Electrodialysis of groundwater with heavy metal and nitrate ions under low conductivity and effects of superficial velocities

Choi, Su Young,Park, Keun Young,Yu, Yongjae,Kim, Hee Jun,Park, Ki Young,Kweon, Ji Hyang,Choe, Jae Wan Balaban Publishers 2016 Desalination and Water Treatment Vol. No.

<P>The efficiency of separation of lead, manganese, arsenic, and nitrate from groundwater with relatively low conductivity by electrodialysis (ED) was investigated. The effects of the superficial velocities in either the diluate or concentrate cell were also evaluated to understand the relative separation rate of the four ionic compounds by ED and to examine the possibility of reducing the energy for pumping. Significant removal (i.e. 92.8-99.2%) of manganese, arsenic, and nitrate from Ilgam (Seoul, Korea) groundwater was achieved, along with removal (61.3%) of lead comparable to that of Sungbuk (Seoul, Korea) water. The superficial velocity in the concentrate cell exerted no effects on either the conductivity or current reduction, or on the separation ratios. The superficial velocity in the diluate cell increased the operation time required to obtain the requisite conductivity reduction, but exerted little effect on the separation ratios. ED could be performed at reduced water velocity to treat groundwater with low conductivity.</P>

Analysis of reverse osmosis system performance using a genetic programming technique

Park, Seung-Min,Han, Jihee,Lee, Sangho,Sohn, Jinsik,Kim, Young-Min,Choi, June-Seok,Kim, Suhan Balaban Publishers 2012 Desalination and Water Treatment Vol.43 No.1

<P> Reverse osmosis (RO) membrane process has been considered a promising technology for water treatment and desalination. However, it is difficult to predict the performance of pilotor full-scale RO systems because numerous factors are involved in RO performance, including membrane scaling, fouling, and deterioration. This study was intended to develop a practical model for the analysis of pilot-scale RO processes. A genetic programming (GP) technique was applied to correlate key operating parameters and RO permeability statistically. The GP model was trained using a set of experimental data from a RO pilot plant with a capacity of 1,000m3/day and then used to predict its performance. The comparison of the GP model calculations with the experiment results revealed that the GP model was a useful tool for predicting the efficiency of pilot-scale RO systems. The GP model also allowed the in-depth analysis of RO system performance even under unsteady conditions. </P>

Two-effect distillation of a seawater distiller utilizing waste heat of a small electric generator

Park, Chang-Dae,Lim, Byung-Ju,Chung, Kyung-Yul Balaban Publishers 2011 Desalination and water treatment Vol.33 No.1

<P> We have designed and developed a stand-alone small-scale desalination unit using waste heat of exhaust gas from a small diesel electric generator which is used in various places such as islands and remote areas. The distiller developed consists mainly of a multiple-effect diffusion still and an evaporation chamber that recovers waste heat of exhaust gas from the generator engine. With experimental results of two-effect distillation of this distiller, we have shown its production capability of 6.80 kg/d fresh water and have estimated at least 19.4 kg/d for a ten-effect distiller. The distiller suggested is considered to be applicable for a small-scale distillation unit, comparing to performance of a solar thermal distillation unit. Moreover, the distillation part of our designed unit is easily converted to a solar still type-distiller by changing the evaporation chamber to a solarheating wall, if the engine is not available. </P>

Development of a simulation program for the forward osmosis and reverse osmosis process

Choi, Yong-Jun,Hwang, Tae-Mun,Oh, Hyunje,Nam, Sook-Hyun,Lee, Sangho,Jeon, Jei-cheol,Han, Sang Jong,Chung, Yonkyu Balaban Publishers 2011 Desalination and water treatment Vol.33 No.1

<P> 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 RO, FO does not require high pressure for separation, allowing low energy consumption to produce water. Therefore FO, a potential alternative to conventional membrane process, has been considered a novel technology for seawater desalination. There is no forward osmosis (FO) process simulation program yet, though. Therefore, the main objective of this paper is to develop such computer program based on the solution-diffusion model modified with the film theory for simulating and optimizing the FO, RO, and FO-RO hybrid process. The effect of concentration polarization on FO and RO process efficiency was also considered in the model. A MATLAB-based graphical user interface (GUI) program was used to develop the simulation program. Using the program, the effects of various factors, including the draw solution concentration, feed concentration, and feed pressure and temperature, on the FO and RO process performance were examined. The simulation results showed that the FO-RO hybrid process has higher recovery (66.8%) with reasonable flux (13.1 L/m2-h) and permeate concentration (382 mg/L) than the FO and RO process. Thus, the advantages of the FO-RO hybrid process over the FO and RO process are its low permeate concentration and high recovery, which are difficult to attain in the FO and RO process, respectively. </P>

Proposing a new fouling index in a membrane bioreactor (MBR) based on mechanistic fouling model

Kim, M.J.,Kang, O.Y.,Rao, B.S.,Kim, J.R.,Hwang, H.J.,Kim, M.H.,Yoo, C.K. Balaban Publishers 2011 Desalination and water treatment Vol.33 No.1

<P> Membrane fouling is the most serious problem in membrane bioreactor (MBR) process, which is restricting the widespread application of MBRs in wastewater treatment processes. In recent years, several studies on the precise diagnosis and prediction of the membrane fouling have been carried out to obtain an efficient operation of MBRs. The aims of this study are 1) to predict the membrane fouling and to determine the chemical cleaning interval of membrane using traditional mechanistic fouling model; and 2) to propose the new fouling index based on the usually obtained traditional technique. As the traditional fouling technique use an exponential fouling model, however, this method has some shortcomings, such as inadequate comprehension of the fouling mechanism and steady state assumption. Therefore, in this study, the coefficient (κ) of the exponential fouling model is proposed as a new fouling index to overcome the inadequate understanding of the fouling mechanism and steady state assumption in traditional technique. To propose the coefficient (κ) as the new fouling index, least-square (LS) method and recursive least-square (RLS) methods are applied in the exponential fouling model. The coefficient (κ) shows the similar tendency with the permeability which is another kind of fouling index. It is verified that the coefficient has been validated as the new index for diagnosis of the fouling progress as well as the prediction of membrane fouling. </P>

Dual media filtration and ultrafiltration as pretreatment options of low-turbidity seawater reverse osmosis processes

Kim, S.,Lee, I.S.,Kim, K.J.,Shon, D.M.,Kang, L.S. Balaban Publishers 2011 Desalination and water treatment Vol.33 No.1

<P> Well-controlled laboratory scale experiments were carried out to estimate the performance of dual media filtration (DMF) and ultrafiltration (UF) as a pretreatment for seawater reverse osmosis (SWRO) processes. Raw seawater was taken from the place close to the construction site of the SEAHERO test-bed of 45,000 m3/d in capacity, which is planning to be operated from 2013. The raw seawater turbidity was rather low and the focus of this study is to find out the better process between DMF and UF for the pretreatment of low turbidity seawater. The UF process exhibited a good performance to produce qualified RO feed water and coagulation added the removal of aromatic organics and better resistance to the membrane fouling. However the DMF process could not make RO feed water to satisfy the SDI standard and variations in operation conditions did not change the product water quality. In order to enhance the performance of DMF process, a multipass design or an improved coagulation strategy for low turbidity water should be necessary, which makes a proper design of DMF more difficult. Therefore, UF can be a better option for the pretreatment of low turbidity seawater. </P>

A case study on the automatic ozone dose control system based on the ozone decay rate in a full-scale advanced water treatment plant

Jeon, Jei-cheol,Jo, Chang-Hyun,Kwon, Soon-Buhm,Lee, Kyung-Hyuk Balaban Publishers 2011 Desalination and water treatment Vol.33 No.1

<P> Recently, a growing concern about algae-origin taste and odor in drinking water made it possible to introduce ozone and granular activated carbon (GAC) processes to large-capacity (more than 300,000 m<SUP>3</SUP>/d) water treatment plants in the Han River area in South Korea. Especially, concerning the ozone process, the ozone residual of ozone contactor effluent may affect on the biological destabilization, poor physical properties of the following GAC process and operators’ health due to high ozone gas concentration in GAC contactor. Therefore, maintaining an optimal ozone dose based on the ozone demand is essential to the operation of the ozone process. The Koyang Advanced Water Treatment Plant (KAWTP) has been utilizing a new type of ozone control method since July 2009, which automatically calculates required ozone dosed based on the instantaneous ozone demand (ID) and the ozone decay rate constant (K<SUB>c</SUB>). The ID and the first-order K<SUB>c</SUB> values are calculated based on the measured dissolved-ozone concentrations from at least three points of ozone contactor. After the calculations of ID and K<SUB>c</SUB> values, the values were applied for the proportional integral derivative (PID) ozone dose control system. PID control is operated through two different methods. The first involves automatic controlling the ozone dose, by which the ozone residual of the effluent from the ozone contactor will be maintained at the desired value set by the operator. The second method was the modified extended CSTR method, which was appropriately modified to fit the KAWTP site specifications, to calculate the Cryptosporidium, Giardia and virus log inactivation automatically. An automatic ozone dose control system based on the ozone decay rate overcomes the disadvantages of the previous ozone control systems, including late response and variation of effluent ozone residual. In the earlier pilot scale research, an extra device for measuring K<SUB>c</SUB> and ID was used. In this study, the ozone dose was determined by measuring Kc in the full-scale ozone process. It is the first case in Korea that applied ID-K<SUB>c</SUB>-based ozone dose control to a full-scale water treatment plant. According to the operation results of the automatic ozone dose control system based on K<SUB>c</SUB> calculation, adequate-ozone-dose calculation along with the various water quality and inflow rate was performed successfully, and the ozone residual of the effluent was also maintained below the lowest set value during operation. Moreover, the process was adequately run to maintain the target log inactivation the Cryptosporidium. Also, calculating the optimal ozone dose that could completely oxidize ozone-consuming matters and leave minimum residual, could be economical due to excessive ozone dose saving, and the biological and physical stability of GAC granule in GAC process. </P>

Effect of chemical cleaning on membrane biofouling in seawater reverse osmosis processes

Kim, Lan Hee,Jang, Am,Yu, Hye-Weon,Kim, Sung-Jo,Kim, In S. Balaban Publishers 2011 Desalination and water treatment Vol.33 No.1

<P> Reverse osmosis (RO) membranes are widely used for desalination plant. However, membrane biofouling cause decreasing membrane performance. This work focused on finding optimum cleaning conditions in RO membrane processes. The effect of cleaning conditions such as agent concentration, temperature and cleaning time on cleaning efficiency were investigated in Centers for Disease Control (CDC) annular biofilm reactor. Alkaline cleaning agent, sodium hydroxide (NaOH) which is well known for removing organic foulant on membrane, was used. Total bacteria number was measured with diamidino-2-phenylindole (DAPI) dye and cell viability were analyzed by using two different DNA-binding dyes (SYTO9/PI). The optimum temperature, cleaning time and cleaning agent concentration were found as 30°C, 20 min and 1.0 wt%, respectively. </P>

Investigation of stormwater runoff strength in an agricultural area, Korea

Cha, Sung Min,Lee, Seung Won,Kim, Lee-Hyung,Min, Kyung Suk,Lee, Seungyoon,Kim, Joon Ha Balaban Publishers 2012 Desalination and water treatment Vol.38 No.1

<P> To manage and control the nonpoint source (NPS) pollution and to improve the water quality of impaired streams, rivers and lakes, practices including constructed wetlands, permeable pavement, swales and others are being attempted in the world. Before applying these techniques, an analysis of stormwater runoff characteristics should be understood due to the complexity in estimating system design factors for best management practices (BMPs). This study investigates the stormwater discharge from an agricultural area in Korea. Based on this investigation, pollutant and fl ow coeffi cient of variation (PFCoV) values were developed in an attempt to explain the stormwater runoff in the agricultural area. Four fi eld studies categorized by rainfall type were then employed to assess the PFCoV values. The results show that the physical meaning of PFCoV values indicates the variation of NPS pollutants during a storm event. As such, this simple and meaningful result can be applied to a wide range of stormwater management designs or water quality controls in agricultural areas. </P>

The effect of fluctuation in flow rate on the performance of conventional and membrane water treatment for a smart water grid

Park, No-Suk,Kim, Seong-Su,Chae, Seon-Ha,Kim, Suhan Balaban Publishers 2012 Desalination and Water Treatment Vol.47 No.1

<P> A smart water grid can save water and energy by delivering the water to consumers according to the time-dependent demands. One of the key water treatment technologies for a smart water grid is to control the water supply rate as per the consumers’ demand. However, a conventional water treatment plant is designed for a constant production rate operation, which is not appropriate for a smart water grid. The present study focuses on the effect of fluctuation on the production rate of three water treatment technologies: i.e. (1) sedimentation followed by ozonation and coagulation/flocculation, (2) sand filtration followed by coagulation/ flocculation and sedimentation, and (3) membrane process (microfiltration [MF]). For sedimentation and sand filtration processes, the pilot- and real-scale plant data were analyzed to investigate the fluctuation patterns of the flow rate and water quality. For the membrane process, an MF operation was simulated to investigate the effect of fluctuation flux on the membrane fouling rate. Two key findings emerged from the pilot and field data analyses and simulation results in the present study. First, there exists a time delay between the input and output flow fluctuations for sedimentation and sand filtration processes, and the water quality is changed during and after the time delay for the flow rate fluctuation. Second, in the MF process, the flow rate fluctuation does not have any significant effect either on the permeate water quality or on the fouling behavior. </P>