Song Bae Kim

Bacteria transport through goethite-coated sand: Effects of solution pH and coated sand content

This study investigated the transport of bacteria through goethite-coated sand, focusing on the effects of solution pH and coated sand content on the transport of Escherichia coli ATCC 11105. The first set of column experiments was performed in columns (length 30 cm, diameter 5 cm) packed with quartz sand coated with goethite in solution having a pH in the range of 6-9. The second was carried out in columns (length 30 cm, diameter 2.5 cm) with varying coated sand contents ranging from 0 to 100%. Results indicate that the bacteria transport in the coated sand was influenced by solution pH. Around pH 6 and 7, bacterial mass recoveries were low at 2.4-6.7% while they were high at 76.3-81.6% around pH 8 and 9. Around pH 8, the positively charged coated sand may convert to being negatively charged, causing an electrostatically repulsive interaction between the coated sand and bacteria, thus effecting a sharp change in the mass recovery. Results also reveal that the mass recovery decreased from 76.7 to 2.7% as the coated sand content increased from 0 to 100%, showing the nonlinear dependency of mass recovery on the content of coated sand. This study demonstrates the importance of the solution pH and coated sand content in the adhesion of bacteria to goethite-coated sand and furthermore contributes to the knowledge of bacterial removal in positively charged porous media.

Comparative analysis of fixed-bed sorption models using phosphate breakthrough curves in slag filter media

AbstractFixed-bed kinetic sorption (Bohart–Adams, Thomas, Yoon–Nelson, Clark, Wolborska, and modified dose-response) models are commonly used to simulate breakthrough curves (BTCs) from fixed-bed systems. However, more caution should be taken in using these models. Some researchers misused the equation, which is a totally different type from the original model, as a simplified model. Others used the same equation expressed in different forms as an independent model. The aim of this study was to clarify the fixed-bed sorption models via comparative analysis using the phosphate BTCs in slag filter media. For the analysis, the breakthrough data for phosphate (initial phosphate concentration = 1.0 and 2.0 mg/L) sorption in fixed-bed columns (inner diameter = 2.5 cm and column length = 10, 20, and 30 cm) were obtained from the experiments. The original Bohart–Adams model was simplified in the literature to the convergent- and divergent-type models in order to be used for the BTC analysis. However, the divergen...

Determination of bromacil transport as a function of water and carbon content in soils

This study was conducted to determine the significance of bromacil transport as a function of water and carbon content in soils and to explore the implications of neglecting sorption when making assessments of travel time of bromacil through the vadose zone. Equilibrium batch sorption tests were performed for loamy sand and sandy soil added with four different levels of powdered activated carbon (PAC) content (0, 0.01, 0.05, and 0.1%). Column experiments were also conducted at various water and carbon contents under steady-state flow conditions. The first set of column experiments was conducted in loamy sand containing 1.5% organic carbon under three different water contents (0.23, 0.32, and 0.41) to measure breakthrough curves (BTCs) of bromide and bromacil injected as a square pulse. In the second set of column experiments, BTCs of bromide and bromacil injected as a front were measured in saturated sandy columns at the four different PAC levels given above. Column breakthrough data were analyzed with both equilibrium and nonequilibrium (two-site) convection-dispersion equation (CDE) models to determine transport and sorption parameters under various water and carbon contents. Analysis with batch data indicated that neglect of the partition-related term in the calculation of solute velocity may lead to erroneous estimation of travel time of bromacil, i.e. an overestimation of the solute velocity by a factor of R. The column experiments showed that arrival time of the bromacil peak was larger than that of the bromide peak in soils, indicating that transport of bromacil was retarded relative to bromide in the observed conditions. Extent of bromacil retardation (R) increased with decreasing water content and increasing PAC content, supporting the importance of retardation in the estimation of travel time of bromacil even at small amounts of organic carbon for soils with lower water content.

Adsorption of bacteriophage MS2 to magnetic iron oxide nanoparticles in aqueous solutions

The aim of this study was to investigate the adsorption of bacteriophage MS2 by magnetic iron oxide nanoparticles in aqueous solutions. The characteristics of synthetic nanoparticles were analyzed using various techniques. The adsorption of MS2 to the nanoparticles was examined under various conditions using batch experiments. The results showed that the nanoparticles were mainly composed of maghemite along with goethite. The nanoparticles had a specific surface area of 82.2 m2 g−1, with an average pore diameter of 13.2 nm and total pore volume of 0.2703 cm3 g−1. The results demonstrated that the removal of MS2 by the nanoparticles was very fast. A 3.15 log removal (99.93%) was achieved within 60 min (adsorbent dose = 2 g L−1; MS2 concentration = 2.94 × 106 pfu mL−1). The log removal decreased from 3.52 to 0.36 with increasing MS2 concentration from 1.59 × 104 to 5.01 × 107 pfu mL−1. Also, the effect of solution pH on MS2 removal was minimal at pH 4.2–8.4. The removal of MS2 decreased in the presence of anions such as carbonate and phosphate, with the latter showing a greater hindrance effect on removal. This study demonstrated that magnetic iron oxide nanoparticles are very effective in the removal of MS2 from aqueous solutions.

Laboratory and pilot-scale field experiments for application of iron oxide nanoparticle-loaded chitosan composites to phosphate removal from natural water

ABSTRACT The aim of this study was to apply iron oxide nanoparticle-chitosan (ION-chitosan) composites to phosphate removal from natural water collected from the Seoho Stream in Suwon, Republic of Korea. Laboratory batch experiments showed that phosphate removal by the ION-chitosan composites was not sensitive to pH changes between pH values of 5.0 and 9.0. During six cycles of adsorption–desorption, the composites could be successfully regenerated with 5 mM NaOH solution and reused for phosphate removal. Laboratory fixed-bed column experiments (column height = 10 and 20 cm, inner diameter = 2.5 cm, flow rate = 8.18 and 16.36 mL/min) demonstrated that the composites could be successfully applied for phosphate removal under dynamic flow conditions. A pilot-scale field experiment was performed in a pilot plant, which was mainly composed of chemical reactor/dissolved air flotation and an adsorption tower, built nearby the Seoho Stream. The natural water was pumped from the Seoho Stream into the pilot plant, passed through the chemical reactor/dissolved air flotation process, and then introduced into the adsorption tower (height = 100 cm, inner diameter = 45 cm, flow rate = 7.05 ± 0.18 L/min) for phosphate removal via the composites (composite volume = 80 L, composite weight = 85.74 kg). During monitoring of the adsorption tower (33 days), the influent total phosphorus (T-P) concentration was in the range of 0.020–0.046 mgP/L, whereas the effluent T-P concentration was in the range of 0.010–0.028 mgP/L. The percent removal of T-P in the adsorption tower was 52.3% with a phosphate removal capacity of 0.059 mgP/g.

Determination of optimum isotherm and kinetic models for phosphate sorption onto iron oxide nanoparticles: nonlinear regression with various error functions

AbstractThe aim of this study was to determine optimum kinetic and isotherm models for phosphate (P) sorption onto iron oxide nanoparticles through nonlinear regression analysis. Equilibrium batch experiments were conducted at the experimental conditions of initial P concentration = 0.5–20 mg/L, adsorbent doses = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 g/L, and shaking time = 24 h. Kinetic batch experiments were also performed at the experimental conditions of initial P concentrations = 1, 2, 4, 6, 8, and 10 mg/L, adsorbent dose = 0.6 g/L, and shaking time = 10 min–24 h. Six isotherm models (Langmuir, Freundlich, Temkin, Redlich–Peterson, Khan, and Sips) were used to analyze the equilibrium data through nonlinear regression analysis. Three kinetic models (pseudo-first-order, pseudo-second-order, and Elovich) were used to analyze the kinetic data through nonlinear regression. Error functions including the sum of the squared errors, hybrid fractional error function (HYBRID), average relative error, Marquardt’s per...

Deposition and transport of Pseudomonas aeruginosa in porous media: lab-scale experiments and model analysis

In this study, the deposition and transport of Pseudomonas aeruginosa on sandy porous materials have been investigated under static and dynamic flow conditions. For the static experiments, both equilibrium and kinetic batch tests were performed at a 1:3 and 3:1 soil:solution ratio. The batch data were analysed to quantify the deposition parameters under static conditions. Column tests were performed for dynamic flow experiments with KCl solution and bacteria suspended in (1) deionized water, (2) mineral salt medium (MSM) and (3) surfactant+MSM. The equilibrium distribution coefficient (Kd) was larger at a 1:3 (2.43 mL g−1) than that at a 3:1 (0.28 mL g−1) soil:solution ratio. Kinetic batch experiments showed that the reversible deposition rate coefficient (katt) and the release rate coefficient (kdet) at a soil:solution ratio of 3:1 were larger than those at a 1:3 ratio. Column experiments showed that an increase in ionic strength resulted in a decrease in peak concentration of bacteria, mass recovery and tailing of the bacterial breakthrough curve (BTC) and that the presence of surfactant enhanced the movement of bacteria through quartz sand, giving increased mass recovery and tailing. Deposition parameters under dynamic condition were determined by fitting BTCs to four different transport models, (1) kinetic reversible, (2) two-site, (3) kinetic irreversible and (4) kinetic reversible and irreversible models. Among these models, Model 4 was more suitable than the others since it includes the irreversible sorption term directly related to the mass loss of bacteria observed in the column experiment. Applicability of the parameters obtained from the batch experiments to simulate the column breakthrough data is evaluated.