Chul Park University of Massachusetts Amherst
Most municipalities in the US currently use the activated sludge process to treat wastewater. The process achieves secondary treatment but is energy intensive, mainly due to its need of aeration for organic matter and nutrient treatment. Interest in algae-based wastewater treatment has increased in recent years because of its ability to treat wastewater without aeration through the symbiotic growth of photosynthetic algae and bacteria and generate biofuel feedstock. Despite these benefits, the lack of microalgae bioflocculation, which accounts for the difficulty in separating biomass from water, and an inability to control algal species in the wastewater environment have hindered the development of algae processes for wastewater treatment. The objective of this research is to elucidate biogranulation of microalgae and bacteria that yields novel algal-sludge granules. These granules are large, dense, and spherical bioaggregates composed of both microalgae and bacteria. Preliminary research has found that algal-sludge granules can be naturally formed in the wastewater environment and be used for treating wastewater in a flow-through bioreactor. Due to physical characteristics, granules readily separate out from water, overcoming one of the major challenges of algae processes. In addition, symbiosis of algae and bacteria within the same granular biomass facilitates the engineering of an algae process for wastewater and nutrient treatment. To unveil the mechanisms of biogranulation of microalgae and bacteria this research will employ a series of batch and a flow-through reactor studies and investigate the effect of light, temperature, and growth rates on algal-bacterial granulation. To determine the microbiological nature and characterize physiochemical properties of algal-sludge granules, the investigators will conduct genetic, microscopic, and physicochemical analyses on the biogranules through this research. The project will also use a compliment of microsensor approaches to document the transport of key metabolic chemicals across the granules, thus studying microbial activity and function of the granules and their link to wastewater treatment performances. Finally, the research will conduct anaerobic digestion study on harvested biogranules to investigate its fate, digestibility, and methane bioenergy yield by anaerobic digestion, especially compared to other feedstock, such as sewage sludge and pure cultures of algal biomass.
The contribution of this research will reveal the fundamental science behind the development of novel algal-sludge granules and their growth in the context of real wastewater treatment. This research is significant, because biogranules of algae and bacteria will result in a controllable and effective algae-based wastewater treatment process. Additionally, the symbiotic growth of algae and bacteria will lead to meaningful biomass yield for biofeedstock generation from wastewater treatment. Collectively, the outcome of this research will not only advance the field of wastewater treatment, it will also have a substantially broad impact and benefit to society by reducing the energy consumed during wastewater treatment and increasing opportunity to recover chemical energy of wastewater in the form of bioenergy feedstock and biomethane through its anaerobic digestion.
