Fixing CO₂ and treating wastewater from beer brewery using microalgae

Beer plants usually treat wastewater using a technology that combines Up-flow Anaerobic Sludge Bed/Blanket (UASB) and Cyclic Activated Sludge System (CASS). This technology aims at only treatment but not utilization of wastewater. It has many disadvantage, such as high-energy consumption for aeration, filamentous sludge bulking and large sludge problem. Using algae technology to replace CASS can realize CO₂ fixation, wastewater purification and algae biomass production. Beer wastewater contains few toxic ingredients, so the lipid, protein and other high value ingredients in the algae cells can be extracted for food application beside for biofuels. The objectives of the project were to study the interaction between algae growth and pH, the effect of aeration on algae growth and pH, the effect of initial inoculation on algae growth, the relationship between pH and bubbling with air containing 5% CO₂, and algae growth in beer wastewater comparing with BG11 for different periods. It was concluded that: (1) Scenedesmus obliquus FACHB-276 can adapt to a wide pH range; (2) Aeration level affected the pH and algae growth; (3) Non-aseptic culture was possible with suitable initial algae inoculation to establish their dominance; (4) Beer wastewater slowed down the pH change when CO₂ was injected to the water; (5) CO₂ injection promoted algae growth in beer wastewater; (6) Algae could accumulate lipid in the algae cells grown in the beer wastewater but not in BG11. Based on this study, we believe that it is possible to build an algae based system coupling beer wastewater treatment and CO₂ sequestration with algae biomass production.