Advanced monitoring of high‐rate anaerobic reactors through quantitative image analysis of granular sludge and multivariate statistical analysis

Abstract

Four organic loading disturbances were performed in lab-scale EGSB reactors fed with ethanol. In load disturbance 1 (LD1) and 2 (LD2), the organic loading rate (OLR) was increased between 5 and 18.5 kg COD m(-3) day(-1), through the influent ethanol concentration increase, and the hydraulic retention time decrease from 7.8 to 2.5 h, respectively. Load disturbances 3 (LD3) and 4 (LD4) were applied by increasing the OLR to 50 kg COD m(-3) day(-1) during 3 days and 16 days, respectively. The granular sludge morphology was quantified by image analysis and was related to the reactor performance, including effluent volatile suspended solids, indicator of washout events. In general, it was observed the selective washout of filamentous forms associated to granules erosion/fragmentation and to a decrease in the specific acetoclastic activity. These phenomena induced the transitory deterioration of reactor performance in LD2, LD3, and LD4, but not in LD1. Extending the exposure time in LD4 promoted acetogenesis inhibition after 144 h. The application of Principal Components Analysis determined a latent variable that encompasses a weighted sum of performance, physiological and morphological information. This new variable was highly sensitive to reactor efficiency deterioration, enclosing variations between 27% and 268% in the first hours of disturbances. The high loadings raised by image analysis parameters, especially filaments length per aggregates area (LfA), revealed that morphological changes of granular sludge, should be considered to monitor and control load disturbances in high rate anaerobic (granular) sludge bed digesters.

Multiposition Sensor Technology and Lance-Based Sampling for Improved Monitoring of the Liquid Phase in Biogas Processes

“…13 The application of organic residues, in which compositions per batch are highly fluctuating, 14 or, in general, a changing feedstock can cause considerable process instabilities. Any disturbance occurs in the reaction phase at first, i.e., in the microbial cell.…”

Morphology and physiology of anaerobic granular sludge exposed to an organic solvent

“…Since the biogas production and methane content decreased, while acetate concentration increased, and the ethanol concentration remained undetected in the effluent, is clear that the methanogenesis was inhibited. It is possible to speculate that the Methanosaeta genera, which is a very slow growing archaea could have been selectively washed out, as already observed during organic loading disturbances [21].…”

Quantitative image analysis for the characterization of microbial aggregates in biological wastewater treatment: a review

“…According to Costa et al (2007Costa et al ( , 2009a, the optimal dilution factor is between 1:5 and 1:10 for anaerobic granular sludge samples with volatile solids around 30 g L −1 . Regarding aerobic activated sludge (Mesquita et al 2010b), an optimum 1:5 dilution factor was found for samples with total suspended solids (TSS) ranging from 2.3 to 4.7 mg L −1 .…”

“…Four organic loading disturbances were performed in labscale EGSB reactors fed with ethanol (Costa et al 2009a). Granule erosion/fragmentation was observed after increase the organic loading rate (OLR) from 5 to 18.5 kg COD m −3 day −1 , given the decrease from 90 to 70 % of the percentage of aggregate projected area with D eq >1 mm.…”