Gyu Tae Seo

Kinetic development and evaluation of membrane sequencing batch reactor (MSBR) with mixed cultures photosynthetic bacteria for dairy wastewater treatment

This experimental study was conducted to evaluate a membrane sequencing batch reactor (MSBR) with mixed culture photosynthetic bacteria for dairy wastewater treatment. The study was undertaken in two steps: laboratory and pilot scale experiments. In the first step, kinetics analysis of the MSBR was carried out in a laboratory scale experiment with influent COD concentration of 2500 mg/L. The pilot scale experiment was conducted to investigate the performance of the MSBR and checked the suitability of the kinetics for an engineering design. The kinetic coefficients K(s), k, k(d), Y and mu(m) were found to be 174-mg-COD/L, 7.42/d, 0.1383/d, 0.2281/d and 1.69/d, respectively. There were some deviations of COD removal efficiency between the design value and the actual value. From the kinetics estimation, COD effluent from the design was 27 mg/L while the average actual COD effluent from the experiment was 149 mg/L. Due to the different light source condition, the factors relating to light energy (i.e. L(f) and IR(%)) must be incorporated into engineering design and performance prediction with these kinetic coefficients of the photosynthetic MSBR.

Biological powdered activated carbon (BPAC) microfiltration for wastewater reclamation and reuse

Abstract The experiment was conducted to evaluate a biological powdered activated carbon (BPAC) microfiltration (MF) system as an alternative for wastewater reclamation and reuse. A synthetic secondary sewage effluent contains refractory organic compounds such as humin, tannin, lignin, protein and high molecular carbohydrates as well as coliphage Qs as a model virus. The system performance was investigated at the activated carbon concentration of 20 g/1, water temperature 25°C and transmembrane pressure of 55 kPa. It was noted that organic removal occurred mainly at the membrane module. This was caused by the accumulation of the powdered activated carbon in the membrane module. The average organic removal efficiency was 83%, resulting in an effluent TOC concentration of 1–2 mg/1. The performance of the process did not deteriorate at water temperature of 15°C, showing an organic removal efficiency of 89.6%. It was estimated that the higher removal efficiency at lower water temperature was mainly due to the less self-degradation of microorganisms because the permeate flux of the membrane was maintained at the same level by increasing the transmembrane pressure up to 80 kPa. The removal of virus by the BPAC-MF system was significant. From the mass balance at steady state, 99.9997% of fed coliphage Qs was removed from the system. Especially coliphage Qs showed a strong adsorbability on powdered activated carbon (PAC). For 1 h contact with PAC, the removal of Qs was 99.999% even at PAC concentrations of 0.55 g/l. It was obvious that the virus removed was inactivated in the system.

Effect of volumetric organic loading rate (OLR) on H2 and CH4 production by two-stage anaerobic co-digestion of food waste and brown water

Two-stage anaerobic digestion system consisting of two continuously stirred tank reactors (CSTRs) operating at mesophillic conditions (37°C) were studied. The aim of this study is to determine optimum Hydraulic Retention Time (HRT) of the two-stage anaerobic digester system for hydrogen and methane production. This paper also discusses the effect of OLR with change in HRT on the system. Four different HRTs of 48, 24, 12, 8h were monitored for acidogenic reactor, which provided OLR of 17.7, 34.8, 70.8, 106gVS/L·d respectively. Two HRTs of 15days and 20days were studied with OLR of 1.24 and 1.76gVS/L·d respectively in methanogenic reactor. Hydrogen production at higher OLR and shorter HRT seemed favorable 106gVS/L·d (8h) in acidogenic reactor system. In methanogenic reactor system HRT of 20day with OLR of 1.24gVS/L·d was found optimum in terms of methane production and organic removal. The result of this study illustrated the optimum HRT of 8h and 20days in acidogenic stage and methanogenic stage for maximum hydrogen and methane production.

Effect of ion composition on nanofiltration rejection for desalination pretreatment

Abstract This experiment investigated and explains the rejection of calcium and magnesium ions and conductivity under the influence of the coexisting ions. Nanofiltration (NF) membranes have been used as pressure-driven type of cross-flow system in water treatment. The evolution of flux and rejection was followed in time during 2 h. For analysis and comparison, the values after 1 h of filtration were used. The NF membranes used in this study were thin film composite NF membranes NE90 (Woojing, Korea). The experiment indicated that Donnan exclusion had strong effect with cation when operated at low flux. However, the overall ion rejection, which was conducted by conductivity value, was high due to influence of dielectric phenomenon. For anion, electric repulsion between the NF membrane and chloride was high enough to push calcium and magnesium ions through the membrane by Donnan exclusion phenomenon. Chloride ion had stronger effect on the rejection of magnesium ion than the calcium ion. The results indica...

Degradation of Azo Dyes by the Reduction and Oxidation with Nano Sized Zero Valented Iron

The objective of this study is to investigate the efficient method to maximize both color and TOC removal of the azo dye solution by reduction and oxidation with a laboratory synthesized nano-sized zero valent iron (nZVI). The decolorization efficiency increased with the decrease of pH and increase of zero valent iron dosage. The optimum dosage of nano-sized zero-valent iron was 20mg/L at pH 3. The surface normalized constant of nZVI was higher than those reported for the discoloring of azo dye with other ZVIs. The sequential dose of nZVI/H2O2 remove color and TOC more effectively than the simultaneous dose. Pre-reduction by nZVI could convert azo dye to products whose oxidation is more degradable and therefore enhances the removal efficiency.

A Density Functional Theory Study on the Ozone Oxidation of Sulfonamide Antibiotics

Abstract The electronic structures of sulfonamide antibiotics (the ground state and the lowest singlet excited-state geometries) have been investigated by using density functional theory (DFT) simulations. Experimental studies on the removal of sulfamethazine, sulfathiazole and sulfamethoxazole by ozone have also been conducted by using liquid chromatography with tandem mass spectrometric detection (LC/MS/MS). The calculated ground and excited state geometries exhibited low energy of the inter-ring bonds, which suggests the weakest bonds that can be broken during the ozone oxidation process. The orbital energy calculations (HOMO-LUMO and its energy gap) demonstrate that the smaller HOMO-LUMO energy gap, the higher reactivity toward ozone oxidation. Additionally, the current study suggests potential products of the three pharmaceutical compounds based on their electronic properties, which may help better understand the unknown reaction pathways of the pharmaceutical compounds.

Characteristics of Pollutants Removal by Carbonized Porous Media Made from Sewage Sludge

In this study, carbonized porous media was manufactured using sewage sludge and analyzed for pollutants removal characteristics. Sewage sludge produced by activated sludge sewage treatment contained much organics to be carbonized, so it was mixed with other mixtures, extruded and formed in ∅ 5~10 mm ball shape, and sintered at 900°C and 1 hour in furnace for carbonization under N2 purge. The characteristics of the porous media was BET 35 m2/g and average pore size 39.3Å, pore volume 0.0092 cm3/g, Iodine number 45.9 and bulk density 0.91 cm3/g. Experiments were performed for SS, phosphate, nitrate and heavy metals (Cu, Zn). Its removal characteristics of SS and fertilizer components were compared with gravel’s used in filtration and its heavy metals removal was characterized by derivation of its adsorption equilibrium equations. In result, the carbonized porous media could be utilized as massive adsorption media for pollutant removal or fertilizer adsorption in fields of roof planting or non-point source pollutants control.

Degradation of Sulfonamide Antibiotic Substances by Ozonation: An Experimental and Computational Approach

Concern has grown over a presence of micropollutants in natural water since sulfonamide antibiotic substances such as sulfamethazine, sulfamethoxazole, sulfathiazole have been frequently detected in Nakdong River, Korea. The current work investigates the degradation of the three sulfonamide substances by using quantum chemistry calculations of density functional theory (DFT) and experimental measurement techniques of Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectrophotometer (UV-VIS). DFT calculations demonstrate that the lowest energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbitals (LUMO) lies in sulfanilamide functional group of sulfonamide, implying that the sulfanilamide functional group would be the most active site for ozone oxidation. Also, UV-VIS spectra and FT-IR analysis reveal that 260 nm band originated from sulfanilamide group was absent after ozone oxidation, indicating that a functional group of amine (N-H) was removed from sulfanilamide. Both theoretical and experimental observations agree well with each other, demonstrating the DFT calculation tool can be an alternative tool for the prediction of chemical reactions in purification treatment processes.

A Study on the Adsorption of Sulfonamide Antibiotics on Activated Carbon Using Density Functional Theory

The removal of sulfonamide antibiotics (SAs) by activated carbon was investigated by using granular activated carbon (GAC) tests and density functional theory (DFT) simulations. The GAC absorption tests show the removal efficiency of 68.4~90.7% and 99.0~99.9% in 1 and 24 hours, respectively. In both GAC tests, the removal efficiency of sulfamethazine (SMZ) was the highest followed by those of sulfathiazole (STZ) and sulfamethoxazole (SMTZ): SMZ > STZ > SMTZ. In DFT adsorption simulations, we found that the 4-aminobenzenesulfonamide parts of SMZ and STZ and the 3-methyl-1,2-oxazol-5-amine part of SMTZ are preferentially adsorbed on the edges of graphene model, provided that the adsorbates keep their structures without dissociation upon adsorption process. The adsorption energies of SMZ, STZ, and SMTZ are -4.91, -4.64, and -4.62 eV, respectively. This adsorption strength (SMZ > STZ > STMZ) agrees with the trend of the removal efficiency of SAs by GAC. In addition, dissociative adsorption configurations of SAs are discussed.

Synthesis of Zeolite Added Clay and Sewage Sludge

Zeolite has been used as catalyzer, absorbent, ion-exchange matter and dehydrating agent due to its excellent catalytic property and ion-exchange. In recent years, many studies have been conducted to apply zeolite as new materials such as zeolite membranes and zeolite sensor films. To introduce properties of zeolite, it should be examined how zeolite could be reacted other materials. In this study, it is investigated whether zeolite is successfully synthesized or not when clay and/or sewage sludge coexist with zeolite precursor. Zeolite precursor was made of liquid sodium silicate and sodium aluminate. Mixing ratio of caly and/or sewage sludge is 0-10%(wt.). To compare two processes, the mixture was synthsized by hydrothermal method and high temperature sintering process. It is synthesized by hydrothermal with sintering at high temperature process. The resulting materials were characterized by XRD and SEM. As a result, various type of zeolite such as zeolite X, zeolite A and zeolite P1 was successfully synthesized by hydrothermal method when clay and/or sewage coexist with zeolite precursor. However, zeolite was rarely synthesized by high temperature sintering process. Therefore, when preperation of zeolite material mixed with other material such as clay and sewage sludge, hydrothermal method is more effective than sintering at high temperature process.