Hybrid sediment microbial fuel cells utilizing Spirulina platensis for concurrent energy harvesting, pollutant removal, and algal biomass production

BACKGROUND AND OBJECTIVES: Oxygen availability in the cathode chamber is crucial for electricity generation in sediment microbial fuel cells. Microalgae, such as Spirulina platensis, can enhance dissolved oxygen through photosynthesis. Microalgae integration in sediment microbial fuel cells enhances power output, pollutant removal, and biomass recovery. The study objectives were to assess electricity generation, pollutant removal, cathode biofilm formation, and Spirulina platensis growth in an sediment microbial fuel cells system.METHODS: Sediment microbial fuel cells were assembled using sediment and overlying water from a polluted artificial lake. Spirulina platensis was obtained from a local aquaculture center and added in four volumetric ratios to lake water (0/2000, 400/1600, 1200/800, and 1600/400 milliliters) as catholyte. The reactors operated in closed-circuit mode for 28 days. Parameters measured included current and power density, sediment microbial fuel cell -based biofilm formation, and algal biomass and chlorophyll content.FINDINGS: The 1600 to 400 milliliters configuration achieved the highest power density of 83.61 milliwatts per square meter and current density of 48.43 milliamperes per square meter, approximately 43 percent higher than the control. The 1200 to 800 milliliters setup exhibited the best pollutant removal performance. The 1200 to 800 milliliters showed, chemical oxygen demand on overlying water was reduced from 139.44 ± 6.97 milligrams per liter to 69.42 ± 8.37 milligrams per liter (p = 0.0025), ammonia nitrogen from 1.72 ± 0.27 milligrams per liter to 0.06 ± 0.03 milligrams per liter. The 1200/800 condition achieved the highest biomass levels during day 21 with 0.96 grams per liter. Scanning electron microscopy revealed dense biofilm and filamentous microalgae structures on the cathode, facilitating oxygen production and electron transfer.CONCLUSION: Spirulina platensis significantly improves sediment microbial fuel cells performance through oxygen generation, pollutant removal, and biomass growth. The 1600/400 ratio is optimal for electricity generation, while 1200/800 is preferable for bioremediation and microalgae productivity. Further research should target long-term performance and nutrient management.