Sludge volume index and suspended solids estimation of mature aerobic granular sludge by quantitative image analysis and chemometric tools

Abstract

Aerobic granular sludge (AGS) is considered a promising technology for wastewater treatment. Furthermore, it is recognized that the stability of the process is related to the balanced growth of the suspended (floccular) and granular fractions. Therefore, the development of adequate techniques to monitor this balance is of interest. In this work the sludge volume index (SVI), volatile suspended solids (VSS) and total suspended solids (TSS) of mature AGS were successfully predicted with multilinear regression (MLR) models using data obtained from quantitative image analysis (QIA) of both fractions (suspended and granular). Relevant predictions were obtained for the SVI (R 2 of 0.975), granules TSS (R 2 of 0.985), flocs TSS (R 2 of 0.971), granules VSS (R 2 of 0.984) and flocs VSS (R 2 of 0.986). The estimation of the granular fraction ratio from the predicted TSS and VSS was also successful (R 2 of 0.985). The predictions help to avoid instability episodes of the AGS system, such as changes in biomass morphology, structure and settling properties.

Increased extracellular polymeric substances production contributes for the robustness of aerobic granular sludge during long-term intermittent exposure to 2-fluorophenol in saline wastewater

“…After granules collection (during the aeration phase of the treatment cycle), samples were subjected to a procedure described elsewhere to preserved biomass properties until analysis [28]. Image analysis evaluated the equivalent diameter (Deq), area (%), number (%), and roundness of granules as described elsewhere [21,29,30].…”

Variability in the composition of extracellular polymeric substances from a full-scale aerobic granular sludge reactor treating urban wastewater

“…The granules were divided into three classes based on the equivalent diameter (Deq): small granules (Deq below 150 μm), intermediate granules (Deq between 150 and 1500 μm), and large granules (Deq above 1500 μm). A specially developed program in Matlab (The Mathworks, Inc., Natick) allowed the treatment of the collected images in order to characterize AGS samples, in terms of some relevant morphological parameters: size, roundness, area, robustness, and compactness [33][34][35].…”

Validation of a quantitative image analysis methodology for the assessment of the morphology and structure of aerobic granular sludge in the presence of pharmaceutically active compounds

“…The separation of the granular and suspended (floccular) mature AGS was obtained using a 500 µm sieve, allowing for the floccular aggregates to pass through, and with the retained granules carefully picked up by rinsing with distilled water (Leal et al, 2020b) to avoid physical disruption. Care was also taken to avoid the formation of a filtration cake by carefully pouring the sampled volume throughout the available filtration area.…”

“…In this sense, QIA is an objective, time and cost-effective methodology that has already been applied to monitor disturbances in anaerobic granular sludge (Costa et al, 2010). Recently, QIA coupled with chemometric analysis, was successfully used for mature and stable AGS systems' monitoring, evaluating both granular and suspended (floccular) biomass (Leal et al, 2020b). However, studies encompassing the validation of these techniques, in terms of floccular and granular continuity under transient conditions (after fractions separation by sieving), mainly in the presence of pharmaceutically active compounds (PhAC), are still unexplored.…”