Effect of dosage strategy on Al-humic flocs growth and re-growth

Abstract

a b s t r a c tThe ability of flocs growth has a significant effect on the efficiency of solid/liquid separation during coagulation process. The growth and re-growth of flocs by one time or continuous dosage were explored at neutral pH, including one time and continuous additional dosage strategy after flocs breakage. The size of flocs formed by continuous dosage before breakage was much larger than the one formed by one time dosage. There was significant irreversibility of floc breakage when no additional coagulant was added. For the one with one time initial dosage strategy, the size of re-grown flocs by one time additional dosage was nearly the same as that before breakage. The re-grown flocs formed by continuous additional dosage were a little smaller than that formed by one time additional dosage. It definitely showed that the growth or connection of flocs was probably not determined by the flocs size distribution and fractal dimension, but by the surface activity of flocs. Additional dosage could improve flocs re-grown ability because the surface activity of broken flocs was repaired by adding new alum.

Probing the application of a zirconium coagulant in a coagulation–ultrafiltration process: observations on organics removal and membrane fouling

“…As reported, humic acid (HA, Sigma-Aldrich, USA) and kaolinite (Fuchen, Tianjin, China) were usually selected as the representatives of the typical organic substances and particulates presenting in the surface water. 25,26 The preparation of HA and kaolin stock solutions are similar to those reported in the ref. 19 and 26 And the nal concentration of HA and kaolin stock solutions in this work were determined to be 10 g L À1 and 50 g L À1 respectively.…”

Breakage and regrowth of flocs formed by sweep coagulation using additional coagulant of poly aluminium chloride and non-ionic polyacrylamide

“…The average size of flocs after breakage was obviously smaller than that before breakage without additional coagulant, suggesting that there was irreversible breakage of small fragments and difficulty in regenerating without additional coagulant. Some lectures stated a similar conclusion that flocs were hard to fully regrow after breakage under sweep flocculation, but could be fully reversible under charge neutralization mechanism (Yu et al 2012). With extra addition of two coagulants on the determined broken time, floc size sustained to increase and reached the steady state before 22 min, rather faster than that with no additional coagulant.…”

Investigation of the property of kaolin–alum flocs at acidic pH

“…Increased humic acid concentration had a slight influence on the cohesion of kaolin flocs and resulted in much worse floc re-growth [16,17]. Complete re-growth of flocs can occur if a small additional coagulant dose is added during breakage, depending on the coagulant type [18,19] and strategy of application [20]. But until now, there is little investigation of flocs breakage and re-growth at acidic pH.…”