Fundamentals of ballasted flocculation reactions

Ballasted flocculation processes were studied at laboratory scale to establish new models for assessing: (a) the mechanisms by which ballasting agent is incorporated into the floc matrix and (b) the settling velocity behavior of ballasted flocs. Ballasted flocs were found to be formed by a mechanism in which the ballasting agent is incorporated into the floc matrix by differential momentum, and the ballasting agent taking the place of the bound water content. Floc density and floc settling velocity were found to be a linear function of the ballasting agent dose. A floc density-mirosand dose relationship was suggested for simplifying a general settling velocity equation. The relationship was in the form of: &rgr;_s = k₁M + k₂. A fractal model was also proposed for modeling the settling velocity of ballasted flocs represented by: nS=f1M+f2 d^f where k₁, k₂, f₁, and f ₂ were coefficients that depended on floc chemical characteristics and ballasting agent dose, and the exponent f had a value of 0.45.; Results obtained from this research provided a better understanding of the ballasted flocculation process and a basis for improving existing ballasted flocculation process designs.