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The potassium (K) sorption characteristics with three adsorbents, natural zeolite, ammonium acetate-treated zeolite, and manganese nodule, were studied and compared to see the potential use of manganese nodule as an alternative K adsorbent. In general, the Langmuir isotherm could fit the K sorption in the KCl solutions at different pH conditions better than the Freundlich isotherm. Based on the Langmuir parameters, the maximum K sorption was greater for the zeolite-based adsorbents (i.e., 40–42 mg g−1) than the manganese nodule (i.e., 2.0 mg g−1) at acidic conditions, while the manganese nodule (i.e., 9.7 mg g−1) showed better K sorption at neutral conditions. With the seawater samples, the zeolite-based adsorbents showed higher K recovery (4–14%) than the manganese nodule (0–8.8%). The K sorption on the zeolite-based adsorbents followed the pseudo-second-order kinetics and the K sorption rates were higher for the treated zeolite than the natural zeolite. The repeated sorption tests showed that the natural zeolite could potentially be reused up to three times without any significant loss of K sorption capacity, while the ammonium acetate-treated zeolite lost its K sorption capacity after the single sorption test. Overall, the results show that the manganese nodule may potentially be the alternative to zeolite for K recovery under certain conditions, yet the zeolite-based adsorbents are generally better than the manganese nodule. Thus, more studies to enhance the K recovery using zeolite, including surface modified zeolite, are recommended.

Heavy metals are naturally occurring trace elements present in the environment, including soil, water, and air. However, high heavy metal concentration contamination from waste is a serious environmental problem brought on by industrial activities. The research in this study evaluated different biomineralized CaCO3 forms from individual bacteria species in heavy-metal-contaminated soils and mine tailings. Scanning electron microscope (SEM) images of the crystals were used to characterize the precipitated CaCO3. Generally, urea-hydrolysis bacteria form minerals via a microbiologically induced calcite precipitation (MICP) process. These bacteria produce the urease enzyme, which leads to urea-hydrolysis. These bacteria were isolated from heavy-metal-contaminated soils and characterized for their potential utilization in the S/S process. Optimum conditions for indigenous bacterial growth were 30 °C and a pH range of 7–8; and growth patterns were further affected by the growth medium salinity. SEM and X-ray diffraction (XRD) analyses demonstrated that bioaccumulated heavy metal ions were deposited around the cell envelope as rhombohedral and sphere shaped crystalline carbonate minerals in optimum conditions. In this study, the authors hypothesize that the indigenous bacteria can effectively precipitate heavy metals in soil and mine tailing with the urea-hydrolysis enzyme, and play an important role in heavy metal stabilization.

© 2016 Elsevier B.V. In this study, colloidal fouling behavior in pressure retarded osmosis (PRO) was systematically investigated in terms of the effects of draw solution concentration, applied hydraulic pressure at the draw side, feed solution pH, and particle size. Commercially-available cellulose triacetate (CTA) membranes were fouled with feed solution containing silica colloidal particles. Two different silica particles with mean diameter of 27 and 152 nm were used as model foulants. Our findings demonstrated that the colloidal fouling in PRO was dominantly affected by the cake layer buildup at the membrane surface. Fouling was further exacerbated by diffused salts from the draw side because retained salts within the cake layer elevated the salt concentration on the membrane surface, and consequently reduced the driving force of PRO. Substantial flux decline with the smaller particles was attributed to the high cake layer resistance due to the formation of the void-less cake layer. In addition, our approaches to mitigate the colloidal fouling revealed that the hydraulic cleaning by increasing the cross-flow rates was not effective to eliminate the compact cake layer. However, adjusting the feed solution pH showed the high potential to relieve the colloidal fouling resulting from the more stabilization of particles at low solution pH.

Providing high-resolution monitoring data is essential in promoting decision-making activities for surface water quality protection such as scientific modeling and data analysis. In this study, statistical models using multiple linear regression (MLR) were developed to estimate Chlorophyll-a (Chl-a) and total suspended solid (TSS) concentrations in a mesotrophic reservoir, the Yeongam Reservoir in Korea, from satellite observations. Two types of satellite data that covered different spectral regions, for wavelengths in 412–865 nm (for the Geostationary Ocean Color Imager) and those in 405–14,385 nm (for the Moderate Resolution Imaging Spectroradiometer), were used as inputs for statistical models, after bias correction. The MLR models for Chl-a and TSS were initially constructed and evaluated with 39 image data-sets obtained during 2011–2014. Subsequently, they compared with their corresponding algorithms that were developed under different environmental settings as well as the CE-QUAL-W2 model, a...

A performance analysis of a tri-combined process that consists of reverse osmosis (RO), membrane distillation (MD), and pressure-retarded osmosis (PRO) was conducted by using numerical approaches in order to evaluate its feasibility. In the hybrid process, the RO brine is partially used as the MD feed solution, and the concentrated MD brine is then mixed with the rest of the RO brine to be considered as the PRO draw solution. Here, the brine division ratio, incoming flow rate of RO, dimensions of the MD and PRO processes, and the supply cost of the MD heat source were considered as influential parameters. Previously validated process models were employed and the specific energy consumption (SEC) was calculated to examine the performance of the RO–MD–PRO hybrid process. The simulation results confirmed that the RO–MD–PRO hybrid process could outperform stand-alone RO in terms of reducing the SEC and the environmental footprint by dilution of the RO brine in locations where free or low-cost thermal energy can be exploited. Despite the need for further investigations and pilot-tests to determine its commercial practicability, this study provides insights into future directions for water and energy nexus processes for energy efficient desalination.

Pressure retarded osmosis (PRO) is a promising membrane-based process for producing clean and renewable energy. Since the major driving force is the salinity gradient between the feed and draw solutions, PRO can operate without a large environmental footprint. However, the performance of PRO can be severely limited by fouling, with organic fouling commonly deemed the main factor influencing PRO performance, since even a small amount of organic foulants can cause a significant flux decline. In spite of its importance, however, few studies have focused on PRO fouling. Therefore, the objectives of this study were to investigate the effect of hydraulic pressure as an influencing factor and to adjust the feed solution pH in order to alleviate fouling in the PRO process. Alginate was chosen as the model foulant due to its common existence in feed water. Based on our results, a higher hydraulic pressure caused an increase in the reverse solute flux, such that organic fouling became aggravated. In additio...

A hybrid forward osmosis (FO)/crystallization/reverse osmosis (RO) process for seawater desalination was proposed, and the theoretical analysis of the process was conducted. When the FO unit is considered as the main desalination unit, the crystallization and RO units can be regarded as a draw solute recovery process. First, in the FO process, fresh water is extracted from seawater and permeates into draw solution. This diluted draw solution is cooled down in the crystallization process and the draw solute is precipitated up to the saturation at low temperature. As a result, the feed stream of the RO process has lower concentration, and consequently, total energy consumption is expected to be reduced. In order to apply the proposed process in practice, the selection of suitable draw solute should be carefully determined. In the present work, five substances were suggested as draw solutes in the proposed system: ammonium oxalate, ammonium aluminum sulfate, sodium periodate, sodium phosphate and sodium sulfate. Based on properties of the substances, total energy consumption was analyzed for each draw solute. The total energy was calculated by the sum of cooling energy in crystallization process and pumping energy in RO process. Through the hybridization of these three unit processes, the energy requirement for fresh water production can be reduced to 2.15 kW h/m3. Thus, it is concluded that the proposed process can be highly competitive.

In this study, unlike the previous researches, the pretreatment equipment composed of a 40- μm disk filter and a hollow fiber ultra-filtration (UF) membrane was constructed. The performances of the pretreatment facilities were analyzed on the basis of 5-week-long continuous experiments using sea water. The results confirmed that the newly constructed pretreatment equipment could be used for the pretreatment of sea water reverse osmosis as evidenced by silt density index15 values below two for a long period and measured turbidities of about 0.4 NTU. The membrane fouling could be removed by using chemical enhanced backwash. Trans-membrane pressure and the permeability could be returned to the initial conditions. It reveals that UF membrane performances of the pretreatment were dependent on the sea water conditions and operating conditions.

A thorough investigation of membranes as well as their transport and material properties is a key to understanding the governing principles and unresolved issues of membrane processes. Through molecular dynamics (MD) simulations, static and dynamic properties of membrane separation systems may be investigated on a molecular level. By reviewing over 70 articles, this paper aims to highlight the usefulness of applying molecular dynamics in membranes (MDM) in order to broaden our knowledge of membrane-based water treatment processes. Here, the theoretical foundations of classical MD are described together with the results that are obtainable from MDM simulations. By compiling results from published works, we emphasize the ability of MD to determine membrane transport and material properties from simulations. The authors conclude by suggesting the further use of MDM for prospective research areas pertaining to membrane-based water treatment processes.

A numerical model for predicting the flux decline due to colloidal fouling was developed for a forward osmosis (FO) membrane system. We derived the kinetic equation of the cake layer growth based on a first-order reaction and control volume approach. Based on the model simulation, it was found that the deposited particles on a membrane surface are proportional to the feed concentration and the permeate flux. Moreover, the simulation result reveals that the cake-enhanced osmotic pressure (CEOP) is a key factor diminishing the permeate flux for large colloidal foulants. For small colloidal foulants, the hydraulic resistance of the cake layer is dominant in flux decline at the beginning of the fouling and CEOP increasingly become significant as fouling progresses. The effects of the reverse draw solute permeation on the flux decline were also simulated. Interestingly, the increased reverse draw solute permeation obtained by increasing the solute permeability showed little effect on the flux decline. Contrarily, variation of the diffusivity significantly influenced the flux decline. Consequently, the numerical model developed in this paper suggests that the selection of draw solute for an FO membrane process should be carefully regarded, along with the fouling mechanism.

Understanding the mass transfer in membrane separation processes plays a crucial role in improving the process performance. In this study, we numerically scrutinized the impacts of spacers—a structure enhancing the mass transfer in the vicinity of the membrane—on the concentration polarization (CP) in a forward osmosis (FO) process. To quantitatively measure the extent of CP, we introduce a concentration polarization index (CPI), which is proportional to the degree of CP and inversely proportional to the permeate flux. Based on the CPI, we simulated the impact of spacers on FO performance at various concentration conditions and found that the FO spacers generally reduce the extent of the CP; subsequently, this shows that FO spacers are important factors for the advancement of FO technology. In FO processes it was found that the boundary layer compression is more efficient for diminishing the CP than the boundary layer disruption, whereas the disruption mechanism was more successful in alleviating the CP in reverse osmosis (RO) processes. This contradiction was subsequently attributed to the intrinsic characteristics of the boundary layer disruption, which inevitably caused a dead zone near the spacer attachment and thereby boosted the CP in the FO process. Moreover, it was observed that spacers in feed channels increase the CP even when the concentration of the feed solution is zero, unless the membrane completely rejects salt, because any solute penetrating through the active layer of the membrane by a reverse diffusion mechanism accumulates near the spacer attachment. Hence, it is crucial to minimize the adverse impacts of FO spacers to maximize the beneficial effects of spacers to decrease the CP and improve the performance of FO processes.

Finding a suitable osmostically active solute is the most important problem in forward osmosis (FO). Even though there are a number of osmotically active compounds that exist, the major problem occurs during the separation of product water from the solute. Osmotically active macromolecules (polyethylene glycol [PEG] and humic acid [HA]) were investigated in this research as possible draw solutes for FO. Cellulose triacetate FO membranes (Hydration Technology Innovations, LLC) and several ultrafiltration and nanofiltration membranes were used in osmosis and filtration steps of the system, respectively. Molecular weights (MW) of PEG were selected as 2 k, 10 k, and 20 kDa for 400 and 600 g/L concentrations. HA solutions were prepared in concentrations ranging from 200 to 800 g/L. Increased MW resulted in higher water permeation when PEGs were used. The relationship between the reflection coefficient and the viscosity was investigated for PEG/water separation by membrane filtration. The combined effe...

The fouling behavior of seawater reverse osmosis membranes has yet to be definitively investigated due to the complexity of seawater compositions. In this study, a time-series image analysis (TSIA) was performed to investigate the fouling mechanism using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The fouling experiments were conducted with synthetic seawater (SS) and SS mixed with humic acid substances (SHA). The effect of operational time was investigated for 2, 4, 6, 8, 12, and 20 h. According to the TSIA results, different fouling characteristics between SS and SHA experiments were observed. In the SS case, the fouling mechanism is the interaction between inorganic particles and the membrane surface as well as interaction between inorganic particles and the deposited foulants. Then, increased accumulation of deposited foulants was observed with respect to the operational time. However, in the presence of humic acid, the fouling mechanism was significantly influenced ...

Mo–N/Cu films were deposited on silicon and steel substrates by inductively coupled plasma sputtering using Mo–Cu alloy targets having different Cu concentrations. The structure and mechanical properties of the Mo–N/Cu films were investigated. The (200)-oriented γ-Mo2N–Cu films were obtained at a nitrogen flow rate higher than 1.5 sccm, whereas metallic films were deposited at a nitrogen flow rate lower than 1 sccm. Cu contents in the films increased from 3 at.% to 8 at.% with corresponding increase in Cu concentrations in the target from 5 at.% to 20 at.%. Hardness of the films varied between 19 and 35 GPa as the Cu concentration and nitrogen flow rate were changed. HRTEM and XPS analyses showed that Mo–N/Cu films consisted of γ-Mo2N grains lower than 10 nm in size and a copper amorphous phase. The minimum value of coefficient of friction (CoF) of the films was 0.17 when the film tested by alumina ball.

The membrane structure parameter (S) is an intrinsic membrane parameter used to determine the degree of internal concentration polarization (ICP) in the porous support structure of forward osmosis (FO) membranes, and is crucial in evaluations of FO membrane performance. Although S values only depend on membrane properties, and should be close to a constant value, experiments to determine the S values produce various values, which vary with respect to the concentrations of the feed and draw solutions. In this study, we develop a numerical model based on the finite element method (FEM) to determine a constant membrane structure parameter. In contrast to other FO models, the developed model successfully simulates the performance of FO processes, and maintains a consistent S value. Here, the most influential factor causing inconsistent S values is found to be the assumption that the ratio of concentrations is approximately identical to the ratio of osmotic pressures, as is frequently used in FO modeling due to lack of availability of concentration profiles at the active layer–support layer interface. However, use of a constant diffusion coefficient had little influence on either the simulation result or the S value consistency.

A modified version of the IAWQ activated sludge model No. 1 (ASM 1) is adopted for the simulation of a sequencing batch reactor (SBR) to optimize the removal of nitrogen (T-N) and organic matters (COD) from wastewater. Since the removal of nitrogen requires both aerobic nitrification and anaerobic denitrification, we seek to find the optimal strategies of substrate fill and aeration. Substrate filling strategy critically influences the removal efficiency of T-N and COD; one fast discrete fill in the beginning of a cycle leads to the best result, while a slow continuous fill results in poor nitrification. In addition, the total aeration time is more important for the removal efficiency than the aeration frequency. A short aeration is beneficial for T-N removal, while a long aeration is beneficial for COD removal as expected. As a result, there is an optimal condition of aeration for the simultaneous removal of T-N and COD.

Scale formation of soluble salts is one of the major factors limiting the performance of reverse osmosis (RO) membranes for desalination. However, it is difficult to predict membrane fouling due to scale formation in a complicated feed water containing dissolved organics such as humic substances. This study aims at prediction of the complicated fouling phenomenon by scale formation in the presence of dissolved organic matters. Experimental studies with model solutions were conducted in a small batch filtration device. Humic acid and calcium sulfate were used as model dissolved organic matters and scale-forming salts. A genetic programming technique was applied to predict the effect of dissolved organic matters on scale formation.

Forward osmosis (FO) is a membrane-based desalination technique using an osmotic pressure gradient as a driving force. FO enables lower energy consumption to produce water than reverse osmosis (RO) because it does not require high transmembrane pressure. However, FO needs to be combined with other processes such as RO or evaporation because the draw salts in the FO products should be removed. This paper focused on theoretical investigation of combined systems with FO and RO for seawater desalination. A theoretical model to predict the performance of the combined systems was developed based on the solution—diffusion model and the modified film theory. The effect of internal concentration polarization on FO efficiency was also considered in the model. A pilot-scale system of FO and RO was assumed for model calculations. Results showed that the combinations of FO with seawater reverse osmosis (SWRO) have potential for desalination with high recovery (up to 80%). It was also found that FO may be incorporated ...

The model of salt transport through the membrane in multi-component system was developed with the irreversible thermodynamics theory considering the effect of the interaction between the salt ions. With the proposed transport model, the model for spiral-wound module was built based on the mass conservation law and concentration polarization derived by film theory. Through the parameter estimation, the frictional coefficients related to permeability of water and each ion was determined and then phenomenological analysis was conducted. The simulation results show that the salt rejection is increasing as the applied pressure and feed flow rate increasing. Also, the predictions by present model are in good agreement with the experimental data in the literature.

To date, over 80 papers on transport modeling and natural organic matter (NOM) relating to seawater reverse osmosis (SWRO), have been reviewed. As a result of such focus, NOM, one of the main foulants related to reverse osmosis (RO) membranes, has been shown to possess intrinsic chemical complexities and ambiguities, necessitating further investigation. Consequently, since such NOM fouling and transport mechanisms associated with SWRO are not fully understood, a summation of previous studies has been included in the paper in question to systematize information, not only as to RO membrane transport modeling, but NOM fouling characteristics, as well. Accordingly, RO transport models in the review are classified into three categories: diffusion-based, pore, and irreversible thermodynamic models. In addition, specific features, unique assumptions, and applications for each model are examined. The paper consists of the following components towards meaningful understanding of NOM fouling model development durin...

The successful operation of a seawater reverse osmosis desalination plant depends greatly on the performance of the pretreatment step. The start-up of a pretreatment filtration process usually begins with a dynamic part called ripening, during which the filter media increases its adsorption ability and improves the removal of foulants from the seawater. In that period (typically lasting 30–60 min, depending on the system's conditions) the effluent often does not meet the quality requirements of the RO membranes and must often be disposed of. An observation and analysis of the ripening phenomena was performed using lab scale acrylic filter columns containing granular activated carbon. The seawater originated from the Yellow Sea in Korea and an inline coagulation was performed prior to filtration using an optimal dose of FeCl3 based on a jar test. The turbidity, total suspended solids concentration and dissolved organic carbon were measured before and after filtration with the goal of assessing the filtrati...

Reverse osmosis (RO) membranes have high rejection for most of solutes in seawater except for boron. Therefore, boron rejection should be considered in the design and operation of the RO process for seawater desalination. In this paper, we investigated boron rejection and its relation to salt rejection using an irreversible thermodynamic model. Permeability constants for commercially-available RO membranes were obtained using theoretical model and the simulation data from membrane performance test program provided by membrane manufacturers. The effect of pH and concentration of the feed water on the boron rejection was also theoretically investigated under various operating conditions. The model calculations revealed that the rejection of boron follows a different mechanism from those of other ionic solutes and could not be readily correlated with ion rejections. To overcome the limit of mechanistic models, we explored an alternative approach for predicting boron permeability from membrane properties and ion permeability. It appears that this alternative approach can aid to achieve a better understanding of boron rejection by seawater RO membranes.

This study focused on the analysis of As levels in human hair samples collected from six villages in the Kandal Province of Cambodia. Of interest were the influence of, and interactions among, certain factors affecting As intake into the human body: As concentrations in groundwater, period of groundwater consumption, age and gender. The results revealed As levels in human hair ranging from 0.06 to 30 μg g −1 with median and arithmetic mean values of 0.61 and 3.20 μg g −1 ( n = 68), respectively. Furthermore, a linear relationship was found between As concentrations in human hair and in the local groundwater. Arsenic (III) is the dominant species in Kandal groundwater, constituting in most cases at least 60% of the total As. Arsenic concentration ranged from 5 to 1543 μg L −1 , with the median value 348 μg L −1 and arithmetic mean 454 μg L −1 . In large rural, poor areas holding most of Kandal’s 1.1 million people, up to 2 in 1000 people are believed to be at risk of cancer through the As-enriched water they drink. A toxicity risk assessment provides a hazard quotient (HQ) equaling 5.12, also a clear indication of non-carcinogenic exposure risk. On the authors’ visit to Kampong Kong commune, Kandal Province, cases of arsenicosis were diagnosed in patients as a result of drinking As-enriched groundwater.

Forward osmosis (FO) is an osmotic process that uses a semi-permeable membrane to effect separation of water from dissolved solutes by an osmotic pressure gradient. Unlike reverse osmosis (RO), FO does not require high pressure for separation, allowing low energy consumption to produce water. However, the internal concentration polarization in FO is an important factor affecting the performance of FO processes. This paper was intended to investigate the characteristics of FO and RO processes. A simple film theory model was applied to consider concentration polarization in FO and RO processes. This model allows the estimation of internal and external concentration polarization effects in FO process. A laboratory-scale FO device was used to find the model parameters for further calculations. The calculated flux was compared with experimental flux under a variety of operating conditions. It was found that the combination of FO and RO may result in a higher flux than FO-only process under some operating conditions. Further research will be required to investigate the effect of membrane materials on energy efficiency of FO and RO hybrid system.

The present study proposes a methodology for determining the effective dispersion coefficient based on the field measurements performed in Gwangju (GJ) Creek in South Korea which is environmentally degraded by the artificial interferences such as weirs and culverts. Many previous works determining the dispersion coefficient were limited in application due to the complexity and artificial interferences in natural stream. Therefore, the sequential combination of N-Tank-In-Series (NTIS) model and Advection-Dispersion-Reaction (ADR) model was proposed for evaluating dispersion process in complex stream channel in this study. The series of water quality data were intensively monitored in the field to determine the effective dispersion coefficient of E. coli in rainy day. As a result, the suggested methodology reasonably estimates the dispersion coefficient for GJ Creek with 1.25 m2/s. Also, the sequential combined method provided Number of tank-Velocity-Dispersion coefficient (NVD) curves for convenient evaluation of dispersion coefficient of other rivers or streams. Comparing the previous studies, the present methodology is quite general and simple for determining the effective dispersion coefficients which are applicable for other rivers and streams.

Scale formation of soluble salts is one of the major factors limiting the performance of reverse osmosis (RO) membranes for desalination. In this study, a dynamic model based on the crystallization theory was developed to analyze the effect of CaSO4 scale formation on RO desalination process. Taking into consideration two mechanisms in scale formation including surface and bulk crystallization, the performance of RO filtration was predicted as a function of crossflow velocity, transmembrane pressure, permeate recovery, and operation mode. The model results indicated that RO fouling due to surface crystallization is important in batch filtration whereas both surface and bulk crystallization is important in crossflow filtration. This is because concentration polarization is directly related to surface crystallization. RO fouling due to bulk crystallization appeared to increase with increasing crossflow velocity and permeate recovery. The effects of background organic matters and antiscalant on scale formation were quantified using the model. The effect of operating parameters on RO fouling and concentration polarization was explored based on the model analysis.

The effect of inductively coupled plasma (ICP) treatment on the surface activation of the polycarbonate (PC) substrate was studied. At high working pressure and ICP power the wetting angle could be decreased as low as 5°. The wetting angle was decreased effectively when the impinging ions had proper energy ∼ 8 eV. Excess ion energy interfered with reducing the wetting angle. The polar functional group (C O) significantly affected the change of surface energy. Compared with the deposited Al2O3 film on the PC substrate treated at a low wetting angle, that on the PC substrate treated at a high wetting angle adhered very well.

Well-crystallized tin oxide films were successfully synthesized without additional heating by inductively coupled plasma assisted chemical vapor deposition (ICP-CVD). The degree of crystallization was affected by the ICP power and hydrogen flow rate. The substrate temperature was increased only up to 423–453 K by plasma heating, which suggests that the formation of the SnO 2 crystals was not caused by plasma heating, but by enhanced reactivity of precursors in high density plasma. The micro-hardness of deposited tin oxide films ranged from 5.5 to 11 GPa at different hydrogen flow rates.

Surface-flow wetlands constructed with Acorus and Typha plants, connected to a wastewater treatment plant, were investigated with respect to organics (dissolved organic matter), anions (nitrate, sulfate, and phosphate), metals (Cu, Ni, Zn, Fe, and Mn), and metalloids (As). The results of the research indicated: (1) effluent organic matter (EfOM), based on dissolved organic carbon (DOC), was not efficiently removed by the wetlands. However, the hydrophobic, transphilic, and hydrophilic EfOM fractions varied throughout the wetlands, as identified by XAD-8/4 resins. (2) Nitrate, as compared to sulfate and phosphate, was efficiently removed, especially in the Typha wetland pond that had long retention time, under anoxic condition. (3) Most of the heavy metals were ineffectively removed via the wetland ponds. However, the iron concentration increased in the Typha wetland pond, which was probably due to its reduction under anoxic condition.

To characterize fluorescent dissolved organic matter (FDOM) in Yeongsan River in Korea, 110 water samples were acquired from March 2008 to November 2009 around the watershed. Excitation emission matrix data of fluorescence was obtained using spectrophotometric analysis and parallel factor (PARAFAC) model was used to characterize FDOM. The spatiotemporal variation and effect on FDOM were studied using an exploratory analysis and analysis of variance (ANOVA). According to the spatial and seasonal characteristics, we used post hoc analysis to identify significantly different sites and season. The PARAFAC results identified three most important PARAFAC components explaining 95.32% of total variance of original data-set. Seasons and sites had a significant effect on PARAFAC Components I and II (p ≤ 0.05), whereas season had a significant effect on Component III (p ≤ 0.05). There was no significant interaction between seasons and sites for all the three PARAFAC components (p > 0.05). For Components I and II, summer season was significantly different from other seasons (p ≤ 0.05), whereas for Component III, the fall season was significantly different from winter and summer seasons (p ≤ 0.05). These results indicate that ANOVA and post hoc analysis in our study not only confirmed the results of previous studies, but also revealed differences in seasons and sites for identified FDOMs as a new information. The methodology proposed in this paper can be a useful tool for finding sources and sinks of FDOMs in a riverine system influenced by natural organic matter impairment.

Biofouling is a crucial issue, and it causes seawater reverse osmosis membrane to deteriorate the performance of desalination. In this study, excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) were used to monitor the strength of biofouling on the fouled membrane which was obtained from real plant. Based on EEM and PARAFAC results of raw seawater, feed water, permeate, brine and fouled membrane, three components were identified as the major peaks: (1) microbial product-like materials at Ex/Em = 280/370 nm, (2) humic-like substances at Ex/Em = 330/420 nm, and (3) aromatic proteins at Ex/Em = 240/320 nm. Using the fluorescence intensity changes, the effects of replacing fouled RO membranes were found to be most significant at one of the components (Ex/Em = 270–300/350–380 nm) which could be considered the substances desorbed from fouled RO membrane. Compared to the data for salt rejection, this component monitoring of the brine EEM image is shown to be more sensitive than conductivity monitoring for predicting the biofouling strength during the desalination process.

The coagulation and sedimentation of particles is central to many environmental and industrial processes. Kinetic descriptions of this process can be divided into two approaches. Population balance equation (PBE) theory accounts for mass transfer between particle size classes by coagulation and loss of particle mass by sedimentation. Its practical application is limited by the fact that the rate constants, or kernels, for coagulation between all combinations of cluster sizes are unknown, and only a few solutions are available for simplified forms of the coagulation kernel. A second approach involves the use of simple rate expressions for the loss of particle mass with time, where the order of the reaction is determined by the mathematical properties of the coagulation kernel and the sedimentation term. Two different theories (similarity theory, ST, and the quasi-steady-state hypothesis, QSSH) give conflicting estimates for the order of the reaction. In this paper, we derive a PBE solution for the choice of a constant kernel and a particle removal rate that increases linearly with cluster volume. The kinetics of mass removal predicted by this solution are then compared directly to generalized forms of ST and QSSH which we also derive. We find that the PBE solution does not rigorously conform to either ST or QSSH, although the predictions of ST may be close enough for practical applications. This paper presents the first rigorous comparison of PBE, ST, and QSSH descriptions of particle coagulation and sedimentation. Copyright 2001 Academic Press.

The objective of the present study was to conduct a preliminary assessment for perchlorate in surface water, drinking water, and wastewater treatment plant effluent samples obtained from the Nakdong and Yeongsan watersheds in the Republic of Korea. Samples were analyzed for perchlorate using ion chromatography with suppressed conductivity detection (IC-CD) and/or liquid chromatography with tandem mass spectrometry detection (LC-MS/MS). Method reporting limits were 5.0 microg/L for IC-CD and 0.05 microg/L for LC-MS/MS analysis. At perchlorate levels above 5.0 microg/L, IC-CD and LC-MS/MS provided comparable results. The levels of perchlorate detected in the samples procured from the Yeongsan watershed were < 5.0 microg/L in each case. However, Nakdong watershed samples contained perchlorate at levels up to 60 microg/L. The highest concentrations of perchlorate were found in surface water samples, although drinking water contained perchlorate at concentrations up to 35 microg/L. In a subset of samples analyzed by LC-MS/MS, chlorate and bromate also were detected at concentrations ranging from < 0.10 to 44 microg/L and < 0.10 to 2.6 microg/L, respectively. To the best of the authors' knowledge, this is the first perchlorate assessment reported for water sources in the Republic of Korea.

An unstructured model was developed for batch cultivation of Corynebacterium lactofermentum (ATCC 21799) under controlled dissolved oxygen. The model is capable of predicting batch experiments performed at various initial substrate concentrations. By extending the batch culture model to a fed-batch model and using a heuristic approach to optimize the fed-batch cultivation, it is shown that fed-batch cultivation is superior to batch operation due to increased productivity at high substrate concentrations.

To clarify nitrogen (N) sources, the overall N budget in a forested watershed in Kanagawa Prefecture, Central Japan was estimated by measuring dissolved inorganic N (DIN; NH4 + + NO3 – + NO2 –) from Nov 2004 through Oct 2005. The estimated N budget (–1.43 kg N ha–1 year–1) showed that the N output rate (stream water N) was higher than the N input rate (bulk deposition N) in the watershed. The annual NO2 – and NO3 – input rates were 0.02 and 1.99 kg N ha–1 year–1, respectively. NH4 + was the predominant source in this forested watershed, accounting for 71% (4.99 kg N ha–1 year–1) of DIN input rate. In addition, this study estimated rainfall pH, air temperature, and wind direction, which were considered as controlling factors related to the atmospheric deposition rate of NH4 +. This study showed that the rainfall NH4 + was inversely proportional to the initial pH of the rainfall, which was calculated by adding the amount of H+ consumed by the dissociation process of NH3(aq) to the measured rainfall pH. This result implies that acid rain can elevate the solubility of NH3(g) and the dissociation capacity of NH4 + throughout the process of precipitation. Also, this study provides strong evidence that the high NH4 + deposition rate is mainly derived from NH3(g) emitted from livestock wastes under the NH3 transport condition of warm summer and favorable wind direction.