Enhancing fermentation wastewater treatment by co-culture of microalgae with volatile fatty acid- and alcohol-degrading bacteria

Co-culture of microalgae and bacteria is a promising method for wastewater treatment. The suitable selection of the bacteria in co-cultures with microalgae is critical for wastewater treatment. Three bacteria, Exiguobacterium aurantiacum, Stenotrophomonas acidaminiphila, and Chryseobacterium scophthalmus, were the dominant bacterial species in fermentation wastewater treated by microalgae and activated sludge. Pure cultures and co-cultures of microalgae (Chlorella sorokiniana L3) and these bacteria were evaluated for the treatment of fermentation wastewater, which contains high concentrations of acetate acid, butyric acid, ethanol and butanol. The performance of the co-cultures was better than that of pure cultures of microalgae or bacteria for the removal of four organic compounds, and the removal efficiency of volatile fatty acids and alcohols in the best co-culture case was increased by 22.70% compared to that of pure cultures. Butanol and butyric acid were much more difficult for microalgae and bacteria to remove than were acetic acid and ethanol. The co-cultures of Chlorella sorokiniana L3 with Stenotrophomonas acidaminiphila or Chryseobacterium scophthalmus had the highest removal efficiencies for the four organic compounds in all treatments. The co-cultures of Chlorella sorokiniana L3 with Exiguobacterium aurantiacum, Stenotrophomonas acidaminiphila or Chryseobacterium scophthalmus promoted not only chlorophyll a + b production but also biomass accumulation of Chlorella sorokiniana L3 during the 3 days of cultivation compared with those in pure cultures. More than 77.8% of NH4+-N, 45.6% of total PO43−-P and 63.7% of COD (chemical oxygen demand) were removed in all co-cultures. These three bacteria are potential candidates for wastewater treatment through co-culture with microalgae.