Storage strategy of aerobic algae-bacteria granular consortia in photo-sequencing batch reactor

Aerobic algae-bacteria granular consortia (AAG) is a novel biotechnology for wastewater treatment, although the optimal storage operation is in favor of practical application and commercial production of AAG, the information about the performance response and microbial community evolution of AAG during storage process and activation process are still sparse. This experiment selected temperature, time and illumination condition as target parameters to firstly study the influence of storage process on the AAG. The results indicated that AAG could maintain the integrated granular structure under different storage conditions, yet the influence of storage conditions on the properties of AAG was significant. After storage and activation process, the specific removal rates of total phosphorus and ammonia nitrogen of AAG that stored at 25 degrees C were 1.41-1.98 mg/g SS and 15.44-17.92 mg/g SS, respectively, which were significantly higher than those stored at 4 degrees C and-25 degrees C (0.88-1.16 mg/g SS and 8.46-14.14 mg/g SS). The stored time showed significant negative relationship with the EPS concentration (R =-0.47, P < 0.001) and the polysaccharides/protein ratio (R =-0.50, P < 0.001) of AAG, while illumination was conducive to maintain the polysaccharides/protein ratio of AAG (R = 0.43, P < 0.05). In term of target microalgae viability (Scenedesmus obliquus), temperature and illumination were the significant factors explaining the change of its relative abundance in AAG at the end of activation process (P < 0.05), which contributed 64.9% and 33.1% of the variation, respectively. Holistic evaluation of seven storage strategies in this study by analytic hierarchy process furtherly indicated that the storage strategy with 25 degrees C of operational temperature, 30 d of storage time and protect from illumination was preferable for AAG (total weight score = 0.188), while cryopreservation was the least desirable (total weight score = 0.077).

Automated summary

Aerobic algae-bacteria granular consortia (AAG) is a novel biotechnology for wastewater treatment. This study investigated the influence of storage process on AAG, finding that AAG could maintain its granular structure under different storage conditions. Storage at higher temperatures resulted in better performance of AAG. Storage time was negatively related to EPS concentration and polysaccharides/protein ratio of AAG, while illumination was conducive to maintaining the polysaccharides/protein ratio. During the activation process, temperature and illumination were significant factors influencing the relative abundance of target microalgae.