Techno Press
Tp_Editing System.E (TES.E)
Login Search


mwt
 
CONTENTS
Volume 8, Number 5, September 2017
 

Abstract
Membrane bioreactor (MBR) is a compact and efficient wastewater treatment and reclamation technology; but, it is limited by membrane fouling. The control of membrane fouling significantly increases operational and maintenance costs. Bacteria and their byproducts - extracellular polymeric substances (EPS) - are major contributors to membrane fouling in MBRs. A recent attempt at fouling mitigation is the development of aerobic granular sludge membrane bioreactor (AGMBR) through the integration of a novel biotechnology - aerobic granulation - and MBR. This paper provides an overview on the development of AGMBR to mitigate membrane fouling caused by bacteria and EPS. In AGMBR, EPS are used up in granule formation; and, the rigid structure of granules provides a surface for bacteria to attach to rather than the membrane surface. Preliminary research on AGMBR using synthetic wastewater show remarkable membrane fouling reduction compared to conventional MBR, thus improved membrane filtration. Enhanced performance in AGMBR using actual municipal wastewater at pilot-scale has also been reported. Therefore, further research is needed to determine AGMBR optimal operational conditions to enhance granule stability in long-term operations and in full-scale applications.

Key Words
aerobic granulation; AGMBR; membrane bioreactor (MBR); membrane fouling; wastewater treatment

Address
Oliver T. Iorhemen, Rania A. Hamza and Joo Hwa Tay : Department of Civil Engineering, University of Calgary, 2500 University Drive NW, Calgary,
AB., T2N 1N4, Canada

Abstract
Forward osmosis (FO) is an emerging technology which can possibly make the desalination process more cost and energy efficient. One of the major factors impeding its growth is the lack of an appropriate draw solute. The present study deals with the identification of potential draw solutes, and rank them. The comparison was carried out among ten draw solutes on the basis of four main parameters namely; water flux, reverse salt diffusion, flux recovery and cost. Each draw solute was given three 24 hour runs; corresponding to three different concentrations; and their flux and reverse salt diffusion values were calculated. A fresh membrane was used every time except for the fourth time which was the flux recovery experiment conducted for the lowest concentration and the change of flux and reverse salt diffusion values from the initial run was noted. The organic solutes inspected were urea and tartaric acid which showed appreciable values in other parameters viz. reverse salt diffusion, flux recovery and cost although they generated a lower flux. They ranked 5th and 8th respectively. All the experimented draw solutes were ranked based on their values corresponding to each of the four main parameters chosen for comparison and Ammonium sulfate was found to be the best draw solute.

Key Words
forward osmosis; draw solute; water flux; reverse salt diffusion; and fouling

Address
G. Sudeeptha and Arun Kumar Thalla : Department of Civil Engineering, NITK Surathkal, Mangalore-575025, India

Abstract
Settling Basins are one of the most important and popular methods for removal of suspended sediments irrigation and drainage networks or power canals taking off from an alluvial river and wastewater treatment plant. Improving the performance and so increasing sediment removal efficiency of settling basins by an alternative method is necessary. In the present work, the effect of baffle and its angle of attack with the flow (9) on the sediment removal efficiency is investigated by conducting a series of experiments on a straight canal with 8 m length, 0.3 m width and 0.5 m height and 3 m length of basin equipped with an adjustable glass baffle. A numerical analysis has been carried out using ANSYS Fluent 3D software (a general purpose computational fluid dynamics simulation tool) for three Froude numbers from the experiments. The numerical and experimental results were found to match reasonably well.

Key Words
baffle angle; removal efficiency; sedimentation basins; suspended sediment

Address
Alireza Zamani Nouri : Department of Civil Engineering, College of Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran
Mohammad Mehdi Heydari : Kahana Water and Wastewater Company, Iran

Abstract
A high quality Na-X zeolite membrane was synthesized on a seeded a-alumina disc by the secondary growth method. Structural characterization was done by X-ray spectroscopy, FT-IR spectroscopy, SEM and AFM imaging. The performance evaluation of the membrane was firstly tested in separation of glucose/water solutions by pervaporation process. There was obtained a separation factor 182.7+-8.8, while the flux through the membrane was 3.6+-0.3 kg m-2 h-1. The zeolite membrane was then used for desalination of aqueous solutions consisting of Na+, Ca2+, Cs+ and Sr2+ because of the importance of these ions in water and wastewater treatments. The effects of some parameters such as temperature and solution concentration on the desalination process were studied for investigating of diffusion/adsorption mechanism in membrane separation. Finally, high water fluxes ranged from 2 up to 9 kg m-2 h-1 were obtained and the rejection factors were resulted more than 95% for Na+ and Ca2+ and near to 99% for Cs+ and Sr2+. Based on the results, fluxes were significantly improved due to convenient passage of water molecules from large pores of NaX, while the fouling was declining dramatically. Based on the results, NaX zeolite can efficiently use for the removal of different cations from wastewaters.

Key Words
desalination; NaX zeolite; membrane; pervaporation; water and wastwaters

Address
Akbar Malekpour and Hamed Nasiri : Department of Chemistry, University of Isfahan, Isfahan, Iran

Abstract
Direct treatment of municipal wastewater by forward osmosis (FO) process was evaluated in terms of water flux decline, reverse salt diffusion, pollutants rejection and concentration efficiency by using synthetic seawater as the draw solution. It was found that when operating in PRO mode (active layer facing the draw solution), although the FO membrane exhibited higher osmotic water flux, more severe flux decline and reverse salt diffusion was also observed due to the more severe fouling of pollutants in the membrane support layer and accompanied fouling enhanced concentration polarization. In addition, although the water flux decline was shown to be lower for the FO mode (active layer facing the feed solution), irreversible membrane fouling was identified in both PRO and FO modes as the water flux cannot be restored to the initial value by physical flushing, highlighting the necessity of chemical cleaning in long-term operation. During the 7 cycles of filtration conducted in the experiments, the FO membrane exhibited considerably high rejection for TOC, COD, TP and NH4 +-N present in the wastewater. By optimizing the volume ratio of seawater draw solution/wastewater feed solution, a concentration factor of 3.1 and 3.7 was obtained for the FO and PRO modes, respectively. The results demonstrated the validity of the FO process for direct treatment of municipal wastewater by using seawater as the draw solution, while facilitating the subsequent utilization of concentrated wastewater for bioenergy production, which may have special implications for the coastline areas.

Key Words
forward osmosis (FO); municipal wastewater; seawater; membrane foulin

Address
Yan Sun, Yang Bai, Jiayu Tian, Shanshan Gao and Fuyi Cui : State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology,
Harbin 150090, China
Zhiwei Zhao : Department of National Defense Construction Planning and Environmental Engineering,
Logistical Engineering University, Chongqing 401311, China

Abstract
Bacteria have been considered as a major foulant that initiates the formation of biofilm on the polymeric membrane surface. Some polymeric membranes are naturally antibacterial and have low fouling properties, however, numerous efforts have been devoted to improve their antibacterial performance. These modifications are mostly carried out through blending the membrane with an antibacterial agent or introducing the antibacterial agent on the membrane surface by chemical grafting. Currently, a significant number of researches have reported nanocomposite membrane as a new approach to fabricate an excellent antibacterial membrane. The antibacterial nanoparticles are dispersed homogenously in membrane structure by blending method or coating onto the membrane surface. Aim of the modifications is to prevent the initial attachment of bacteria to membrane surface and kill bacteria when attached on the membrane surface. In this paper, several studies on antibacterial modified membranes, particularly for water treatment, will be reviewed comprehensively. Special attention will be given on polymeric membrane modifications by introducing antibacterial agents through different methods, such as blending, grafting, and coating.

Key Words
antibacterial membrane; biofouling; membrane modification; antibacterial agents; water treatment

Address
P.T.P. Aryanti : Chemical Engineering Department, Jenderal Achmad Yani University, Jl. Terusan Jend. Sudirman, Cimahi, Indonesia
M. Sianipar : Research Center of Nanosciences and Nanotechnology, ITB, Jl. Ganesa 10, Bandung - 40132, Indonesia
M. Zunita and I.G. Wenten : Chemical Engineering Department, ITB, Jl. Ganesa 10, Bandung - 40132, Indonesia

Abstract
Novel mixed matrix membranes of Sodium Alginate (NaAlg) were developed by the incorporation ofunmodified, modified Phosphomolybdic acid (PMA) then cross-linked with glutaraldehyde externally. These membranes were prepared by the solution casting technique. Pervaporation (PV) experiments have been performed with pure NaAlg, unmodified NaAlg-PMA5, NaAlg-PMA10, modified NaAlg-mPMA5, and NaAlg-mPMA10 (wt. % of PMA 5 and 10) at 30, 40 and 50 \'C, to separate water-isopropanol feed mixtures containing 10-30 wt. % of water. Pervaporation results of NaAlg-mPMA10 produced a highest separation factor of 9028 with a flux of 0.269 kg/m2.h for 10 wt. % of water containing feed mixture. Both separation factor and flux for water increased significantly with increasing content of mPMA into NaAlg; a significant improvement in PV performance was observed for NaAlg-mPMA5 and NaAlg-mPMA10 membranes when compared to pure NaAlg& PMA-5, PMA-10 membrane.

Key Words
pervaporation; flux; azeotrope;phosphomolybdic acid; water-isopropanol mixture; sodium alginate; membrane

Address
Vanarch RajiniKanth, Sakey Ravindra and Priya M Madalageri : Department of Physics, College of Science, Engineering and Technology, University of South Africa, Johannesburg -1709, South Africa
Praveen B. Kajjari : Department of Extraction Metallurgy, Doornfontein Campus, Faculty of Engineering and the Built Environment, University of Johannesburg, P.O Box 17011, Johannesburg-2028, South Africa
Antoine F Mulaba-Bafubiandi : Department of Chemistry, Karnatak University, Dharwad 580 003, India

Abstract
The purpose of this study was to investigate membrane fouling caused by microalgal cells in submerged membrane systems consisting of polymeric and ceramic microfiltration membranes. In this study, one polymeric (flat-sheet, pore size: 0.2 um) and two ceramic (flat-sheet, pore size: 0.2 um and cylindrical, pore size: 1 um) membranes were used. Physical cleaning was performed with water and air to determine the potential for reversible and irreversible membrane fouling. The study results showed that substantial irreversible membrane fouling (after four filtration cycles, irreversible fouling degree 27% (cleaning with water) and 38% (cleaning with air)) occurs in the polymeric membrane. In cleaning studies performed using water and air on ceramic membranes, it was observed that compressed air was more effective (recovery rate: 87-91%) for membrane cleaning. The harvesting performance of the membranes was examined through critical flux experiments. The critical flux values for polymeric membrane with a pore size of 0.20 um and ceramic membranes with a pore size of 0.20 um and 1 um were <=95 L/m2hour, <=70 L/m2hour and <=55 L/m2hour, respectively. It was determined that critical flux varies depending on the membrane material and the pore size. To obtain more information on membrane fouling caused by microalgal cells, the characterization of the fouled polymeric membrane was performed. This study concluded that ceramic membranes with a pore size of 0.2-1 um in the submerged membrane system could be efficiently used for microalgae harvesting by cleaning the membrane with compressed air at regular intervals.

Key Words
membrane; microalgae; critical flux; fouling; reversibility

Address
Harun Elcik : Department of Environmental Engineering, Yildiz Technical University, Istanbul, Turkey
/Department of Environmental Engineering, Bayburt University, Bayburt, Turkey
Mehmet Cakmakci : Department of Environmental Engineering, Yildiz Technical University, Istanbul, Turkey


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2018 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com