Granular Sludge—State of the Art

TheSludge ecological engineeringEcological engineering of granular sludgeGranular sludge relies on a continuumContinuum from microbiological research to process engineeringProcess engineering. Designing granular sludge systemsGranular sludge system for biological nutrient removalBiological nutrient removal should thrive on the 100 years of activated sludgeActivated sludge research and practicePractice. FlocsFlocs and granulesGranule are made of the same guildsGuild of microorganisms that convert nutrientsNutrient. GranulesGranule are suspended biofilmBiofilm particlesParticle that form by self-aggregation of microbesMicrobes. GranulesGranule (0.5–2 mm scale) differ from flocsFlocs (10–100+ µm) in metricsMetrics and are prone to substrateSubstrate diffusionDiffusion limitationsLimitation. Niches of microbial populationsPopulation involved in C–N–P conversionsConversion establish at different locations along substrateSubstrate and redoxRedox gradientsGradient in the architectureArchitecture of granulesGranule, enabling an almost simultaneous removalRemoval of all nutrientsNutrient. GranulationGranulation densifies the biomassBiomass and increases its concentrationConcentration for faster volumetric conversionsConversion, and more compactCompact bioreactorsBioreactor. FundamentalFundamental processesProcess of bioaggregationBioaggregation need to get uncovered in relation to microbial selectionMicrobial selection and process performancesProcess performance. Deriving microbial ecology principlesMicrobial ecology principles is important to understand the compositionComposition and functioning of the granular sludgeGranular sludge ecosystemEcosystem, and to manage the microbial resourceResource for an efficient granulationGranulation and nutrient removalNutrient removal. Reactor engineeringReactor engineering relies on a multi-scaleMulti-scale knowledge from processProcess to granulesGranule, microorganisms, and their metabolisms. Combining systems microbiologySystems microbiology, environmental biotechnologyEnvironmental biotechnology, and mathematical modellingMathematical modelling enables conceptsConcept and methodologiesMethodology for engineeringEngineering.