The expansion of the sugar industry has resulted in large amounts of untreated effluent, necessitating the development of energy-efficient treatment technologies, like microbial desalination cells (MDCs). However, the high cost and potential toxicity of chemical cathode catalysts limit MDC performance, making biocathodes a promising alternative. This study investigates the efficiency of a Scenedesmus obliquus-inoculated photosynthetic microbial desalination cell (PMDC) in the cathode chamber to treat sugar industry effluent, desalinate water, and generate electricity. The performance of the PMDC is compared to that of traditional MDCs. The results showed that the PMDC achieved 21.6% desalination, 73.8% anode COD removal, and a maximum power density of 6.8 mW/m², outperforming MDC by 6.43%, 18.5%, and 112.5%, respectively. These results demonstrate that the PMDC offers an effective, energy-efficient alternative to MDCs with added benefits of nutrient removal and algal biomass production at the cathode, making it a promising solution for water and wastewater treatment.