Water reclamation and reuse for urban agriculture-a solution for key water-food nexus challenges?

TorOve LEIKNES 대한환경공학회 2019 대한환경공학회 학술발표논문집 Vol.2019 No.-

Environmental and economic impacts of fertilizer drawn forward osmosis and nanofiltration hybrid system

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>

An advanced online monitoring approach to study the scaling behavior in direct contact membrane distillation

Lee, Jung-Gil,Jang, Yongsun,Fortunato, Luca,Jeong, Sanghyun,Lee, Sangho,Leiknes, TorOve,Ghaffour, Noreddine Elsevier 2018 Journal of membrane science Vol.546 No.-

<P><B>Abstract</B></P> <P>One of the major challenges in membrane distillation (MD) desalination is scaling, mainly CaSO<SUB>4</SUB> and CaCO<SUB>3</SUB>. In this study, in order to achieve a better understanding and establish a strategy for controlling scaling, a detailed investigation on the MD scaling was performed by using various analytical methods, especially an in-situ monitoring technique using an optical coherence tomography (OCT) to observe the cross-sectional view on the membrane surface during operation. Different concentrations of CaSO<SUB>4</SUB>, CaCO<SUB>3</SUB>, as well as NaCl were tested separately and in different mixed feed solutions. Results showed that when CaSO<SUB>4</SUB> alone was employed in the feed solution, the mean permeate flux (MPF) has significantly dropped at lower volume concentration factor (VCF) compared to other feed solutions and this critical point was observed to be influenced by the solubility changes of CaSO<SUB>4</SUB> resulting from the various inlet feed temperatures. Although the inlet feed and permeate flow rates could contribute to the initial MPF value, the VCF, which showed a sharp MPF decline, was not affected. It was clearly observed that the scaling on the membrane surface due to crystal growth in the bulk and the deposition of aggregated crystals on the membrane surface abruptly appeared close to the critical point of VCF by using OCT observation in a real time. On the other hand, NaCl + CaSO<SUB>4</SUB> mixed feed solution resulted in a linear MPF decline as VCF increases and delayed the critical point to higher VCF values. In addition, CaCO<SUB>3</SUB> alone in feed solution did not affect the scaling, however, when CaSO<SUB>4</SUB> was added to CaCO<SUB>3</SUB>, the initial MPF decline and VCF met the critical point earlier. In summary, calcium scaling crystal formed at different conditions influenced the filtration dynamics and MD performances.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A comprehensive analysis of calcium-based scaling behavior in DCMD was investigated. </LI> <LI> OCT was employed to monitor the scaling behavior in real-time during MD operation. </LI> <LI> CaSO<SUB>4</SUB>, CaCO<SUB>3</SUB>, and NaCl were tested separately and in mixed feed solutions. </LI> <LI> CaSO4 scaling occurred by deposition of bulk crystal on the membrane surface. </LI> <LI> A critical point of VCF at which MPF decreased significantly has been observed. </LI> </UL> </P>

Effect of engineered environment on microbial community structure in biofilter and biofilm on reverse osmosis membrane

Jeong, Sanghyun,Cho, Kyungjin,Jeong, Dawoon,Lee, Seockheon,Leiknes, TorOve,Vigneswaran, Saravanamuthu,Bae, Hyokwan Pergamon Press 2017 Water research Vol.124 No.-

<P><B>Abstract</B></P> <P>Four dual media filters (DMFs) were operated in a biofiltration mode with different engineered environments (DMF I and II: coagulation with/without acidification and DMF III and IV: without/with chlorination). Designed biofilm enrichment reactors (BERs) containing the removable reverse osmosis (RO) coupons, were connected at the end of the DMFs in parallel to analyze the biofilm on the RO membrane by DMF effluents. Filtration performances were evaluated in terms of dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Organic foulants on the RO membrane were also quantified and fractionized. The bacterial community structures in liquid (seawater and effluent) and biofilm (DMF and RO) samples were analyzed using 454-pyrosequencing. The DMF IV fed with the chlorinated seawater demonstrated the highest reductions of DOC including LMW-N as well as AOC among the other DMFs. The DMF IV was also effective in reducing organic foulants on the RO membrane surface. The bacterial community structure was grouped according to the sample phase (i.e., liquid and biofilm samples), sampling location (i.e., DMF and RO samples), and chlorination (chlorinated and non-chlorinated samples). In particular, the biofilm community in the DMF IV differed from the other DMF treatments, suggesting that chlorination exerted as stronger selective pressure than pH adjustment or coagulation on the biofilm community. In the DMF IV, several chemoorganotrophic chlorine-resistant biofilm-forming bacteria such as <I>Hyphomonas</I>, <I>Erythrobacter</I>, and <I>Sphingomonas</I> were predominant, and they may enhance organic carbon degradation efficiency. Diverse halophilic or halotolerant organic degraders were also found in other DMFs (i.e., DMF I, II, and III). Various kinds of dominant biofilm-forming bacteria were also investigated in RO membrane samples; the results provided possible candidates that cause biofouling when DMF process is applied as the pretreatment option for the RO process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Four dual media filters (DMFs) were operated under different engineered conditions. </LI> <LI> DMF with pre-chlorination treatment was effective to reduce organic matter. </LI> <LI> Functional biofilm bacterial structure in DMF and RO membranes were investigated. </LI> <LI> Pre-chlorination acted stronger selective pressure on biofilm community. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A closed-loop forward osmosis-nanofiltration hybrid system: Understanding process implications through full-scale simulation

Phuntsho, Sherub,Kim, Jung Eun,Hong, Seungkwan,Ghaffour, Noreddine,Leiknes, TorOve,Choi, Joon Yong,Shon, Ho Kyong Elsevier Scientific Pub. Co 2017 Desalination Vol. No.

<P><B>Abstract</B></P> <P>This study presents simulation of a closed-loop forward osmosis (FO)-nanofiltration (NF) hybrid system using fertiliser draw solution (DS) based on thermodynamic mass balance in a full-scale system neglecting the non-idealities such as finite membrane area that may exist in a real process. The simulation shows that the DS input parameters such as initial concentrations and its flow rates cannot be arbitrarily selected for a plant with defined volume output. For a fixed FO-NF plant capacity and feed concentration, the required initial DS flow rate varies inversely with the initial DS concentration or vice-versa. The net DS mass flow rate, a parameter constant for a fixed plant capacity but that increases linearly with the plant capacity and feed concentration, is the most important operational parameter of a closed-loop system. Increasing either of them or both increases the mass flow rate to the system directly affecting the final concentration of the diluted DS with direct energy implications to the NF process. Besides, the initial DS concentration and flow rates are also limited by the optimum recovery rates at which NF process can be operated which otherwise also have direct implications to the NF energy. This simulation also presents quantitative analysis of the reverse diffusion of fertiliser nutrients towards feed brine and the gradual accumulation of feed solutes within the closed system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Initial DS flow rate and concentration cannot be set at any arbitrary values. </LI> <LI> Initial DS flow rate and concentration vary inversely for a fixed plant capacity. </LI> <LI> Net DS mass flow rate <I>m</I> <SUB>D</SUB> is the most important parameter for a closed system. </LI> <LI> <I>m</I> <SUB>D</SUB> is constant for a fixed plant capacity but increases with capacity and feed TDS. </LI> <LI> FO and NF rejection rates influence feed solute accumulation in the closed system. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Assessing the removal of organic micropollutants by a novel baffled osmotic membrane bioreactor-microfiltration hybrid system

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>

Performance assessment of oxidants as a biocide for biofouling control in industrial seawater cooling towers

Mohammed Al-Bloushi,Jayaprakash Saththasivam,Sari Al-Sayeghc,정상현,Kim Choon Ng,Gary L. Amy,TorOve Leiknes 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.59 No.-

Biofouling can significantly hamper the efficiency of seawater cooling towers. The aim of this study was to investigate the effectiveness of alternative oxidants (i.e. ozone (O3) and chlorine dioxide (ClO2)) comparing with commonly being used chlorine in biofouling control. Effects of cycle of concentration, temperature and oxidant dosage along with residual decay and kinetics were studied. Even at lower oxidant dosage (total residual oxidant equivalent = 0.1 mg/l Cl2), ClO2 showed a better disinfection effect compared to chlorine and O3. Results of bench-scale studies will be helpful in the selection of appropriate oxidant for seawater cooling tower operation.

An investigation into the efficiency of biocides in controlling algal biofouling in seawater industrial cooling towers

Al-Bloushi Mohammed,Saththasivam Jayaprakash,Jeong Sanghyun,Al-Refaie Abdullah,Raju S. Arun Kumar1,Choon NG Kim,Amy L. Gary,Leiknes TorOve 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.6

Biofouling in the open recirculating cooling water systems may cause biological corrosion, which can reduce the performance, increase the energy consumption and lower heat exchange resulting in reduced efficiency of the cooling tower (CT). Seawater CTs are prone to bio-fouled due to the presences of organic and inorganic compounds which act as nourishment for various microorganisms like (algae, fungi, and bacteria) for their growth under certain environmental conditions. The most commonly being used method to control the biofouling in CT is by addition of biocides such as chlorination. In this study, diatom and green algae were added to the CT basin and its viability was monitored in the recirculating cooling seawater loop as well as in the CT basin. Three different types of oxidizing biocides, namely chlorine, chlorine dioxide (Chlorine dioxide) and ozone, were tested by continuous addition in pilot-scale seawater CTs and it was operated continuously for 60 d. The results showed that all biocides were effective in keeping the biological growth to the minimum regardless of algal addition. Amongst the biocides, ozone could reduce 99% of total live cells of bacteria and algae, followed by Chlorine dioxide at 97%, while the conventional chlorine showed only 89% reduction in the bioactivities.

An investigation into the efficiency of biocides in controlling algal biofouling in seawater industrial cooling towers

Al-Bloushi Mohammed,Saththasivam Jayaprakash,Jeong Sanghyun,Al-Refaie Abdullah,Raju S. Arun Kumar,Kim Choon NG,Amy L. Gary,Leiknes TorOve 대한환경공학회 2021 Environmental Engineering Research Vol.26 No.6

Biofouling in the open recirculating cooling water systems may cause biological corrosion, which can reduce the performance, increase the energy consumption and lower heat exchange resulting in reduced efficiency of the cooling tower (CT). Seawater CTs are prone to bio-fouled due to the presences of organic and inorganic compounds which act as nourishment for various microorganisms like (algae, fungi, and bacteria) for their growth under certain environmental conditions. The most commonly being used method to control the biofouling in CT is by addition of biocides such as chlorination. In this study, diatom and green algae were added to the CT basin and its viability was monitored in the recirculating cooling seawater loop as well as in the CT basin. Three different types of oxidizing biocides, namely chlorine, chlorine dioxide (Chlorine dioxide) and ozone, were tested by continuous addition in pilot-scale seawater CTs and it was operated continuously for 60 d. The results showed that all biocides were effective in keeping the biological growth to the minimum regardless of algal addition. Amongst the biocides, ozone could reduce 99% of total live cells of bacteria and algae, followed by Chlorine dioxide at 97%, while the conventional chlorine showed only 89% reduction in the bioactivities.