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Multiscale investigation of a symbiotic microalgal-integrated fixed film activated sludge (MAIFAS) process for nutrient removal and photo-oxygenation
Citation:
Church, J., H. Ryu, A. Sadmani, A. Randall, J. Santodomingo, AND W. Lee. Multiscale investigation of a symbiotic microalgal-integrated fixed film activated sludge (MAIFAS) process for nutrient removal and photo-oxygenation. Bioresource Technology. Elsevier Online, New York, NY, 268:128-138, (2018). https://doi.org/10.1016/j.biortech.2018.07.123
Impact/Purpose:
In recent years, interest in algae-based wastewater treatment has dramatically increased because of its low energy consumption via photosynthetic oxygenation, particularly given the high fraction of wastewater treatment energy associated with mechanical aeration. In algal-based treatment processes, suspended algae need to be separated from the effluent, posing a drawback in implementing such processes. As a result, several studies have incorporated algal biofilms into their treatment systems. This study represents a novel strategy for achieving net energy production while meeting stringent effluent standards using a hybrid symbiotic microalgae-based IFAS (MAIFAS) technology. The primary objective of this study was to better understand symbiotic interactions between fixed film and suspended populations of microalgae-based biofilm processes that promote N and P removal with low energy consumption.
Description:
The removal of nitrogen (N) and phosphorus (P) from synthetic wastewater was investigated in a novel microalgae integrated fixed film activated sludge (MAIFAS) sequencing batch reactor (SBR) to better understand microalgal/bacterial biofilms in wastewater treatment. The MAIFAS system removed >99% ammonia and 51% P without the need for mechanical aeration, a marked improvement over the suspended microalgae sludge control, which only removed 57% ammonia and 49% P from synthetic wastewater. A microscopic investigation using microelectrodes showed well-defined photo-oxygenation by the MAIFAS biofilms with surface DO concentrations reaching 6.7 mg O2/L compared to 1.2 mg O2/L in the bulk solution. This localized oxygenation appears to contribute to increased ammonia removal within the biofilm. Ammonia microprofiles revealed no significant ammonia removal in the algal portion of the biofilm indicating the role of algae biofilm in the MAIFAS reactor is mostly aiding photo-oxygenation. Genetic sequencing revealed that the addition of microalgae to the IFAS system promoted significant changes in the bacterial community structure and altered metabolic activity of several bacterial groups. In particular, the MAIFAS biofilms showed a large population of Candidatus Accumulibacter compared to the IFAS control (55% vs. <1%). Overall, this research represents a novel strategy for achieving net energy production while meeting stringent effluent standards using a hybrid symbiotic microalgae-based IFAS technology.
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DOI: Multiscale investigation of a symbiotic microalgal-integrated fixed film activated sludge (MAIFAS) process for nutrient removal and photo-oxygenation
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