CHLORELLA VULGARIS AUTO-FLOCCULATION IN WASTEWATER TREATMENT. PREFACE TO GRANULATION

Microalgae wastewater treatment technology has not only the function of wastewater treatment but also biomass production, resource recovery, and biological carbon fixation with significant economic and environmental benefits. Good sedimentation of microalgae cells is the key to realize wastewater treatment and microalgae cell proliferation. In this study, short settling time in sequence batch reactors (SBRs) was utilizable as an environmental selection pressure to promote the auto-flocculation of Chlorella vulgaris treating synthetic domestic wastewater. After 60 days of operation, bacteria-microalgae consortia formed in the reactors, improving the settling efficiencies. Microalgae cultivation reactor with 30 min settling time had the largest flocs size and highest settling efficiency. Bacteria-microalgae granular sludge had a relatively high content of P, Fe, Mg, and Ca elements that both bacteria and microalgae coexisted and adhered to each other. The dominant bacteria distribution of bacteria-microalgae granular sludge was like that of aerobic granular sludge, which implied bacteria played a vital role in Chlorella vulgaris auto-flocculation. Lastly, the mechanism of Chlorella vulgaris auto-flocculation in wastewater treatment was interpreted.