Auto-floating oxygenic microalgal-bacterial granular sludge

摘要

As an emerging green wastewater treatment technology, the microalgal-bacterial granular sludge (MBGS) process has attracted increasing interest under the current situation of global climate change. However, little information is avail-able for its performance in treating municipal wastewater under outdoor conditions. Thus, this study evaluated the be-haviors of MBGS for treating simulated and real municipal wastewater under natural diel conditions. The results showed that a significant accumulation of oxygen bubbles during daily operation led to the auto-floating of the con-ventional settable MBGS. The removal of organics was relatively stable during day-night cycles, while the removals of total nitrogen and total phosphorus were dependent on the saturated oxygen concentration over 10 mg/L in MBGS system. Furthermore, oxygen bubbles generated by photosynthesis of microalgae (Scenedesmaceae and Cyanobacteria) due to microalgae phototaxis were found to be attached onto the surface of granules, causing the auto-flotation of MBGS. The formation process of the auto-floating oxygenic MBGS was clarified and further analysis suggested that the non-aerated settable MBGS would be able to auto-float at an average outdoor light intensity of 140 mu mol/m2/s. Overall, the auto-floating oxygenic MBGS process was demonstrated to be feasible for real municipal waste-water treatment, even under rainy and cloudy days, advancing the knowledge and adding theoretical basis for its further applications.

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