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CONTENTS
Volume 11, Number 5, September 2020
 

Abstract
With the increasing demand on reverse osmosis (RO) membranes for water purification worldwide, the number of disposed membrane elements is expected to increase accordingly. Thus, recycling and reuse of end-of-life RO membranes should be a global environmental action. In this work, we aim to reuse the spent RO membrane for nanofiltration (NF) and ultrafiltration (UF) process by subjecting the spent membrane to solvent and oxidizing solution treatment, respectively. Our results showed that solvent-treated RO membrane could perform as good as commercial NF membrane by achieving similar separation efficiencies, but with reduced water permeability due to membrane surface fouling. By degrading the polyamide layer of RO membrane, the transformed membrane could achieve high water permeability (85.6 L/m2.h.bar) and excellent rejection against macromolecules (at least 87.4%), suggesting its reuse potential as UF membrane. More importantly, our findings showed that in-situ transformation on the spent RO membrane using solvent and oxidizing solution could be safely conducted as the properties of the entire spiral wound element did not show significant changes upon prolonged exposure of these two solutions. Our findings are important to open up new possibilities for the discarded RO membranes for reuse in NF and UF process, prolonging the lifespan of spent membranes and promoting the sustainability of the membrane process.

Key Words
end-of-life membrane; RO; UF; oxidizing agent; membrane transformation

Address
Zhi Chien Ng, Chun Yew Chong, Woei Jye Lau, Ahmad Fauzi Ismail: Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia
Muhammad Hamdan Sunarya: School of Applied Science, Republic Polytechnic, 9 Woodlands Avenue 9, 738964, Singapore
Yong Yeow Liang: Faculty of Chemical and Natural Resources Engineering, Universiti Malaysia Pahang, Lebuhraya Tun Razak,
26300 Gambang, Kuantan, Pahang, Malaysia
See Yin Fong: Oneness Water Sdn Bhd, 21, Jalan Serendah 26/39, Kawasan Perindustrian HICOM, Seksyen 26, 40400 Shah Alam, Selangor, Malaysia

Abstract
Advances in industrial development and waste management over several decades have reduced many of the impacts that previously affected ecosystems, however, there are still processes which discharge hazardous materials into environments. Among industries that produce industrial wastewaters, textile manufacturing processes play a noticeable role. This study was conducted to test a novel continuous combined commercial membrane treatment using polyvinylidene fluoride (PVDF), ultrafiltration (UF), and polyamide (PA) nanofiltration (NF) membranes for textile wastewater treatment. The synthetic textile wastewater used in this study contained sodium silicate, wax, and five various reactive dyes. The results indicate that the removal efficiency for physical particles (wax and resin) was 95% through the UF membrane under optimum conditions. Applying UF and NF hybrid treatment resulted in total effective removal of dye from all synthetic samples. The efficiency of sodium silicate removal was measured to be between 2.5 to 4.5% and 13 to 16% for UF and NF, respectively. The chemical oxygen demand in all samples was reduced by more than 85% after treatment by NF.

Key Words
textile; wastewater treatment; dye removal; nanofiltration; ultrafiltration

Address
Hamidreza Rashidi, Lori Bradford: School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Canada
Nik Meriam Nik Sulaiman: Nik Meriam Nik Sulaiman, Nur Awanis Hashim
Hashem Asgharnejad:School of Chemical Engineering, College of Engineering, University of Tehran, Tehran, Iran
Maryam Madani Larijani: Department of Community Health and Epidemiology, University of Saskatchewan, Saskatoon, Canada




Abstract
Eutrophication of surface waters is commonly caused by excessive inputs of nutrients such as nitrogen and phosphorus. Nakdong River basin was chosen as the study area to investigate the effect of point and non-point source pollution of nitrogen on eutrophication in water body. Non-point source inputs of nitrogen accounted for approximately 84% in the total nitrogen input of the upper Nakdong river watershed, which mainly consists of agricultural land and forests. However, point source inputs of nitrogen accounted for 58~85% in the total nitrogen input of the middle and lower watersheds, including urban area. Therefore, for watershed near urban area, control of point source inputs of nitrogen may be an optimal method to control eutrophication. In this respect, the enforcing reduction of nitrogen in the final effluent of wastewater treatment facilities is needed. On the other hand, to enact more stringent nitrogen regulations, the LOT (limit of technology) and environmental impact should be considered. In this study nitrogen data were analyzed to propose new nitrogen regulations.

Key Words
dissolved organic nitrogen; eutrophication; limit of technology; nitrogen budget; nitrogen regulation

Address
Sunggue Kwak: Department of water and sewerage, Yooshin Engineering Corporation 8.4 Gil Yeoksam-ro, Gangnam-gu, Seoul 06252, Republic of Korea
Zuwhan Yun: Department of Environmental Engineering, Korea University Sejong Campus, 2511 Sejong-ro, Sejong City 30019, Republic of Korea

Abstract
The present study deals with a numerical investigation of heat and mass transfer in a Sweeping Gas Membrane Distillation (SGMD) used for desalination. The governing equations expressing the conservation of mass, momentum, energy and species with coupled boundary conditions were solved numerically. The slip boundary condition applied on the feed saline solution-hydrophobic membrane interface is taken into consideration showing its effects on profiles and process parameters.The numerical model was validated with available experimental data and was found to be in good agreement particularly when the slip condition is considered. The results of the simulations highlighted the effect of slip boundary condition on the velocity and temperature distributions as well as the process effectiveness. They showed in particular that as the slip length increases, the permeate flux of fresh water and process thermal efficiency rise.

Key Words
membrane distillation, desalination, heat and mass transfer, slip flow, SGMD

Address
Nizar Loussif: 1 École Nationale d'Ingénieurs de Monastir, Université de Monastir, Monastir, Tunisie
2 Département Génie des Procédés, Institut Supérieur des Etudes Technologiques Ksar Hellal, Tunisie
Jamel Orfi: 3 Mechanical Engineering Department, King Saud University, Riyadh, KSA
4 KA.CARE Energy Research and Innovation Center at Riyadh, Saudi Arabia

Abstract
Membrane distillation (MD) is a process used for water desalination. However, its commercialization is still hindered by its increased specific cost of production. In this work, several process configurations comprising Direct Contact and Permeate Gap distillation membrane units (PGMD/DCMD) were investigated to maximize the production rate and consequently reduce the specific water cost. The analysis was based on a cost model and an experimentally validated MD model. It was revealed that the best achievable water cost was approximately 5.1 $/m3 with a production rate of 8000 m3/y. This cost can be further decreased to approximately 2 $/m3 only if the heating and cooling energies are free of cost. Therefore, it is necessary to decrease the MD capital investment to produce pure water at economical prices.

Key Words
water desalination; cost analysis; membrane distillation; cascade configurations

Address
Jehad M Saleh, Emad M. Ali; Chemical Engineering Department, King Saud University, Riyadh, Saudi Arabia
Jamel A Orfi and Abdullah M Najib: Mechanical Engineering department, King Saud University, Riyadh, Saudi Arabia


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