Abstract
An understanding of particle-particle interactions in filtration requires studying the detachment as well as the attachment of nanoparticles. Nanoparticles captured in a granular media filter can be released by changing the physicochemical factors. In this study, the detachment of captured silver nanoparticles (AgNPs) in granular media filtration was examined under different ionic strengths, ion type, and the presence or absence of natural organic matter (NOM). Filtration velocity and ionic strength were chosen as the physical and chemical factors to cause the detachment. Increasing filtration velocity caused a negligible amount of AgNP detachment. On the other hand, lowering ionic strength showed different release amounts depending on the background ions, implying a population of loosely captured particles inside the filter bed. Overall detachment was affected by ionic strength and ion type, and to a lesser degree by NOM coating which resulted in slightly more detachment (in otherwise identical conditions) than in the absence of that coating, possibly by steric effects. The secondary energy minimum with Na ions was deeper and wider than with Ca ions, probably due to the lack of complexation with citrate and charge neutralization that would be caused by Ca ions. This result implies that the change in chemical force by reducing ionic strength of Na ions could significantly enhance the detachment compared to that caused by a change in physical force, due to a weak electrostatic deposition between nanoparticles and filter media. A modification of the 1-D filtration model to incorporate a detachment term showed good agreement with experimental data; estimating the detachment coefficients for that model suggested that the detachment rate could be similar regardless of the amount of previously captured AgNPs.
Key Words
detachment; nanoparticles; secondary energy minimum; granular media filtration model
Address
1School of Urban and Civil Engineering, Hongik University, 94 Wausan-ro, Mapo-gu, Seoul, Republic of Korea
2Arcadis-US, Inc., 1717 West 6th Street, Ste. 210, Austin, TX 78703, USA
3Division of Marine Science, University of Southern Mississippi, Stennis Space Center, MS 39529, USA
4Department of Civil, Architectural and Environmental Engineering, The University of Texas at Austin, 1 University Station C1786,
Austin, TX 78712, USA
Abstract
The effectiveness of in situ sediment capping as a technique for heavy metal risk mitigation in Hyeongsan River estuary, South Korea was studied. Sites in the estuary were found previously to show moderate to high levels of contamination of mercury, methylmercury and other heavy metals. A 400 m x 50 m section of the river was selected for a thin layer capping demonstration, where the total area was divided into 4 sections capped with different combinations of capping materials (zeolite, AC/zeolite, AC/sand, zeolite/sand). Pore water concentrations in the different sites were studied using diffusive gradient in thin film (DGT) probes. All capping amendments showed reduction in the pore water concentration of the different heavy metals with top 5 cm showing %reduction greater than 90% for some heavy metals. The relative maxima for the different metals were found to be translated to lower depths with addition of the caps. For two-layered cap with AC, order of placement should be considered since AC can easily be displaced due to its relatively low density. Investigation of methylmercury (MeHg) in the site showed that MeHg and %MeHg in pore water corresponds well with maxima for sulfide, Fe and Mn suggesting mercury methylation as probably coupled with sulfate, Fe and Mn reduction in sediments. Our results showed that thin-layer capping of active sorbents AC and zeolite, in combination with passive sand caps, are potential remediation strategy for sediments contaminated with heavy metals.
Key Words
Diffusive Gradient in Thin Film (DGT), sediment, mercury, heavy metal, capping
Address
1Department of Environmental Systems Engineering, Korea University, Sejong City, Republic of Korea
2 Department of Environmental Engineering, Chungnam National University, Daejeon City, Republic of Korea
3 Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, Texas, USA
Abstract
The purpose of this study was to investigate the characteristics of lignin fractionated from waste wood (WW) using a two-step process of ethanol organosolv pretreatment followed by ultrafiltration with membranes of different molecular weight cut-offs (1, 5 and 20 kDa). The different permeates obtained were characterized by fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). The analysis by FT-IR and NMR of these lignins showed that the lignin core was successfully separated from WW. TGA curves confirmed that the thermal properties of lignin fractionated by ultrafiltration were almost identical to each other. The results from GPC confirmed that fractionating of lignin was achieved by ultrafiltration. For the membrane fractionation process, values of molecular weight decreased as the cut-offs used to obtain the fractions became smaller. As a result, fractionating lignin by a two-step process allowed separating different fractions of lignin of different molecular weights yielded high purity without interference from existing pollutants in WW. The two-step process offers the possibility of using fractionated WW as an untapped source of lignin.
Key Words
waste wood; lignin; ultrafiltration; fractionation; characterization
Address
1Department of Marine Environmental Engineering and Institute of Marine Industry, Gyeongsang National University,
Tongyeong, Gyeongnam 650-160, Republic of Korea
2School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology,
Gwangju 61005, Republic of Korea
3Department of Civil and Environmental Engineering, Hanyang University,
Seongdong-gu, Seoul, 04763, Republic of Korea
4Department of Environmental System Engineering, Chonnam National University,
Yeosu, Jeonnam, 59626, Republic of Korea
Abstract
Anaerobic membrane bioreactor (AnMBR) treatment has been widely studied in recent years because of the potential for production of bio-energy from wastewater and energy-positive operation of wastewater treatment plants. Several AnMBR systems, including those that incorporate ceramic membranes, take advantage of enhanced water permeability and low membrane fouling potentials. Given that differences in the ceramic membranes may influence the results of AnMBR studies, relevant details are discussed in this review, which focuses on the profiles of common ceramic membranes used in AnMBR, treatment and filtration performances of different anaerobic ceramic membrane bioreactors (AnCMBRs), and the membrane fouling mitigation methods available for effective AnCMBRs operation. The aim of this review is to provide a comprehensive summary of AnCMBR performance, feed wastewater characteristics, operating conditions, and the methods available for effective fouling mitigation.
Abstract
Lead is a highly toxic heavy metal that causes serious health problems. Nonetheless, it is increasingly being used for industrial applications and is often discharged into the environment without adequate purification. In this study, Pb(II) was removed by powdered waste sludge (PWS) based on the biosorption mechanism. Different PWSs were collected from a submerged moving media intermittent aeration reactor (SMMIAR) and modified Ludzack-Ettinger (MLE) processes. The contents of extracellular polymeric substances were similar, but the surface area of MLE-PWS (2.07 m2/g) was higher than that of SMMIAR-PWS (0.82 m2/g); this is expected to be the main parameter determining Pb(II) biosorption capacity. The Bacillaceae family was dominant in both PWSs and may serve as the major responsible bacterial group for Pb(II) biosorption. Pb(II) biosorption using PWS was evaluated for reaction time, salinity effect, and isotherm equilibrium. For all experiments, MLE-PWS showed higher removal efficiency. At a fixed initial Pb(II) concentration of 20 mg/L and a reaction time of 180 minutes, the biosorption capacities (qe) for SMMIAR- and MLE-PWSs were 2.86 and 3.07 mg/g, respectively. Pb(II) biosorption using PWS was rapid; over 80% of the maximum biosorption capacity was achieved within 10 minutes. Interestingly, MLE-PWS showed enhanced Pb(II) biosorption with salinity values of up to 30 g NaCl/L. Linear regression of the Freundlich isotherm revealed high regression coefficients (R2 > 0.968). The fundamental Pb(II) biosorption capacity, represented by the KF value, was consistently higher for MLE-PWS than SMMIAR-PWS.
Key Words
lead; biosorption; activated sludge; Freundlich isotherm; bacterial community structure
Address
1Graduate School of Environmental Engineering, Pusan National University, 63 Busandeahak-ro,
Geumjeong-gu, Busan 46241, Republic of Korea
2Aquaculture Management Division, National Institute of Fisheries Science, 216 Giganghaean-ro,
Gijang-eup, Gijang-gun, Busan, 46083, Republic of Korea
3Department of Civil and Environmental Engineering, Pusan National University, 63 Busandeahak-ro,
Geumjeong-gu, Busan 46241, Republic of Korea
Abstract
The effect of Combined Sewer Overflow on the river system was investigated throughout three preliminary field tests and three main ones. As a result of the study, Combined Sewer Overflow did not affect water qualities on the main stream since the concentration of the main stream did not significantly changed during rainfall events although the water quality of tributaries has rapidly deteriorated due to the influence of the Combined Sewer Overflow during rainfall events. The main cause of the result is that the flow rate of the tributaries is considerably lower than that of the main stream, so that the tributaries with deteriorated water quality during rainfall events did not significantly affect the quality of the actual main stream. Therefore, the water quality of the Kumho River is more affected by the wastewater treatment facilities that discharges water continuously to the main stream than pollutants from non-point pollution sources during rainfall events. As a result, managements for discharges from wastewater treatment facilities should be strengthened in order to improve the water quality of the river.
Key Words
Combined Sewer Overflow; rainfall event; water quality; wastewater treatment facility
Address
Department of Global Environment, School of Environment, Keimyung University, 203 Osan Hall,
1095 Dalgubuldaero, Dalsegu, Daegu, South Korea
Abstract
The study objective was to evaluate the enhanced removal of high concentrations of phosphorus from synthetic wastewater (solely phosphorus-containing) and real wastewater (pig manure) by using carbon nanotube (CNT)-coated steel slag. Generally, phosphorus removal by steel slag is attributed to Ca2+ eluted from the slag. However, in this study, CNT was used to control the excess release of Ca2+ from steel slag and increase the phosphorus removal. The phosphorus removal rate by the uncoated steel slag was lower than that of the CNT-coated steel slag, even though the Ca2+ concentrations were higher in the solution containing the uncoated steel slag. Therefore, the phosphorus removal could be attributed to both precipitation with Ca2+ eluted from steel slag in aqueous solution and adsorption onto the surface of the CNT-coated steel slag. Furthermore, the protons released from the CNT surface by exchanging with divalent cations acted to reduce the pH increase of the solution, which is attributed to the OH- eluted from the steel slag. The adsorption isotherm and kinetics of the CNT-coated steel slags followed the Freundlich isotherm and pseudo-second-order model, respectively. The maximum adsorption capacity of the uncoated and CNT-coated steel slags was 6.127 and 9.268 mg P g-1 slag, respectively. In addition, phosphorus from pig manure was more effectively removed by the CNT-coated steel slag than by the uncoated slag. Over 24 hours, the PO4-P removal in pig manure was 12.3% higher by the CNT-coated slag. This CNT-coated steel slag can be used to remove both phosphorus and metals and has potential applications in high phosphorus-containing wastewater like pig manure.
Key Words
pig manure; high concentration of phosphorus; phosphorus removal; steel slag; carbon nanotube; adsorption isotherm; adsorption kinetics
Address
1Institute for Environment and Energy, Pusan National University, 2 Busandaehak-ro 63beon-gil,
Geumjeong-gu, Busan 46241, Republic of Korea
2Department of Environmental Engineering, Pusan National University, 2 Busandaehak-ro 63beon-gil,
Geumjeong-gu, Busan 46241, Republic of Korea
3Department of Chemical and Environmental Engineering, Pusan National University, 2 Busandaehak-ro 63beon-gil,
Geumjeong-gu, Busan 46241, Republic of Korea
Abstract
Former studies revealed that sepiolite thermally treated at high temperature have high adsorption capacity for phosphate. However, its micron size (75 micro-m) limits its application to water treatment. In this study, we synthesized sepiolite impregnated polysulfone (PSf) beads to separate it easily from an aqueous solution. PSf beads with different sepiolite ratios were synthesized and their efficiencies were compared. The PSf beads with 30% impregnated sepiolite (30SPL-PSf bead) possessed the optimum sepiolite ratio for phosphate removal. Kinetic, equilibrium, and thermodynamic adsorption experiments were performed using the 30SPL-PSf bead. Equilibrium adsorption was achieved in 24 h, and the pseudo-first-order model was suitable for describing the phosphate adsorption at different reaction times. The Langmuir model was appropriate for describing the phosphate adsorption onto the 30SPL-PSf bead, and the maximum adsorption capacity of the 30SPL-PSf bead obtained from the model was 24.48 mg-PO4/g. Enthalpy and entropy increased during the phosphate adsorption onto the 30SPL-PSf bead, and Gibb\'s free energy at 35 degree Celcius was negative. An increase in the solution pH from 3 to 11 induced a decrease in the phosphate adsorption amount from 27.30 mg-PO4/g to 21.54 mg-PO4/g. The competitive anion influenced the phosphate adsorption onto the 30SPL-PSf bead was in the order of NO3- > SO42- > HCO3-. The phosphate breakthrough from the column packed with the 30SPL-PSf bead began after ~2000 min, reaching the influent concentration after ~8000 min. The adsorption amounts per unit mass of 30SPL-PSf and removal efficiency were 0.775 mg-PO4/g and 61.6%, respectively. This study demonstrates the adequate performance of 30SPL-PSf beads as a filter for phosphate removal from aqueous solutions.
Key Words
sepiolite; polysulfone; beads; phosphate; adsorption
Address
1Department of Integrated System Engineering, Hankyong National University, Anseong, 17579, Republic of Korea
2Department of Environmental and Safety Engineering, Ajou University, Suwon 16499, Republic of Korea
3Department of Environmental Engineering, Pusan National University, Busan, 46241, Republic of Korea
4Department of Bioresources and Rural System Engineering, Hankyong National University, Anseong, 17579, Republic of Korea
Abstract
A single-stage deammonification with a sequencing batch reactor (SBR) that simultaneous nitritation, anaerobic ammonia oxidation (anammox), and denitrification (SNAD) occur in one reactor has been widely applied for sidestream of wastewater treatment plant. For the stable and well-balanced SNAD, a feeding strategy of influent wastewater is one of the most important operating factors in the single-stage deammonification SBR. In this study, single-stage deammonification SBR (working volume 30L) was operated to treat a high-strength ammonium wastewater (1200 mg NH4+-N/L) with different feeding strategies (single feeding and nine-step feeding) under the condition without COD. Each cycle of the step feeding involved 6 sub-cycles consisted of aerobic and anoxic periods for partial nitritation (PN) and anammox, respectively. Contrary to unstable performance in the single feeding, the step feeding showed better deammonification performance (0.565 kg-N/m3/day). Under the condition with COD, however, the nitrogen removal rate (NRR) decreased to 0.403 kg-N/m3/day when the Nine-step feeding strategies had an additional denitrification period before sub-cycles for PN and anammox. The NRR was recovered to 0.518 kg-N/m3/day by introducing an enhanced multiple-step feeding strategy. The strategy had 50 cycles consisted of feed, denitrification, PN, and anammox, instead of repeated sub-cycles for PN and anammox. The multiple-step feeding strategy without sub-cycle showed the most stable and excellent deammonification performance: high nitrogen removal efficiency (98.6%), COD removal rate (0.131 kg-COD/m3/day), and COD removal efficiency (78.8%). This seemed to be caused by that the elimination of the sub-cycles might reduce COD oxidation during aerobic condition but increase the COD utilization for denitrification period. In addition, among various sensor values, the ORP pattern appeared to be applicable to monitor and control each reaction step for deammonification in the multiple-step feeding strategy without sub-cycle. Further study to optimize the number of multiple-step feeding is still needed but these results show that the multiple-step feeding strategy can contribute to a well-balanced SNAD for deammonification when treating high-strength ammonium wastewater with COD in the single-stage deammonification SBR.
Key Words
deammonification; sequencing batch reactor; single feeding; step feeding; sub-cycle; multiple, ORP
Address
Department of Civil and Environmental Engineering, Pusan National University, Busan 46241
