A laboratory-scale sequencing batch reactor (SBR) was operated for 450 days to assess aerobic granule formation when treating brewery/bottling plant wastewater by consistent application of a feast/famine regime. The experiment was divided into three major periods according to the different operational conditions: (I) no pH control and strong fluctuations in organic loading rate (OLR) (1.18 ± 0.25 kgCOD·(m·day)), (II) pH control and aeration control strategy to reduce OLR fluctuations (1.45 ± 0.65 kgCOD·(m·day)) and (III) no pH control and stable OLR (1.42 ± 0.18 kgCOD·(m·day)). Aerobic granule formation was successful after 80 days and maintained during the subsequent 380 days. The aerobic granular sludge was characterized by SVI and SVI values below 60 mL.g and dominated by granular, dense structures. An oxygen uptake rate based aeration control strategy insured endogenous respiration at the end of the aerobic phase, resulting in stable SBR operation when the influent composition fluctuated. The quantitative polymerase chain reaction results show no significant enrichment of Accumulibacter or Competibacter during the granulation process. The 16S rRNA sequencing results indicate enrichment of other, possibly important species during aerobic granule formation while treating brewery wastewaters.

A lab-scale SBR 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 characterised by low DSVI10,30 values of 78 ± 27 mL·g−1 and 52 ± 17 mL·g−1, respectively, and a CST/MLSS value of 0.9 sec.(g·L−1)−1. The 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·min−1) for the flocs was 10 L.(m2·h)−1 while for AGS the SF0.5 is higher than 45 L(m2·h)−1 since the FR never exceeded 0.1 mbar·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. Secondly, the AGS-MBR filtration performance shows strong advantages compared to a floccular MBR system due to a high increase of the SF0.5 and reduced reversible and irreversible fouling.

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This study investigated the application of a dynamic control strategy in an aerobic granular sludge (AGS) reactor treating real variable brewery/bottling wastewater. For 482 days, the anaerobic and aerobic reaction steps in a lab-scale AGS system were controlled dynamically. A pH-based control was used for the anaerobic step, and an oxygen uptake rate (OUR) based control for the aerobic step. Additionally, the effect of an elongated aerobic step, and the effect of the removal of the suspended solids from the influent, on AGS formation were also investigated. In comparison to a static operation, the dynamic operation resulted in similar reactor performance, related to effluent quality and the anaerobic dissolved organic carbon (DOC) uptake efficiency, while the organic loading rate was significantly higher. The removal of suspended solids from the influent by chemical coagulation with FeCl3 turned hybrid floccular-granular sludge into fully granular sludge. The granulation coincided with a significant increase in the abundance of the glycogen-accumulating Candidatus Competibacter and an increase in the content of gel-forming EPS to respectively around 14% and 30%. In conclusion, this study showed the successful application of a dynamic control strategy based on common and low-cost sensors for AGS treatment of industrial wastewater.

In this study, the influence of the anaerobic mixed feeding rate on granule stability and reactor performance in a conventional sequencing batch reactor (C-SBR) was investigated while treating various industrial wastewaters. A laboratory-scale SBR fed with malting wastewater rich in phosphorus was operated for approximately 250 days, which was divided into two periods: (I) mixed pulse feed and (II) prolonged mixed feed. Initially, no bio-P activity was observed. However, by lowering the feeding rate biological P-removal was rapidly established and no effect on the aerobic granular sludge (AGS) characteristics was observed. Additionally, to investigate the effect of the mixed feeding rate when treating an industrial effluent with low phosphorus content, i.e. brewery wastewater, a laboratory-scale reactor was operated for approximately 400 days applying different mixed feeding rates. Morphological and molecular analysis indicated that a low substrate concentration promoted the enrichment of anaerobic carbon storing filaments when fed with brewery wastewater. Findings suggest that a prolonged mixed feeding regime can be used as a tool to easily establish bio-P removal in a C-SBR system for the treatment of phosphorus-rich wastewaters. It should however be considered that under P-limiting conditions, enrichment of poly-P storing filaments may occur, possibly due to their higher substrate affinity under anaerobic conditions.