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Produced water is a by-product produced from the oil and gas industry. It poses a significant threat to the environment due to its high salinity and high pollutant concentration. In this paper, steel slag was used to enhance the efficiency of the electrocoagulation process for the treatment of produced water. The impact of current density, residence time and quantity of steel slag were studied. Results revealed that the slag particles introduced an adsorption surface for the pollutants to adhere to and produced extra coagulating agents which resulted in higher pollutant removal efficiency. For a residence time and current density of 10 min and 10 mA/cm2, respectively, the steel slag containing system (with slag concentration of 5 g/L) achieved 89.7% removal for total suspended solids compared to 55.7% for the conventional system without steel slag. The total operating cost which is comprised of the electrical energy and electrode material costs was maintained minimal at 0.039 $/m3. 2020 Desalination Publications. All rights reserved. The authors wish to acknowledge Qatar University for financial support. In addition, the authors wish to thank Qatar Foundation for the financial support provided to one of the co-authors through a graduate sponsorship research award (GSRA4-2-0402-17013). The authors also wish to thank Qatar Steel for the supply of the steel slag. Scopus

In this study, dewatered construction water was used for the first time as the feed solution in a combined pretreatment-forward osmosis process to dilute seawater (i.e. draw solution) for further desalination. It was found that at a feed solution and a draw solution flow rate of 2.2 L min−1 gave the optimum membrane flux with minimal fouling effects. The addition of a spacer in the membrane feed side was effective at low flow rates (0.8 and 1.5 L min−1). The feed solution was then pretreated using two methods: settling and multimedia filtration and used in the forward osmosis unit at a low flow rate of 0.8 L min−1 using a spacer at the feed side. Results revealed a significant increase in the forward osmosis membrane flux by 64.3% when multimedia filtration was carried out with a flux reduction of 7.7%. While the settling method achieved only 13.5% increase in the permeate flux and 12.5% flux reduction. The multimedia filtration process removed most of the particles that would cause fouling which resulted in an elevated and more consistent membrane flux. Results also showed that the water flux was 1.3 times higher when the membrane's active layer was facing the draw solution than when it was facing the feed solution. Cost analysis showed that forward osmosis treatment of dewatered construction water was 7.88 $.day−1 and it was slightly cheaper when the forward osmosis operates in the pressure retarded osmosis mode. The authors wish to acknowledge Qatar University for the financial support and the Centre for Water and Wastewater Technology at the University of Technology Sydney for their help. Scopus

This study aims to investigate the effect of dielectrophoretic (DEP) force on microorganisms' viability in a membrane bioreactor (MBR). The impact of different electrical potentials (5-150 V) and different exposure durations (20-120 min) on the viability of microorganisms were studied. An interdigitated cylindrical electrode (IDE) configuration was used in the membrane module. Each electrical potential application was operated intermittently with 10 s of the electric field on and 15 s of the electric field off. It was found that the bacteria were able to withstand voltage up to 50 V, and their activity even increased with time with the application of 5 V. At high electrical potentials (100 and 150 V), the microbial activity decreased as a result of the increased current flow and temperature build up due to the Joule heating effect. The decrease of the microbial activity caused the increase of the total organic carbon (TOC) and ammonium (NH4+) concentrations in the bulk solution. A comparison between the continuous and intermittent voltage supply for the 50 V further proved the Joule heating impact on the bacteria viability. This research is made possible by NPRP award (NPRP7-089-2-044) from Qatar National Research Fund (QNRF). The statements made herein are solely the responsibility of the authors. The support from Mr. Naveen Francis and Mr. Steve Green from Doha South Waste Water Treatment Plant is also gratefully acknowledged. Scopus

Submerged membrane bioreactor (MBR) is currently believed to be an efficient biological treatment for reusing and recovering wastewater to extenuate the ever increasing water scarcity crisis. To mitigate the main problem, membrane fouling, in MBR systems, we propose a solution that avoids usage of chemicals, and allows uninterrupted operation using a novel concept of obstacle dielectrophoresis (oDEP). The utilization of obstacles, insulator or metal (floating) electrodes, between electrically excited electrodes, can extend the DEP force field to move suspended particles away from membranes without having to increase voltage, for suppressing fouling with low energy consumption. Experimental investigation verified our theoretical simulation prediction and demonstrated that insulator membrane modules provide longer membrane service time for maintaining normalized permeate flux of 55% than those by floating electrode membrane modules, with a maximum intensification factor of 7.8 when applied 220 V voltage and 50 Hz as well as the transmembrane pressure of 0.1 bar. Although stronger DEP force and hence better performance of fouling suppression can be generated by higher voltage, 50 V insulator membrane module demonstrated to be the most energy efficient process with a specific energy consumption of 0.295 kWh/m3 product and 13 times higher efficient factor than the 220 V. - 2017 This research is made possible by NPRP award ( NPRP7-089-2-044 ) from Qatar National Research Fund (QNRF). The statements made herein are solely the responsibility of the authors. Scopus