Rapid Development of Microalgae-Bacteria Granular Sludge Using Low-Strength Domestic Wastewater

Recently, the symbiosis between microalgae and bacteria for wastewater treatment system receives more attention as microalgae and bacteria coexist symbiotically under suitable environmental condition. Moreover, the microalgae and bacteria interaction in granular form had been considered as an environmental friendly alternatives due to the synergistic cooperation between microalgae and bacteria in treating wastewater. This study aims to develop microalgae-bacteria aerobic granular sludge using low-strength domestic wastewater. A mixture of Scenedesmus obliquus and activated sludge at ratio of 17% microalgae to 83% activated sludge (v/v) was used as the seed sludge to develop microalgaebacteria aerobic granular sludge. Upon 30 days of experimental period, granular sludge was successfully developed with largest granular diameter of 6 mm. The developed granules exhibited excellent settling properties with 62.8 m/h settling velocity. Better granular settleability indicated by low sludge volume index (SVI₃₀) was detected at 8 mL/g. Observation using field-emission scanning electron microscope (FESEM) showed the attachment of microalgae cells on the outer layer of granular sludge. Moreover, microalgae-bacteria aerobic granular sludge demonstrated good COD and ammoniacal nitrogen removal at 72% removal efficiency.