Anoxic-biocathode microbial desalination cell as a new approach for wastewater remediation and clean water production Simone Perazzoli, José Pedro de Santana Neto and Hugo M. Soares ABSTRACT Bioelectrochemical systems are emerging as a promising and friendly alternative to convert the energy stored in wastewater directly into electricity by microorganisms and utilize it in situ to drive desalination. To better understand such processes, we propose the development of an anoxic biocathode microbial desalination Cell for the conversion of carbon- and nitrogen-rich wastewaters into bioenergy and to perform salt removal. Our results demonstrate a power output of 0.425 W m À3 with desalination, organic matter removal and nitrate conversion efficiencies of 43.69, 99.85 and 92.11% respectively. Microbiological analysis revealed Proteobacteria as the dominant phylum in the anode (88.45%) and biocathode (97.13%). While a relatively higher bacterial abundance was developed in the anode chamber, the biocathode showed a greater variety of microorganisms, with a predominance of Paracoccus (73.2%), which are related to the denitrification process. These findings are promising and provide new opportunities for the development and application of this technology in the field of wastewater treatment to produce cleaner water and conserve natural resources. Simone Perazzoli (corresponding author) Hugo M. Soares Department of Chemical and Food Engineering, Federal University of Santa Catarina, 88034-001 Florianópolis, SC, Brazil E-mail: perazzoli.simone@gmail.com José Pedro de Santana Neto Department of Mechanical Engineering, Federal University of Santa Catarina, 88034-001 Florianópolis, SC, Brazil Key words | bioelectrochemical systems, bioenergy, desalination, pollutants removal, water reuse INTRODUCTION Due to global warming, population growth, urbanization and increasing consumption of water and energy, the world is ever more focused on the conservation of these, two resources. Although wastewaters are known to have high pollution potential, with the presence of pathogens, hydrocarbons, metals and nutrients, they are a potential source for renewable energy generation due to their high energetic value. In this context emerges the concept of bio- electrochemical technologies (BES). BES applications are attractive as a complement to traditional wastewater treatment technologies, reducing energy requirements as well as recovering resources and synthesizing new products by using wastes as raw material. However, the small amount of energy generated would be sufficient only for low-power applications. Alternatively, it would be an advantage to uti- lize the electricity to conduct desalination (Al-Mamun et al. ) or even to synthesize new products. In this con- text, we emphasize microbial desalination cells (MDCs). These devices enable conversion of the energy stored in wastewater directly into electricity by microorganism activity and utilization of it in situ to drive the desalination process, producing clean water (Wang & Ren ; Dong et al. ). Numerous studies are proving the concept of MDCs using chemicals, e.g. potassium ferricyanide, as electron acceptor (Saba et al. ). However, due to their toxicity, new alternatives have been developed, such as biocathodes (Kokabian et al. a, b; Zuo et al. ) enabling nutri- ents removal and recovery and synthesis of valuable bioproducts. Therefore, biocathodes appear as a promising alternative, due to their potential for self-regeneration, scal- ability and sustainable nature (Al-Mamun et al. ). In biocathodes, the microorganisms accept the electrons directly from the electrode surface reducing the compounds of interest and, thus, improving the coulombic and desalina- tion efficiencies (Wen et al. ). According to the electron acceptor, they are classified into oxic or anoxic (Santoro et al. ; Al-Mamun et al. ). In oxic biocathodes, O 2 is the most popular electron acceptor due to its high redox potential (þ0.82 V) (Logan et al. ), having bacterial or microalgae consortia as bioca- talysts (Meng et al. ; Arana & Gude ; Zhang et al. 550 © IWA Publishing 2020 Water Science & Technology | 81.3 | 2020 doi: 10.2166/wst.2020.134 Downloaded from http://iwaponline.com/wst/article-pdf/81/3/550/767468/wst081030550.pdf by guest on 02 October 2021