# Performance of the Dual-Chamber Fungal Fuel Cell in Treating Tannery Wastewater  
[PERSON]  
1 National Research Base of Intelligent Manufacturing Service, Chongqing Technology and Business University, Chongqing 400067, China; [EMAIL_ADDRESS] (M.S.M. ); [EMAIL_ADDRESS] (J.-H.W. ); [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (Z.-W.G. ); [EMAIL_ADDRESS] (Y.X)  
[PERSON]  
1 National Research Base of Intelligent Manufacturing Service, Chongqing Technology and Business University, Chongqing 400067, China; [EMAIL_ADDRESS] (M.S.M. ); [EMAIL_ADDRESS] (J.-H.W. ); [EMAIL_ADDRESS] (Y.S. ); [EMAIL_ADDRESS] (Z.-W.G. ); [EMAIL_ADDRESS]  
and production phases, the tanning process utilizing chromium salts is efficient, quick, stable, and inexpensive [4; 5]. Due to that process, high chromium concentrations remain in the effluent [6]. Since heavy metals (especially chromium), toxic chemicals, chlorides, lime with high levels of dissolved and suspended salts, total organic matter represented by chemical oxygen demand (COD) and biological oxygen demand (BOD), as well as other pollutants, are present in tanny wastewater, it is recognized as a highly contaminated industrial effluent [7; 8]. For every ton of hide, 300 kg of chemicals are applied during the tanning process [9]. About 30 to 35 L of effluent are generated using this method for every kilogram of skin or hide handled [10]. This type of wastewater is considered to be a significant challenge in terms of treatment due to high organic loads along with high salt concentrations [11]. Color, low pH values, high concentrations of sodium chloride indicated by TDS, organic components indicated by COD, certain nitrogenous compounds indicated by total nitrogen (TN), and heavy metals represented as Cr\({}^{6+}\) are the most common features of tanny wastewater during the tanning process [12; 13]. The direct release of this wastewater without proper treatment would result in a decline in water quality [14]. Due to the importance of wastewater reuse in the circular economy and green building themes [15], the treatment of tanny wastewater that is produced in large quantities from the tanning industry has become necessary [16]. There are a number of physico-chemical and bio-chemical technologies that have been developed for treating tanny wastewater [17], including thermal techniques [18], advanced chemical oxidations [19; 20], coagulation-flocculation [21], ion exchange [22], and membrane techniques [23]. However, these techniques have several limitations, including high operational costs, high chemical consumption, and secondary pollution need to be addressed using online intelligent management methods [24; 25]. Bio-treatment is an another alternative treatment technology that could be considered as an eco-green method. Beside the low cost of biomaterials that have the ability to degrade and absorb a large number of pollutants, it has a number of limitations that can be represented via its slower operation rate and the requirement for continuous monitoring of all operating parameters affecting the biological behavior of pH and nutrients [17]. To obtain successful treatment, the implementation of design parameters and continuous optimization of conditions need to be adjusted as it changes according to microbial growth factors. At the end of this process, the biological mass representing bio-waste materials will increase and in many cases will require post-treatment to ensure that the old biological mass can be reused or dealt with as part of hazardous organic materials. Bio-materials are considered to be cultures of bacterial species or fungal species that have the ability to degrade organic materials and produce energy. Although limitations exist for the bio-treatment methodology of operational costs, chemical consumption, and secondary pollution compared to other treatment technologies, the methodology is still considered as a unique approach for generating energy from organic materials [26]. Energy is one of the most important gains from wastewater treatment.