Exploring the Bioelectrochemical Characteristics of Activated Sludge Using Cyclic Voltammetry Dena Z. Khater 1 & K. M. El-khatib 1 & Rabeay Y. A. Hassan 2 Received: 9 May 2017 /Accepted: 2 June 2017 # Springer Science+Business Media, LLC 2017 Abstract Due to the potential interest, bioelectrochemical responses of activated sludge using the three-electrode system are tested. From the cyclic voltammograms, the oxidation current output is increasing due to incubation time increase, whereas 5, 25 and 39.33 μA are obtained after 3, 72 and 96 h, respectively. Changing the working electrode from glassy carbon to carbon paste led to the increase in the electrochemical signal from 0.3 to be 3.72 μA. On the other hand, the use of the lipophilic redox mediator (2,6-dichlorophenolindophenol (DCIP)) amplified the oxidation current to reach 19.9 μA instead of 2.1 μA. Based on these findings, the mixed microbial community of the activated sludge is exploited as a catalyst for the bio- oxidation of the degradable organic substrates, while DCIP is used as a mobile electron carrier from the intracellular matrix of the metabolically active cells to the carbon paste electrode which served as the final electron acceptor. Therefore, the extracellular electron transfer from the formed active biofilm at the electrode surface is assisted by the existence of DCIP. Keywords Microbial fuel cells (MFCs) . Activated sludge . Electroactive biofilm formation . Electron mediator (DCIP) Introduction In principle, a microbial fuel cell (MFC) is considered as an alternative and simple energy resource [1–4]. It can be used for production of electricity and treatment of water from pollutants[5–9]. Construction of microbial fuel cells requires electroactive microorganisms, Appl Biochem Biotechnol DOI 10.1007/s12010-017-2528-y * K. M. El-khatib kamelced@hotmail.com 1 Chemical Engineering & Pilot Plant Department, National Research Centre (NRC), El-Tahrir Street, Dokki, Cairo 12311, Egypt 2 Microanalysis Laboratory, Applied Organic Chemistry Department, National Research Centre (NRC), El-Tahrir Street, Dokki, Cairo 12311, Egypt