Cultivation of aerobic granular sludge for the treatment of food-processing wastewater and the impact on membrane filtration properties

摘要

A laboratory-scale sequencing batch reactor was operated for approximately 300 days, divided into four periods based on the feeding strategy, to develop stable aerobic granular sludge (AGS) while treating chocolate processing wastewater. Application of a prolonged mixed anaerobic feeding was not sufficient to develop AGS and reach stable reactor performance. Through the application of a partially non-mixed and a partially mixed feeding strategy, the reactor performance was increased and stable AGS formation was established characterized by low diluted sludge volume index (D)SVI DSVI10,30) values of 78 +/- 27 mL center dot g(-1) and 52 +/- 17 mL center dot g(-1), respectively, and a capillary suction time/mixed liquor suspended solids value of 0.9 sec center dot(g center dot L-1)(-1). The membrane bioreactor (MBR) filtration tests showed a reduction of the fouling rate (FR) and an increase of the sustainable flux (SF0.5) for AGS compared to flocs treating the same industrial wastewater. The SF0.5 (FR > 0.5 mbar center dot min(-1)) for the flocs was 10 L center dot(m(2)center dot h)(-1) while for AGS the SF0.5 is higher than 45 L center dot(m(2)center dot h)(-1) because the FR did not exceed 0.1 mbar center dot min(-1). Additionally, the AGS showed reduced irreversible fouling tendencies due to pore blocking. Our results underline the need for an increased substrate gradient during anaerobic feeding for the development and long-term maintenance of AGS under minimum wash-out conditions. The AGS-MBR filtration performance also shows strong advantages compared to a floccular MBR system due to a high increase of the SF0.5 and reduced reversible and irreversible fouling.