Filamentous microorganisms predominating and resulting in a large flocs size with two peak size distribution at lower pH have been observed by SEM images.

• 此外，在酸性条件下，丝状菌大量生长，导致污泥絮体的平均粒径增大，并且呈现双峰粒径分布，絮体分形维数较低，结构松散；