Microbial and Colloidal Deposition to Solid Surfaces: Effect of Heterogeneity

Microbial and colloidal particle transport and deposition onto solid surfaces are of great significance to many environmental and technological processes. Initial attachment of particles is governed by the interactions between particles and surfaces. Classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory is utilized to predict interactions between particles and surfaces. However, discrepancies between experimental observations and theoretical predictions exist and the failure of the predictive model is often attributed to particle and solid collector physical and chemical heterogeneities.This work sought to elucidate the contribution of heterogeneity to the initial particle deposition behavior in a radial stagnation point flow system or a parallel plate flow chamber system by systematically adjusting particle type and size, as well as collector surface chemical and/or physical properties. In Chapter 2 and 3, the role of particle heterogeneity (type and size) was examined. Comparable deposition trends were observed between particles, in this case groundwater and marine bacteria, Burkholderia cepacia G4g and Halomonas pacifica g, respectively. However, the deposition kinetics of H. pacifica g appeared to be more sensitive to solution chemistry than that of B. cepacia G4g. Experimental results also demonstrated that particle size (colloidal and bacterial) had a considerable impact on the transport and interaction with surfaces. In Chapter 4, a method to influence collector surface charge and subsequent colloid deposition was described. Experimental results suggest colloids respond to local variations in surface potential through electrostatic interactions, altering particle streamlines flowing along the surface, and ultimately the extent of deposition. In Chapter 5, cell deposition onto bare and zeolite coated aluminum alloy and stainless steel surfaces was investigated using bacterium H. pacifica g. Collector surface properties found to have the most notable effect on cell attachment were the electrokinetic and hydrophobic nature of the bare metal and zeolite coated surfaces. In Chapter 6, the relative impact of physical roughness on antifouling nature of zeolite surfaces, as compared to these other chemical mechanisms was investigated.This comprehensive dissertation project established both particle and collector surface heterogeneity has a significant effect on particle deposition, which was clearly identified by altering various physical and chemical interaction parameters between particles and surfaces