr(VI) onto MAC. The adsorption capacity of MAC for Cr(V) was enhanced compared to that of AC. MAC modified by hexadecyltrimethylammonium had a higher adsorption capacity for the removal of Cr(VI) than that modified by cetylpyridinium. The modification of AC by a cationic surfactant enhanced both its Cr(VI) adsorption rate and its Cr(VI) adsorption capacity. The breakthrough point of MAC for Cr(VI) was 100 times greater than for the raw AC. As a result, MAC is a promising adsorbent to treat Cr(VI) in an aqueous stream.

Electrolyte conditioning-enhanced electrokinetic remediation of arsenic-contaminated mine tailing.

Feasibility of electrolyte conditioning with strong acidic or alkaline solution on electrokinetic remediation of arsenic-contaminated mine tailing was investigated in the laboratory. The mine tailing contained calcium oxide of more than 50%. At alkaline condition, arsenic was precipitated with calcium, and formed calcium arsenate which is very stable solid. Catholyte conditioning with strong acidic solution and anolyte conditioning with strong alkaline solution showed similar efficiency to remove arsenic. At 4mAcm(-2) of current density, the removal efficiency of arsenic was 62% after 28 days operation with catholyte conditioning with 0.1M nitric acid.

Extraction behavior of As, Pb, and Zn from mine tailings with acid and base solutions.

The aim of this study was to investigate the extraction behavior of As, Pb, and Zn from mine tailings for considering the feasibility of soil washing. Extraction of metals was studied for different extractant doses, solid/liquid ratios, and equilibrium times. Generally, high extraction efficiency was achieved with HCl, H(3)PO(4), and H(2)SO(4), while H(2)SO(4) proved to be problematic with respect to Pb. NaOH was found to be favorable in removing As, while it was not effective at extracting Pb and Zn. With optimum conditions, which were a 1:5 solid-liquid ratio and 2h of extraction time, 0.5M of HCl extracted 21.1-72.5%, 9.9-86.5%, and 6.1-74.1% of As, Pb, and Zn, respectively. The power and Elovich function were adequate to describe adsorption kinetics. These results suggest that HCl and NaOH could be used to effectively extract all metals without selectivity and As with selectivity, respectively, in mine tailings and could be used for the design of soil washing process.

Electrokinetic remediation of fluorine-contaminated soil: Conditioning of anolyte

The feasibility of anolyte conditioning on electrokinetic remediation of fluorine-contaminated soil was investigated with a field soil. The initial concentration of fluorine, pH and water content in the soil were 414mg/kg, 8.91 and 15%, respectively. Because the extraction of fluorine generally increased with the soil pH, the pH of the anode compartment was controlled by circulating strong alkaline solution to enhance the extraction of fluorine during electrokinetic remediation. The removal of fluorine increased with the concentration of the alkaline solution and applied current density and fluorine removed up to 75.6% within 14 days. Additionally, anolyte conditioning sharply increased the electro-osmotic flow, which enhanced the removal of fluorine in this study. In many respects, anolyte conditioning in electrokinetic remediation of fluorine-contaminated soil will be a promising technology.

Assessment of metals contamination of soils in Ulaanbaatar, Mongolia.

The purpose of this survey is to investigate the current status of metal pollution of the soil in Ulaanbaatar, the capital city of Mongolia. During the last decade, the city has been rapidly urbanized. Twenty-two soil samples were collected from different parts of the city and analyzed by aqua regia extraction. Generally, metal pollution was not a serious problem in the city and there was no significant evidence of infiltration of metal solutions into subsoil (at a depth of 30 cm). However, it was recently found that the arsenic(As) concentration in the soil was higher than the guideline value and the lead(Pb) content in some samples was higher than normal. The source of As pollution appears to be the coal combustion in three power plants in the city. The sources of the increase in Pb pollution might be the remarkable increase in the number of used vehicles and the increase in the use of leaded fuel in the last few years. To evaluate the leaching potential of heavy metals, sequential extraction was conducted. The quantity of the easily extractable fraction of metals was lower than that of the hardly extractable (residual) fraction. As a result, the leaching potential of heavy metals in Ulaanbaatar was found to be quite low.

Electrokinetic remediation of contaminated soil with waste-lubricant oils and zinc.

The feasibility of electrokinetic technology on the remediation of mixed-waste-contaminated railroad soil, contaminated by lubricant oil and zinc, was investigated. To enhance the removal efficiency, catholyte purging with 0.1M HNO(3) and a supply of non-ionic surfactant, secondary alcohol ethoxylate, was applied to the anode to remove Zn and to solubilize the lubricant oil. The catholyte purging maintained the soil pH as acidic and enhanced desorption of zinc from the soil, where the zeta potential of the acidic soil became positive. Thereafter, the direction of electro-osmotic flow was changed from the cathode to anode and the flow rate was reduced. The lesser in magnitude reverse electro-osmotic flow inhibited the migration of zinc and the lubricant oil was removed by the electro-osmotic flow. The removal of zinc and lubricant oil was enhanced with an increase in voltage gradient; however, a higher voltage gradient resulted in higher energy expenditure. After electrokinetic operation over 17 days, the removal efficiency of zinc was 22.1-24.3%, and that of lubricant oil was 45.1-55.0%. Although the removal of lubricant oil was quite high, the residual concentration did not meet Korean regulation levels.

Biosorption of heavy metals and uranium by starfish and Pseudomonas putida

Biosorption of heavy metals and uranium from contaminated wastewaters may represent an innovative purification process. This study investigates the removal ability of unit mass of Pseudomonas putida and starfish for lead, cadmium, and uranium by quantifying the adsorption capacity. The adsorption of heavy metals and uranium by the samples was influenced by pH, and increased with increasing Pb, Cd, and U concentrations. Dead cells adsorbed the largest quantity of all heavy metals than live cells and starfish. The adsorption capacity followed the order: U(VI)>Pb>Cd. The results also suggest that bacterial membrane cells can be used successfully in the treatment of high strength metal-contaminated wastewaters.

Influence of cationic surfactant on adsorption of Cr(VI) onto activated carbon

The effect of a cationic surfactant on the adsorption of Cr(VI) on activated carbon was investigated using cetylpyridinium chloride (CPC). At a concentration below the critical micelle concentration (CMC) of CPC, the adsorption of CPC and Cr(VI) reached equilibrium within 60 min, while it took 180 min at the concentration above CMC. CPC decreased the adsorption rate of Cr(VI) and increased the adsorption amount of Cr(VI) onto activated carbon. To analyze adsorption phenomena of Cr(VI), adsorption kinetic and isotherm were used and fitted well with the pseudo-second order kinetic model and Langmuir adsorption model, respectively. CPC introduced a cationic functional group on the surface of activated carbon and provided an adsorption site for Cr(VI).

Pulsed Electrokinetic Decontamination of Agricultural Lands around Abandoned Mines Contaminated with Heavy Metals

Abstract The feasibility of pulsed electrokinetic remediation under laboratory conditions was investigated using soil samples from contaminated agricultural land around an abandoned area. The major contaminants of the soil were zinc and cadmium. Sequential extraction showed that most heavy metals existed as strongly bound residual fractions, meaning that they were very difficult to remove. Based upon the overall removal of the cadmium and zinc, pulsed electrokinetic has an advantage over normal electrokinetics, and the electromigration was superior to the electroosmotic flow in this study. Catholyte circulation of 0.1 N HNO3 in the cathode chamber enhanced the overall removal of heavy metals. The electric energy expenditure for pulsed electrokinetics was half of that for normal electrokinetics under identical conditions yet still had similar removal efficiency. Therefore, pulsed electrokinetics significantly affects energy consumption in a beneficial way. These results suggest that enhanced pulse eletrokinetic remediation is a cost-effective and economical technique.