The presence in excess of carbon (organic matter) and nitrogen (ammonium) in wastewater of urban, agro-food or industrial origin is an environmental problem of worldwide concern. Currently, most wastewater treatment plants (WWTs) remove these compounds through activated sludge and anaerobic digestion. Both treatments present relevant shortages: insufficient efficiency to treat nitrogen; high economic cost (1/3 of WWTs energy balance is devoted to aeration, indispensable for ammonium treatment); and, in many times, the need for an additional treatment. Due to this, it’s necessary to explore new technologies able to remove simultaneously carbon and nitrogen from wastewaters in an efficient and sustainable way.
Bioelectrochemical systems (BES), which have aroused great interest in the international scientific community for the past ten years, are one of these technologies. BESs combine biological and electrochemical processes, and are based on oxidation/reduction reactions in which the release/capture of electrons is facilitated by microorganisms. In the wastewater treatment field, BES could oxidise organic matter and ammonium, and reduce the resulting nitrogen compounds (nitrites and nitrates) while producing energy. Thus, water would be treated in a more efficient and sustainable way, and the WWTs electricity consumption and their associated costs would be diminished. The potential of BES is, thus, very high. Nevertheless, further R&D work is still required to make its implementation at industrial scale real.
The doctoral thesis entitled “Carbon and nitrogen treatment in industrial wastewaters using bioelectrochemical systems” by Anna Vilajeliu Pons has focused on the simultaneous removal of carbon and nitrogen in BES to treatmanure, with a relevant environmental impact in Catalonia and in many other European regions. The researcher has studied different bacteria to use the electrode as electron acceptor (bioanode) and as electron donor (biocathode) to reduce the high concentration of organic matter and nitrogen compounds in such wastewaters. The work was partially supported by a technology transfer contract by company Abengoa Water. Main results obtained are a better knowledge of the technology and the microbial community involved; optimisation of nutrients treatment (1.2 kg COD m-3d-1 and 370 g Nm-3d-1); improvement of processes electrochemical efficiency (5 Wm-3); and the identification of system limitations in terms of design and materials. These achievements have culminated, on the one hand, in the construction of a pilot bioelectrochemical system of 65L capacity to assess the technology feasibility and, on the other hand, in the industrial patent WO/2015/150610 by Abengoa Water, which has four LEQUIA researchers as inventors – among them, Anna Vilajeliu.