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- 저자 : Chekli, (검색결과 21 건)
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Chekli, L.,Eripret, C.,Park, S.H.,Tabatabai, S.A.A.,Vronska, O.,Tamburic, B.,Kim, J.H.,Shon, H.K. Elsevier Science B.V 2017 Separation and purification technology Vol.175 No.-
<P><B>Abstract</B></P> <P>Seasonal green algae blooms in freshwaters have raised attention on the need to develop novel effective treatment processes for the removal of algae in water. In the present study, the performance of newly developed polytitanium tetrachloride (PTC) coagulant for the removal of freshwater microalga <I>Chlorella vulgaris</I> has been investigated and compared with titanium tetrachloride (TiCl<SUB>4</SUB>) coagulant and the conventional ferric chloride (FeCl<SUB>3</SUB>) coagulant. The main benefit of using titanium-based coagulants is that the sludge produced after flocculation may be recycled into a valuable product: titanium dioxide photocatalyst. Both titanium-based coagulants achieved good flocculation over a broader pH range and coagulant dose compared to conventional FeCl<SUB>3</SUB> coagulant. All three coagulants achieved comparable performance in terms of turbidity removal (i.e. turbidity removal efficiency >97%); although TiCl<SUB>4</SUB> performed slightly better at the lower tested dose (i.e. <9mg/L). Zeta potential measurements indicated that charge neutralisation may not be the sole mechanism involved in the coagulation of algae for all three coagulants. Analysis of the dynamic floc size variation during floc breakage showed no regrowth after floc breakage for the three coagulants. The flocs formed by both Ti-based coagulants were larger than those formed by FeCl<SUB>3</SUB> and also grew at a faster rate. This study indicates that Ti-based coagulants are effective and promising coagulants for algae removal in water.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ti-based coagulants were compared with FeCl<SUB>3</SUB> for algal turbid water treatment. </LI> <LI> TiCl<SUB>4</SUB> and PTC achieved good flocculation over a broader pH range and coagulant dose. </LI> <LI> Turbidity removal efficiency was similar amongst the tested coagulants. </LI> <LI> PTC showed the fastest floc growth rate and also the largest floc sizes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Chekli, L.,Corjon, E.,Tabatabai, S.A.A.,Naidu, G.,Tamburic, B.,Park, S.H.,Shon, H.K. Academic Press 2017 Journal of Environmental Management Vol. No.
<P>During algal bloom periods, operation of seawater reverse osmosis (SWRO) pretreatment processes (e.g. ultrafiltration (UF)) has been hindered due to the high concentration of algal cells and algal organic matter (AOM). The present study evaluated for the first time the performance of titanium salts (i.e. titanium tetrachloride (TiCl4) and polytitanium tetrachloride (PTC)) for the removal of AOM in seawater and results were compared with the conventional FeCl3 coagulant. Previous studies already demonstrated that titanium salts not only provide a cost-effective alternative to conventional coagulants by producing a valuable by-product but also minimise the environmental impact of sludge production. Results from this study showed that both TiCl4 and PTC achieved better performance than FeCl3 in terms of turbidity, UV234 and dissolved - organic carbon (DOC) removal at similar coagulant dose. Liquid chromatography organic carbon detection (LC-OCD) was used to determine the removal of AOM compounds based on their molecular weight (MW). This investigation revealed that both humic substances and low MW organics were preferentially removed (i.e. up to 93% removal) while all three coagulants showed poorer performance for the removal of high MW biopolymers (i.e. less than 50% removal). The detailed characterization of flocs indicated that both titanium coagulants can grow faster, reach larger size and present a more compact structure, which is highly advantageous for the design of smaller and more compact mixing and sedimentation tanks. Both titanium coagulants also presented a higher ability to withstand shear force, which was related to the higher amount of DOC adsorbed with the aggregated flocs. Finally, TiCl4 had a better recovery after breakage suggesting that charge neutralization may be the dominant mechanism for this coagulant, while the lower recovery of both PTC and FeCl3 indicated that sweep flocculation is also a contributing mechanism for the coagulation of AOM. (C) 2017 Elsevier Ltd. All rights reserved.</P>
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Chekli, L.,Phuntsho, S.,Kim, J.E.,Kim, J.,Choi, J.Y.,Choi, J.S.,Kim, S.,Kim, J.H.,Hong, S.,Sohn, J.,Shon, H.K. Elsevier Scientific Pub. Co 2016 Journal of membrane science Vol.497 No.-
Forward osmosis (FO) has been increasingly studied in the past decade for its potential as an emerging low-energy water and wastewater treatment process. However, the term ''low-energy'' may only be suitable for those applications in where no further treatment of the draw solution (DS) is required either in the form of pretreatment or post-treatment to the FO process (e.g. where the diluted DS is the targeted final product which can be used directly or simply discarded). In most applications, FO has to be coupled with another separation process in a so-called hybrid FO system to either separate the DS from the final product water or to be used as an advanced pre-treatment process to conventional desalination technologies. The additional process increases the capital cost as well as the energy demand of the overall system which is one of the several challenges that hybrid FO systems need to overcome to compete with other separation technologies. Yet, there are some applications where hybrid FO systems can outperform conventional processes and this study aims to provide a comprehensive review on the current state of hybrid FO systems. The recent development and performance of hybrid FO systems in different applications have been reported. This review also highlights the future research directions for the current hybrid FO systems to achieve successful implementation.
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NOx removal of mortar mixed with titania produced from Ti-salt flocculated sludge
박세민,Laura Chekli,김종범,Mohammad Shahid,손호경,김판석,이운식,이웅의,김종호 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5
Norms for the emissions of NOx are becoming stricter and stricter, leading to an increase in the research interest for the development of novel gas cleaning technologies. In this study, the use of titania (TiO2) produced from Ti-salt flocculated sludge, mixed with mortar, has been investigated as a cost-effective novel solution for the removal of these pollutant gases. This work not only presents an advanced solution for sludge reduction but also proposes a novel production method of TiO2 powders from waste water and investigates the potential use of this material blinded with mortar for a novel application which is air purification. Detailed characterization of the produced TiO2 powders was performed and results showed that the primary particles present a uniform size and spherical shape with a diameter of less than 50 nm. The main constitutive elements were Ti, O, C and P, where the Ti content was found to increase slightly with increasing temperature. The anatase phase was observed at 600 ℃ and 800 ℃ and converted to rutile structure at 1000 ℃. Two contents (i.e. 3.0 and 5.0 wt%) of TiO2 were tested for mixing with mortar and photocatalytic properties of the mortar containing TiO2 were evaluated for the removal of NOx and were found to be similar to commercial TiO2 (P-25) in terms of photocatalytic activity. Further investigations under direct sunlight were conducted after 28 days of water curing to evaluate the removal of NOx. The NO rejection was about 50% after 5 h.
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Lotfi, Fezeh,Chekli, Laura,Phuntsho, Sherub,Hong, Seungkwan,Choi, Joon Young,Shon, Ho Kyong Elsevier Scientific Pub. Co 2017 Desalination Vol. No.
<P><B>Abstract</B></P> <P>We investigated the possible underlying mechanism of the low fouling potential in the forward osmosis (FO) process during the osmotic dilution of seawater as part of the simultaneous desalination and wastewater reuse by FO and reverse osmosis hybrid system. Long-term experiments revealed an interesting water flux pattern highly dependent on the different operating parameters. The most interesting observation made was the spontaneous increase in the FO permeate flux at regular time interval during the FO operation using synthetic wastewater as feed and seawater. This sinusoidal FO flux pattern related well with the build-up of loose fouling layer and their natural peel-off from the membrane surface upon reaching certain layer thickness due to crossflow velocity shear. This flux pattern was more prominent at higher cross-flow velocity rates, lower feed water pH, for a smoother membrane surface and at lower operating pressure during pressure assisted osmosis (PAO) mode. Based on these results, membrane cleaning strategies were proposed by targeting a higher cross-flow velocity shear at a time when the permeate flux started to just increase. The approach of physical membrane cleaning was observed efficient and was able to almost fully restore the initial flux even under the PAO operation at 4bar.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An interesting water flux pattern was observed during osmotic dilution of seawater. </LI> <LI> It was related to the build-up of loose fouling layer peeled-off from the surface. </LI> <LI> This sinusoidal flux pattern was highly dependent on the operating parameters. </LI> <LI> Intrinsic membrane cleaning strategies can be adopted; avoiding plant down time. </LI> <LI> Increasing the feed cross-flow velocity at specific time was found most efficient. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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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>
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Pathak, Nirenkumar,Li, Sheng,Kim, Youngjin,Chekli, Laura,Phuntsho, Sherub,Jang, Am,Ghaffour, Noreddine,Leiknes, TorOve,Shon, Ho Kyong Elsevier 2018 Bioresource technology Vol.262 No.-
<P><B>Abstract</B></P> <P>A novel approach was employed to study removal of organic micropollutants (OMPs) in a baffled osmotic membrane bioreactor-microfiltration (OMBR-MF) hybrid system under oxicanoxic conditions. The performance of OMBR-MF system was examined employing three different draw solutes (DS), and three model OMPs. The highest forward osmosis (FO) membrane rejection was attained with atenolol (100%) due to its higher molar mass and positive charge. With inorganic DS caffeine (94–100%) revealed highest removal followed by atenolol (89–96%) and atrazine (16–40%) respectively. All three OMPs exhibited higher removal with organic DS as compared to inorganic DS. Significant anoxic removal was observed for atrazine under very different redox conditions with extended anoxic cycle time. This can be linked with possible development of different microbial consortia responsible for diverse enzymes secretion. Overall, the OMBR-MF process showed effective removal of total organic carbon (98%) and nutrients (phosphate 97% and total nitrogen 85%), respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A hybrid OMBR-MF examined for OMPs and nutrient removal from simulated sewage. </LI> <LI> Performance of inorganic and organic draw solutes in OMBR-MF system assessed. </LI> <LI> Baffled OMBR-MF achieved high removal for nutrient and OMPs. </LI> <LI> Persistent OMP like atrazine exhibited high anoxic removal compared to oxic. </LI> <LI> Atenolol showed highest forward osmosis rejection due to high molar mass. </LI> <LI> Large microbial flocs contributed to lower membrane fouling propensity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Kim, Jung Eun,Phuntsho, Sherub,Chekli, Laura,Choi, Joon Yong,Shon, Ho Kyong Elsevier Scientific Pub. Co 2018 Desalination Vol. No.
<P><B>Abstract</B></P> <P>A hybrid forward osmosis (FO) and reverse osmosis (RO)/nanofiltration (NF) system in a closed-loop operation with selected draw solutes was evaluated to treat coal mine impaired water. This study provides an insight of selecting the most suitable draw solution (DS) by conducting environmental and economic life cycle assessment (LCA). Baseline environmental LCA showed that the dominant components to energy use and global warming are the DS recovery processes (i.e. RO or NF processes) and FO membrane materials, respectively. When considering the DS replenishment in FO, the contribution of chemical use to the overall global warming impact was significant for all hybrid systems. Furthermore, from an environmental perspective, the FO-NF hybrid system with Na<SUB>2</SUB>SO<SUB>4</SUB> shows the lowest energy consumption and global warming with additional considerations of final product water quality and FO brine disposal. From an economic perspective, the FO-NF with Na<SUB>2</SUB>SO<SUB>4</SUB> showed the lowest total operating cost due to its lower DS loss and relatively low solute cost. In a closed-loop system, FO-NF with NaCl and Na<SUB>2</SUB>SO<SUB>4</SUB> had the lowest total water cost at optimum NF recovery rates of 90 and 95%, respectively. FO-NF with Na<SUB>2</SUB>SO<SUB>4</SUB> had the lowest environmental and economic impacts. Overall, draw solute performances and cost in FO and recovery rate in RO/NF play a crucial role in determining the total water cost and environmental impact of FO hybrid systems in a closed-loop operation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The feasibility of FO hybrid systems for mine impaired water treatment was evaluated. </LI> <LI> SRSF and draw solute replenishment cost play a crucial role in reducing life cycle impacts of the FO hybrid systems. </LI> <LI> RO/NF permeate quality influences the total DS replenishment costs in a closed system. </LI> <LI> FO-NF with Na<SUB>2</SUB>SO<SUB>4</SUB> showed the lowest environmental and economic impacts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Kim, Jung Eun,Phuntsho, Sherub,Chekli, Laura,Hong, Seungkwan,Ghaffour, Noreddine,Leiknes, TorOve,Choi, Joon Yong,Shon, Ho Kyong Elsevier 2017 Desalination Vol.416 No.-
<P><B>Abstract</B></P> <P>Environmental and economic impacts of the fertilizer drawn forward osmosis (FDFO) and nanofiltration (NF) hybrid system were conducted and compared with conventional reverse osmosis (RO) hybrid scenarios using microfiltration (MF) or ultrafiltration (UF) as a pre-treatment process. The results showed that the FDFO-NF hybrid system using thin film composite forward osmosis (TFC) FO membrane has less environmental impact than conventional RO hybrid systems due to lower consumption of energy and cleaning chemicals. The energy requirement for the treatment of mine impaired water by the FDFO-NF hybrid system was 1.08kWh/m<SUP>3</SUP>, which is 13.6% less energy than an MF-RO and 21% less than UF-RO under similar initial feed solution. In a closed-loop system, the FDFO-NF hybrid system using a TFC FO membrane with an optimum NF recovery rate of 84% had the lowest unit operating expenditure of AUD $0.41/m<SUP>3</SUP>. Besides, given the current relatively high price and low flux performance of the cellulose triacetate and TFC FO membranes, the FDFO-NF hybrid system still holds opportunities to reduce operating expenditure further. Optimizing NF recovery rates and improving the water flux of the membrane would decrease the unit OPEX costs, although the TFC FO membrane would be less sensitive to this effect.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Environmental impacts of the FDFO-NF(TFC) hybrid system can be lower than RO hybrid systems. </LI> <LI> The FDFO-NF hybrid system consumes 21% less energy than the UF-RO hybrid system. </LI> <LI> The unit OPEX cost of FDFO-NF (TFC) system is 14% lower than UF-RO hybrid system. </LI> <LI> Improving flux and lowering the cost of the CTA FO membrane can make the FDFO-NF cost effective. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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