Serially connected forward osmosis membrane elements of pressure-assisted forward osmosis-reverse osmosis hybrid system: Process performance and economic analysis

Kook, Seungho,Lee, Chulmin,Nguyen, Thanh Tin,Lee, Jangho,Shon, Ho Kyong,Kim, In S. Elsevier 2018 Desalination Vol.448 No.-

<P><B>Abstract</B></P> <P>Due to the improved dilution of draw streams, employing pressure-assisted forward osmosis (PAFO) to the hybrid system of forward osmosis (FO) followed by reverse osmosis (RO) for seawater desalination has been expected to reduce the overall economics. However, replacing FO with PAFO causes an additional energy cost in the seawater dilution step which inevitably leads to a question that PAFO-RO hybrid is truly an economically beneficial option. More importantly, though serial connection of FO elements improves the dilution of initial draw water, this economic benefit is also compensated with the additional membrane. To rationalize its overall performance and economic benefit, thorough performance and economic evaluations were conducted based on actual pilot-scale PAFO operations for serial connection of up to three 8040 FO elements. The results showed the FO-RO hybrid is not an economically feasible option unless a significant unit FO element cost cut-down is guaranteed. Meanwhile, PAFO-RO showed benefits with regards to target RO recovery and unit FO element cost, particularly when two FO elements are serially connected (SE2). It was found that PAFO-RO, indeed, has higher economic potential than FO-RO. A graphical overlapping method suggested in this work can help determine optimal serial configuration and operating conditions of PAFO-RO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Significant impact of initial draw flowrate and hydraulic pressure on the PAFO-RO economics </LI> <LI> Hydraulic pressure dependence of FO membrane element performance </LI> <LI> Drastic pressure-drop in the draw channel of the last element in serial configuration </LI> <LI> Target RO recovery and unit FO element cost in PAFO-RO hybrid are important for economics </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Phytochemical-based Tannic Acid Derivatives as Draw Solutes for Forward Osmosis Process

김태형,주창하,강효,Kim, Taehyung,Ju, Changha,Kang, Hyo The Membrane Society of Korea 2018 멤브레인 Vol.28 No.3

우리는 정삼투 공정의 유도용질로서 잠재적인 활용 가능성을 확인하기 위해 식물화학물질인 tannic acid (TA)에 알칼리 염 처리한 alkali tannate 염 중 하나인 potassium tannate (TA-K)를 평가하였다. TA-K의 정삼투 특성과 회수 특성은 체계적으로 조사되었다. 정삼투 공정을 active layer facing feed solution (AL-FS) 방식으로 적용했을 때, TA-K 유도용액의 투수량은 TA 유도용액의 투수량 보다 훨씬 많은 반면, TA 유도용액의 투수량이 거의 확인되지 않았다. 100 mM 저농도에서의 TA-K 유도용액의 삼투압(1,135 mOsmol/kg)은 NaCl 수용액의 삼투압(173 mOsmol/kg)의 약 6.5배로 확인되었다. 100 mM 농도의 TA-K의 투수량과 specific salt flux (6.14 LMH, 1.26 g/L)는 동일한 농도의 NaCl 유도용액의 투수량과 specific salt flux (2.46 LMH, 2.63 g/L)의 약 2.5배 및 0.5배로 각각 확인되었다. TA-K를 재사용하기 위해, 금속 이온 침전법을 이용하여 TA-K유도용질을 침전시킨 후, membrane filtration을 이용하여 유도용질을 회수하였다. 이 연구는 식물화학물질을 정삼투 공정의 유도용질로서의 적용 가능성을 보여준다. Potassium tannate (TA-K), which is prepared by base treatment of the bio-renewable tannic acid (TA), was evaluated for its potential application as a draw solute for water purification by forward osmosis. The forward osmosis and recovery properties of TA-K were systematically investigated. In the application of forward osmosis through the active layer facing feed solution (AL-FS) method, the water flux of TA-K draw solution was significantly higher than that of the TA draw solution, while that of the latter was not identified. At a low concentration of 100 mM, the osmotic pressure (1,135 mOsmol/kg) of the TA-K draw solution was approximately 6.5 times that (173 mOsmol/kg) of the NaCl draw solution. Furthermore, the water flux and specific salt flux (6.14 LMH, 1.26 g/L) of the TA-K draw solution at 100 mM were approximately 2.5 and 0.5 times those of the NaCl draw solution (2.46 LMH, 2.63 g/L) at the same concentration, respectively. For reuse, TA-K was precipitated by using a metal ion and recovered through membrane filtration. This study demonstrates the applicability of a phytochemical material as a draw solute for forward osmosis.

정삼투식 담수공정의 유도용질 회수를 위한 흡수용액 성능 평가

이공훈 ( Kong Hoon Lee ),김영 ( Young Kim ),이종훈 ( Jong Hoon Lee ),김유창 ( Yu Chang Kim ),오동욱 ( Dong Wook Oh ),이정호 ( Jung Ho Lee ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.2

Although forward osmosis desalination technology has drawn substantial attention as a next-generation desalination method, the energy efficiency of its draw solution treatment process should be improved for its commercialization. When ammonium bicarbonate is used as the draw solute, the system consists of forward-osmosis membrane modules, draw solution separation and recovery processes. Mixed gases of ammonia and carbon dioxide generated during the draws solution separation, need to be recovered to re-concentrate ammonium bicarbonate solution, for continuous operation as well as for the economic feasibility. The diluted ammonium bicarbonate solution has been proposed as the absorbent for the draw solution regeneration. In this study, experiments are conducted to investigate performance and features of the absorption corresponding to absorbent concentration. It is concluded that ammonium bicarbonate solution can be used to recover the generated ammonia and carbon dioxide. The results will be applied to design and operation of pilot-scale forward-osmosis desalination system.

정삼투 공정의 유도용질로서의 식물 화학물질 기반의 탄닌산 유도체

김태형,주창하,강 효 한국막학회 2018 멤브레인 Vol.28 No.3

우리는 정삼투 공정의 유도용질로서 잠재적인 활용 가능성을 확인하기 위해 식물화학물질인 tannic acid (TA)에 알칼리 염 처리한 alkali tannate 염 중 하나인 potassium tannate (TA-K)를 평가하였다. TA-K의 정삼투 특성과 회수 특성은 체계적으로 조사되었다. 정삼투 공정을 active layer facing feed solution (AL-FS) 방식으로 적용했을 때, TA-K 유도용액의 투수량은 TA 유도용액의 투수량 보다 훨씬 많은 반면, TA 유도용액의 투수량이 거의 확인되지 않았다. 100 mM 저농도에서 의 TA-K 유도용액의 삼투압(1,135 mOsmol/kg)은 NaCl 수용액의 삼투압(173 mOsmol/kg)의 약 6.5배로 확인되었다. 100 mM 농도의 TA-K의 투수량과 specific salt flux (6.14 LMH, 1.26 g/L)는 동일한 농도의 NaCl 유도용액의 투수량과 specific salt flux (2.46 LMH, 2.63 g/L)의 약 2.5배 및 0.5배로 각각 확인되었다. TA-K를 재사용하기 위해, 금속 이온 침전법을 이용 하여 TA-K유도용질을 침전시킨 후, membrane filtration을 이용하여 유도용질을 회수하였다. 이 연구는 식물화학물질을 정삼투 공정의 유도용질로서의 적용 가능성을 보여준다. Potassium tannate (TA-K), which is prepared by base treatment of the bio-renewable tannic acid (TA), was evaluated for its potential application as a draw solute for water purification by forward osmosis. The forward osmosis and recovery properties of TA-K were systematically investigated. In the application of forward osmosis through the active layer facing feed solution (AL-FS) method, the water flux of TA-K draw solution was significantly higher than that of the TA draw solution, while that of the latter was not identified. At a low concentration of 100 mM, the osmotic pressure (1,135 mOsmol/kg) of the TA-K draw solution was approximately 6.5 times that (173 mOsmol/kg) of the NaCl draw solution. Furthermore, the water flux and specific salt flux (6.14 LMH, 1.26 g/L) of the TA-K draw solution at 100 mM were approximately 2.5 and 0.5 times those of the NaCl draw solution (2.46 LMH, 2.63 g/L) at the same concentration, respectively. For reuse, TA-K was precipitated by using a metal ion and recovered through membrane filtration. This study demonstrates the applicability of a phytochemical material as a draw solute for forward osmosis.

Organic fouling and reverse solute selectivity in forward osmosis: Role of working temperature and inorganic draw solutions

Heo, J.,Chu, K.H.,Her, N.,Im, J.,Park, Y.G.,Cho, J.,Sarp, S.,Jang, A.,Jang, M.,Yoon, Y. Elsevier 2016 Desalination Vol.389 No.-

The water flux of several draw solutions (DSs, solutes: KCl, NaCl, CaCl<SUB>2</SUB>, Na<SUB>2</SUB>SO<SUB>4</SUB>) and fouling propensity of two different organic foulants (humic acid and alginate) were systematically investigated using forward osmosis (FO) and unpressurized pressure-retarded osmosis. In addition, reverse solute selectivity was evaluated to characterize the water and salt transport mechanisms at different temperatures and in the presence of four different inorganic DS compounds. The influence of solution viscosity has significant implications in FO applications, because the water molecules easily penetrated and diffused throughout the FO membrane active layer (AL) and supporting layer (SL) with increasing temperatures, which is mainly correlated with the lower water viscosities with increasing temperatures. The results indicated that the water flux on average significantly increased from 9.5 to 13.7 and 24.9 LMH when the operating temperature was increased from 5 to 20 and 45<SUP>o</SUP>C, which corresponded to a 44 and 262% increase in the water flux, compared to the FO mode at 5<SUP>o</SUP>C. However, the water flux and viscosity exhibited generally constant trends with respect to the elevating temperature. In addition, elevating temperature increased the reverse solute flux selectivity (RSFS), not only by decreasing the internal concentration polarization (the AL and SL) and the wettability within the effective porosity of the SL, but also via the improvement of water molecule diffusion kinetics rather than solute diffusion. In addition, the RSFS was inversely related to the solute permeability of the different DSs and followed the order Na<SUB>2</SUB>SO<SUB>4</SUB>>CaCl<SUB>2</SUB>>NaCl>KCl. These results have significant implications for the prediction of water flux behavior and the selection of DSs at different temperatures in osmotically driven FO processes.

Boron transport in forward osmosis: Measurements, mechanisms, and comparison with reverse osmosis

Kim, C.,Lee, S.,Shon, H.K.,Elimelech, M.,Hong, S. Elsevier Scientific Pub. Co 2012 Journal of membrane science Vol.419 No.-

The physical and chemical factors affecting boron solute flux behavior and membrane transport mechanisms in forward osmosis (FO) have been systematically investigated. Boron solute flux behavior in FO was further compared with that in reverse osmosis (RO) by employing identical plate-and-frame cells and membranes under the same filtration conditions. The influence of draw solution pH, draw solution type, and membrane orientation on boron solute flux was examined for FO, and the effects of water flux, cross-flow velocity, feed water boron concentration, and solution pH on boron solute flux were examined for both FO and RO. Results show that reverse salt diffusion, a unique feature of FO, is a key mechanism governing boron solute flux in FO. Boron solute flux through the FO membrane was inversely proportional to the degree of reverse salt diffusion by draw solution. The higher boron rejection observed in FO compared to RO is also attributed to reverse salt diffusion in FO. It is also shown that membrane orientation in FO plays an important role, affecting boron solute flux due to different degrees of internal concentration polarization. In both FO and RO, boron solute flux increased with increasing water flux. However, the influence of water flux on boron solute flux was less significant in FO than RO. Furthermore, boron solute flux decreased with increasing feed water pH due to the conversion of the neutral boric acid to borate anions. The findings provide new insight into the mechanisms and factors controlling boron solute transport in FO.

Hybrid forward osmosis-reverse osmosis for wastewater reuse and seawater desalination: Understanding the optimal feed solution to minimise fouling

Volpin, Federico,Fons, Emilie,Chekli, Laura,Kim, Jung Eun,Jang, Am,Shon, Ho Kyong Elsevier 2018 Process safety and environmental protection Vol.117 No.-

<P><B>Abstract</B></P> <P>To enhance the seawater desalination energy efficiency forward osmosis – reverse osmosis (FO-RO) hybrid system has recently been developed. In this process, the FO “pre-treatment” step is designed to use seawater (SW) as draw solution to filter the wastewater (WW) while reducing the seawater osmotic pressure. Thereby reducing the operating pressure of the RO to desalinate the diluted SW. However, membrane fouling is a major issue that needs to be addressed. Proper selection of suitable WWs is necessary before proceeding with large-scale FO-RO desalination plants. In this study, long-term experiments were carried out, using state-of-the-art FO membrane, using real WW and SW solutions. A combination of water flux modelling and membrane characterisation were used to assess the degree of membrane fouling and the impact on the process performance. Initial water flux as high as 22.5Lm<SUP>−2</SUP> h<SUP>−1</SUP> was observed when using secondary effluent. It was also found that secondary effluent causes negligible flux decline. On the other hand, biologically treated wastewater and primary effluent caused mild and severe flux decline respectively (25% and 50% of flux decline after 80 hours, compared to no-fouling conditions). Ammonia leakage to the diluted seawater was also measured, concluding that, if biologically treated wastewater is used as feed, the final NH<SUB>4<SUP>+</SUP> </SUB> concentration in the draw is likely to be negligible.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Commercial state-of-the-art FO membranes were tested with real wastewater and seawater. </LI> <LI> Initial water flux of 22.5 Lm<SUP>−2</SUP> h<SUP>−1</SUP> was observed. </LI> <LI> Secondary effluent wastewater caused negligible fouling over long term operation. </LI> <LI> Ammonia leakage to the seawater was negligible. </LI> </UL> </P>

Potassium Pentane-1,3,3,5-tetracarboxylate 유도용질 합성 및 이를 이용한 정삼투 공정 응용

이혜진,최진일,권세이,김인철 한국막학회 2019 멤브레인 Vol.29 No.2

An organic citrate series draw solute was synthesized using diethyl malonate for forward osmosis. The structure of the final compound potassium pentane-1,3,3,5-tetracarboxylate was confirmed by 1 H-NMR and 13C-NMR analysis. Osmotic pressure, solubility, water permeability and reverse salt flux were measured for the properties of the draw solute. Forward osmosis results showed that the draw solute exhibited higher water flux than other draw solutes of trisodium citrate and tripotassium citrate. Reverse salt flux of all the organic daw solutes was much lower than that of NaCl. The osmotic pressure of the synthesized draw solute was 25% lower than that of NaCl. The solubility of the draw solute was 317 g/ 100 g water, which is 8.8 times higher than that of NaCl. A commercialized nanofiltration membrane was used for the recovery of the draw solute. The draw solute could be effectively recovered at low pressure. 정삼투 공정에 유용한 유도용질로서 diethyl malonate를 사용한 citrate 계열의 유기 화합물을 합성하였다. 최종적으로 얻은 potassium pentane-1,3,3,5-tetracarboxylate는 1 H-NMR과 13C-NMR을 통하여 확인하였다. 유도용질의 물성을 확인하기 위해 삼투압, 용해도, 수투과도, 역염 투과도를 측정하였다. 합성한 유도용액을 사용하여 정삼투 공정을 진행한 결과, 동일한 citrate 계열인 trisodium citrate 및 tripotassium citrate보다 높은 수투과량을 나타내었으며 염의 역확산 정도는 NaCl에비하여 매우 낮은 값을 나타내었다. 합성된 유도용질의 삼투압은 NaCl보다 약 25% 낮았으나 물에 대한 용해도는 NaCl의 8.8 배인 317 g/100 g water의 값을 나타내었다. 정삼투 종료 후 유도용질의 회수를 위해 상용화된 나노여과막을 사용하였고, 낮은 압력에서 효율적으로 회수가 가능하였다.

Application of volume-retarded osmosis and low-pressure membrane hybrid process for water reclamation

Im, Sung-Ju,Choi, Jungwon,Lee, Jung-Gil,Jeong, Sanghyun,Jang, Am Elsevier 2018 CHEMOSPHERE - Vol.194 No.-

<P><B>Abstract</B></P> <P>A new concept of volume-retarded osmosis and low-pressure membrane (VRO-LPM) hybrid process was developed and evaluated for the first time in this study. Commercially available forward osmosis (FO) and ultrafiltration (UF) membranes were employed in a VRO-LPM hybrid process to overcome energy limitations of draw solution (DS) regeneration and production of permeate in the FO process. To evaluate its feasibility as a water reclamation process, and to optimize the operational conditions, cross-flow FO and dead-end mode UF processes were individually evaluated. For the FO process, a DS concentration of 0.15 g mL<SUP>−1</SUP> of polysulfonate styrene (PSS) was determined to be optimal, having a high flux with a low reverse salt flux. The UF membrane with a molecular weight cut-off of 1 kDa was chosen for its high PSS rejection in the LPM process. As a single process, UF (LPM) exhibited a higher flux than FO, but this could be controlled by adjusting the effective membrane area of the FO and UF membranes in the VRO-LPM system. The VRO-LPM hybrid process only required a circulation pump for the FO process. This led to a decrease in the specific energy consumption of the VRO-LPM process for potable water production, that was similar to the single FO process. Therefore, the newly developed VRO-LPM hybrid process, with an appropriate DS selection, can be used as an energy efficient water production method, and can outperform conventional water reclamation processes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> New energy saving forward osmosis-low pressure membrane hybrid process was tested. </LI> <LI> The system could produce final product with an increase in inner pressure of tank. </LI> <LI> A polymeric draw solute was effective in the operation of this hybrid system. </LI> <LI> A mass balance modeling was used for optimization. </LI> <LI> An applicability of this hybrid process in wastewater treatment was confirmed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Feasibility study of a forward osmosis/crystallization/reverse osmosis hybrid process with high-temperature operation: Modeling, experiments, and energy consumption

Park, Kiho,Heo, Hwan,Kim, Do Yeon,Yang, Dae Ryook Elsevier 2018 Journal of membrane science Vol.555 No.-

<P><B>Abstract</B></P> <P>This paper presents a comprehensive analysis of a forward osmosis (FO)/crystallization/reverse osmosis (RO) hybrid process with high-temperature operating conditions to assess its feasibility as desalination technology. A process configuration and draw solute candidates are suggested. A mathematical model was developed to describe transport phenomena at the described operating conditions and an experimental study was conducted to investigate the amounts of water and reverse salt fluxes and to validate the developed model. Based on the experimental data, suitable membrane parameters for each process were estimated, and the applicability of the operating conditions was confirmed. An energy consumption model for the hybrid process was also developed and a comparative study with the conventional seawater reverse osmosis (SWRO) process was conducted. The equivalent work in the hybrid process is around 1.66–2.72 kW h/m<SUP>3</SUP> when heat-electricity energy cost conversion is considered. The energy requirement of the hybrid process is competitive with that of conventional SWRO process. Of the total energy requirement of the process, thermal energy comprises 0.6–1.1 kW h/m<SUP>3</SUP>. Thus, the energy requirement can be lowered to less than 1.0 kW h/m<SUP>3</SUP> if very cheap waste energy is available.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High temperature operation for FO/crystallization/RO hybrid process was suggested. </LI> <LI> Appropriate draw solute candidates were selected. </LI> <LI> Transport and energy consumption model for the hybrid process were developed. </LI> <LI> Appropriate membrane parameters condition were estimated from experimental data. </LI> <LI> The energy consumption of the hybrid process was calculated for each draw solute. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>