BUSCADOR RECOLECTA

Microbial desalination cell (MDC) is a sustainable and energy-self-sufficient technology that simultaneously treats wastewater, produces electric energy, and desalinates water in a single device. The optimal desalination process depends on the potential generated in the system, which is mainly limited by cathode reaction, high external load values used, initial salinity of saline stream, or other conditions such as anolyte buffer concentration. As transport processes (i.e., migration and diffusion) in the device overlap under such conditions, it is difficult to identify the factors that affect desalination performance. Most of the existing MDC studies have used oxygen reduction (at neutral pH) as a cathode reaction limiting the performance. The removal of the cathode reaction limitation could help to clarify the operation of the MDC and identify different transport phenomena and their influence on the performance (current efficiency, freshwater production, and salt removal rate). This study presents a systematic analysis of a laboratory-scale MDC (cross-section 100 cm2, batch mode) behaviour under different initial saline concentrations from slightly brackish water (1.3 g L−1 NaCl) to seawater (40 g L−1 NaCl) without limitation in the desalination process (i.e., using a low value of external resistance and potassium ferricyanide as a liquid catholyte). For each initial salinity, the parameters of wastewater treatment capacity, energy and freshwater production are discussed and compared with the literature. The values of freshwater production between 0.5 and 10.6 L m−2 h−1 for each initial saline concentration in the saline compartment are achieved with optimal current efficiency values (80–100%). Additionally, the influence of anolyte buffer capacity on current density in the MDC system (from 0.8 to 1.2 mA cm−2) is analysed. Furthermore, the behaviour of the system during a seawater desalination process is discussed in terms of treatment capacity and Coulombic efficiency. This study could help understand the performance of these systems in possible natural saline scenarios where MDC technology can be implemented in the future.

This paper describes some of the work carried out within the Horizon 2020 project MIDES (MIcrobial DESalination for low energy drinking water), which is developing the world’s largest demonstration of a low-energy sys-tem to produce safe drinking water. The work in focus concerns the support for operational decisions on desalination plants, specifically applied to a mi-crobial-powered approach for water treatment and desalination, starting from the stages of process modelling, process simulation, optimization and lab-validation, through the stages of plant monitoring and automated control. The work is based on the application of the environment IPSEpro for the stage of process modelling and simulation; and on the system DataBridge for auto-mated control, which employs techniques of Machine Learning.

As non-conventional wastewater treatment, vegetation filters make the most of the natural attenuation processes that occur in soil to remove contaminants, while providing several environmental benefits. However, this practice may introduce contaminants of emerging concern (CECs) and their transformation products (TPs) into the environment. A potential improvement to the system was tested using column experiments containing soil (S) and soil amended with woodchips (SW) or biochar (SB) irrigated with synthetic wastewater that included 11 selected CECs. This study evaluated: i) known CECs attenuation and ii) unknown metabolites formation. Known CECs attenuation was assessed by total mass balance by considering both water and soil media. An untargeted metabolomic strategy was developed to assess the formation of unknown metabolites and to identify them in water samples. The results indicated that SB enhanced CECs attenuation and led to the formation of fewer metabolites. Sorption and biodegradation processes were favored by the bigger surface area of particles in SB column, especially for compounds with negative charges. Incorporating woodchips into soil shortened retention times in the column, which reduced attenuation phenomena and resulted in the formation of significantly more metabolites. Incomplete biodegradation reactions, fostered by shorter retention times in SW column could mainly explain these results.