Chromium is wildly used in electroplating, resistant alloys, leather tanneries and dye productions. Hexavalent chromium (Cr6+) is a priority toxic, mutagenic and carcinogenic chemical, whereas its reduced trivalent form (Cr3+) is much less toxic. Hence, the basic process for chromium detoxification is the transformation of Cr6+ to Cr3+. Some physico-chemical processes have been used to decrease Cr6+ concentrations from wastewater. In this study, microbial fuel cell (MFC) was applied to simultaneously remove Cr6+ and recovery energy. Cr(OH)3 precipitate is easily occurred in the Cr6+ reduction process because of the low solubility product constant (Ksp) of Cr(OH)3(s). Cr(OH)3 precipitate results in the decrease in MFC performance, therefore, precipitate removal from system is critical. Usually, a separation system is commonly used to remove Cr(OH)3 precipitate. In this study, Bacillus pumilus was inoculated into the anode to remove 150 mg/L Cr6+ with an outer-loop membrane filter (pore size, 5, 10, 15, 20 μm). Results indicated the power density of MFC was 102±5.6, 100±3.2, 88±3.8, 72±9.5 mW/m2 when MFC constituted with pore size 5-, 10-, 15-, and 20-μm filter. Results also showed that the removal efficiency of Cr6+ by B. pumilus was 97.2±0.8%, 96.5±1.2%, 96.3±0.9%, 81.5±1.3% when MFC constituted with pore size 5-, 10-, 15-, and 20-μm filter. Some Cr(OH)3 precipitates were coated on the surface of the electrode observed by SEM while MFC constituted with pore size 15-, and 20-μm membrane filter. None of Cr(OH)3 precipitates were observed with other pore sizes. Although Cr(OH)3 precipitate insignificantly affects Cr6+ removal (pore size 5-15 μm), it highly affects power generation of MFC by covering partial surface of electrode. In conclusion, Cr(OH)3 precipitate affects electron transfer and reduces the electricity generation. Thus, using appropriate size filter (i.e. ≤10-μm) to remove the Cr(OH)3 precipitate is vital for better MFC performance during the Cr6+ treatment process.