Enhancing pollutant removal and desalination in microbial desalination cells using a rotating algal biofilm cathode

Currently, most photosynthetic microbial desalination cells (PMDCs) employ suspended algae as cathode organisms to produce oxygen. However, this method requires expensive platinum as a catalyst to catalyze the binding of oxygen to cathode electrons. In this study, a PMDC using a rotating algal biofilm (RAB) as a biocathode was demonstrated. RAB not only generates enough oxygen as an electron acceptor but also enhances the combination of oxygen and electrons on the cathode. Furthermore, the RAB-MDC system exhibited excellent performance in pollutant removal and desalination. When using simulated wastewater as anolyte and catholyte, the RAB-MDC achieved impressive removal efficiencies for COD, TOC, and NH4+-N, reaching 91.0 ± 0.1 %, 74.7 ± 0.03 %, and 95.0 ± 0.05 %, respectively. The power density reached 89.5 mW/m3 at an external resistance of 1000 Ω, while the desalination efficiency was 36.0 %, with a desalination rate of 190.9 mg/d. Additionally, high-throughput 16S rDNA sequencing was employed to assess the relative abundance of microorganisms in the RAB-MDC device, facilitating guided culture in subsequent studies. In conclusion, this research demonstrates the potential of RAB as a biocathode in MDCs for comprehensive wastewater treatment, desalination, power generation, and nutrient recovery.