Monitoring morphological changes from activated sludge to aerobic granular sludge under distinct organic loading rates and increasing minimal imposed sludge settling velocities through quantitative image analysis

Quantitative image analysis (QIA) was used for monitoring the morphology of activated sludge (AS) during a granulation process and, thus, to define and quantify, unequivocally, structural changes in microbial aggregates correlated with properties rates. Two sequencing batch reactors fed acetate at organic loading rates 1.1 ± 0.6 kgCOD m−3 d−1 (R1) 2.0 0.2 (R2) three minimal imposed settling velocities (0.27 m h−1, 0.53 5.3 h−1) induced distinct processes QIA results evidenced turning point from flocculation by revealing differences aggregates’ stratification patterns quantifying equivalent diameter (Deq) 200 μm ≤ Deq 650 μm. Multivariate statistical data allowed distinguish status both systems, clustering observations according aggregation granules maturation status, successfully predicting volume index measured 5 min (SVI5) 30 (SVI30). These evidence possibility defining unequivocally rate anticipating early stages using data. Hence, could be predict episodes disruption hindered ability aerobic processes.