The effect of immobilisation of electroactive bacteria as 3D-printed bioelectrodes on water desalination in microbial desalination cells

Water scarcity affects approximately 2.8 billion people globally. Conventional desalination methods like reverse osmosis are energy-intensive and produce concentrated brine, necessitating sustainable alternatives. Microbial Desalination Cells (MDCs) are a promising technology integrating desalination with wastewater treatment and bioenergy generation, but their efficiency is limited by poor anode performance and membrane biofouling. This study investigated the effect of novel 3D-printed bioelectrodes with immobilised Shewanella oneidensis in sodium alginate-graphene nanoplatelets (SAGNP), sodium alginate (SA), and gelatin methacrylate (GelMA) bio-inks. The 3D-printed bioelectrodes were tested in MDCs operated in fed-batch mode for 33 days. Results showed that MDCs with the 3D-printed bioelectrodes outperformed conventional MDCs (p < 0.05). SAGNP MDC achieved the highest desalination rate of 0.84 mS/h for brackish water (10 g/L, EC 37.5 mS/cm), compared to the SA MDC (0.74 mS/h) and the GelMA MDC (0.56 mS/h). For artificial seawater (38.2 g/L, EC 53.4 mS/cm), SAGNP exhibited 0.63 mS/h. SAGNP MDC recorded a maximum power density of 22 mW/m 2 , a 1.1- and 1.85- fold increase over the SA and GelMA MDCs, respectively, alongside 84.4 % COD removal (0.34 g/m 3 /day). This work demonstrates the potential of 3D-printed bioelectrodes to optimise MDC efficiency, advancing their technical feasibility as a sustainable and energy-efficient solution for water desalination. • Immobilised electroactive bacteria as 3D-printed bioelectrode showed potential to mitigate membrane biofouling. • SAGNP 3D-printed bioelectrode MDC exhibited the highest desalination rate of 0.84 mS/h in brackish water. • SAGNP 3D-printed bioelectrode MDC achieved a desalination rate of 0.63 mS/h in artificial seawater. • SAGNP MDC achieved peak power density of 22 mW/m 2 , a 1.1- and 1.85-fold increase over the SA and GelMA MDCs, respectively.