No abstract

Electrochemical process like Electrodialysis (ED) and Electrodialysis with BipolarMembranes (EDBM) can contribute to the production of freshwater and to the valorization of waste streams. In particular, EDBM can valorise the waste from desalination technologies using electric power, producing acids (HCl) and basis (NaOH) from seawater rejected brines. The use of a variable current intensity coming from a lowcarbon source such as photovoltaic (PV) solar energy means a decrease of the associated carbon footprint of the obtained products. In this work, the reduction of the specific energy consumption (SEC) of the acid from an EDBM process thanks to a feedback control loop under variable current intensity is presented. The EDBM process works in continuous or semi-continuous mode under constant or variable current intensity by means of a PV solar array simulator for 30 hours. A concentration around 1 mol•L -1 HCl has been obtained in all experiments even under variable current intensity. A noticeable drop in the SEC from a reference value of 7.3 kWh•kg -1 HCl (constant current intensity) to 4.4 kWh•kg -1 HCl (variable current intensity and feedback control loop) was reported.

The integration of electrodialysis with bipolar membranes (EDBM) with seawater reverse osmosis (SWRO) process influences the two main environmental burdens of SWRO desalination process: climate change, associated to the high-energy consumption, and the environmental alteration of the vicinities of the facility, due to brine disposal. EDBM powered by photovoltaic (PV) solar energy is able to meet the abovementioned challenges that arise in SWRO desalination. In addition, HCl and NaOH, both employed in desalination industry, can be produced from the brines. Hence, environmental benefits regarding the potential self-supply can be achieved. The environmental sustainability assessment by means of Life Cycle Assessment (LCA) of a SWRO and EDBM has been carried out considering four different scenarios. The percentage of treated brines and the influence of the grid mix used for electric power supply has been taken into account. The three different electric power supplies were: 100.0% renewable energy (PV solar energy), 36.0% renewable energy

The assessment of the environmental greenness in the process industry has been quantified by means of the development of an integrated index, i.e., Monetized Footprint Index (MFI), based on

Electrodialysis with bipolar membranes (EDBMs) is a technology that offers a great potential for the introduction of the principles of a circular economy in the desalination industry, by providing a strategy for the recovery of HCl and NaOH from brine via the process of seawater reverse osmosis (SWRO). Both chemicals are widely employed in desalination facilities, however NaOH presents a special interest due to its higher requirements and cost. Nevertheless, the standard commercial concentrations that are commonly employed in the facilities cannot be obtained using the state of the art EDBM technology itself. Therefore, the aim and main purpose of this work is to prove the technical and environmental feasibilities of a new approach to produce commercial NaOH (50%wt.) from SWRO brine by means of an integrated process of EDBMs followed by a triple effect evaporation. The global process has been technically evaluated in terms of the specific energy consumption (SEC) (kWh·kg−1 NaOH) and the environmental sustainability performance has been analyzed by its carbon footprint (CF) (kg CO2-eq.·kg−1 NaOH). The influence of the current density, and the power source in the EDBM stage have been evaluated on a laboratory scale while the influence of the feed stream concentration in the evaporation stage has been obtained through simulations using Aspen Plus. The lowest SEC of the integrated process (SECOV), 31.1 kWh·kg−1 NaOH, is obtained when an average current density of 500 A·m−2, provided by a power supply (grid mix), is applied in the EDBM stage. The environmental burdens of the integrated process have been quantified by achieving reductions in the CF by up to 54.7% when solar photovoltaic energy is employed as the power source for EDBMs, with a value of 5.38 kg CO2-eq.·kg−1 NaOH. This study presents a great potential for the introduction of the principles of a circular economy in the water industry through the recovery of NaOH from the high salinity waste stream generated in SWRO facilities and opens the possibility of the reuse of NaOH by its self-supply in the desalination plant.