2024 AIChE Annual Meeting
(682c) Advanced Light-Tolerant Microalgae-Nitrifying Bacteria Consortia for Stable Ammonia Removal Under Strong Light Irradiation Using Light-Shielding Hydrogel
Authors
Ida, J. - Presenter, Soka University
Aramoto, K., Soka University
Durán, B., Guanajuato University
Nishi, K., Soka University
Cervantes-Avilés, P., Tecnológico de Monterrey
Rodríguez, G. C., Guanajuato University
Akizuki, S., Soka University
Matsuyama, T., Soka University
The consortium of microalgae and nitrifying bacteria has attracted attention owing to its advantages, such as energy- and cost-efficiency in terms of using only light irradiation without aeration. However, high light intensity can easily cause photoinhibition of nitrifying bacteria, resulting in process breakdown of the consortium. This challenge limits its practical application in outdoor environment. To overcome this challenge, we developed a “light-shielding hydrogel” which entrapped nitrifying bacteria in carbon black-added alginate hydrogel beads in this study and confirmed its effectiveness of protecting the nitrifying bacteria from intense light up to 1600 µmol photons m-2 s-1. Then, we aimed to establish consortia of Chlorella sorokiniana and nitrifying bacteria immobilized in light-shielding hydrogel and evaluate their nitrification performance under strong light. Three nitrifying bacteria conditions were used: light-shielding hydrogel, hydrogel containing only nitrifying bacteria without carbon black (‘hydrogel’), and dispersed nitrifier without immobilization (‘dispersion’) as a control. At 1600 µmol photons m-2 s-1, the dispersion afforded a significant decrease in nitrification activity and subsequent process breakdown. In contrast, light-shielding hydrogel achieved complete nitrification without nitrite accumulation and had nitrification rates of approximately nine and two times higher than those for the dispersion and hydrogel conditions, respectively. Finally, the developed system was tested in Mexico using real anaerobic digestion effluent at the outside for long-term ammonia removal. In the 77-day experimental period, the average ammonia removal efficiency of 75.2% was obtained. This study demonstrated that the light-shielding hydrogel/consortia combination had potential for applications, which require mitigation of photoinhibition under strong light irradiation. Further, it is expected that the proposed method will contribute to realize the practical application of microalgae–nitrifying bacteria consortia in various countries that experience high sunlight intensity due to their location in the sunbelt areas.