Establishment of a comprehensive analysis method for the microfaunal movement in activated sludge

Microfaunal identification and analysis are very complex; thus, an image analysis method was utilized in this paper to overcome the shortcomings of using the number, dominant species, and diversity of population structure of microfauna as activated sludge indicators. Based on a classification of microfaunal movement, the quantitative processing and analysis of the micro-video frame image of microfaunal movement were carried out by using the Image J software. Background subtraction method was utilized to detect target microfauna by matching target area features to track microfaunal movement. Three parameters, namely, motion trajectory (L), consecutive frame of motion paths (S_i), and average change rate of extent [Formula: see text], were selected to represent the motion trajectory and mass center of microfauna. Four motion-velocity parameters, namely, the left and right rotation angles of adjacent frames (∆α_i), instantaneous velocity (V_i), average linear velocity ([Formula: see text]), and average angular velocity ([Formula: see text]), were selected to characterize the movement modes of microfauna. Finally, a motion analysis method based on the Image J software was established to demonstrate the different motion modes of microfauna in activated sludge. This study provides a methodological foundation for the establishment of a new method of microfauna as indicator. Based on this method, the correlation between the microfaunal motion velocity and activated sludge flocs was analyzed.