Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal Evaluating the performance of Microbial Desalination Cells subjected to diferent operating temperatures Mostafa Ragab a , Abdelsalam Elawwad b, ⁎ , Hisham Abdel-Halim b a Sanitary and Environmental Engineering Institute, Housing and Building National Research Center, 87 Tahir St., 11511 Dokki, Giza, Egypt b Environmental Engineering Dept., Faculty of Engineering, Cairo University, El-Gamaa St., 12613 Giza, Egypt ARTICLEINFO Keywords: Operation conditions Fuel cells Desalination Power generation ABSTRACT Operational conditions have a tremendous efect on the performance of Microbial Desalination Cells (MDCs). In this study, MDCs were tested at three diferent temperatures zones; 45, 27 and 12 °C. Average COD removal efciencies were 78 ± 5, 80 ± 6 and 46 ± 10% at 45, 27, and 12 °C, respectively and the average desalination efciencies were 22.7 ± 5.8, 17.5 ± 5 and 9.4 ± 4.3% respectively. High columbic efciencies were obtained of 9.7% at 45 °C and 11.28% at 27 °C, compared with a signifcantly lower value of 1.04% at 12 °C. Higher columbic efciencies were correlated to lower COD removal rates. The increase in temperature resulted in a reduction in the internal resistance which improves the desalination. The maximum current densities of 402, 407 and 31 mA/m 2 were recorded at 45, 27 and 12 °C respectively. Higher current densities were attained at both 45 and 27 °C while the cell operated at 27 °C only achieved sustained stable densities. The results of microbial community qualifcation indicated prevalence of three common strains at the three cells and a selective strain at each temperature zone. Scanning electron microscopy results revealed colour changes and distortion of the membranes. This study demonstrated that the MDCs are adaptable to function at diferent operation tempera- tures. 1. Introduction Dramatic population growth threatens the availability of the fresh water with adequate quality and quantity [1]. Desalination of sea and brackish water is therefore a viable alternative. Energy consumption is the key challenge fronting the expanded application of the desalination technologies, particularly in lesser economically developed countries. The average energy consumption for the prevalent desalination tech- nologies (i.e. reverse osmosis and distillation processes) ranges from 3 to 6 kWh/m 3 [2]. These energy-intensive technologies necessitate searching for energy efcient alternatives [3]. Wastewater is a viable source of energy where typical ranges from 1.8 to 2.1 kWh/m 3 can be attained [4–6]. A Microbial Fuel Cell (MFC) is a device that uses bac- teria known as exoelectrogenic as a catalyst to transform the chemical energy that exists in wastewater in the form of organic complex sub- strates into electricity via electrochemical reactions [7–9]. MFCs com- monly consist of an anode and a cathode in an electrolyte separated by a cation selective membrane and is externally connected via a con- ductive material holding a resistor to form the electrical circuit [7,8]. Electrons are produced at the anode and fow to the cathode through the external circuits while a number of cations are transferred through the membrane to combine with the electrons in presence of a chemical oxidizer (commonly the oxygen) to act as electron acceptor [9,10]. The aerobic and anaerobic environment should be maintained in the cathode and anode compartments, respectively [11]. It was reported that MFCs could produce superior power densities when mixed bac- terium cultures are employed instead of pure ones [12,13]. Surrounding environmental conditions also have a signifcant efect on the growth of the mixed bacterium and consequently the acclimatized microorgan- isms will dominate. This phenomenon is not only benefcial due to the signifcant power generation but can also make the MFCs capable of dealing with diferent types of wastes, which will result in a reduction of operational costs in practical applications [14]. A Microbial Desalination Cell (MDC) is a device derived from MFCs, recently introduced for the frst time by Cao et al. [15] to achieve three goals: wastewater treatment, water desalination and power production in a single reactor [4,15]. MDCs employ an additional chamber, or chambers, between the anode and the cathode that contains salty water (i.e. brackish water, seawater). It's concept of operation is similar to water electrodialysis but the MDC obtains the electrical energy from the bacteria via oxidation of the organic matter. MDCs contain ion ex- change membranes separating the three chamber and permit salt ions to https://doi.org/10.1016/j.desal.2019.04.008 Received 9 September 2018; Received in revised form 1 April 2019; Accepted 5 April 2019 ⁎ Corresponding author. E-mail address: elawwad@cu.edu.eg (A. Elawwad). Desalination 462 (2019) 56–66 0011-9164/ © 2019 Elsevier B.V. All rights reserved. T