Large scale applications of microbial fuel cells (MFCs) have been severely hindered by several problems such as high internal resistance, low power output, expensive materials, and complicated configuration. To address these issues, a granular activated carbon based single chamber microbial fuel cell (GACB-SCMFC) has been designed using GAC-biocathodes without using any expensive materials for the simultaneous decolorization of real dye wastewater and electricity generation. The GACB-SCMFC produced a power density of 8W/m3 which indicates the GAC-biocathode can be a good alternative to platinum and other chemical catalysts. The dye wastewater was primarily treated at the anode and further polishing steps were occurred at the aerobic cathode. Toxicity measurement shows that the effluent after GACB-SCMFC operation was much less toxic compared to the original dye wastewater. Additional advantage of the GACB-SCMFC is that pH was automatically adjusted from 12.2 to 8 during 48h of hydraulic retention time (HRT).