Fate and Transport of Heavy Metals in the Subsurface: Effects of Polymer-Surfactant Aggregates

EPA Grant Number: R826188
Title: Fate and Transport of Heavy Metals in the Subsurface: Effects of Polymer-Surfactant Aggregates
Investigators: Dentel, Steven K. , Cha, Daniel K. , Huang, C. P.
Institution: University of Delaware
EPA Project Officer: Lasat, Mitch
Project Period: September 1, 1997 through August 31, 2000
Project Amount: $295,582
RFA: Exploratory Research - Environmental Chemistry (1997) RFA Text |  Recipients Lists
Research Category: Water , Land and Waste Management , Air , Engineering and Environmental Chemistry

Description:

Concentrations and loadings of heavy metals are key criteria in recently implemented regulations concerning biosolids application to land. Although it has been assumed that biosolids offer a medium that enhances the ability of a soil to immobilize metals, the interactions of biosolids with soils are complex, and the mechanisms that may be responsible for the ability of biosolids to immobilize metals are poorly understood. We hypothesize that polymer-surfactant aggregates (PSAs) are a unique ingredient in biosolids that enhances immobilization of heavy metals. In biosolids, PSAs are formed by combination of the surfactants present in biosolids--due to the high concentrations of anionic soaps and detergents in waste- water--with the cationic polymers used to chemically condition the biosolids prior to dewatering. The primary objective of the proposed research is therefore to examine the metal binding effects of polymer-surfactant combinations added to soils, particularly in comparison to soils with neither, or with one, of the two additives.

Approach:

Many variables will play a role for a particular biosolids or soil, such as the presence or absence of a clay, the percent and relative hydrophobicity of soil organic matter, and the ionic makeup of soil water. With regard to surfactants and polymers, the relative charge concentrations present, the specific chemical structures involved, and any factors that alter the critical micelle concentration and critical aggregation concentration will also be determinants of the ultimate fate of heavy metals in such an environment. Two types of biosurfactant will also be used to explore their role in PSAs.

Expected Results:

PSAs may play a governing role in metal retention where biosolids have been land-applied. In identifying the important variables and mechanisms, a more realistic, long-term assessment of the mobility of heavy metals may become possible. Improved practices for biosolids application, or for land use thereafter, may accrue from project results.

Publications and Presentations:

Publications have been submitted on this project: View all 6 publications for this project

Supplemental Keywords:

heavy metals, polymers, surfactants, soil, sludge, biosolids, groundwater, environmental chemistry, Scientific Discipline, Air, Waste, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Ecology, Environmental Chemistry, Chemistry, Fate & Transport, Engineering, Chemistry, & Physics, fate and transport, wastewater treatment, soil , cationic polymers, subsurface, biosolid surfactants, metal binding, polymer surfactant aggregates, anionic soaps, sludge, clay

Progress and Final Reports:

  • 1998 Progress Report
  • 1999 Progress Report
  • Final Report