Effects of temperature on biofilm formation and resource recovery during anoxyphototrophic treatment of fuel-synthesis wastewater

BACKGROUND: Fuel-synthesis wastewater (FSW), a byproduct of the Fischer-Tropsch process, requiring efficient treatment and resource recovery strategies. This study aimed to optimize temperature conditions for purple non-sulfur bacteria (PNSB) biofilm formation and bioproduct recovery while simultaneously treating FSW. Experiments were conducted in biofilm photobioreactors operated at 30 °C, 35 °C, and 45 °C under illuminated anaerobic conditions. The study evaluated PNSB growth, wastewater treatment efficiency, and the yields of bioproducts, including polyhydroxybutyrate (PHB), single cell protein (SCP), lipids, carbohydrates and pigments. RESULTS: No PNSB growth was observed at 45 °C, while the highest suspended growth occurred at 35 °C and biofilm growth at 30 °C. Biofilm formation significantly increased PHB accumulation (17%) compared to suspended growth (4.3%–7.4%), highlighting the efficiency of biofilm-based cultivation. Temperature had a minimal effect on PHB composition but influenced its crystallinity and morphology. The protein content remained consistent across conditions, while lipids increased with temperature. CONCLUSION: Temperature selection between 30 °C and 35 °C significantly influences biofilm versus suspended biomass ratios and differentially affects bioproduct yields. Biofilm cultivation is preferable for maximizing PHB recovery, indicating potential for sustainable resource recovery and wastewater treatment strategies, particularly in tropical regions where external temperature regulation may be unnecessary.