Simultaneous Precipitation and Flocculation in Water Treatment: Modeling and ExperimentsEPA Grant Number: FP916407
Title: Simultaneous Precipitation and Flocculation in Water Treatment: Modeling and Experiments
Investigators: Nason, Jeff A.
Institution: The University of Texas at Austin
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Environmental Engineering , Engineering and Environmental Chemistry
The objective of this research is to improve the quantitative understanding of the changes in particle size distributions (PSD) in drinking water treatment processes when flocculation and precipitation occur simultaneously. This work focuses on two such processes: (1) the precipitation of CaCO3(s) in lime softening; and (2) the precipitation of Al(OH)3(s) in “sweep-floc” coagulation. The anticipated product of the research will be a mathematical model capable of predicting the changes in PSD brought about by simultaneous precipitation and flocculation.
The project objectives will be accomplished through a combination of mathematical modeling and laboratory experiments. Batch precipitation experiments will be performed for both CaCO3(s) and Al(OH)3(s) using pH-stat and pH-drift techniques. The rates of precipitation calculated using these methods will be validated through comparison with measurements of the dissolved concentration of the precipitating metal. During each experiment, detailed measurements of the time-varying PSD will be made with a Coulter Counter. The rates of precipitation and PSD measurements will be utilized to determine the rate expressions for particle nucleation and growth as a function of several independent variables ( e.g., degree of supersaturation; size, quantity, and physical/chemical nature of any seed particles present; mixing intensity). Once determined, these rate expressions will be translated into mathematical form and incorporated into an existing flocculation model.