| In wastewater treatment plants, polymer-surfactant aggregates, PSAs, are likely to be formed by combination of the surfactants present in biosolids—due to high concentrations of anionic soaps and detergents in wastewater—with the cationic polymers used for chemical conditioning prior to dewatering. The PSAs may be responsible for rheological, electrokinetic, and solubilization properties of the colloidal environment and, consequently, the mobility and fate of contaminants in the biosolids.; In order to characterize such PSAs relevant to environmental systems, sodium dodecyl sulfate (SDS), an anionic surfactant, and Percol 757, a cationic polymer, were utilized as a model system. Their interactions and the resulting PSA structures were indirectly characterized via surface tension, viscosity, charge on aggregates, water-insoluble dye solubilization capacity, free surfactant concentration, and solution phase polymer concentration in aqueous solution and in dispersions. Although PSAs were formed in all concentration regimes, six distinct types of interaction were identified, each responsible for distinct behavior. In all soil and clay particles, the presence of PSAs free from and bound to clay/soil particles was observed.; The most direct analysis of PSA structures was accomplished using proton NMR techniques. These spectroscopic analyses confirmed structural behavior inferred from macroscopic characterizations.; The hydrophobic domains formed by PSAs and free micelles were examined based on their capacity to solubilize a hydrophobic dye. This technique also indicated the effects of a cationic polymer and an anionic surfactant on the fate of hydrophobic contaminants. Possible environmental effects of PSAs on ionic contaminants were evaluated at a constant polymer concentration using copper as a model heavy metal and varying the initial copper concentration, pH, and dispersion concentrations. PSAs were found to affect copper speciation.; Significant concentrations of biosurfactants are produced by activated sludge microorganisms and soil microorganisms. The possible effects of these biosurfactants on the fate of contaminants were examined by using a commercial biosurfactant, JBR 515. Percol 757 and JBR 515 were found to interact with each other, but not to the extent observed with Percol 757 and SDS. |
