Abstract
In this study, we investigated the cultivation possibility using Hydrodictyon reticulatum in a continuous raceway pond as a tertiary sewage treatment plant. The cultivation possibility was evaluated by varying the light quantity, wavelength, and hydraulic retention time (HRT). Experimental results showed that the growth rates of algae and the removal efficiencies of nutrients increased as the light quantity increased, and the maximum photosynthetic rate was maintained at 100 umol/m2.s or higher. When wavelength was varied, nutrient removal efficiency and growth rate increased in the following order: green light, red light, white light, and blue light. The nutrient removal efficiencies and algae productivity in HRT 4 d were better than in HRT 8 d. We conclude that if Hydrodictyon reticulatum is cultivated in a raceway pond and used as a tertiary treatment facility in a sewage treatment plant, nutrients can be effectively removed, and production costs can be reduced.
Abstract
In this study, we performed an electrowinning process for effective removal of metals (Cu and Ni) in solution and their recovery as solid forms. A complete removal of Cu and Ni (1,000 mg/L) was observed during four times recycling test, indicating that our electrowinning system can ensure the efficient metal removal with high stability and durability. In addition, we investigated effect of operation parameters (i.e., concentration of boric acid only for Ni, variation of pH, concentration of electrolyte (H2SO4), and cell voltage) on the efficiency of metal removal (Cu and Ni) during the electrowinning. The addition of boric acid significantly enhanced removal efficiency of Ni as the concentration of boric acid increased up to 10 g/L. Compared to negligible pH effect (pH 1, 2, and 4) on the Cu removal, we observed the increase in removal efficiency of Ni as the pH increased from 1 to 4. The electrolyte concentration did not significantly influence the removal of Cu and Ni in this study. We also obtained great removal rates of Cu and Ni at 2.5 V and 4.0 V, which were much faster than those at lower voltages. Finally, almost 99% of each Cu and Ni (1,000 mg/L) was selectively removed from the mixture of metals by adjusting pH and addition of boric acid after the completion of Cu removal. The findings in this study can provide a fundamental knowledge about effect of important parameters on the efficiency of metal recovery during the electrowinning.
Key Words
electrowinning; extractive metallurgy; metal recovery; anode
Address
Department of Civil and Environmental Engineering, Konkuk University,
120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea
Abstract
Non-aqueous solvents (NASs) are generally known to be barely miscible, and reactive with polar compounds, such as water. However, water can interact with some NASs, which can be used as a new means for water recovery from saline water. This study explored the fate of water and salt in NAS, when saline water is mixed with NAS. Three amine solvents were selected as NAS. They had the same molecular formula, but were differentiated by their molecular structures, as follows: 1) NAS \'A\' having the hydrophilic group (NH2) at the end of the straight carbon chain, 2) NAS \'B\' with symmetrical structure and having the hydrophilic group (NH) at the middle of the straight carbon chain, 3) NAS \'C\' having the hydrophilic group (NH2) at the end of the straight carbon chain but possessing a hydrophobic ethyl branch in the middle of the structure. In batch experiments, 0.5 M NaCl water was blended with NASs, and then water and salt content in the NAS were individually measured. Water absorption efficiencies by NAS \'B\' and \'C\' were 3.8 and 10.7%, respectively. However, salt rejection efficiency was 98.9% and 58.2%, respectively. NAS \'A\' exhibited a higher water absorption efficiency of 35.6%, despite a worse salt rejection efficiency of 24.7%. Molecular dynamic (MD) simulation showed the different interactions of water and salts with each NAS. NAS \'A\' formed lattice structured clusters, with the hydrophilic group located outside, and captured a large numbers of water molecules, together with salt ions, inside the cluster pockets. NAS \'B\' formed a planar-shaped cluster, where only some water molecules, but no salt ions, migrated to the NAS cluster. NAS \'C\', with an ethyl group branch, formed a cluster shaped similarly to that of \'B\'; however, the boundary surface of the cluster looked higher than that of \'C\', due to the branch structure in solvent. The MD simulation was helpful for understanding the experimental results for water absorption and salt rejection, by demonstrating the various interactions between water molecules and the salts, with the different NAS types.
Key Words
non-aqueous solvent (NAS); desalination; directional solvent extraction (DSE); salt rejection; molecular dynamics
Address
Ohkyung Choi, Jae Woo Lee: Department of Environmental Engineering, Korea University, Sejong 30019, Republic of Korea
Minsup Kim, Art E. Cho: Department of Bioinformatics, Korea University, Sejong 30019, Republic of Korea
Young Chul Choi:Water Research Center, Southern Research, GA 30120, USA
Gyu Dong Kim:Energy, Environment & Engineering, RTI International, NC 27709, USA
Dooil Kim:Department of Civil and Environmental Engineering, Dankook University, Yongin 16890, Republic of Korea
Abstract
Anaerobic digestion (AD) has been widely used to valorize food waste (FW) because of its ability to convert organic carbon into CH4 and CO2. Korean FW has a high content of fruits and vegetables, and efficient hydrolysis of less biodegradable fibers is critical for its complete stabilization by AD. This study examined the digestates from different anaerobic digesters, namely Rs, Rr, and Rm, as the inocula for the AD of vegetable waste (VW) and cellulose (CL): Rs inoculated with anaerobic sludge from an AD plant, Rr inoculated with rumen fluid, and Rm inoculated with anaerobic sludge and augmented with rumen fluid. A total of six conditions (3 inocula x 2 substrates) were tested in serial subcultures. Biogas yield was higher in the runs inoculated with Rm than in the other runs for both VW (up to 1.10 L/g VS added) and CL (up to 1.05 L/g VS added), and so was biogas production rate. The inocula had different microbial community structures, and both substrate type and inoculum source had a significant effect on the formation and development of microbial community structures in the subcultures. The overall results suggest that the bioaugmentation with rumen microbial consortium has good potential to enhance the anaerobic biodegradability of VW, and thereby can help more efficiently digest high fiber-content Korean FW.
Key Words
anaerobic digestion; bioaugmentation; rumen culture; vegetable waste; cellulose
Address
Yeadam Jo and Changsoo Lee: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST),
50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919, Republic of Korea
Kwanghyun Hwang: Environmental Process Engineering Team, Global Engineering Division, GRAN SEOUL, 33 Jong-ro,
Jongno-gu, Seoul 03159, Republic of Korea
Abstract
Titania modified by 2-ethylimidazole (2-EI) (denoted as 2-EI-TiO2) demonstrated visible light photocatalytic activity for the degradation of organic compounds. 2-EI-TiO2 was a bright brown powder that exhibited similar crystallinity and morphology with the control TiO2. A diffuse reflectance spectrum indicated that 2-EI-TiO2 absorbs visible light of all wavelengths. X-ray photoelectron spectroscopy (XPS) confirmed the cationic state of nitrogen species (e.g. Ti-O-N) on the surface of 2-EI-TiO2. Visible light-illuminated 2-EI-TiO2 degraded 10 M 4-chlorophenol (4-CP) by approximately 85% in 4 h. The photochemical activity of 2-EI-TiO2 was selective in targeting the organic compound. The repeated use of 2-EI-TiO2 decreased the photocatalytic activity for the 4-CP degradation. Experiments using radical scavengers and oxidant probes revealed that the oxidation by photogenerated holes is responsible for the degradation of organic compounds by illuminated 2-EI-TiO2 and the role of •OH is negligible.
Key Words
visible light; photocatalysis; titanium dioxide; 2-ethylimidazole; oxidation
Address
Jiwon Seo and Changha Lee: School of Chemical and Biological Engineering, Institute of Engineering Research, Seoul National University,
Jiwon Seo, Junyoung Jeong: Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
2School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST),
50 UNIST-gil, Ulju-gun, Ulsan 44919, Republic of Korea
Abstract
Peroxymonosulfate (PMS) in combination with Cu(II) was examined to inactivate E. coli and MS2 coliphage in natural water. The combined system (i.e., the Cu(II)/PMS system) caused a synergistic inactivation of E. coli and MS2, in contrast with either Cu(II) or PMS alone. Increasing the concentration of PMS enhanced the inactivation of E. coli and MS2, but after a certain point, it decreased the efficacy of the microbial inactivation. In the Cu(II)/PMS system, adding reactive oxidant scavengers marginally affected the E. coli inactivation, but the inhibitory effects of copper-chelating agents were significant. Fluorescent assays indicated that the Cu(II)/PMS system greatly increased the level of reactive oxidants inside the E. coli cells. The sequential addition of Cu(II) and PMS inactivated more E. coli than did adding the two simultaneously; in particular, the inactivation efficacy was much higher when Cu(II) was added first. The observations from the study collectively showed that the microbial inactivation by the Cu(II)/PMS system could be attributed to the toxicity of Cu(I) as well as the intracellular oxidative stress induced by Cu(III) or radical species.
Key Words
microbial inactivation; E. coli; MS2 coliphage; copper; peroxymonosulfate
Address
Hyung-Eun Kim: Center for Water Resource Cycle Research, KIST School, Korea Institute of Science and Technology (KIST),
5 Hwarang-ro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea
Hye-Jin Lee: Department of Chemical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada
Min Sik Kim, Changha Lee: School of Chemical and Biological Engineering, Institute of Engineering Research,
Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
Joon-Young Choi: Hyorim Industries Inc., 96-8, Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13517, Republic of Korea
Abstract
Plating wastewater containing various heavy metals can be produced by several industries. Specifically, we focused on the removal of copper (Cu2+) and nickel (Ni+) ions from the plating wastewater because all these ions are strictly regulated when discharged into watershed in Korea. The application of both nanofiltration (NF) and reverse osmosis (RO) technologies for the treatment of wastewater containing copper and nickel ions to reduce fresh water consumption and environmental degradation was investigated. In this work, the removal of copper (Cu2+) and nickel (Ni+) ions from synthetic water was studied on pilot scale remove by before using two commercial nanofiltration (NF) and reverse osmosis(RO) spiral-wound membrane modules (NE2521-90 and RE2521-FEN by Toray Chemical). The influence of main operating parameters such as feed concentration on the heavy metals rejection and permeate flux of both membranes, was investigated. Synthetic plating wastewater samples containing copper (Cu2+) and nickel (Ni2+) ions at various concentrations(1, 20, 100, 400 mg/L) were prepared and subjected to treatment by NF and RO in the pilot plant. The results showed that NF, RO process, with 98% and 99% removal for copper and nickel, respectively, could achieve high removal efficiency of the heavy metals.
Key Words
nanofiltration; reverse osmosis; plating wastewater; heavy metal; rejection rate
Address
Jaehyun Jung, Bora Shin, Jinwoo Cho: Department of Environment and Energy, Sejong University, Seoul 05006, Korea
Jae Woo Lee: Department of Environmental Engineering, Korea University, Sejong 339-700, Korea
Ki Young Park: Department of Civil and Environmental System Engineering, Konkuk University, Seoul 05029, Korea
Seyeon Won: Han-River Environment Research Center, Water Environment Chemistry Research Lab, Gyeonggi-do 12585, Korea
Abstract
Prussian blue (PB) is well known for its excellent Cs+ ions adsorption capacity. Due to the high dispersibility of PB in aqueous phase, composite materials imbedding PB in supporting materials have been introduced as a solution. However, building PB particles inside porous supporting materials is still difficult, as PB particles are not fully formed and elute out to water. In this study, we suggest layer-by-layer (LBL) assembly to provide better immobilization of PB on supporting materials of poly vinyl alcohol sponge (PVA) and cellulose filter (CF). Three different PB attachment methods, ex-situ/in-situ/LBL assembly, were evaluated using PB leaching test as well as Cs+ adsorption test. Changes of surface functionality and morphology during PB composite preparation protocols were monitored through Fourier transform infrared spectroscopy and scanning electron microscopy. The results indicate that LBL assembly led to better PB attachment on supporting materials, bringing less eluting PB particles in aqueous phase compared to other synthesis methodologies, such as ex-situ and in-situ synthesis. By enhancing the stability of the adsorbent, adsorption capacity of PVA-PB with LBL improved nine times and that of CF-PB improved over 20 times. Therefore, the results suggest that LBL assembly offers a better orientation for growing PB particles on porous supporting materials
Key Words
prussian blue; cesium; polyvinyl alcohol sponge; cellulose filter; layer by layer
Address
Hyobin Wi, Hyowon Kim and Yuhoon Hwang: Department of Environmental Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
Sung-Won Kang : Environmental and Plant Engineering Research Institute, Korea Institute of Civil Engineering and Building Technology,
Goyang-si, 10223, Korea
