###### Abstract  
The treatment of real waste extracts with simultaneous energy production is currently under research. One method of addressing this dual task is using biochemical reactors named microbial fuel cells (MFCs). MFCs consist of a bioanode and a cathode where the oxygen reduction reaction (ORR) occurs. Cathodes are currently under optimization regarding the nature of their support, their catalytic efficiency and their configurations. In this work, we present facile preparation methods for the production of activated carbon ceramic-supported cathodic electrodes produced with three different techniques (wash-coat, brush-coat, and ultrasound-assisted deposition/infiltration). The produced cathodic electrodes were tested in a single-chamber MFC, filled with the concentrated liquid residue, after the reverse osmos (RO-CLR) treatment of leachate from a municipal waste landfill, in order to exploit their electrochemical potential for simultaneous waste treatment and energy production. The electrode produced utilizing 20 kHz ultrasounds proved to be more effective in terms of energy harvesting (10.7 mW/g-L or leachate) and wastewater treatment (COD removal 85%). Internal resistances of the ultrasound-produced electrodes are lower, as compared to the other two methods, opening new exploitation pathways in the use of ultrasound as a means in producing electrodes for microbial fuel cells. municipal leachate treatment; microbial fuel cell; single chamber; waste treatment; ceramic cathodes; ultrasound-assisted deposition/infiltration; wash coat; brush coat; energy production; facile preparation +
Footnote †: journal: _Sciencedence_  
Footnote †: journal: _Sciencedenced_  
Footnote †: _Scienced_
values [2]. The management of leachates needs to be seriously addressed before choosing the treatments for lowering its contaminant (inorganic and organic) concentrations. A first step is always established with biological processes mainly for nitrogen removal. Moving bed biofilm reactors (MBBR) and activated sludge loop reactors are the types of reactors commonly employed [3; 4; 5]. In order to further remove the biological content, filtration with activated carbon or/and ozonization is used [2; 6]. Moreover, due to the large holding time in control tanks the organic content of the leachate is increased. To address this issue, reverse osmosis is commonly used in order to eliminate as many pollutants as possible [7; 8]. The reverse osmosis product, in most cases, is returned to the landfill, leading to a stronger leachate. Additionally, the reverse osmosis technology is more expensive than biological processes. Regarding the electrochemically active bacteria, a time period of acclimation is required to form the biofilm [1; 9]. In order for the microorganisms to deposit on the anodic electrode high specific surface is required [10]. Additionally, the anodic electrode should have high conductivity [11] and biocompatibility [12]. Common electrodes used in the MFC anode are plain or coated graphite/carbon-based materials such as graphite granules [13], felt [14], paper [15] and brush [16]. On the other hand, for the cathode electrode depending on the electron acceptor, a presence of catalyst may be necessary. An example of a cathodic reaction requiring catalysis is the oxygen reduction; although spontaneous, it is a slow reaction, so in order to maximize the rate, a catalyst such as platinum is coated on the cathodic surface [17]. Furthermore, instead of expensive catalysts such as platinum, microbia have been used to catalyze the oxygen reduction in MFC [18]. Other electron acceptors such as silver or copper do not require a catalyst and plain carbon or graphite-based materials are suitable. Between the anode and the cathode, a separator is present in the MFCs. Two basic configurations have been developed, one requiring two chambers and a separator (dual chamber MFC) and a second one requiring one chamber and a separator with the cathode electrode exposed to air (single chamber MFCs).