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

Abstract

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.

Granulation strategies applied to industrial wastewater treatment: from lab to full-scale

“…The anaerobic fill time ratio (FTR), describing the ratio of the anaerobic feeding time to (active) cycle time was 13.6% in the lab-scale test, and 20% in the full-scale installation. These FTRs are comparable to values reported earlier: Martins et al (2004a) applied an anaerobic FTR of .35% and achieved good settling sludge fed with acetate-based synthetic wastewater, while Stes et al (2020) and Meunier et al (2016) applied FTRs of respectively 25.6% and 17% yielding AGS fed with real industrial wastewaters. On a full-scale dairy wastewater treatment plant, Henriet et al (2017) applied an anaerobic FTR of 31% and obtained well-settling densified sludge.…”

“…During the first week of operation (P1 in Table 1), a mixed unaerated feeding pattern was applied, which was subsequently changed to a static feeding regime (P2 to P4 in Table 1). The latter was done to create a build-up of substrate in the SBR, resulting in a feast-famine regime (Stes et al 2020).…”

“…Other works, only applying a metabolic selection for granulation in systems fed with real industrial wastewater, report granule formation times of 30-150 days (e.g. Meunier et al 2016;Caluwé et al 2017;Stes et al 2020).…”

“…No hydraulic selective pressure was applied. Stes et al (2020) applied an anaerobic feast/ aerobic famine strategy only, using slow anaerobic feeding (127 min), to form granules in a SBR treating chocolate processing effluent low in phosphorus. Stable AGS was formed when a partial static feeding step was introduced in the SBR operation.…”

Effect of an Increased Particulate COD Load on the Aerobic Granular Sludge Process: A Full Scale Study

“…This is attributed to hydrolysis of pCOD into rbCOD during the aeration phase on the granule surface, leading to substrate concentration gradients and aerobic rbCOD consumption by fast-growing OHO [20]. Nevertheless, AGS has been cultivated successfully on domestic wastewater [21,22], high-strength industrial wastewaters [23][24][25] and faecal sludge-containing wastewater [26]. Even though the influent to these reactors contained a high concentration of particulates, no filamentous outgrowth was observed.…”