International Journal of Technology (2016) 6: 952-961 ISSN 2086-9614 © IJTech 2016 EFFECT OF METHYLENE BLUE ADDITION AS A REDOX MEDIATOR ON PERFORMANCE OF MICROBIAL DESALINATION CELL BY UTILIZING TEMPE WASTEWATER Fachryan Zuhri 1* , Rita Arbianti 1 , Tania Surya Utami 1 , Heri Hermansyah 1 1 Bioprocess Engineering Study Program, Department of Chemical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia (Received: September 2015 / Revised: July 2016 / Accepted: September 2016) ABSTRACT The microbial desalination cell (MDC) is a modification of the microbial fuel cell (MFC) system. The microbial desalination cell is a sustainable technology to desalinate saltwater by directly utilizing the electrical power generated by bacteria during the oxidation process of organic matter. In this study, tempe wastewater will be used as a substrate. Methylene blue (MB) at concentrations of 100 μM, 200 μM, and 400 μM in the anolyte is added as a redox mediator, and the effect on electricity production and desalination performance are evaluated. The average power density increases by 27.30% and 54.54% at MB concentrations of 100 μM and 200 μM, respectively. On the other hand, the increase of the MB concentration in the anolyte results in a decrease in the salt removal percentage. The observation made using a scanning electron microscope showed the presence of MB adsorption on the surface of the anion exchange membrane (AEM) and is suspected to be the cause of the disruption of anion transfer between MDC chambers causing a decrease in the salt removal percentage. Keywords: AEM; Desalination; Methylene blue; Microbial desalination cell; Tempe wastewater 1. INTRODUCTION The microbial desalination cell (MDC) is a modification of the microbial fuel cell (MFC) system (Cao et al., 2009). MDC is a sustainable technology to desalinate saltwater by directly utilizing the electrical power generated by bacteria during the oxidation process of organic matter. This enables the MDC system to carry out the desalination process without external electrical energy (Luo et al., 2012). The simple MDC reactor was first introduced by Cao et al. (2009). It consists of three chambers separated by an anion exchange membrane (AEM) next to the anode chamber, a cation exchange membrane (CEM) next to the cathode chamber, and the center chamber containing saline solution between the two membranes. The potential of using waste as a substrate in the MDC has begun to attract a great deal of attention. Luo et al. (2011) have successfully tested the MDC by utilizing domestic wastewater as a substrate to carry out the desalination process. Other waste that can be used is tempe wastewater. In Indonesia, there are a great number of tempe industries; however, the wastewater produced by these industries is unutilized and directly dumped into the environment. Yet, it contains nutrients, such as nitrogen, phosphor, and other organic materials as carbohydrates, vitamins, and proteins that act as nutrients for the growth of microorganisms. Moreover, *Corresponding author’s email: fachryan.zuhrii@gmail.com, Tel. +6287888620178 Permalink/DOI: https://doi.org/10.14716/ijtech.v7i6.1795