Modeling the Hydraulic Transport of Wastewater and Anaerobic Uptake of Organics by PAOs and GAOs During the Feeding of a Granular Sludge Reactor

The designDesign of biomassBiomass bedsBed and feeding conditionsFeeding conditions is crucial for an optimal loading, microbial selectionMicrobial selection, and biological nutrient removalBiological nutrient removal (BNRBNR) in granular sludge processesGranular sludge process. PolyphosphatePolyphosphate- (PAOsPAO) and glycogenGlycogen-accumulating organisms (GAOsGAO) compete for organic substratesOrganic substrate during anaerobicAnaerobic phasesPhase of sequencing batchBatch reactorsReactor (SBRsSBR). System analysisSystem analysis and mathematical modeling was engaged to elucidate the hydraulic transportHydraulic transport pattern during the up-flow feedingUp-flow feeding of wastewaterWastewater in granular sludgeGranular sludge bedsBed and the impact of environmental conditions (pHPH, temperatureTemperature) on PAO/GAO selectionPAO/GAO selection. Tracer experimentsTracer experiment across the granular sludgeGranular sludge column displayed a plug-flow regime with dispersionDispersion under both rapid (9 m h−1) and slow (0.9 m h−1) up-flow feedingsUp-flow feeding. FillFill/draw-and-drawFill/draw phasesPhase canFill-and-draw be implemented in SBRsSBR to feedFeed the influentInfluent at foot and extract the treated effluentEffluent at the top. Metabolic simulationsSimulation disclosed the effectsEffect of feeding durationFeeding duration, pHPH, and temperatureTemperature on PAO/GAO competitionPAO/GAO competition for the uptakeUptake of volatile fatty acidsVolatile fatty acid (VFAsVFA) under anaerobicAnaerobic slow feedingSlow feeding. Feeding timeFeeding time should be set in functionFunctions of conversionsConversion of intracellular storage polymersIntracellular storage polymers that do not move with the liquid phaseLiquid phase. The anaerobicAnaerobic metabolismMetabolism of PAOsPAO relies on both polyphosphatePolyphosphate and glycogenGlycogen as energyEnergy and reducing equivalentsReducing equivalents to store VFAsVFA as poly-β-hydroxyalkanoatesPoly-β-hydroxyalkanoates. PAOsPAO withstand a feedFeed period twice as long as GAOsGAO in which only glycogenGlycogen serves as pool of electronsElectron and energyEnergy. Applying alkaline conditions (pHPH 7.25–8.0) by, e.g., dosing limeLime in the feedFeed selects for PAOsPAO independent of temperatureTemperature (10–30 °C). TemperatureTemperature determines the bed heightBed height necessary for optimal contact between wastewaterWastewater and biomassBiomass in a full anaerobic selectorAnaerobic selector for PAOsPAO, and BNRBNR. Almost twice higher bedsBed are needed at 10 °C than at 20 °C for a complete anaerobicAnaerobic uptakeUptake of VFAsVFA. This hydraulic-metabolic modelHydraulic-metabolic model sustains the designDesign of bed geometriesBed geometry and feeding conditionsFeeding conditions to manage the microbial resourceResource in granular sludgeGranular sludge.