Investigations of Chemical Influence on Activated Sludge Flocs

The size distribution, strength, fractal dimension and extracellular polymeric substances (EPS) of activated sludge flocs were investigated by contrast test in order to figure out the chemical influence on activated sludge. These experimental results suggested that the properties of activated sludge flocs could be changed after chemical agents adding, which subsequently affected the process and effectiveness of flocculation. With the size and fractal dimension of flocs increasing, the strength of floc was enhanced with higher compactness; however, the surface porosity of flocs decreased significantly. Although the mechanical strength of floc was increased, recovery ability declined. As to the influence on EPS, such as proteins, polysaccharides and DNA, the proportions of protein and polysaccharide were increased, rather the proportion of the DNA was decreased. It was suggested that special design according to the characteristics of flocs adding chemical agents could be carried out.