US EPA

2070883 

Journal Article 

Physical characteristics of flocs: I. The floc density function and aluminum floc 

Tambo, N; Watanabe, Y 

1979 

1 

Water Research
ISSN: 0043-1354
EISSN: 1879-2448 

HEEP/80/00186 

13 

5 

409-420 

eng 

HEEP COPYRIGHT: BIOL ABS. Some characteristics of floc density were illuminated by experiments and model floc simulation by using clay-Al flocs. As an Al floc is a very fragile particle, an experimental method was adopted in which the settling velocity and diameter of a discrete floc were measured in a quiescent water column. Floc density was calculated by introducing the measured values and some constants such as water density and viscosity into a suitable settling velocity equation. A modified Stokes equation was used. Floc density decreased as floc size increased; the floc diameter and floc effective density (buoyant density = floc density-water density) had a straight line relationship on a log paper. This line was characterized by 2 constants, Krho and a, which showed the slope of the line and the floc effective density of 1 cm diameter floc. This relationship was designated floc density function. ALT ratio (Al ion concentration dosed/suspended particle concentration) greatly affected the clay-Al floc density. As ALT ratio decreased, the floc density at the fixed size increased. Other effects of coagulation condition on floc density function were also discussed. The floc density function of coagulated colored water was studied. Fe, Mg and Ca flocs with clay were also studied for reference purposes. The floc density function was verified by the model floc simulation. Model flocs were produced by computer and the floc density function was derived by substituting the number of the primary particles contained in a floc and the model floc diameter into a mass balance equation of a floc particle.