Practical Imaging Techniques for Monitoring Granulation of Activated Sludge

Monitoring of activated sludge biomass using image analysis can be a useful approach for observing effects from process changes, environmental factors and other impacts on water resource recovery facilities (WRRFs). Changes in microbial consortia, such as the development of polyphosphate accumulating organisms (PAO) or activated sludge granules, could drive changes in biomass morphology that can be observed with microscopy equipment. However, quantitative tracking of morphological changes can be strongly influenced by image analysis algorithms, thresholding difficulties, and biases introduced in sample preparation (such as drying steps used in staining). This research focuses on developing and evaluating some practical methods for analyzing the physical morphology of activated sludge with the open source software Fiji, based on the ImageJ software. The effects of an “erode” function, staining, drying, and fixation are discussed.