Identifying different types of bulking in an activated sludge system through quantitative image analysis

Abstract

The present study proposes an image analysis methodology for the identification of different types of disturbances in wastewater treatment activated sludge systems. Up to date, most reported image analysis methodologies have been used in activated sludge processes with the aim of filamentous bulking detection, however, other disturbances could be foreseen in wastewater treatment plants. Such disturbances can lead to fluctuations in the biomass contents, affecting the mixed liquor suspended solids (MLSS), and in the sludge settling ability, affecting the sludge volume index (SVI). Therefore, this work focuses on predicting the MLSS and SVI parameters for different types of disturbances affecting an activated sludge system. Four experiments were conducted simulating filamentous bulking, zoogleal or viscous bulking, pinpoint floc formation, and normal operating conditions. Alongside the MLSS and SVI determination, the aggregated and filamentous biomass contents and morphology were studied as well as the biomass Gram and viability status, by means of image analysis.

Microbial-based evaluation of foaming events in full-scale wastewater treatment plants by microscopy survey and quantitative image analysis

“…The area percentages of each aggregate class were then calculated and used to determine the predominant aggregate size class. The usefulness of this parameter has already been demonstrated in diagnosing sludge settling problems due to viscous bulking (higher macrofloc area percentages), and high mixed liquor turbidity problems due to pinpoint floc formation (higher microfloc area percentages) in AS systems (Mesquita et al 2011). Again, it was expected that this parameter would also be useful in assessing foaming occurrences.…”

“…Furthermore, the microfloc area percentage averaged 36.4 % (ranging from 27.8 to 48.9 %) and the macrofloc area percentage remained always below 2.5 % in the CAS WWTP. Thus, it could be inferred that both WWTP presented a sludge with good morphological characteristics, with respect to the microbial aggregates, given that it was mainly composed by mesoflocs (Amaral 2003;Mesquita et al 2008Mesquita et al , 2011, and that the macrofloc area percentage remained always below the values characterizing viscous bulking phenomena (above 5 % according to Mesquita et al 2011).…”

“…Furthermore, the total filament length per total aggregate area ratio (TL/TA) was also determined (Amaral 2003), expressing the ratio between filamentous and aggregated biomass in the AS system, and together with the above parameters can be used to diagnose sludge settling problems. In fact, these parameters have been already found helpful to assess AS system malfunctions (Mesquita et al 2008(Mesquita et al , 2011Costa et al 2013) such as filamentous bulking (with large contents of filamentous bacteria, thus high TL/Vol and TL/TA values) or viscous bulking (presenting large contents of microbial aggregates, thus high TA/ Vol values). Therefore, it was expected that these parameters would also be useful in assessing foaming occurrences.…”

“…However, the large data contents provided by QIA render indispensable the use of chemometric techniques to organize the overwhelming information, such as principal components analysis (PCA), cross-correlation analysis, and decision trees. As matter of fact, chemometric techniques have already proven to be a valuable tool for the correlation of WWTP operating conditions with the sludge characteristics (Singh et al 2005;Mesquita et al 2008Mesquita et al , 2011Tharrault et al 2009). …”

New automated procedure to determine the contribution of filamentous bacteria in activated sludge flocs

“…Inną procedurę pomiaru ilości bakterii nitkowatych na obrazach z pomocą metod komputerowych proponuje Mesquita et al [8,9,10]. Procedura ta jest udoskonaloną wersją wcześniejszej, opracowanej w tym samym zespole badawczym przez Amarala i Ferreirę [1].…”